Ok here is what I have from the last person that owned the car..

chev 350 block #14093638

355 cuin
.30 over
small chamber heads
460 lift cam
278 duration

I just did a compression test and i had :
1 at 180
1 at 160
6 at 170

I am pulling the engine to fix what I hope is just a rear main seal and leaky valve covers.. My question is :

1. is this a good setup?
2. can anyone tell me more about the block?
3. do i need to be worred about the cylnder that was 160 ?

Thanks in advance...
Joe 80VetteMan2008-06-25 20:43:54

Compression looks ok, and the one lower cyl could be due to several factors, such as battery state of charge, and the method used to test.
Did you have all of the plugs out?
Did you have the throttle open all the way for the tests?

One lower cyl. could be from a too loose/tight valve adjustment, a bad lifter/cam lobe, or ring/cyl wear.
If you haven't already pulled it, you might try squirting a little engine oil down in that cylinder, and check the compression again, to see if it comes up. If it does, than you may have a little more leakage past the rings than on the other cylinders. I would run the test again, just to be sure, and make sure to have all of the same conditions while checking all of the cylinders....all plugs out, and throttle wide open.(remove the 12v power from the coil first, of course)

I like the cam specs, what I can see, tho it might have a bit too much duration, depending on the compression ratio. Anything that close to 300 is gonna be a bit lumpy, and vacuum is prolly suffering, too. If, however, the engine has a 10-10 1/2 compression ratio, it looks perfect.

I don't have my casting book handy, but it looks like the block may be a later casting, but don't quote me on that.

yes on all plug out, throttle open,hei coil unpluged..

I made sure the battery was charged for all of the testing.

I am going to do the "wet test" today on the one cylinder.

Question: how do I know what compression ratio I have? and how do I do the math to figure out what I have?   

Question 2: what creates the duration value and can I change it? is this base on timing?

Thanks, Joe :)80VetteMan2008-06-26 04:27:59

Comp ratio has to do with bore size, stroke, rod length, pin location(height) in the piston, piston shape(dome/flat/dish), and the chamber volume of the heads. There has been a couple of threads posted with the basic method of checking comp ratio, but I'm not sure where they are...might need to do a search.

The cam duration is a mechanical function of the cam lobe design...it is how long the valve is held open in regards to the degree of crankshaft rotation. The only way to change that is by changing the cam itself. Not saying that what you have won't work, but it does appear to be best suited for a low rear gear/4 speed vehicle, which your car may be...I don't know what you have. There are other variables too, such as lobe separation, and cam timing specs that need to be considered here.
Hopefully Ken, or someone else can elaborate.

Joel is right in saying you seem to have a lot of cam duration.  And that much duration with only .460 lift doesn't seem right.  Assuming "small chamber heads" means 64cc, you can look into a cylinder with a small light and see if you have flat pistons.  If you do, depending a lot of small variables such as deck height, gasket thickness, etc, compression should be in the range of 9.8:1 or so.  With a cam of about 268 duration, .490 lift and conservative lobe spacing, you should have a very nice driving car.  To support 278 degrees, you should have well over 10:1 compression and either deep gears (4-speed) or a high stall speed torque converter (automatic).  If you are pulling your engine, changing the cam is not a big deal.  Call Comp Cams and ask their recommendation.

Larry

14093638

1987-95

350

2/4

Roller or flat tappet cam one-piece rear seal

thats the casting # the years it was produced, cubic inch  2 or 4 bolt main...and note the one piece rear seal stingrayjim2008-06-27 12:12:56

IF you can picture the space in the cylinder, not in the cylinder head, when the piston is down, the picture the space that is gone when the piston is all the way up, this is the cubic inch displacement.  Hence, how much volume is displaced by the piston.  The space above the piston is what the air in the cylinder is squished into.  If the space from the piston is 10 times as much as the space in the head, it is a 10:1 compression ratio.   If it is only 8.5 times as much, the compression ratio is 8.5:1.