Low Compression ? Head Gasket ?
Thread Starter
|
Freshman User
Joined: Feb 2005
Posts: 30
Likes: 0
From: Texas
Low Compression ? Head Gasket ?
I have a 1980 302. The engine has 3500 miles on a rebuilt long block from ProEngines. After an 800 mile trip it had developed a bad idle. I replaced the carb/fuel system with new parts. Replaced the complete ignition system also re-curved the distributor. All the Pollution control has been removed or capped. The cats are removed. Checked for any possible vacuum leaks. Vaccum gauge reads 21hg. Still bad idle. Off idle runs great. I took it by a shop and they diagnosed low spark on #7 cyl. Suggested I run a compression check. Results: cylinders 1-6 were at 155#, #7 & #8 were at 120#. I don't see any oil in the radiator or coolant in the oil. Mechanic friend suggests a bad head gasket.
Also said the truck was orginally a Variable venturi carb and they were prone to head gasket leaks due to problems with the EGR system. I am going to replace the intake with a pre-EGR manifold. Since I have a brand new 2150 carb. Going to stick with the 2bbl.
Anyone out there have any other suggestions before I spend a weekend trying to replace a head gasket.
Also said the truck was orginally a Variable venturi carb and they were prone to head gasket leaks due to problems with the EGR system. I am going to replace the intake with a pre-EGR manifold. Since I have a brand new 2150 carb. Going to stick with the 2bbl.
Anyone out there have any other suggestions before I spend a weekend trying to replace a head gasket.
More Turbo
Joined: Oct 2004
Posts: 621
Likes: 2
From: Marana, AZ
Normally when you have low compression on 2 adjacent cylinders, it usually points to a head gasket problem. But only 3500 miles on a rebuild is not a hole lot of miles. I would re-do the compression test to be absolutly sure, plus I would also shoot a couple squirts of oil in #7 & #8 cylinders and re-test those to see if you get a higher reading. If so they could be some bad rings. Another scenario is maybe the valve seats weren't ground exactly right on those 2 cylinders causing a minor leak of pressure on the compression stroke.
Did you not get a warranty with this motor? They should stand behind that and fix it for free.
Did you not get a warranty with this motor? They should stand behind that and fix it for free.
Thread Starter
|
Freshman User
Joined: Feb 2005
Posts: 30
Likes: 0
From: Texas
[
Did you not get a warranty with this motor? They should stand behind that and fix it for free.[/QUOTE]
Yes the warranty would cover the repair. It had a 3 yr warranty. And it is already up. I rarely use the truck just for occasional trips to Home Depot ect. Mainly a toy/extra vehicle. Oh well ! Not too expensive of a job just a weekend worth of time.
Did you not get a warranty with this motor? They should stand behind that and fix it for free.[/QUOTE]
Yes the warranty would cover the repair. It had a 3 yr warranty. And it is already up. I rarely use the truck just for occasional trips to Home Depot ect. Mainly a toy/extra vehicle. Oh well ! Not too expensive of a job just a weekend worth of time.
, well hopefully it will be something simple like a head gasket, would be a pain to have to tear her down to replace the rings if that was the case.
Thread
Thread Starter
Forum
Replies
Last Post
AZcowboypilot
1987 - 1996 F150 & Larger F-Series Trucks
29
Jul 6, 2019 12:33 AM
autox65
1973 - 1979 F-100 & Larger F-Series Trucks
10
Apr 25, 2016 09:11 AM
buckin69bronco
335 Series- 5.8/351M, 6.6/400, 351 Cleveland
13
Jun 23, 2015 01:37 PM
bebad96
1987 - 1996 F150 & Larger F-Series Trucks
19
Jul 31, 2004 05:53 PM
