454 build questions on cam and carb
 

Im in need of some one to tell me a good size of the cam and carb needed for my build up of the 454 so here is what I have so far

SCAT
crankshaft 4.25
forged I beams 6.135
flat top forged pistons .030 over
9.0-1 compression
cast iron 336781 heads with 2.25I 1.88E
edelbrock rpm air gap
looking for cam size
looking for carb size

this is a gen 6 roller cam block and has stock manifolds and quick silver through hall exhaust
I am now looking in to EMI thunder exhaust after reading the posts can any one tell me if this exhaust will flow good for this set up
any help would be very appreciated thanks guys

If it's a mark 4 this cam.
http://www.summitracing.com/parts/CRN-139011/

This carb.
http://www.jegs.com/i/Holley/510/0-9...oductId=743728

One of the biggest factors for a cam is
WHAT exhaust do you have or plan on having?

sorry its a gen6 with a roller cam and im runing stock manifolds with quick silver through hall exhaust on a 1997 baja 202 islander

With stock Merc exhaust, you are severly limiting the cam choice and ability to make more power. You can really only use slightly more than a stock magnum cam or you will get water reversion.

This is the cam for the Gen 6.
http://www.summitracing.com/parts/CRN-168731/
As mentioned exhaust will be a big factor.

call BOB Medara !!!!!

I have similar set up with approx .6 lift cam setup...

What horsepower do you think he will see with this setup?

I run a 750 dp holly carb, if i dont ease into the top end it stutters occasionally but thats prop a fuel pump concern..

I had to add 10" pipes welded onto my risers with a stainless marine exhaust bc of reversion.

looking in to EMI exhaust

Get the exhaust with long risers.
Your compresion will be lower than 9 to 1, more like 8.7 to 1. I have 8.9 to 1 and I have 489 with flat tops and 110cc chambers. A crane 731 would be good, or get a custom roller from RMbuilder. You may want to use 2.19 valves, you will want to do a good job on bowl blending with bigger valves. Here are the head specs 336781.....73-85...oval...OPEN...454, 118cc chamber, 256/114cc ports

What Jeff said. Additionally, make sure you get the heads cc'd. There can be quite a bit of variance on chamber size. I have a set of 781's that cc'd at 124 cc's. This would drop you to around 8.5:1 CR. To get back up, you may have to mill heads and deck block, and/or run a thinner head gasket.

If you are going to run the 2.25 valves on a 4.25 bore, it woudl be a good idea to bore notch the top of the cylinders to unshroud the valves.

I put in the forged domed pistons from speedpro :) over 9:1 compression

Still farting in the wind put a blower on it.
Go with rm builder youll be pissn in the wind :)

Yea, I have never ran anything with a blower, the thought has entered my mind many times. I am maxed out on HP and speed with my current setup. Maybe I should just be happy and leave it alone for a while. Damn "speed bug" got me and its hard to shake :drink:
Bob really knows what he is doing on engine/cam design.

Is that good or bad? Doesn't sound like the reputation I've always heard he's been known for.

It all worked out, but it took a real long time, between hard to get in contact with, long shipping, and him ruling out reversion and blaming my new head gasket and intake manifold gaskets, basically doing a top end job on a rebuilt motor after asking if reversion was a possibility.
I went with him bc i read so much about him knowing marine cams to avoid reversion.

Bob's customer service is unbelievable and he's always easy to get ahold of. If you had to weld in 10" extensions then you've got other issues and you're crutching the problem with your long pipes. What's your base timing, port volume on your heads, what intake, what's your idle speed, how'd you lash your valves, how's the rocker geometry, you running silent choice? There are many thing's that contribute to reversion and in my experience Bob's cams aren't one of them. I've got a dozen or so customers running Bob's valve train's and ZERO reversion issues.