I took my car over to a mechanic friend of mine so he could look it over and double check everything since this is my first BHG job. After replacing the HG and putting everything back together, the 1st and 5th cylinders are getting very low compression and won't allow the car to turn over. I have read a little bit and what I have read is that it could be as minor as the head bolts not torqued down tight enough, or as major as the seals, rings being bad, or a valve is either bent or sticking. Any input would be greatly appreciated!
Low compression
- Thread starter mkIII213
- Start date
Did you deck the head at a machine shop?
Is mechanical timing correct?
What did you tq the head bolts to?
Is mechanical timing correct?
What did you tq the head bolts to?
DegreE;935585 said:
I took the head to a machine shop and they pressure tested it and it was perfect.
Timing is right.
I used the stock head bolts. I had an extra parts engine that I was able to use some of the good head bolts off of it, only the ones that had a good thread. I torqued them down to, I believe, 65 or 70 lbs.
Because I read that if I went any higher, the stock bolts could break since I was reusing them.
Probably your first mistake was reusing the headbolts. They should have been checked to make sure they hadn't streched. Did you clean out the bolt holes with a tap? You said "only the ones that had good thread"? If you had bolts you took off that had bad threads you have more problems. Why would the threads be bad do you think?mkIII213;935592 said:
AJ'S 88NA;935604 said:
Yes I cleaned them out. There were maybe two or three from each engine that the threads weren't perfect, all the others were fine. Not sure on why the threads would be bad though. But they weren't like horrible, just not perfect.
DegreE;935617 said:
But that seemed to be the arguement that I have read about over and over again. I read that they were alright to use, but then again I read they weren't. I think a valve is bent because of having no compression on the 5th cylinder. Looks like I need to go take it apart again. :3d_frown:
Studs/bolts aren't even that expensive? Why even re-use them?
I'd spend the extra $100 bux towards a HG job or rebuild or the peace of mind.
I'd spend the extra $100 bux towards a HG job or rebuild or the peace of mind.
Just because you reused bolts wouldn't necessarily cause you to lose compression on a few cylinders.
There was a thread just a few weeks/month back that went over this whole re-using of the bolts and IJ and a few others I thought said they were good to be reused unless someone had torqued the living hell out of them.
I still bought new arp studs for mine, however.
I wouldn't expect the bolts to be your problem... Try putting a teaspoon of oil in the bad cylinders and recheck compression. If the compression is good then you know you have ba d rings.
I think you're jumping to conclusions by just ripping the head off again.
There was a thread just a few weeks/month back that went over this whole re-using of the bolts and IJ and a few others I thought said they were good to be reused unless someone had torqued the living hell out of them.
I still bought new arp studs for mine, however.
I wouldn't expect the bolts to be your problem... Try putting a teaspoon of oil in the bad cylinders and recheck compression. If the compression is good then you know you have ba d rings.
I think you're jumping to conclusions by just ripping the head off again.
Plug a compressor into #5 at low pressure while it's at TDC on the compression stroke and listen for leakage at the manifolds this will confirm if it's a leaking valve or not.
The stock headbolts get a LOT of bad press when in reality they're very good parts.
ARP's can be reused.
The stock headbolts get a LOT of bad press when in reality they're very good parts.
ARP's can be reused.
There is absolutely no compression on cylinder 5, and very low compression on cylinder 1. All the others are fine. So it can't be the head bolts, because the other cylinders are holding pressure just fine. It's either valves or bad rings. ugh...
I know a lot of peeps who re-use stock bolts and don't have issues. I would recommend against reusing them if you know the engine has been overheated a shit ton of times.
With my last car, I had to drive it on BHG for awhile until I could afford the repair. Bc I knew the head was more than likely warped and the bolts stretched, we torqued the bolts to about 80 ft/lbs. They did not bottom out and the bolts did not back off the torque (like they usually do after the first few miles bc of the alum/iron). Held together very well until the block grenaded itself, lol Which had nothing to do w/ the head bolts
With my last car, I had to drive it on BHG for awhile until I could afford the repair. Bc I knew the head was more than likely warped and the bolts stretched, we torqued the bolts to about 80 ft/lbs. They did not bottom out and the bolts did not back off the torque (like they usually do after the first few miles bc of the alum/iron). Held together very well until the block grenaded itself, lol Which had nothing to do w/ the head bolts