Pat McPherson

OK, my shopping list is getting shorter.
Thanks to everyone for the help

1999 7.4MPI conversion to a Carb. Engine that will hopefully make 400HP.

I have read Dennis Moore's book cover to cover a couple of time now, and I'm rereading about the valve train components.

My heads are at a machine shop being worked for bigger valves so it's time to decide what parts to by.

Keep in mind, I can't go too wild here do to my exhaust system. Stainless Marine manifolds with the short stainless risers for captain's call.

The least expensive way to go is to buy GM performance goodies:

- 454ho/502ho crate motor steel hydraulic roller camshaft 211°/230° duration, .511"/.540" lift, 112° lobe separation
- Double Valve Springs, Retainers, Locks and Seals to Match
- Reuse Non-adjustable Rockers and Shoulder Bolts

Cost would be under $300

Aftermarket Option:

- Crower, Crane, or Other Manufacturer, hydraulic roller camshaft with 222°/229°, .540"/.560", 114°
- New Lifters ???
- Springs, Retainers, Locks, Seals to Match
- Extra Machining may be required ???
- Conversions Rocker Studs
- Roller Rockers

Cost would be $800 to $1200

Will the extra $$ be worth it ???

Dennis Moore

I like your first option except for the camshaft selection. Go with the 502/502 camshaft instead. The stock roller lifters, pushrods and non adjustable rockers will work fine with this camshaft too. The GM dual valvesprings will work well with that valvetrain and cam.
Should get you to 400 horsepower and be very reliable.
Sincerely
Dennis Moore

formula31

Not enough lift. And lift is what will force you to go to aftermarket valve train components.

Madmax

Watch your piston to valve clearance on the non-gm cam. These pistons are not notched. I'm running the 454HO cam you are thinking about, and it makes loads of torque, but poops out over 4K. I also would go with the 502/502 cam. Change the springs, and run the stock non-adjustable setup.

Pat McPherson

OK Guys,

If the 454HO cam is not enough, then I guess the best upgrade for the money is the ZZ502/502 cam.

Spec. 224°/234°, .527"/.544", 110°

GM has two different double springs listed, one has 110lbs seat pressure, the other 140lbs.
Which should I use?

The Guys at both CP Performance and Stainless Marine have told me that I can not use a captain's call system with this cam. Too much exhaust duration and overlap.
Are they being too conservative ?
Has anybody used captain's call with this cam?
I don't want to suck water into my engine.

Should I scrap the captains call and use mufflers ?
If so, I will need the longer riser, right ?

Thanks for the help!

Madmax

Use the 140lb spring. That's the one GM uses with the crate 502/502. Their springs,retainers,seals,etc are all available from www.competitionproducts.com really cheap. They buy mercruisers stuff when they turn 502's into HP500's. Can't say about the reversion issue, cause the friend that I know that's using it has Teague switchables. Pretty mild cam tho, I think you'd be fine.

blue thunder

I am running comp cams, 226/234 @.050 with .547/.564 lift on 111 lsa with 4 degrees advance. No problem with stock mercruiser manifolds and imco ss risers. You may be crossing the line with the 110 lsa, but it is close. I run 125# seat pressures with no trouble.

BT

tripps

Hey Pat,make sure they port under the valve seats,called the pockets!!! Tripps

MAG502NUM

Jack/Budah-Would you mind posting the @.050 overlap numbers on the Crane 741 and the 502/502 "junk" cam? Is there a new unknown lobe design that allows a cam with more duration to actually have less applicable overlap even with 2 degrees difference in LSA?

Pat McPherson

OK Guys,

While we are still debating which camshaft I should use, I did take your advise BUDAH. I bought some good double valve springs 128lbs @1.880", 0.670" max lift. The retainers and lock I bought are the 10° version.

Back to the cam:
I spoke to Crane about the 731, and they told me that I can not use my stock lifters, too much lift. I can use the 721, but the last time I asked you guys, You told me it was kind of mild.
Madmax also brought up a good point about a cam with more lift than the GM. Will there be a clearance problem with the L-29 pistons?

Thanks for the help everyone.