Need help from "engine guys"...
Thread Starter
Track Day
Joined: Jan 2002
Posts: 20
Likes: 0
From: Fresno, California
Need help from "engine guys"...
I am looking into a 1977S with a 78sc motor. Car has 124000mi mileage on the motor is unknown...The car has been sitting for two years. We had a compression test done today and here are the numbers: 130, 110, 115, 130, 140, 130. Shop says it is normal for a car that sat for two years to show low numbers...After driving it for 50-100 miles it should show "higher". I asked the owner to re-do a compression test and a leak-down test (at my expense) and here is my question: Is this normal? I know "healthy engines" are up to 140-150 psi...Is his motor pretty much gone? Thanks in advance for all your input!
Intermediate
Joined: Apr 2002
Posts: 47
Likes: 0
From: By the lake, MN
More important than the 'high' number, is the differential between all cylinders. Normally, for a 'street' engine, + or - 15psi is acceptable. For 'extreme' or hard use, + or - 5psi is the limit. The engine you quote having a high of 140 and a low of 110 warrants some concern IMO.
Hope that helps. Mike
Hope that helps. Mike
Instructor
Joined: Feb 2003
Posts: 202
Likes: 0
From: Carlsbad, NM
That doesn't sound good man, even for having 8.5:1 compression on the early engine, it should be better than that. The 944 turbo i used to have had 95000 miles on it and considering it's compression is 8:1, it had 150-160psi compression between all 4 cylinders. Plus the compression differences between the cylinders are substantial as stated by the previous post.
Instructor
Joined: Jul 2002
Posts: 217
Likes: 1
From: Buffalo, NY
I would agree with the previous posters, the big concern is the difference in compression. Running it might get the rings to expand and up the overall compression number but the fact that two are noticeably worse than the others signals to me that something is amiss in those two cylinders. The bigger problem is that the only way to find out exactly was is wrong is to tear the motor apart. You could have bad rings, bad valve seats, a cracked head, . . . These are all VERY expensive problems.
That being said, this car could be a good candidate for a 3.6 swap if the price is low enough and the rest of the car is solid. Just a thought . . .
Good luck!
That being said, this car could be a good candidate for a 3.6 swap if the price is low enough and the rest of the car is solid. Just a thought . . .
Good luck!
Instructor
Joined: Jul 2002
Posts: 217
Likes: 1
From: Buffalo, NY
$16k!!!!!!!! He's nuts. This would be a 10-12k car at best with an original engine, with a bad SC motor this car is worth around 8k. Check out Panorama, the 2.7 liter cars don't hold their value too well and a modified version may be worth even less.
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