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540 Build Reversion Prevention

A series of unfortunate events led to the demise of my 502 mag mpi In my 2001 271 Formula Fastech. So as a typical male I'm shooting for better, faster, stronger.

What I have now is a Dart 540 block, callies compstar rotating assembly, mahle 10.2:1 coated pistons, 315cc AFR cnc heads, and the 168741 cam full roller. Edlebrock single plane intake, 850 quick fuel marine carb.
I am trying to copy a build I saw that made 600-650hp. I am hoping to do this on 93 octane.

Motor is almost assembled and I'm doing plenty of reading about exhausts now. I decided to go with a manifold style (EMI Thunder, Stainless Marine, Imco Powerflow) because this whole build is based on reliability.

What I am having trouble with is riser style, they will need to be custom as formula's exit doesn't line up with normal bravo measurements. The original manifolds had a 3 inch riser block. If I go with a 3" riser or more depending on hatch clearance can I get away from needing a dry exhaust like EMI and SM have told me I need due to the 741 Cam? Just do long wet tails with a high rise?

Learning alot here and have read a lot, I hope to someday contribute instead of ask questions.

Cam Specs:
Grind Number:HR-236/359-2S-12 IG
Operating Range:3000-6500 RPM
Duration Advertised:298° Intake / 306° Exhaust
Duration @ .050'' Lift:236° Intake / 244° Exhaust
Valve Lift w/1.7 Rockers:.610'' Intake / .632'' Exhaust
Lobe Separation Angle:112°
Max Lift Angle:107° ATDC Intake / 117° BTDC Exhaust
Open/Close @.050'' Cam Lift:Intake - 11° BTDC (opens) / 45° ABDC (closes)
Exhaust - 59° BBDC (opens) / 5° ATDC (closes)

I added (welded on) 9 inch tails to the riser. Just add/weld on to the riser exhaust tube as close to the transom as you can and still use the standard rubber exhaust bellows. Its a workaround for semi-dry exhaust risers.

you have pictures of your installation, thank you in advance

Moving the exhaust holes is really easy and will save a bunch of custom pipe manipulation. Just cut the hole slightly to the outboard side of each existing hole. (Use standard bravo template to mark this) Then bond and glass the tiny crescent on the opposite side and reinstall the thru hull fitting

Look at the thunder n lightning exhaust. They will help you make the power you want. Also if you haven’t bought a carb yet I’d go bigger. My 850s are too small on my 502s. I’m contemplating changing out to 1050s.

I have a quick fuel 850 on my 540 as per the guidance of quick fuel tech and the builder that assembled my heads. Motor runs like a raped ape. They both said anything under 600 hp only needs an 800. I tried to run a 850 on my 502 and lost 3 mph and a bunch of mid range torque compared to my 800 cfm. Just my experience. My motor only turns 5400 with the prop I run which may be a factor.

Lots of variables for sure. One being VE. Here’s a good article on carb sizing and I was mistaken. Mine wants 950 range.

https://www.hotrod.com/articles/how-...-you-need/amp/

what was done to your 502 with the 800? The hp500 came with an 800.

Quote:

Originally Posted by Crude Intentions (Post 4673055)

My 502 was a garden variety gen6 mag. 415 hp. To the OP’s question, getting the tails to run down hill to the transom as much is possible Goes a long way to prevent reversion. I’m not sure why formula has odd ball exhaust location on some models. May be a hold over thing from alpha or trs?

Yes agreed. That’s why I suggested the thunder and lightning the. Manifolds arc up and back down plus the cam will like the longer runners much better than an open manifold.