Click on image for the lowdown. 
====
| | | Forums66 Topics128,057 Posts1,055,810 Members48,426 | | Most Online14,466
Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
| | THANKS!
For helping keep this great
old truck web site
on the Internet for over 30 years! and not clogged down
with Ads!  Again, thanks!
| | | | Joined: Oct 2006 Posts: 18 Apprentice | | Apprentice Joined: Oct 2006 Posts: 18 | Can some tell me what cylinder compression for a 1938 216 engine should be?. I just took it cold and have 90lbs. of compression.I'm trying to get this engine running after 30 yrs. of sitting in a barn.Any tips would help. Thanks Jack | | | | | Joined: Jun 2008 Posts: 1,388 Shop Shark | | Shop Shark Joined: Jun 2008 Posts: 1,388 | Mine is about 90 pounds cold, and 127 pounds hot. My engine has those new fangled pistons made of aluminum in it, and it is over-bored, but by how much I don't know. | | | | | Joined: Oct 2006 Posts: 18 Apprentice | | Apprentice Joined: Oct 2006 Posts: 18 | Mr. Lang, Thanks for the reply. Would you know what a stock 216 compression should be hot. Jack M. | | | | | Joined: Aug 2005 Posts: 6,377 Ex Hall Monitor | | Ex Hall Monitor Joined: Aug 2005 Posts: 6,377 | 90 lbs. is fine. The more important figure is that all six cylinders be within about 10 PSI from lowest to highest.
Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.
| | | | | Joined: Feb 2004 Posts: 29,773 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,773 | If all the cylinders are pretty close to each other, 90 PSI should be plenty. A 10% variation (+/- 9 PSI) is acceptable on a low-compression engine like a 216. On the engines with 9.5:1 or higher compression, the rule of thumb used to be 5% pressure difference, but very few engines even today get up into that territory. The era of the high-compression, high-performance engine died with the end of leaded gasoline.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Jun 2008 Posts: 1,388 Shop Shark | | Shop Shark Joined: Jun 2008 Posts: 1,388 | I agree, doesn't matter, long as they are all close.
That being said, my Pontiac, has one cylinder that reads 80 or so when hot, the rest read 120. At idle, you can see with the vacuum gauge, that its not really firing. As soon as the engine is brought above idle, even just to fast idle, the vacuum picks up, and the engine smoothes out. It has been that way for the five thousand miles I have put on it. It has bad rings in that cylinder, and someday I will replace them, someday. | | | | | Joined: Oct 2006 Posts: 18 Apprentice | | Apprentice Joined: Oct 2006 Posts: 18 | Thanks for all the replys,Guess I should be happy they all are 90lbs. Thanks Jack M. | | | | | Joined: Mar 2002 Posts: 9,115 'Bolter | | 'Bolter Joined: Mar 2002 Posts: 9,115 | According to the 1938 Shop manual, the follow is the procedure:
Bring the engine up to operating temperature by running it at 600 RPM for 20 minutes. Remove all the spark plugs and check the compression on each cylinder. The compression should be 90 PSI with a variation of no more than 5 to 10 LBs.
I started my 38 216 after it ahd sat for 31 years in a barn. I used a spare carb, fuel pump and coil and it started right up. The compression cold ranged from 90 LBs to 130 LBs. I think there is a lot of carbon in some of the cylinders.
Oh and the oil pressure was a very good 14 Lbs, even when warm. However I had to shut it down after about 15 minutes because it was going to overheat. I think the rad may be plugged.
Last edited by truckernix; 05/16/2010 2:46 AM.
| | |
|
|
