Pat McPherson

OK, I am using Dennis Moore's Book along with the great advise I have been receiving in this Forum to pick out the goodies for my engine modifications.

I have a 1999 7.4MPI with less than 100hours. I have learned that it has 9:1 compression and the L-29 Vortec heads. The MPI system is coming off and I will be bolting on a RPM Air-gap and four barrel carb. I will have larger valves installed into the heads per Dennis's book.

I have purchased Stainless Marine exhaust manifolds with the short stainless risers for a captain's call setup.

I need advise as to the largest cam that can be used in my 454 with the captain's call system without having a reversion problem. I have not asked Stainless marine as of yet, but I think I may have read somewhere that 230° exhaust duration is the number.

I would like to use the GM 502/500hp crate motor cam, but that has 234° exhaust duration. My second choice would be the 454HO cam which has 230° exhaust duration. If both are too big than I believe crane makes one more mild...

Your advise is appreciated !!!

BADINTN

I used a 500HP Crane cam ,#169611 , with 230deg exhaust duration on my 454 carb magnum along with Stainless marine exhaust. With the short captain's call risers I got droplets of water in the manifolds, not alot,but some. I know this because I had to remove the risers to readjust my rockers. I ended up putting on the slightly longer ( about 1 3/4" ) risers and ran it out the hull with muffler inserts. I just plugged the y-pipe and pulled out the gill system. I recently got back from 2 weeks in LOTO with no signs of reversion.

Dave M

Hey Patrick,

I better get started on my engine project. I can't have you out running me! Do you have the merc silent choice system? Mine had been a pain in the ass. I've had it worked on several times and it still keeps hosing up. I'm going to do a compression check at the end of the season and see where my motor stands. I'm not going to do anything until I have too.

I'm watching the other thread above about the 500 clone.

Dave M.

Pat McPherson

Thanks for your input BADINTN.
I have seen HP500s with Captain's call, but with CMI headers not Stainless Marine exhaust.

I spoke to Stainless Marine today and was told to keep the exhaust duration to 224° or less for captain's call.

I will likely go with a Crane PowerMax hydraulic roller (HR-214/325-2S-12 IG) 214/220 Duration, .553/.564 Lift

Hi Dave,
I'm working on keeping up with you, not out running you. Looking to make 400+HP, I want to see 70+GPS regardless of my load.
I have not purchaced the diverters as of yet, but I'm leaning toward Corsa. My buddy has a Fountain with Corsa from the factory, 7 years, never a problem...
If you are willing to ditch the fuel injection, your engine can be rebuilt to make 500HP no problem...

SSComp

I run 226/230 with 14 degrees lobe separation. Bownee is always conservative. Remember reversion is caused by overlap (intake and exhaust are both open). This is a function of BOTH duration and lobe separation.

You would be totally safe no matter what you configuation at 224/224 with 14 degrees. The can you are talking about may be too conservative.

formula31

I run the gil magnum choice which puts in the water real soon. I have run the edelbrock torqer 2 cam for years with no reversion issues. 224, 232, .527. 553 at 114 degrees sep, timed at 106 intake c/l which is 4 degrees advanced.

SSComp

I just checked 232/234 with 114 L/C

X-Rated30

Pat,

I am assuming you have the manifolds and not the headers. I have a simple solution for you that may boggle the mind.

I had the same question a couple of years ago with EMI Thunders when I was picking new engines. I called EMI and they were very eager to help. First they recommended we keep duration under 230 for the exhaust. Since I was in that ballpark, they said to be safe, I should invest in some nice stainless risers they sell, and that would mix the exhaust and water further from the engine. A good solution, but going through a divorce, I was strapped.

The guy felt sorry for me, I guess. He told me what I should have been able to figure out for myself: I could weld aluminum extentions onto the end of the pipe comingout of the risers -- ie. add a couple of (approx.) 3" i.d. pieces of pipe to them. The water will mix further down the exhaust. (DOH!) No problems so far.

I don't think it would get in the way of your Captain's Call, and you can have some fun with the cams.

Pat McPherson

Thanks for all the great info Fellows!

Maybe I am being a little on the conservative side with my cam selection?

I read some in Dennis's book last night so I am understanding duration, lobe separation and overlap a little better.
Dennis states that a cam with a lobe separation angle between 109° and 112° should be used to make more power than stock cams that my have 113° to 116°

I hunted around on the Comp Cams page and found that they now offer Gen VI cams.
XR270HR 218°/224° duration, .510/.510 lift, 110° separation angle.

Any thoughts? Will it make more power than the Crane I am thinking of? 214°/220° , .553/.564, 112°

I am not sure if the greater lift or longer duration is better. The smaller 110° angle will create more overlap, but at 224° exhaust duration I guess I should not have reversion with the captain's call...

Dennis Moore, you out there? Your book is great!
I had good luck with the last engine I built from info in your book.

formula31

Generally, Marine big blocks repond well to lots of lift and poorly to lots of duration. Thats why a roller cam does so well because it can get the valve open and closed faster and higher than a flat tappet. The more duration you have, the more compression you need to counter the losses from overlap. Your crane choice is better than the comp cam but still mild in my opinion.