Bad Compression, Rebuilt Engine...

john · 08-07-2004

I am looking at a car for sale. It ran fine until the HG blew. The engine had a recent rebuild (within 50k). Compression in now 50-60-50-52 after putting the head on and will not start (compression was on a cold engine). Sound like the valves are smashed now? That is my guess. I will probly get it anyhow, to drive or part out. Thanks, John.

Matt D. · 08-07-2004

I wouldn't bother unless it's super cheap. Without pulling the head or doing a leakdown test you really don't know what's going on.

john · 08-07-2004

I would call it super cheap. I wouldn't have a problem getting my money back if I had to part it out. I am going to do a leakdown test when I get it home. I am making my tester at work today. I assume that the low compression is why it doesn't start...

How does a power transistor work. Does it have to be mounted on the head to function or can it just be sitting there? What does it do?

Matt D. · 08-07-2004

Quote:

Originally posted by 92tsiawd84@Aug 7 2004, 08:39 AM
How does a power transistor work. Does it have to be mounted on the head to function or can it just be sitting there? What does it do?

Are you talking about the flat black thing with lots of pins on it?

Raptor · 08-07-2004

It doesn't have to be mounted to work John. It should be of course, but will work just hanging.

john · 08-09-2004

I have the car in my garage. I took the front apart and found that the timing is off like I expected. Here is a pic. Looks like the intake cam is behind. Would this cause the bad compression? The valves not sealing, thus loosing alot of compression? Do you think the valves are smashed or they are just not sealing the CC?

john · 08-09-2004

Here is a pic of the crankshaft and oil pump. To the best of my knowledge it is all ligned up on the bottom. Look right to you??? When I align the cam marks the crank and oil pump are each a tooth off (past their marks). Should I have the timing belt put on right or pull the head? Do you think the valves are gone? I guess I could throw in some ARP's and get rid of more crap if I pull the head. What do you think? Will it run if I just swap the belt on their right? Pic of aligned front case with pic above:

Thanks for the help, John.

PSI2HI · 08-09-2004

Quote:

Originally posted by 92tsiawd84@Aug 9 2004, 12:04 AM
I have the car in my garage. I took the front apart and found that the timing is off like I expected. Here is a pic. Looks like the intake cam is behind. Would this cause the bad compression? The valves not sealing, thus loosing alot of compression? Do you think the valves are smashed or they are just not sealing the CC?

Take the belt off and put it on the right way before you pull the head. If u pull the head and the valves are good your screwed for an easy fix and finding the problem. No way of knowing if its head problem or not w/o sending them to the machine shop.

john · 08-09-2004

Thanks, but if I pull the head, wont I be able to look at the pistons to see if they have been hit? I think I may just pull the head as it is easy to do with the belt off. Then I can fish out the AC compressor and get rid of the EGR stuff that should be gone. As far as removing AC, the belt is off it (previous owner). Still carrying along all the weight and all the EGR lines and canister are still in there with a EGR blockoff plate. Then I would have to decide if the beater needed head studs which I have laying here. And I wasn't going to mod it at all.....

john · 08-09-2004

Actually, the car hasn't started since the previos owner tried replacing the HG. Would the starter smashing the valves have enough force to gouge the pistons?

john · 08-09-2004

I pulled the head, the valves hit. It appears only on the exhaust side though... That would cause the large drop in compression on the 34k rebuild right? The numbers were posed above.

MustGoFaster · 08-09-2004

Yes, it would. You might want to have the head checked for flatness if it blew a HG(and the block, but that's kinda hard).

Raptor · 08-09-2004

The head is now at the shop for some work. John can give you more info if he wants.

john · 08-09-2004

The previous owner had the head plained so that should be fine. New valves and the car SHOULD start.