Thread: 350 Compression

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I am buying a 96 S10 ext. cab pickup tomarrow with a 350 sbc, 350 turbo tranny, locker rear with 3.45 gear, fully bagged, etc etc.... Anyways, it is supposedly a freshly built 350 with less than 50 miles on it. The guy said his buddy races dirt track cars and built it but couldn't use it because the new local track rules state that you have to run a crate short block to make things more fair. He said he isn't sure of the compression ratio but thought the guy said 12 or 13:1 compression. Does this sound right for a dirt track car? If so I dont want to run that on the street, it is way too much IMO. What can I do to lower the compression? New pistons or what? I hate to have to tear the motor out and do this but if its true then dont you guys think it's way too high? Also, he said it's a VooDoo cam but not sure the exact one.
Any ideas, suggestions or anything here? I am buying this truck because it has quite a bit of money into it (at least it seems) but some things are hacked on it which means a lot of it is. It needs body work and painted inside and out, the bed is tunneled out since the frame is notched with a tower for the air bags to lay frame (which isn't my style but something different I guess I will mess with).
Thanks for any info guys!

Put some smogger heads on it.

What would be the downside to that? If anything I was thinking about going with Edelbrock heads but that would take a while to get the funds to do that. I am going to find out the compression for sure first and go from there. I would love to be able to run this thing on mid grade fuel, I already have a 68 Lincoln that wont run on anything else but high grade and it sucks. I will look into the heads deal. Thanks!

I would do a compression test to determine cranking pressure before getting too geared up for modifications.......although that maybe why there is only 50 miles on it ???
Might be as simple as a cam swap too????????

Yeah I will look into it. I am going to be picking it up soon (within the next 3 hours) so I will bring it home and go over it. He has WAY too big of a carb on it which is a 750 Holley so I will be putting a 600 or 650 tops. Right now IMO it is more for the strip use and just driving around on weekends. I'd like to get it more streetable.

Well I got the truck home and it needs a lot more than expected (which I figured would be the case). The tranny I think needs fluid since it takes a second to hit from park to drive or reverse, etc. There is a loud screaming or whinning noise like a belt but the guy said it is the new 100V Jegs alternator. I did the old broom handle to the ear trick. It is definately NOT the alt. It is the water pump! I dont see how a motor with less than 50 miles has a bad water pump already. Any idea what brand to get? I have to see if it is short or long, I am guessing short. I am guessing something along the lines of this...
http://store.summitracing.com/partde...5&autoview=sku
It does NOT have to be polished though, IMO Weiand makes some good products so not sure...
I am going to do a compression testing on each cylinder in a few weeks when I get home from vacation as well.
Thanks for any info, suggestions and advice!

From where I stand, the guy didn't tell you much of anything. A Voodoo cam, but not sure which one? 12 or 13 compression, but not sure exactly? Looks like you need to inspect everything by the numbers and find out by yourself.

BTW, aA 750 Holley may be to big for some 350 motors, but it certainly isn't way too big.

Not to intentionally pee on your campfire, but you bought a motor that you have to change either the pistons or the heads (or both), the cam, the water pump, the transmission is sucking, etc, etc.....hope you bought this thing for less than $1000!!!

The engine and tranny run fine. Tranny is low on fluid just a touch and that is why it was doing that until it warmed up. I plan tear the entire truck down anyways and will do the same with the motor. The engine runs and starts fine, has a nice lumpy cam and isn't spark knocking or anything. I have a friend that is very good with engines and builds SBC a lot. He is very picky about building them and doing them right and not overdone either so I will see what he thinks. I will probably pull a valve cover today to look at that and see how clean it is in there. With less than 50 miles it should be very clean.

Henry, I am going to do exactly what you said and check it out for myself. And like I said, it runs fine but I am just picky to where I want to know what I have and I want to check over everything to make sure he didn't lie and make sure there are no problems.

One more question now that I think about it. The oil pressure seems to be fine when you start it up and drive around. (about 60 psi) When you put it in park it will go to about 30 psi or just under that. When you put it into gear and just sitting there idle it will go to 15. Is this normal or no? I know my 351W in my 66 stays around 55 driving and 30 idling, after it warms up and you drive around it drops to 20 idling.
15 just seemed a bit too low to me but what do I know?