I will be building a carbed 383, with 200cc dart iron eagle heads. 64cc with 2.05 intake and 1.60 exhaust valves.

My question is what is the highest compression you guys are running or would suggest with iron heads to run pumped gas. Maybe even add a gallon of race fuel to 1 tank of gas.

Post what compression you are running.

thanks

 

You don't say what pump gas. This varies from region to region.
Here we have Sunoco 94. I have used 10.3:1 compression before. It was touchy as to ignition timing but ok . A little too much and it would knock at full throttle. Needed cool plugs too.

Now I have 10.01:1 with Vortec heads and it never knocks
(Same motor.) Seems to be able to run 93 octane ok too.

I would not exceed 10:1.. Although this may not be the absolute limit, there isn't enough extra power there to get to that limit to make it worth it. Remember once you have even a little too much compression, resulting in knock, power and engine life is reduced. Better to build a motor that is near the octane
threshold but with a small tolerance buffer and build for more airflow. You'll be ahead of the game.

 

Im not sure about iron, but my buddy is running 9.8 compression on 89 octane w/ aluminum!

 

93 octane is the highest I can get around here besides racing fuel. So 10.1 should be ok. I was hoping for 10.5 to 1 but what ever it takes to stay with pumped gas. I am looking for around 450 to 500 hp na. Hopefully I can get a good combination.

 

For horsepower think airflow, not compression.
Find a head that flows like crazy and build from there.

For 500 hp naturally asparrated on 93 octane I'd be looking for a head that flows 260+ cfm@28 and go from there.

 

those darts flow pretty well from a chart i seen...... but none the less there still cast iron......

remember the dude i was telling you about that ran 11:1 on duoble humps and has a 10 second time slip.......... the possibilitys are endless!!!!!

one thing.... lopey *** cam!!!!!

 

i am running 10.8-1 on pump gas, and have had some probs with detonation

 

I have 10.7:1, drive it daily, iron heds. It's in the timing, jets and cam...the solid cam I have has 248@.050 with .560 lift..run 93 octane...no problems!

 

gearing, weight, cam duration and lsa.,,not to mention timing curve.

Shoot for 190psi cranking compression. That will allow a full advance curve and run on 93pump

 

you can't just ask what static compression you can run wihtout taking into account other things as well


if you buid the motor right you can run 13:1 on the street using 91 octane


you need to think of things like flow rate on the heads, cam profile... really taking into account the closing point of the intake valve b/c if you let it close right after BDC then you are going to have a lot of pressure built up in there
but if you let it close 30*ABDC you are going to bleed some of that pressure off and let you run higher compression and then when the rpms pick up it running that larger cam is going to help you out quite a bit

also what heads do you want to run.... alum or iron

and design on the comb chamber also makes a big difference

sorry

too much info but hey.... just being honest

 

Just a little bit of info here, LT1's are 10.5:1 and LT4's are 10.8:1 and seem to run great on 93.
I am trying to keep my motor below 11.5:1.

 

well for those that asked here is more info on what I am planning.

383
ported 200cc runners/ 64 cc Iron eagle heads/iron/2.05 &1.60
holley 750vs
wieand #7525 single plane intake
possible comp xe282hr cam
comp magnum roller rockers
700r4
3.73 gears
2800-3000 stall
hedman lt headers
x-pipe into dyno max bullets dumping before the rear end.

 

combo looks good, but I'd change one thing...intake. Not to happy with the Weiand...get an Edelbrock RPM.

 

The intake is a Team-G intake but is not tall. It has a 2000-6500 range on it and I picked it up used for 75 bucks. Its in great (almost new) shape. I figured this would get me in the game and changed over to carb cheap.