Asking for a little advice.

[snowboat]

I'm putting together an 8/71, carbureted gas with two 750's, Mark IV 460 with pretty good stuff. It's going to go in a 1977 Biesemeyer that, at one time, belonged to Lance Faulkner...........so I want to do it right. Merlin cast heads but I don't know the runner volume so I'll assume it's 320. I have an Isky roller cam with 112' lobe separation. I have another blown Biesemeyer with 106' lobe separation and it's quite frisky. I'm not overly wanting to buy another cam but my understanding is that 112' is for a heavier boat. Money isn't really a big deal, but because of the history I'd like to do it best. Should I dump the cam and go for a 106 or 108?

 

[obnoxious001]

Normally on a blown marine engine I would go even wider than 112. Are you certain about the cam specs on the other engine?

 

[snowboat]

I pulled my card and I was wrong on the sep. it's 110. I got this cam recommendation from Fiat48, Bob I forget the last name, for now. I thought it was a bad choice but he is experienced in flats and race engines. So I built it, tall deck, intercooled 8/71 two 750's in a 1981 Biesemeyer. Very lopey and I am able to get the idle down to a more Ranger friendly sound. Part # 138591, 775 intake, 723 exhaust, intake 54 BTDC 90 ABDC duration 324
exhaust 98 BBDC 54 ATDC rpm range 5000 to 8400 The springs that I have are Crane 947-16 338 lbs and 849 lbs.
I'm wanting quick but not as tempermental and no intercooler on this one.

 

[obnoxious001]

How will you be using the boat. That's sort of a "drag" or "race" setup, more spring pressure and a little more lift than I normally do for a "lake" boat that's supposed to last a long time. Opening up the lobe separation will help idle. You can add or remove blower surge by adjusting idle air mixture.

 

[snowboat]

I'm looking for a quick lake boat and a little less of a drag or race. I'm looking at the cam companies for a solid roller, 112 or 114, mid .600 lift 7000 ish max rpm. See what I come up with in a few days.

 

[obnoxious001]

I'm looking for a quick lake boat and a little less of a drag or race. I'm looking at the cam companies for a solid roller, 112 or 114, mid .600 lift 7000 ish max rpm. See what I come up with in a few days.

If I were doing it, lean towards the 114,,, close to 700 lift. Duration is sort of more important to determine rpm range. I run springs for "endurance" builds around 240-250 seat pressure, 600 open, maybe increase the open a little since you are talking 7000 rpm.

 

[snowboat]

This is what I have come up with, but I should have lighter springs or maybe longer valves............
Grind Number:300BR-14

Engine Family:Chevrolet 396-454 c.i. 8 Cylinder (1967-1996)

RPM Operating Range:3500-7,000

Cam Type:Solid Roller

Lifter Style:Solid Roller

Camshaft Series:Blower

Camshaft Gear Attachment:3-Bolt

Usage:Street/Performance

Valve Springs Required:Yes

Camshaft Material:Austempered Ductile Iron

California Proposition 65:WARNING: Cancer and Reproductive Harm P65Warnings.ca.gov

Advertised Intake Duration:300

Advertised Exhaust Duration:308

Intake Duration at .050 Inch Lift:255

Exhaust Duration at .050 Inch Lift:262

Intake Valve Lift:0.652

Exhaust Valve Lift:0.652

Lobe Separation:114

Assembly Lubricant Included:No

Valve Timing @ 0.015 Lift:

Exhaust Close ATDC: 36

Exhaust Open BBDC: 92

 

[obnoxious001]

Guess that one is ok for street. I would choose more lift and duration for a flat.

 

[snowboat]

Thanks, I'll keep looking. Family stuff going on...back in a couple of days.

 

[snowboat]

Howard Cams Summit part# HRS-121133-14. 3,400-7,500, .680, .680, lsa 114, 293 intake, 301 exhaust durations. Without using a custom grind, I think I've reached the end of the internet.