Rectangle or oval port heads

Hi everyone,
Looking for some opinions and possibly combos for a 496 stroker I want to build. This will be going in a Hallett 210. Wanting to be around 450-500 horse power. Most of the time will be cruising at 3000-3500 rpm. Not planning on revving past 5500. I was thinking aluminum oval ports would be the ticket. From what I read that seems to be ideal. I had an engine builder tell me I need rect.
Ports. I will be running imco power flos,and was thinking performer rpm air gap, and either Edelbrock rpm oval ports or gm performance ovalsWhat do you guys think ? Is 500 hp realistic on pump gas and being reliable ? Do I need rectangle ports ? Going aluminum either way.
Thanks in advance.

70sangersean said:

Hi everyone,
Looking for some opinions and possibly combos for a 496 stroker I want to build. This will be going in a Hallett 210. Wanting to be around 450-500 horse power. Most of the time will be cruising at 3000-3500 rpm. Not planning on revving past 5500. I was thinking aluminum oval ports would be the ticket. From what I read that seems to be ideal. I had an engine builder tell me I need rect.
Ports. I will be running imco power flos,and was thinking performer rpm air gap, and either Edelbrock rpm oval ports or gm performance ovalsWhat do you guys think ? Is 500 hp realistic on pump gas and being reliable ? Do I need rectangle ports ? Going aluminum either way.
Thanks in advance.

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500 hp is very conservative, it's easy to get that without the stroker crank. Realistically you should be able to make 550 or more horsepower easily, with a 9 1/2 - 1 pump gas engine.

I had a conversation with a guy wanting to build a stroker from what he has, but he already has a rectangular port 454 that runs pretty strong. I am supposed to see him this weekend and get a ride in his boat (also a 210) to discuss options. I have previously driven the boat and told him in my opinion his engine was not stock, and perhaps 500 or so HP.

Could be a coin toss on the ports, but I am currently building a pair of "budget" 498's for a larger boat, and we will run his existing 049 oval heads to save cost, which should work out fine as his target number is 500 hp.

If I built one for myself, I would likely do a rectangle port engine, and maybe even the single plane intake, although the airgap should work fine.

I had a "wake up call" the other day, about "brand name parts quality" . BARRY

I was installing some #924 Comp Cam springs on some 049's for my turbo truck project .

The Comp Cams web site has a chart listing all their springs and how they are rated at different heights .

At a recommended 1.850" assembled height, the SPEC is 129 lbs, but actually was 121 lbs .

At just .500" lift, that same combo had a SPEC of 303 lbs, however, the actual was 385/390 lbs . (I checked them all, and few were the same)

I even swapped springs and positions on the head to make sure I did not make a measurement mistake .

I took the heads and springs to the local machine shop, just in case I was losing my mind .

They agreed and told me that comp Cams springs have had "poor quality control" for a number of years .

Back in California, our shop used this exact part number on MANY flat tappet hydraulic and solid cams with no problems .

WTF ?

As far as the "oval VS square port" question; I'm thinking that the vacuum created across the power band with the 1/4" arm (piston speed first 90 degrees) could "overpower" the velocity/atomization gains of the oval port heads, right where it makes the power . (dry centers, wet walls)

Even GM's oval port 502's are a 4" arm . I think so for these reasons .

While the square ports will "cool and soften the torque off idle", (lower vacuum but more density) and allow a reasonable cam to pull hard from 1800 on up past 5500 . (X intake, marine 1050, .600"238- .600"244, on 110 @ 105/106)

AzGeo said:

I had a "wake up call" the other day, about "brand name parts quality" . BARRY

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Valve springs should always be checked, in my opinion. Different people like different pressures. I had an issue with some brand new big name heads earlier this year that were no where close to what they were advertised at,, called them and got them to send me some softer springs after they checked some and agreed that I was correct.

I've always checked all of them, but my "vise held spring checker" is for 600 lbs, so the increments are a little "skechy" down in the 100's and 200's, and they were all so far off base .

I just never had 16 (3 pieces springs) so far off of their advertised ratings and overall spring rate .

I had to see the "pro spring checker" for myself, and I was not far off, in fact my numbers were less than 10# off across all 16 sets .


Guess I'm back to Isky or K-Motion ..........

AzGeo said:

I've always checked all of them, but my "vise held spring checker" is for 600 lbs, so the increments are a little "skechy" down in the 100's and 200's, and they were all so far off base .


Guess I'm back to Isky or K-Motion ..........

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I bought a brand new Rimac from Isky a long time ago when I knew I was going to be building some number of engines. I also buy some Lunati springs when looking for something less costly, seem to be fine.

There is a set of GMPP Aluminum ovals for sale on here. The GM heads have 2.25" intake valves as opposed to the Edelbrock's @ 2.19"

The heads for sale were run on a 502 and made good power (around 535HP) I put them on the motor when I put the 4.25" crank in there and even though I messed up on the combination of parts it made 690 FtLbs of Torque. I have been told that the oval ports are better for the torque as they maintain the velocity. I would say that ovals would be good for you application and certainly at your target HP and RPM range.


Here is the link to the heads here on RDP
http://www.riverdavesplace.com/forums/showthread.php?173776-Aluminum-BBC-Cylinder-Heads

I'm currently re-powering my 210. Going to bore the existing 454 mag to a 468. New pistons, rods, lifters, cam etc. Getting rid of the efi and changing to a carb with a Dart intake. The stock heads are rectangular :thumbsup. Keeping the heads and will work them over to match everything. Will be very similar if not identical to a Mercury Marine 500 hp. A proven reliable package that should push the 210 between 75 & 80 and not kill the Bravo drive.

stevesdcb said:

I'm currently re-powering my 210. Going to bore the existing 454 mag to a 468. New pistons, rods, lifters, cam etc. Getting rid of the efi and changing to a carb with a Dart intake. The stock heads are rectangular :thumbsup. Keeping the heads and will work them over to match everything. Will be very similar if not identical to a Mercury Marine 500 hp. A proven reliable package that should push the 210 between 75 & 80 and not kill the Bravo drive.

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Just curious why you would go straight to .060 over and a 468 and not .030 over (460) if you don't have to
BTW the Mercury HP500's were 502cid

BamBam said:

Just curious why you would go straight to .060 over and a 468 and not .030 over (460) if you don't have to
BTW the Mercury HP500's were 502cid

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My mistake, it is going to be .030 over. Yes aware of the 454/502 difference on MM 500hp. My MM 454 mag has some good parts, 4 bolt main, rectangular heads, steel crank. Current 454 ran well, has approximately 400 hrs and looked very clean during disassembly. Major issue was the VST tank that wouldn't stop leaking fuel, not a fan of the VST tank. Won't have any more VST issues after rebuild, will gain 100 to 125hp, and will know that it was put together with good parts by a good builder. Disclaimer: LOL, I was there for disassembly but I'm not building the motor, I'm just writing the check.

I would think that the port size is more relevant to what your doing than the port design (assuming this is an N/A Carb'd deal).

Port velocity is your friend with a carbureted engine. Big ports are not always the answer

stevesdcb said:

I'm currently re-powering my 210. Going to bore the existing 454 mag to a 468. New pistons, rods, lifters, cam etc. Getting rid of the efi and changing to a carb with a Dart intake. The stock heads are rectangular :thumbsup. Keeping the heads and will work them over to match everything. Will be very similar if not identical to a Mercury Marine 500 hp. A proven reliable package that should push the 210 between 75 & 80 and not kill the Bravo drive.

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Do you know if that intake manifold or the edelbrock air rpm air gap will fit under the hatch ?

Is it an outdrive boat or a V drive? Pump gas right ?

With an I/O you have to idle at 900 or less and be all in at 6K.

500' easily doable IN a smaller cube BBC like yours that has to work in that band a D or the Roval works better than a sharp rectangle. I did 500 and 500 in a 406 with relative ease on good heads.

For a few bucks more you could get a set of the small Brodix race rites that will really lay the hurt down.

Bench numbers dont tell the whole truth, many use cheater pipes and its meaningless anyway its what it flows on the engine vs the bench. Ive seen badass heads on the bench that ran like shit and seemingly meager numbered heads that absolutely shredded.

28 eliminator is right - port velocity rules in a pump gas NA (injected or carbed) i/o boat.

70sangersean said:

Do you know if that intake manifold or the edelbrock air rpm air gap will fit under the hatch ?

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I'm hoping it will. Dart intake is what Mercury used on the carbd hp500. I have seen 210's with hp500's w/o anything being noticeably cut. Will probably be cutting down or running a low style breather on the carb. Don't know what the height difference is on the Edelbrock. Long discussion with engine builder today might stroke the motor and go 496

Uncle Dave said:

Is it an outdrive boat or a V drive? Pump gas right ?

With an I/O you have to idle at 900 or less and be all in at 6K.

500' easily doable IN a smaller cube BBC like yours that has to work in that band a D or the Roval works better than a sharp rectangle. I did 500 and 500 in a 406 with relative ease on good heads.

For a few bucks more you could get a set of the small Brodix race rites that will really lay the hurt down.

Bench numbers dont tell the whole truth, many use cheater pipes and its meaningless anyway its what it flows on the engine vs the bench. Ive seen badass heads on the bench that ran like shit and seemingly meager numbered heads that absolutely shredded.

28 eliminator is right - port velocity rules in a pump gas NA (injected or carbed) i/o boat.

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I/o pump gas. Ended up buying the brodix RR oval ports. Hoping that the rpm air gap will clear the hatch. Now I need to figure out a cam.

Anyone know the max lift on the factory hyd roller set up ?

70sangersean said:

I/o pump gas. Ended up buying the brodix RR oval ports. Hoping that the rpm air gap will clear the hatch. Now I need to figure out a cam.

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Good choice brother.

I run a a CNC ported version of that head. It can put the smack down on almost anything.

Im getting 800+ FL LB and 725 HP out of a 588 that idles like a kitten and screams like banshee.

Barry can help you with cam selection, or Alexi he builds a lot of NA brodix head mills and can give you some solid choices.


UD

http://www.jegs.com/i/Speedmaster/746/PCE281.2031/10002/-1
I've been running these on my 468 this year so far no issues, but I'm not trying to set new speed records either

rush1 said:

http://www.jegs.com/i/Speedmaster/746/PCE281.2031/10002/-1
I've been running these on my 468 this year so far no issues, but I'm not trying to set new speed records either

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Hard to beat that price for a set of aluminum bbc heads.

Thanks everyone for your input.