Compression Ratio

[Shawn F.]

I have a 96 S10 Extended cab pickup I bought from a kid that hacked the hell out of it. It has a V8 350 sbc with a 350 turbo tranny. They supposedly have low miles (around 50-100) but the kid could have been lying. I plan to pull it soon and tear the motor apart in my spare time and go over everything. The kid said he bought the motor from a dirt track racer who built it for a dirt car but found out the rules called for a crate motor so he sold it to the kid and the kid put it in this 96 S10. I was going to fix the truck up but found out he put air bags on the truck and did not do it right which caused the frame to crack, bend, he put new frame rails on it built out of small scrap like metal. Pretty much the body is junk and so is the rest of the truck.
The rear end is a plain s10 rear with new seals and freshly rebuilt, auburn posi gear, 3.45 (around there) gears, Moser axles... The tranny is just a plain 350 turbo with a 3000 stall he said which I dont even think it has but will soon find out and then it has a shift kit. Engine is a 1967 350 I think (I have to double check on this since I forget easily what I have since I have quite a few vehicles and engine laying around) with Weiand intake manifold, Jegs Alternator, a Voodoo cam (not sure the size but it's a bit big), and the kid said he thinks the compression is 12:1 or 13:1 which IMO is WAY too high for a engine I want to be reliable in a T bucket project.
So after all this explaining, my question is, how can I tell the compression ratio or get close? Can I check the cylinder compression and tell by that?
Any idea what most guys run in their dirt cars that run the 350's? If I also remember correct the heads are stock and are 67 chambers. Could be wrong here too but will find out as soon as I remember the numbers haha.
I am hoping this motor/tranny will be something I can work with and not have to put much money into to throw into a T bucket.
I really wanted to run a Ford motor (302 or 351W) in the T bucket but this is what I now have and dont have $5000 for another motor and tranny combo.
Thanks for any information and sorry for such a long post.

 

[old round fart]

It may be hard to run that much compression to the street, but if a guy builds a motor without knowing the rules, I think I would check his work before I tried to run it anyway so when you pull the motor down cc chambers and figure it out.

 

[RPM]

To run that kind of compression on the street you will have to run racing gas. $$$$$. When you take the motor down you can tell a lot more about it. There is a way to do it with out taking it apart, but you would have to have a burett to check it all with.

 

[der Spieler]

I've never heard of a dirt track that required crate motors. The object at that level of racing is to be as inexpensive as possible. I think their requirement was probably for bone stock motors.

 

[Shawn F.]

There is a crate class, I did look that up at the local Lancaster dirt track. The guy has a machine/engine shop near the track but I dont have his name or number. I said the same thing though to the kid that if he built the motor then how did he NOT know the rules? The truck is hacked by this kid and he lied a lot to me about a lot of things and that is why I plan to pull the motor out of the truck and tear it down. If the cylinder walls are in great shape with no ridge, scratches, etc and I wanted to put in better compression pistons and a more mild of a cam then can I do that without boring the cylinders and just honing them out to clean them up some and put new pistons, cam, etc in it? I know I will have to check cylinder size and get pistons that fit to the size, new rings, etc if I go this route but I am not sure if it will be the best way to go IF the walls are fine and IF the compression really is that high. Maybe a crate motor is cheaper? I dont know, that is why I need some suggestions. The motor might be 10:1 compression and totally fine or it may be a total piece of crap. I did pull the valve covers off and it did not have any gunk build up and looked to be very clean under there and lifters all looked straight and nice...

 

[TheAntiBoyd]

a guy I worked with has a dirt car and they HAVE to run the GM Sealed crate motor. To do any internal work, you have to remove special fasteners. Its to keep the ringer motors out. Heres the deal though, the shops that are allowed to open these motors up can do anything they want and put the motor back together no one knows. Hell I built a rev limiter for him and had it in an MSD box so he could hit the corners WFO and it would pop like a machinegun, backing the motor down so the tire wouldnt slip.I wont post how to do it, but the kits are out there. Also, the sanctioning body can foce you to run their MSD box for the night if someone complains.

The motor is a 350hp 350 with a GM intake and a 2bbl on it and I think vortec heads

EDIT: I found it http://www.jegs.com/p/GM+Performance/752396/10002/-1

350 HP @ 5000 RPM
390 ft/lbs TQ @ 3800 RPM
9.1:1 Compression Ratio
Cast Iron Four-Bolt Main Block with 1-Piece Rear Main Seal
Nodular Cast Iron Crankshaft
5.7" PM Connecting Rods
Cast Aluminum Pistons
Hydraulic Flat Tappet Camshaft, Lift: .435'' Int/.460'' Exh, Duration @ .050'': 212 Int./222 Exh
Cast Iron Vortec Cylinder Heads w/64cc Combustion Chambers, 1.94'' Int/1.50'' Exh valves
1.5:1 Rocker Arms with ''Kool Nut Design'' Rocker Arm Nuts
High-Rise Dual Plane Intake Manifold
HEI Distributor
All for $3200 from Jegs. Ive seen it cheaper at the local roundyrounder shops $2900 local pick up off the straight truck
Wouldnt be a bad motor minus the break-away fasteners for street rod duty

 

[speedkills502]

Check the static compression with all the plugs out a good charged battery turn it about 3 rev. All readings should be with in 10% of each other. Now this is not the best way to check with cam over lap it may bleed off some till higher RPM's. But if it runs 150 psi are below you can drive it with 93 and if it is just a little higher you can still tune it for the compression and drive it with out racing fuel but it would have a power loss from the tune.

 

[joshuawcolvey]

Well if it has 13:1 it will eaither have race gas in it now and you will be able to smell it. If it is 12: you can run pump gas but anything over 180 temp the thinkg will spark knock bad unless he has a digital box with a timing retard built on it or extra, like , crane, mallory,mad something like that. Did he say anytihg about the block beng decked or what the deck height was. Kinda hard to make that compression with out it being decked and running a small chamber head like 74cc or something. Aslo you said it had a lil big cam, do you know what duration. you can run a wider LSA and bring the compression back down if it is really big, the more overlap the longer the valves overlap each other releaving pressure... I hope some of this helps, run a little thicker head casket will give about .125 to .250 compression releif. A timing retard will help alot aslo....
thanks
Josh

 

[Shawn F.]

Wish I had a lot of the answers to these questions but unfortunately I do not... The kid I bought the truck from was an idiot and lied about a lot of things on the truck so whatever was said on the motor could be bull. I cannot get ahold of him since he pretty much bailed out and wont return emails or anything. :lol:
As for gas, it has pump gas in it now (actually after sitting, the thing wont even crank. I put gas in the carb by hand and it will run on that for 5 seconds and die). I do know it has a VooDoo cam in it but which one I do not know. Ignition is just plain HEI, nothing special, no MSD 6AL box or anything.

 

[joshuawcolvey]

in am almost guessing that it is probable just used a set of flat top pistons, big cam that he could order and probable stock or slitly modified heads, . If so 9.5-1 or 10-1 max but like i said i am guessing. for someone who walk in off the street asking ut to build them a motor and just wants it to run good on a budget, it getsflat tops and stock ported and polished heads, mild cam shorty headers, electric fans, good flowing carb and 8.25 psi mechanical fuel pump. static compresssion on that is about 9.75-10:1

 

[Shawn F.]

Well when I get this thing out of the truck (hopefully soon) I will tear it apart and let you guys know what I find. First I have to get the air bags on this junk to lift up and that way I can get under the truck to undo the transmission. Right now the bags are layed out and it is sitting frame on the ground. I hate air bags.
Now a regular S-10 rear end will work for a T or a 27 T correct? This is not the wider 4x4 one. If it was I would be using this drive train for my 48 Chevy Coupe but the rear end wont fit it so I figured it can be used in a T bucket. :surprised: