[okcatalina]

what would be the highest compression i could have with this cam on pump gas 91 octane? comp cams 51-659-5
http://www.compcams.com/Cam_Specs/Ca...csid=1222&sb=2

[Hillard]

Cast iron or aluminum heads? How heavy is the car? Auto or manual trans? If auto, what converter? Rear end gear ratio? All of this will help determine how high you can go.

[okcatalina]

aluminum kre d-ports 69 2 door coupe catalina 3.23s th 400 3000 stall

[Cliff R]

What size engine, and which version of their heads, stock, or ported?.....Cliff

[okcatalina]

400 and 310cc heads cliff

[okcatalina]

im planning on switch to a lower rear gear soon either 3.90s or 4.11

[Jack Gifford]

There's an old thread titled something like "Static vs. dynamic compression ratio" which attempted to collect real-world octane requirements of various Pontiac engines. Search for it and see if it helps you at all.

[Cliff R]

We haven't built any 400's with those heads to date, and that cam wouldn't be a good choice for them right to start with. Too much duration and overlap for a 400cid powered car with a 3000stall and 3.23 gearing, IMHO.......Cliff

[Hillard]

IMO you would be safe with 11:1 and could push 11.5:1 properly tuned. I've built a couple KRE headed, pump gas motors with 11:1 and less cam than you have. Make sure it's zero-decked. I think Cliff is at 11:1 with 89 octane...right Cliff?

[Hillard]

I didn't pay much attention to the opening and closing events earlier. I have to agree with Cliff. I think a less duration and a wider LSA would be better.

[Cliff R]

Correct Dave. The current 455 uses 76cc heads, zero decked block, 10.99 to 1 SCR, and runs on a steady diet of 89 octane fuel......Cliff

[Half-Inch Stud]

Occurs to me that the Head metal & Chamber are a significant factor to ping-free on pup gas.

Therefore:
For highest ping-free Compression & HP: Aluminum heads is advantage over IRON Heads due to ability to run lowest Total Advance with high CFM numbers.

[DiamondJim]

With the right gear and converter you should be safe at 11-1 with AL heads. The Comp 290B solid is used by many and is a great cam, do a search here and ask the guys that are actually using one. I did a lot of research and was planning on running one, I have a new one sitting on the shelf, when I decided to use E85 and up compression I went larger so PM me if you are interested. -Jim

[okcatalina]

Originally Posted by Cliff R

We haven't built any 400's with those heads to date, and that cam wouldn't be a good choice for them right to start with. Too much duration and overlap for a 400cid powered car with a 3000stall and 3.23 gearing, IMHO.......Cliff

i can change both im not set on anything. im cosidering changing to 3.73s and a larger stall for this cam

[tom s]

as this is in the street section I will throw in another thought.How much driving is the car going to get?You might be OK at 11-1 when you build it BUT after a year or so of street driving,you get carbon build up,a super hot day,stuck in traffic,bad tank of gas etc.IMO,I would not go over 10.25CR for a engine that will be driven for a lot of street miles.Just not worth pushing the detonation limit for the little bit of x tra HP you might gain.Tom

[okcatalina]

i work on the road im only home once or twice a month it wont be driven much but i will drive it on the street

[71 Ventura II]

Originally Posted by okcatalina

aluminum kre d-ports 69 2 door coupe catalina 3.23s th 400 3000 stall

The Comp 290b cam is a great cam but in a 400 combo with large port heads is going to want more converter than a 3000. I'd guess more like a 4000-4500 flash and a minimum 4.10 gear. This is assuming your running it NA without nitrous in a 1/4 mile race type application. JD

[Cliff R]

+1, and at LEAST 11 to 1 compression. My guess is that it can easily be tuned to run on currently available pump fuel. My engine is 455 cid, 11 to 1, 290cfm KRE heads, and manages 89 octane without any issues anyplace with a much smaller cam.....Cliff

[Pontirag]

search! this was discussed about two weeks ago

[performerrpm]

ive heard that 290 b in .030 455s, i cant even imagine how nasty it would sound in a 400.