Recommend me a cam

[72Hondo]

Ok Dave let's test this out.

I'm running a 327, .30 over, 8.1 static, 64cc camel back heads with light port work. A B&M144 sits on top with dual 450's.

In it currently is a solid reproduction 30/30. Motor is at the shop being redone and I never thought the came was right for a jet boat (yeah I said it).

The engine will never see above 6500 and as of right now the OT headers have water going though them.

 

[Carlson-jet]

HAHA. You will NEVER get an actual response with a cam suggestion here. Why?

Read Below

 

[OCMerrill]

Any 3/4 Race cam will do.

 

[waterhorse]

Any 3/4 Race cam will do.

Here we go!

 

[OCMerrill]

Here we go!

He's using a small blower and if he goes full race the engine will surge at idle and RD will loose his lunch.

 

[was thatguy]

As far as profile, I can't help.

But I will say this in the interest of starting a side debate...this is 2015, cam lobes and lifter bodies should ALWAYS have a little wheel between them!

 

[obnoxious001]

Any 3/4 Race cam will do.

Totally would have been my choice!

 

[Carlson-jet]

As far as profile, I can't help.

But I will say this in the interest of starting a side debate...this is 2015, cam lobes and lifter bodies should ALWAYS have a little wheel between them!

My Dad designed an Intake/Exh. system that had neither back in the 70's but there were not good ways to seal it. That is where we should be. Ceramics have come a long way and sealing properties have taken care of the sealing issue. I saw a very similar version a few years ago that was successful but that design has now been superseded by electronics still using an actual valve.

 

[rivermobster]

Ok Dave let's test this out.

I'm running a 327, .30 over, 8.1 static, 64cc camel back heads with light port work. A B&M144 sits on top with dual 450's.

In it currently is a solid reproduction 30/30. Motor is at the shop being redone and I never thought the came was right for a jet boat (yeah I said it).

The engine will never see above 6500 and as of right now the OT headers have water going though them.

Just a suggestion, but you might want to include...

What carb(s)?

What intake?

What exhaust?

What ignition?

What pistons do you have? (design wise)

What compression ratio?

Are the heads ported? Port matched already?

What crank and rods? Stock? Steel? Brand?

What is your intended use of this boat?

Ski boat? Race boat? Weekend warrior boat? Pulling the kids with a tube boat?

What impeller? What Intake? Is the jet stock? Bored?

Ya got one of them jet-o-vator look at me thingys on it?

What hull? Manufacturer? Size?

What rockers does the engine have? Do the heads have guide plates and screw in studs already?

Are you willing to put guide plates and screw in studs on this engine?

What valve springs do you have?

Are you willing to change em?

Pushrods? Describe please.

Are you wiling to change em?

You want hyd? Or solid?

Roller or not?

Is it a roller already? Don't forget to change the dist. gear if you go roller. Chebby dist gears are clocked. Use caution.

Whats your budget?

Or just ignore all this and go with a 3/4 race cam. :tbi

 

[obnoxious001]

Ok Dave let's test this out.

I'm running a 327, .30 over, 8.1 static, 64cc camel back heads with light port work. A B&M144 sits on top with dual 450's.

In it currently is a solid reproduction 30/30. Motor is at the shop being redone and I never thought the came was right for a jet boat (yeah I said it).

The engine will never see above 6500 and as of right now the OT headers have water going though them.

Do you have a shut off valve for water to headers? I normally run a bit more lobe separation on a marine blower deal I do mostly BBC marine engines, not SBC marine don't have specs for 30/30 right in front of me even though it's a famous cam.

 

[BTR]

How about this?

 

[obnoxious001]

Just a suggestion, but you might want to include...

What carb(s)?

What intake?

What exhaust?

What ignition?

What pistons do you have? (design wise)

What compression ratio?

Are the heads ported? Port matched already?

What crank and rods? Stock? Steel? Brand?

What is your intended use of this boat?

Ski boat? Race boat? Weekend warrior boat? Pulling the kids with a tube boat?

What impeller? What Intake? Is the jet stock? Bored?

Ya got one of them jet-o-vator look at me thingys on it?

What hull? Manufacturer? Size?

What rockers does the engine have? Do the heads have guide plates and screw in studs already?

Are you willing to put guide plates and screw in studs on this engine?

What valve springs do you have?

Are you willing to change em?

Pushrods? Describe please.

Are you wiling to change em?

You want hyd? Or solid?

Roller or not?

Is it a roller already? Don't forget to change the dist. gear if you go roller. Chebby dist gears are clocked. Use caution.

Whats your budget?

Or just ignore all this and go with a 3/4 race cam. :tbi

Ummm, many of your questions were answered in his first post?

 

[72Hondo]

Just a suggestion, but you might want to include...

What carb(s)? Dual 450's

What intake? B&M blower

What exhaust? OT headers

What ignition? Mallory 5000 (off the top of my head)

What pistons do you have? (design wise) dished.

What compression ratio? 8.1

Are the heads ported? Port matched already? Light polishing job and no

What crank and rods? Stock? Steel? Brand? All forged, name escapes me.

What is your intended use of this boat?

Ski boat? Race boat? Weekend warrior boat? Pulling the kids with a tube boat?

What impeller? What Intake? Is the jet stock? Bored? Choice of B and c impellers it's a very very worked over WJ with droop and of course diverter

Ya got one of them jet-o-vator look at me thingys on it?

What hull? Manufacturer? Size? Hondo, I thought boats on come in 18' [emoji106]

What rockers does the engine have? Do the heads have guide plates and screw in studs already? Crane gold 1.6 roller rockers

Are you willing to put guide plates and screw in studs on this engine? Already has screw in studs.

What valve springs do you have? Have to grab the head sheet. Off the top of my head, they're triple springs

Are you willing to change em?
Yes
Pushrods? Describe please.
Yes

Are you wiling to change em?
Yes
You want hyd? Or solid?
Either or
Roller or not?
Either or

Is it a roller already? Don't forget to change the dist. gear if you go roller. Chebby dist gears are clocked. Use caution. No

Whats your budget? $400-600 on top end.

Or just ignore all this and go with a 3/4 race cam. :tbi

All questions answered in quotes.

 

[72Hondo]

Do you have a shut off valve for water to headers? I normally run a bit more lobe separation on a marine blower deal I do mostly BBC marine engines, not SBC marine don't have specs for 30/30 right in front of me even though it's a famous cam.

No shut off valve but it's not like I haven't thought of it. Sitting on an airplane waiting on the capt [emoji19] don't have access to the cam numbers.

Reversion scares me......

 

[72Hondo]

Also should mention this is a SJ block and crank. Which I heard can be good until 9-9500k in short bursts.

 

[Bigbore500r]

He's using a small blower and if he goes full race the engine will surge at idle and RD will loose his lunch.

 

[rivermobster]

With your budget, if you do ALL the work yourself, you will should be able to go hyd. roller. You'll need a cam kit, button, new pushrods and gaskets. It will be close, but you can probably fit it all in.

I'm not the best guy for picking cam profiles, but Mike here at the shop is one of the best. He can give you a price on everything you need and what profile to use. Give him a call when you have time...

http://jmsservicecenter.com/

 

[76 Hondo]

With a SBC in a jet boat, small blower I think the 3/4 race would not work well on the torque curve I would suggest the RV grind!

 

[72Hondo]

With a SBC in a jet boat, small blower I think the 3/4 race would not work well on the torque curve I would suggest the RV grind!

Everyone knows the SBC in a boat but it's a fun reliable boat. I won't win any speed contests but I'm in it for reliability, fun, and something different.

 

[Runs2rch]

With a SBC in a jet boat, small blower I think the 3/4 race would not work well on the torque curve I would suggest the RV grind!

Exactly what I was thinking! RV cam for the win!

 

[76 Hondo]

And who said you couldn't get tech advice on RDP?

 

[Bigbore500r]

With a SBC in a jet boat, small blower I think the 3/4 race would not work well on the torque curve I would suggest the RV grind!

Jets dont really start loading the pump until after 3000rpm, then the power demand rises steeply. Depends on impeller size.

 

[Runs2rch]

And who said you couldn't get tech advice on RDP?

Good tech advice!

 

[28Eliminator]

I'll take a stab..

Crane 109671

284/292, 509/528
112 LS

Fire away bitches [emoji12]

 

[AzGeo]

The 'Duntov 30/30 cam' is advertised by most as "224 @ .050" lift" .

Assuming a 'B' impeller, I would want it to start holding cylinder pressure around 3000 RPMs, up to where it runs out of blower speed . (6800 RPMs) Those blowers usually run 45% + over driven, so you can't run the crankshaft much over 6500 for very long .

I would go with; .550" lift-240 @ .050" intake, .550" lift-250 @ .050" exhaust, 110 lobe centers in @ 3 to 4 degrees advanced . Flat tappet hydraulic would go 6200/6500 and a solid flat tappet would go well beyond the 6800 RPM X 1.45 blower speed .

If it's a B&M intake manifold, I would weld up the EGR and heat cross over passages, and then plumb raw water thru them to cool the charge and the intake manifold . Or just install a real intercooler, those 'little blowers' get really hot, turning so fast .

Running 6 or 8 lbs of boost @ 550 degrees (F), is an expensive lesson you won't want to learn . Running a 'too rich mixture' just to stop the detonation, is how most slow blower motors are set up these days, just for looks .

 

[28Eliminator]

110 LC on something with wet exhaust? Just asking..

 

[AzGeo]

I would 'hang' the exhaust open longer as shown above, because this blower is turning so fast at all speeds .

Jet Boat/ALL BOATS with water injected headers should not have water in the head pipes at idle RPMs .

Even 'thru transom water injected headers' use a 'T' valve for the head pipes and also have direct full time water fittings down on their tail pipes .

For 'over transom/traditional 4 tube headers', I use a restriction plug with a 7/32" drilled hole in it, inside the 'T' valve. That is ALL the water I want in BOTH pipes while at speed and on a jet I would set up the 'T' to shut off water to the head pipes @ 2500 RPMs . So when you are SLOWLY CLOSING the throttle from 3000 RPMs to idle, the water is SHUT OFF at 2500 RPMs, and nothing reverts .

Most normally aspirated jet boat motors I use 108 lobe centers on the big blocks and 106 on the serious small blocks .

Tight lobe centers "shorten and raise the PEAK of the torque curve" and that is exactly what a jet pump needs .

Holding cylinder pressure in the motor below where the pump is 'loaded', just makes 'unused power' and 'wears out the motor faster' ......

 

[OCMerrill]

With a SBC in a jet boat, small blower I think the 3/4 race would not work well on the torque curve I would suggest the RV grind!

An RV Cam....Nice choice. :thumbup:

 

[obnoxious001]

Tight lobe centers "shorten and raise the PEAK of the torque curve" and that is exactly what a jet pump needs .

.

So you are saying the blower engines I build and dyno for jet boats shouldn't be running the wide lobe centers that yield me great results?

 

[Carlson-jet]

You guys are way off base.

First and foremost, you need the 10-15k budget "Dealio" on a 60 year old design to make anything work or last. 2nd. It must be approved by an internet board to prove its worthiness. 3rd. Unless Dyno results are posted, lavished over, denied, and finally accepted all else is worthless. 4th. If it can't be made fun of, it has no value.

BTW Bert, Camel humps or FUELIES ( Not Camel Backs [which is a Mountain in Phoenix] suck unless they are 462X or 291's with bolt hole accessory provisions without serious work( Millions of cubic dollars) to correct seats, studs and guide issues. ( I Have about a Pallet of them)

Just buy an Airline ticket with a good flight pattern and fly over a F'n Lake. Take plenty of pictures.

I Bet WITHOUT ANY DOUBT Anyone who has posted on this thread on this subject CAN NOT IN FACT post a picture of themselves doing 3 task in my list below.
1. Checking a crank for cracks prior to.
2. Grinding a journal and polishing.
3. Re-sizing or Balancing a rod. The full set would be icing on the cake.
4. Porting/flowing a set of heads
5.Align boring a block
6. Honing cylinders to within a .0005 of a 10th. Then measuring and cutting the rings to match.
7. 1+ trophy from above personal work while at the wheel.

Post the fuck up Please. :thumbup:

 

[Jimmy]

Just a suggestion, but you might want to include...

What carb(s)?

What intake?

What exhaust?

What ignition?

What pistons do you have? (design wise)

What compression ratio?

Are the heads ported? Port matched already?

What crank and rods? Stock? Steel? Brand?

What is your intended use of this boat?

Ski boat? Race boat? Weekend warrior boat? Pulling the kids with a tube boat?

What impeller? What Intake? Is the jet stock? Bored?

Ya got one of them jet-o-vator look at me thingys on it?

What hull? Manufacturer? Size?

What rockers does the engine have? Do the heads have guide plates and screw in studs already?

Are you willing to put guide plates and screw in studs on this engine?

What valve springs do you have?

Are you willing to change em?

Pushrods? Describe please.

Are you wiling to change em?

You want hyd? Or solid?

Roller or not?

Is it a roller already? Don't forget to change the dist. gear if you go roller. Chebby dist gears are clocked. Use caution.

Whats your budget?

Or just ignore all this and go with a 3/4 race cam. :tbi

Do u wanna see his birth certificate too lol

Longer duration cams rely on the velocity of the gases to become efficient, hence more power at higher RPM.
Reversion? With a big cam, the exhaust valves aren't totally closed at tdc on the exhaust stroke. If the gas flow isn't rushing out of the exhaust ports fast enough, it can allow water to get sucked back in as the piston drops.

The reason you get a lopey idle is cam duration. The pistons are coming up before the valves are totally closed and pushing the fuel/air charge back into the intake..

When your motor is turning 7000 RPM, that air is hauling ass into the cylinders and "packing". The same goes for exhaust. The gases moving down the exhaust ports at high speed will help drag the next charge out as it follows.

This might be relevant.

 

[28Eliminator]

You guys are way off base.

First and foremost, you need the 10-15k budget "Dealio" on a 60 year old design to make anything work or last. 2nd. It must be approved by an internet board to prove its worthiness. 3rd. Unless Dyno results are posted, lavished over, denied, and finally accepted all else is worthless. 4th. If it can't be made fun of, it has no value.

BTW Bert, Camel humps or FUELIES ( Not Camel Backs [which is a Mountain in Phoenix] suck unless they are 462X or 291's with bolt hole accessory provisions without serious work( Millions of cubic dollars) to correct seats, studs and guide issues. ( I Have about a Pallet of them)

Just buy an Airline ticket with a good flight pattern and fly over a F'n Lake. Take plenty of pictures.

I Bet WITHOUT ANY DOUBT Anyone who has posted on this thread on this subject CAN NOT IN FACT post a picture of themselves doing 3 task in my list below.
1. Checking a crank for cracks prior to.
2. Grinding a journal and polishing.
3. Re-sizing or Balancing a rod. The full set would be icing on the cake.
4. Porting/flowing a set of heads
5.Align boring a block
6. Honing cylinders to within a .0005 of a 10th. Then measuring and cutting the rings to match.
7. 1+ trophy from above personal work while at the wheel.

Post the fuck up Please. :thumbup:

Lol... This has a familiar TONE to it [emoji4]

 

[72Hondo]

The 'Duntov 30/30 cam' is advertised by most as "224 @ .050" lift" .

Assuming a 'B' impeller, I would want it to start holding cylinder pressure around 3000 RPMs, up to where it runs out of blower speed . (6800 RPMs) Those blowers usually run 45% + over driven, so you can't run the crankshaft much over 6500 for very long .

I would go with; .550" lift-240 @ .050" intake, .550" lift-250 @ .050" exhaust, 110 lobe centers in @ 3 to 4 degrees advanced . Flat tappet hydraulic would go 6200/6500 and a solid flat tappet would go well beyond the 6800 RPM X 1.45 blower speed .

If it's a B&M intake manifold, I would weld up the EGR and heat cross over passages, and then plumb raw water thru them to cool the charge and the intake manifold . Or just install a real intercooler, those 'little blowers' get really hot, turning so fast .

Running 6 or 8 lbs of boost @ 550 degrees (F), is an expensive lesson you won't want to learn . Running a 'too rich mixture' just to stop the detonation, is how most slow blower motors are set up these days, just for looks .

45% over driven from the factory or 45% of people overdrive them?

I never had a problem with detonation, I run it on the fat side with 36* total with a NGK # 6 or 7 on 93.

Header water doesn't start until 2500.

I think my setup is a tad unique, as I have dual carbs atop the small blower.

 

[AzGeo]

So you are saying the blower engines I build and dyno for jet boats shouldn't be running the wide lobe centers that yield me great results?

I like to use 'smaller cams, with less spring pressures and less violent valvetrain motion' . This example has a blower, so it will run if the valves open anywhere near correct timing . I want to LESSEN the WEAR, and LESSEN the FAILURES, so my cam specs DO NOT MAKE POWER where the jet/V-drive does not need the power . I use minimal spring pressures, for less failures, lighter components, short reasonable lobe ramps= less harmonics= less failures .

This allows more cylinder cooling at 'part throttle', 'does not POUND on the rod bearings, under 3000 RPMs', 'produces a TORQUE SPIKE, and MAXIMUM POWER (for the engine combination) within the usable RPM range for the jet/V-drive .

YES, any blower motor will run with a 'big wide lobe center cam', and it will produce nice numbers on the dyno, just dial up the boost . I choose to go with a 'reasonable cam grind', that makes power 'only where needed', short duration at the right timing points, PEAKING the power for ACCELERATION, and making higher peak torque numbers than the wide cams can make . (equal to equal) I build performance boats, and the motors I build must produce it's max power where I need it, to maximize the boat's performance, and to last a long time with minimal maintenance .

HOW LONG to hold the cylinder pressure, and WHEN to spill off unburnt A/F to help cooling, have always been two of the major questions when building a 'blown play motor' .

I want the close lobe center cam to HIT that impeller, like a trans brake in a car, right when the pump is loaded, and it's near the narrow high peak torque, and that is where all the pulling power is made for a jet .

Using the 'small B&M Blower', this motor will need all the 'overlap cooling' it can get .

 

[Abc123]

The Rex valves work great. Turn the water off at idle and WOT.

 

[Bigbore500r]

You guys are way off base.

First and foremost, you need the 10-15k budget "Dealio" on a 60 year old design to make anything work or last. 2nd. It must be approved by an internet board to prove its worthiness. 3rd. Unless Dyno results are posted, lavished over, denied, and finally accepted all else is worthless. 4th. If it can't be made fun of, it has no value.

BTW Bert, Camel humps or FUELIES ( Not Camel Backs [which is a Mountain in Phoenix] suck unless they are 462X or 291's with bolt hole accessory provisions without serious work( Millions of cubic dollars) to correct seats, studs and guide issues. ( I Have about a Pallet of them)

Just buy an Airline ticket with a good flight pattern and fly over a F'n Lake. Take plenty of pictures.

I Bet WITHOUT ANY DOUBT Anyone who has posted on this thread on this subject CAN NOT IN FACT post a picture of themselves doing 3 task in my list below.
1. Checking a crank for cracks prior to.
2. Grinding a journal and polishing.
3. Re-sizing or Balancing a rod. The full set would be icing on the cake.
4. Porting/flowing a set of heads
5.Align boring a block
6. Honing cylinders to within a .0005 of a 10th. Then measuring and cutting the rings to match.
7. 1+ trophy from above personal work while at the wheel.

Post the fuck up Please. :thumbup:

Do you take selfies while building engines?

 

[was thatguy]

You guys are way off base.

First and foremost, you need the 10-15k budget "Dealio" on a 60 year old design to make anything work or last. 2nd. It must be approved by an internet board to prove its worthiness. 3rd. Unless Dyno results are posted, lavished over, denied, and finally accepted all else is worthless. 4th. If it can't be made fun of, it has no value.

BTW Bert, Camel humps or FUELIES ( Not Camel Backs [which is a Mountain in Phoenix] suck unless they are 462X or 291's with bolt hole accessory provisions without serious work( Millions of cubic dollars) to correct seats, studs and guide issues. ( I Have about a Pallet of them)

Just buy an Airline ticket with a good flight pattern and fly over a F'n Lake. Take plenty of pictures.

I Bet WITHOUT ANY DOUBT Anyone who has posted on this thread on this subject CAN NOT IN FACT post a picture of themselves doing 3 task in my list below.
1. Checking a crank for cracks prior to.
2. Grinding a journal and polishing.
3. Re-sizing or Balancing a rod. The full set would be icing on the cake.
4. Porting/flowing a set of heads
5.Align boring a block
6. Honing cylinders to within a .0005 of a 10th. Then measuring and cutting the rings to match.
7. 1+ trophy from above personal work while at the wheel.

Post the fuck up Please. :thumbup:

Lol...it never occurred to me to take pictures of myself while doing all those things, of course they didn't really have cell phones then.

Anybody with a CK10 and rod hone and digital scale can do those things...and throw in a pin float (bushed or unbushed), as well as a beam polish. You didn't say if you wanted a wide filet grind or not?

 

[AzGeo]

45% over driven from the factory or 45% of people overdrive them?

I never had a problem with detonation, I run it on the fat side with 36* total with a NGK # 6 or 7 on 93.

Header water doesn't start until 2500.

I think my setup is a tad unique, as I have dual carbs atop the small blower.

The B&M 144 blowers come from the factory with 1.45% over driven pulleys in the kit, did you change them ?

I can see where you would need to 'run on the fat side', and with 8 booster venturi's spraying in fuel, plus 36 degrees of spark advance, I feel that the 'dual carbs' have saved your skin .

When testing those blowers for B&M back in the early 80's, I found them to be extremely hot running, even out in the air on boat motors .

We used a 21' Centurion with a '290' Volvo with Volvo drive, 1.50 gear and a 22 pitch Volvo prop . New valve springs on the motor, otherwise totally stock with Volvo manifolds out thru the transom . I installed an 'air inlet temp gauge, vacuum/boost gauge, to the intake manifold, and an oil temp gauge, and water temp gauge to the motor .

At continuous running, between 3000 and 5000 RPMs, 5 lbs of boost the inlet air temps were (aprox) 420/460 degrees (F) with an ambient air temp of (aprox) 80 degrees (F) and water temp of (aprox) 65/68 degrees (F) . Castaic Lake California . Going up to 8 lbs of boost (smaller top pulley) the inlet temps were 500 to 550 degrees (F) at WOT 5400 RPMs, and the oil temp went up almost 100 degrees, water stayed about the same (+ or - 25 degrees) . Single mechanical 750 Holley DP carb with jetting changes for conditions . (always a little on the fat side) Ran best 32/33 degrees total spark advance .

Knowing that gasoline has a usable potential of 1500 degrees (F) in well built engines, my immediate mental note was that "these blowers are OK for street and short bursts of 5 lbs of boost, anything more is going backwards" .

The inlet air temp with 8lbs of boost is 500/550 and that is ONE THIRD OF THE POWER LOST, even before it gets to the cylinders . 400 degrees is little better .

The other 'small problem' here is, the blower has a 'top RPM limit' and if all the factors actually were made to work together, you would over speed the blower . 6500 RPMs X 1.45 = 9425 RPMs .

How about a nice 6-71 with the 2 carbs on it ?

 

[28Eliminator]

Lol...it never occurred to me to take pictures of myself while doing all those things, of course they didn't really have cell phones then.

Anybody with a CK10 and rod hone and digital scale can do those things...and throw in a pin float (bushed or unbushed), as well as a beam polish. You didn't say if you wanted a wide filet grind or not?

Yeah, doesn't everyone have a CK10 laying around their garage?? [emoji13]

 

[was thatguy]

Yeah, doesn't everyone have a CK10 laying around their garage?? [emoji13]

They SHOULD!!:thumbup:

 

[72Hondo]

The B&M 144 blowers come from the factory with 1.45% over driven pulleys in the kit, did you change them ?

I can see where you would need to 'run on the fat side', and with 8 booster venturi's spraying in fuel, plus 36 degrees of spark advance, I feel that the 'dual carbs' have saved your skin .

When testing those blowers for B&M back in the early 80's, I found them to be extremely hot running, even out in the air on boat motors .

We used a 21' Centurion with a '290' Volvo with Volvo drive, 1.50 gear and a 22 pitch Volvo prop . New valve springs on the motor, otherwise totally stock with Volvo manifolds out thru the transom . I installed an 'air inlet temp gauge, vacuum/boost gauge, to the intake manifold, and an oil temp gauge, and water temp gauge to the motor .

At continuous running, between 3000 and 5000 RPMs, 5 lbs of boost the inlet air temps were (aprox) 420/460 degrees (F) with an ambient air temp of (aprox) 80 degrees (F) and water temp of (aprox) 65/68 degrees (F) . Castaic Lake California . Going up to 8 lbs of boost (smaller top pulley) the inlet temps were 500 to 550 degrees (F) at WOT 5400 RPMs, and the oil temp went up almost 100 degrees, water stayed about the same (+ or - 25 degrees) . Single mechanical 750 Holley DP carb with jetting changes for conditions . (always a little on the fat side) Ran best 32/33 degrees total spark advance .

Knowing that gasoline has a usable potential of 1500 degrees (F) in well built engines, my immediate mental note was that "these blowers are OK for street and short bursts of 5 lbs of boost, anything more is going backwards" .

The inlet air temp with 8lbs of boost is 500/550 and that is ONE THIRD OF THE POWER LOST, even before it gets to the cylinders . 400 degrees is little better .

The other 'small problem' here is, the blower has a 'top RPM limit' and if all the factors actually were made to work together, you would over speed the blower . 6500 RPMs X 1.45 = 9425 RPMs .

How about a nice 6-71 with the 2 carbs on it ?

No change from the factory. It was recently rebuilt by BDS last year, Teflon, the whole nine yards lol.

Yeah I just don't like the one carb look. It works under a hood but the look isn't for me. I'm actually surprised they made a dual carb adapter for it. As a complete package, it's gotta be on the rare or extent side lol.

No issues with a 671, problem is finding everything for a SBC at a decent price.

 

[rivermobster]

No change from the factory. It was recently rebuilt by BDS last year, Teflon, the whole nine yards lol.

Yeah I just don't like the one carb look. It works under a hood but the look isn't for me. I'm actually surprised they made a dual carb adapter for it. As a complete package, it's gotta be on the rare or extent side lol.

No issues with a 671, problem is finding everything for a SBC at a decent price.

I get all my blower stuff here: http://dragparts.com/

You couldn't pay me to use BDS! :thumbsdown


I wanted to say also. it sounds like you have one bad azz engine there! I think RD needs it in his Shiada.

 

[72Hondo]

I get all my blower stuff here: http://dragparts.com/

You couldn't pay me to use BDS! :thumbsdown


I wanted to say also. it sounds like you have one bad azz engine there! I think RD needs it in his Shiada.

I will never use BDS again. I won't go into it, but never again.

 

[rivermobster]

I will never use BDS again. I won't go into it, but never again.

I'm by no means an expert at it, but I do know how to rebuild em. I'm not sure why they would teflon a blower in a boat, that's not gonna be race only.

But that's BDS for ya. *shrug*

 

[AzGeo]

No change from the factory. It was recently rebuilt by BDS last year, Teflon, the whole nine yards lol.

Yeah I just don't like the one carb look. It works under a hood but the look isn't for me. I'm actually surprised they made a dual carb adapter for it. As a complete package, it's gotta be on the rare or extent side lol.

No issues with a 671, problem is finding everything for a SBC at a decent price.

The 144 is at 45% over crankshaft speed and it is 'designed to make 5 lbs of boost' using a MILD camshaft .(350/355 cu in)

I consider "1/3 of an atmosphere" (5 lbs VS 14.7) to be 'just adding cubic inches and very little added cylinder pressure' . Under 1/2 an atmosphere (7 lbs) is also considered very mild and 'very streetable/utility/towing' types of uses . When the motor 'actually sees 8 lbs or more' would this be considered a performance adder, and as such would benefit from 'valve timing changes' .

I stand by my original cam choice because it is exactly what you need, since your motor is actually operating as a (aprox) 9.5 + - to one compression motor with the 'mild 470/224 on 114 cam that is in it' .

I would NEVER agree that a 'road racing Corvette cam would be NEAR the best choice for a BLOWN jet boat motor . Even though the BLOWN part is not much of a factor in the whole picture .

Moreover, I would drop the total timing back to 32 degrees, and then start leaning down the jetting, looking for something a little closer than what you have now .

You will be surprised at how the motor will WAKE UP when you use a better cam with a better tune .

Good luck to you ! "nipping spark plugs is a learning curve" . (use 4oz of Marvel Mystery Oil per 10 gallons of gas to get better plug readings)

 

[ColdSteel]

I like to use 'smaller cams, with less spring pressures and less violent valvetrain motion' . This example has a blower, so it will run if the valves open anywhere near correct timing . I want to LESSEN the WEAR, and LESSEN the FAILURES, so my cam specs DO NOT MAKE POWER where the jet/V-drive does not need the power . I use minimal spring pressures, for less failures, lighter components, short reasonable lobe ramps= less harmonics= less failures .

I'm more of an assembler than a builder, but wouldn't a good sized roller cam with a lightened valvetrain be just as reliable, minus the wear on the springs?

 

[72Hondo]

The 144 is at 45% over crankshaft speed and it is 'designed to make 5 lbs of boost' using a MILD camshaft .(350/355 cu in)

I consider "1/3 of an atmosphere" (5 lbs VS 14.7) to be 'just adding cubic inches and very little added cylinder pressure' . Under 1/2 an atmosphere (7 lbs) is also considered very mild and 'very streetable/utility/towing' types of uses . When the motor 'actually sees 8 lbs or more' would this be considered a performance adder, and as such would benefit from 'valve timing changes' .

I stand by my original cam choice because it is exactly what you need, since your motor is actually operating as a (aprox) 9.5 + - to one compression motor with the 'mild 470/224 on 114 cam that is in it' .

I would NEVER agree that a 'road racing Corvette cam would be NEAR the best choice for a BLOWN jet boat motor . Even though the BLOWN part is not much of a factor in the whole picture .

Moreover, I would drop the total timing back to 32 degrees, and then start leaning down the jetting, looking for something a little closer than what you have now .

You will be surprised at how the motor will WAKE UP when you use a better cam with a better tune .

Good luck to you ! "nipping spark plugs is a learning curve" . (use 4oz of Marvel Mystery Oil per 10 gallons of gas to get better plug readings)

The cam you mentioned, is it a custom grind or off the shelf type. Engine builder is buttoning up the short block this week and I want to discuss cams with him, no offense though.

Off topic question for those of you who build motors or have had a motor rebuilt what is a ball park on run frame. I ask because I think this one is going together too fast. He's had it for about 3 weeks and were already buttoning up the short block, that's machining, inspecting everything etc. I told him no rush I don't need to be on the water until next year. Am I just worrying over nothing?

 

[Bigbore500r]

The cam you mentioned, is it a custom grind or off the shelf type. Engine builder is buttoning up the short block this week and I want to discuss cams with him, no offense though.

Off topic question for those of you who build motors or have had a motor rebuilt what is a ball park on run frame. I ask because I think this one is going together too fast. He's had it for about 3 weeks and were already buttoning up the short block, that's machining, inspecting everything etc. I told him no rush I don't need to be on the water until next year. Am I just worrying over nothing?

3 weeks is plenty of time. To be honest you spend more time specifying and chasing parts, ordering stuff and waiting for it to arrive. If they've got everything they need the first time around after mic'ing and checking journals / clearances you can assemble the shortblock in a day. Usually what happens is bearings you ordered are on backorder....the rods and piston combo is heavier than the stuff its replacing and is gonna require mallory to be added to the crank to get it to balance....another trip to the shop...etc etc. If they have an in-house facility and all the typical shit in stock (theyre not a weekender like some of us) they can knock it out pretty quick

 

[AzGeo]

I'm more of an assembler than a builder, but wouldn't a good sized roller cam with a lightened valvetrain be just as reliable, minus the wear on the springs?

A '6500 RPM,hydraulic roller cam system' would need as much if not more spring pressure, unless you went with a 'rev kit' . I'm looking at "performance VS dollars spent", and my deal would be around $500 total while your deal would be around $950/$1000 (springs, rockers, push rods, lifters, cam and guide plates)

Springs suffer from a couple of problems in boats . #1 moisture, it attacks the spring surfaces and then goes inside and attacks the spring structure . #2 gross lift, if the cam has excessive lift (.800" +) it wears down the life of the springs while running . #3 big lift cams and not "loosening rockers when not used" .

The major difference would be in NO performance gains, since this is 'forced induction' and the 'charge' would be blown in and out .

A 'roller cam profile' may help an N/A motor here, (a little) but the REAL FACTOR in this blown deal would be what the heads will flow and what the exhaust will allow out of the motor . This is a mild flat tappet cam .

Any cam grinder who can make cams with 108 lobe centers, will be able to grind a cam for this motor . American Cams (Joe & Jr), Clay Smith (George Streigle), Reed, Lunati, Norris, Camonics (my old buddy Ed), Isky, Engle (Jack), many others I missed . Any cam grinder who knows engines and is still alive can grind this exact cam, and it will work great .

 

[72Hondo]

George,

Here's the pics I found on my phone. Some are pretty old. Lol but it's the same blower