Compression test results.
Team Owner
Joined: Feb 2003
Posts: 30,183
Likes: 313
From: Lake Norman NC
those are nice numbers...with your cam, heads, and that static compression, i don't think your leaving much on the table.?? Your running in teh 11s in a high elevated area. Can't get much better than that.
Thats weird about the octane...I can get 94 at a loca sunoco..and if i want to travel 45 miles, I can get 100 race gas at a sunoco.
Thats weird about the octane...I can get 94 at a loca sunoco..and if i want to travel 45 miles, I can get 100 race gas at a sunoco.
Thread Starter
Melting Slicks
Joined: Dec 2001
Posts: 2,025
Likes: 1
From: Billings MT
George: Yes, the idle is noticeable 
I got the idle down to ~900rpm and it will idle at 800rpm in gear (albiet VERY shaky), so I usually set the idle closer to 950rpm. Vacuum is 12", you have ~20 more cubes than me so that may help a little. So far I am happy with this cam, my static compression ratio is also 10.7: and my dynamic compression ratio is 8.5:1.
Wayne: I am curious to see where your cranking compression numbers come out. I don't suspect they should be much different than mine. I probably could of gone with slightly higher compression but I don't want to take my chances on 91 octane.
What cc are your heads? pistons in the hole? head gaskets? quench? valve reliefs?
I got the idle down to ~900rpm and it will idle at 800rpm in gear (albiet VERY shaky), so I usually set the idle closer to 950rpm. Vacuum is 12", you have ~20 more cubes than me so that may help a little. So far I am happy with this cam, my static compression ratio is also 10.7: and my dynamic compression ratio is 8.5:1.Wayne: I am curious to see where your cranking compression numbers come out. I don't suspect they should be much different than mine. I probably could of gone with slightly higher compression but I don't want to take my chances on 91 octane.
What cc are your heads? pistons in the hole? head gaskets? quench? valve reliefs?
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Mine idles at 750RPM no problem, I have a manual tranny though, it is not rough or anything just sounds like a mean cam ( for the street anyway )
I have 64cc heads .020" in the hole and .039" gasket with flat tops with -5cc reliefs or something like that. I was contemplating reducing the quench distance but I am of the opinion it is overrated and with all the hassle associated with .020" of an inch I did not bother especially when I checked the piston to valve clearance and found i was already on the edge.
Actually come to think of it, I am probably closer to .010" in the hole as the block was square decked
I have 64cc heads .020" in the hole and .039" gasket with flat tops with -5cc reliefs or something like that. I was contemplating reducing the quench distance but I am of the opinion it is overrated and with all the hassle associated with .020" of an inch I did not bother especially when I checked the piston to valve clearance and found i was already on the edge.
Actually come to think of it, I am probably closer to .010" in the hole as the block was square decked
Last edited by MotorHead; Apr 11, 2005 at 10:06 PM.
Thread Starter
Melting Slicks
Joined: Dec 2001
Posts: 2,025
Likes: 1
From: Billings MT
Wayne: So how close are you to getting that running again? I still can't figure out why my timing is retarding so much.... 
What carb are you using? And when are you going to go to the track and put my measly 11.9x's to shame??
What carb are you using? And when are you going to go to the track and put my measly 11.9x's to shame??
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
I just bought a 825 Race Demon but I have a 750 Holley with a ProForm main body on it right now, the ProForm main body boosts the CFM to somewhere in the 800's. The new Race Demon is the drag race version we will see how it runs, it does not have a power valve and the jetting is set up square and it has no vaccum ports, but I have a port tapped in the Vic. Jr. intake.
I will probably be on the road in 2 weeks as I just bought new parts for my 3 inch exhaust. I got a good deal at Summit on stainless 3 in. Flowmaster DeltaFlow 40's for 50 bucks each and I ordered a set of Hooker SuperComp headers.
I will probably be on the road in 2 weeks as I just bought new parts for my 3 inch exhaust. I got a good deal at Summit on stainless 3 in. Flowmaster DeltaFlow 40's for 50 bucks each and I ordered a set of Hooker SuperComp headers.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Change heads.
Originally Posted by TLChydraulics
maybe someone could help me with a problem...... I have a 67 GTO 421 with flat tops, ram air 4 heads, and the previous owner milled the block, heads and intake, bringing my compression to 270 psi per cyl. It runs like a raped ape, with enough acetone in the gas anyway, but I have to replace my head gaskets every 2-3 weeks of racing her. everytime blows the gaskets out between the cylinders. I have tried every brand of gasket I can find, and I get 2-3 weeks of race time. I haven't ran the car now for about 4 years, cause it gets old working on it every other week. I just want to run it, have some fun. I have not a clue where I could find those heads again, and really don't want to spend that kind of money anyway. Is there a place to get extra thick gaskets? or something to get the compression down? I did have eyebrows cut into the pstons out of neccessity when I first got this engine, as the valves bent hitting the pistons. It took me a couple months to find enough new valves to repair the heads. Apparently the ram air 4 heads were an after-market no longer made after 69 and are very rare.
Loren
Loren
Late model Pontiac V8s heads had larger chambers and would lower ur compression TLC. U would need to change heads, headers and intake since the standard Ponco heads/ports are different from the RAM AIR parts. I was lucky enough to tour the boneyards here in LA late last yr and still finding '60s and '70s and '80s Pontiacs with big V8s availible for parts. U may be just a phone call away from finding large chamber late model Poncho heads with big vlvs for almost pocket change at local parts yards.
I have 2 great books but out on loan for Pontiac Performance - by Pete McCarthey and Johnny Angles - that list all the heads by casting number (cast over 2 center exh ports). If u need to ID some replacement heads send me a PM and i'll do my best to help.
BTW Pontiac Performance mag was still printing last yr and may be a good source of information.
cardo0
