Pontiac GTO Forum banner

1 - 3 of 3 Posts

·
Premium Member
Joined
·
210 Posts
Discussion Starter #1
I have some time off in January so going to pull the motor to replace the rear seal. While it's out thinking of replacing heads and cam. Talked to KRE about the heads today not sure if I'll go with them or edlebrock but KRE customer service was great. My question is when it comes to cam what information would I need to pass on to make sure I have the proper cam. I don't want to order and not have the info I need. Also when I accelerate I get a little smoke out the exhaust. I've had problems with #3 cylinder exhaust valve bent 3 push rods. While I will be changing heads and all internally what should I check to make sure the problem is/was just the valve.

BTW pontiac jim going this rout instead of an ls so please all the info you can pass on
 

·
Registered
Joined
·
3,923 Posts
"BTW pontiac jim going this rout instead of an ls so please all the info you can pass on"

Atta-Boy:thumbsup: LOL Geeteeohguy is smiling too.:wink2:

The choice is yours on the heads, but the KRE heads seem good and those guys seem to know their business and provide the needed tech info or simply give you a quick response to your questions, so that is important to me, I have hit them up on questions and purchased some parts from them myself.

To get a good cam grind, you will first need to know what your compression will be. You will need to know what the head chamber volume is, how far down in the bore your pistons are (typical Pontiac is around .020" unless you have had the block decked), size of the bore (ie .030" over), the volume of your valve relief notches in the piston (which I think is typically 6 CC's but can be more depending on design or if dished pistons) the head gasket compressed thickness (typically .038"-.040" but you can go less or more. I am running $$Cometic .027" on my 455 build to get a tighter quench area (without milling my block) between the piston tops and the portion of the head that hangs into the bores). All of these numbers added up should give you a fairly accurate set of numbers in cc's that can then be used in determining your engine's compression. (Note: the thinner head gasket moves your valves closer to the pistons. You want to know how much clearance you will have between the valve and piston top. You don't want a valve hitting your piston if you select a high lift cam/long duration.)

As has been stated before, aluminum heads need about 10-to-1 compression or more depending on what octane gas you plan on running. KRE will help you on all this. Next you will have to know if you want a roller cam or flat tappet (solid or hydraulic). Price is the obstacle here, but if you can, seems the roller is the best choice long term as it has an advantage of working better with today's oil. I'm going with a solid flat tappet cam/lifters just because I like them and don't mind adjusting them -part of the "old school" in me. The solid lifters I will be using are already metered to restrict oil flow to the heads, so no restrictors needed in the lifter bores. I'll add an oil additive to my Rotella 15-40W for the break in period and probably switch to a synthetic blend at some point as this seems to work on the flat tappet cams/lifters. RISLONE makes an Engine Oil Supplement with Zinc treatment and sells at Advance Auto. Trying this in my 1992 Chevy S-10 -can't hurt and is recommended for vehicles 1996 and older & 1997 to 2004 vehicles as well.

Next you want to decide what kind of RPM range your engine works in and where you want your power/torque range to work best -usually mid range & up like 2,500 RPM - 6,000 RPM's. Go for torque over HP on a cam selection. You want to select a cam that will have good vacuum if you have power brakes or you may need an electric vacuum pump or go to a $$hydroboost system like Bear. Keep in mind that your intake and carb choice will also have bearing on all this as well as your exhaust system, ie iron exhaust manifolds, headers, pipe size, etc., as well as transmission and rear gears.

All of these factors come into play when selecting a cam grind and KRE (or any cam supplier) will be able to recommend a cam grind for you using this info. They may even have a cam worksheet for you to fill out? I plan on using KRE for my cam selection as I basically know what I want, but will have them confirm it and order one from them when I get to that point. Already emailed them on it.

So that may help a little to get you started. Do your research and get as many opinions as you can on both KRE heads and Edelbrock heads. The more informed you are, the better your choice will be.:thumbsup:
 

·
64-67 Expert
Joined
·
8,569 Posts
Jim said it all. I'll add this: if I were to upgrade to aluminum heads (and I might on my '65), the KRE D-ports would be my choice. They need less prep work, are high quality, and have good support. Nothing wrong with the Edelbrocks, though. I would shoot for 10.5 CR with an aluminum head on a 389 or 400 engine.....10.0 minimum. Great choice....and you'll end up with much more raw power and real soul compared to that Throw Away Engine!!!
 
1 - 3 of 3 Posts
Top