Desperate Need of Engine Advice

For the past couple of months, my 400 4bbl V-8 has been running quite rough. My "regular" mechanic said my carb was fine, but I had very low compression on cylinder #7 (this alone took two separate visits and $$$ to determine and adjust). Between visits, I had gone to another engine mechanic for a 2nd opinion and he said my carb was definitely bad and gave me a morbid prognosis. :confused: But once the compression was adjusted, the engine ran much better, albeit not as well as before.

That was all about 900 miles ago... In the meantime, I've been exploring options on what to do about my carb. Then, the day before yesterday came......

I'm on the freeway and suddenly the engine starts "ticking" (not knocking) and she felt like she wanted to stall but wouldn't. I pulled off the road and called for a flatbed immediately, towed it back to the mechanic who did the aforementioned adjustment on #7. He tells me that I had absolutely no compression on #7 and is suspect that my exhaust valve might be "burnt". He also mentioned that compression on #5 is low ("125?" where as the other cylinders are closer to "140"?) and suggested I need a valve job. After explaining the work his machine shop would do on all exhaust valves, and that my exhaust manifold is cracked, he arrived at a quote of $2 thousand to $2500. I asked, why not just replace all the valves? He thought that was a good idea (?!?).

A bit more history before I get to why I'm writing and need advice. My engine has two oil leaks; one near the timing chain and the other at the main seal. The same mechanic (different conversation many months ago) quoted me just over $1200 to address the leaks. Classic Industries has a rebuilt engine for under $2 thousand; even with labor I can't imagine this would exceed the total of these piece-meal jobs to get my engine running and leak-free. Even if the new engine option brought me to $5 thousand, at least I'd have a three year warranty.

Question (and thanks for reading this far!): Should I just take the plunge and buy a new/rebuilt engine? Maybe I've already talked myself into replacing the engine, but I'd value some expert opinions and advice.

Thanks for indulging me!

 

Just curious, how did they "adjust" the compression?

 

Probably a sticky ring.
Try some of this stuff:
www.auto-rx.com
Seriously.

 

It's impossible to give advice without more information. How many miles are on the engine and what kind of care has it had over the years? If the bottom end of the engine is in good shape then a good valve job may fix the problem.

As alluded to in a previous post, there's no good way to "adjust" compression in an engine equipped with hydraulic lifters other than the rocker arms. If you have a burned valve, then there's no good options than to replace the valve and probably the seat.

If it's a high mileage engine, you might want to look into a remanufactured or crate engine.

 

I've never heard of anyone "adjusting" compression. And on only one cylinder?

If this were me I'd be asking friends and relatives and people at work who they use for a mechanic, find one that they feel is HONEST, and go see him.

From the information that you have provided it is very difficult to give you more of an answer than that. Try some gunk as Handy Andy suggests - for the couple of dollars it is worth a try. If that doesn't work, regardless,you need a new mechanic.

 

Ah, come on guys. My dad bought a used 1939 Pontiac, I6, back in 1952. Ran rough on one cylinder, so he peeled off the head, and found a wooden plug where the cylinder used to be. They took the rod out and dumbed out the sparkplug.

I'd get the rebuilt, long block and gaskets, unless you can do it. $5,000 sounds high. $3,000 to $3,500 USD$ sounds closer to normal.

 

Thanks everyone.

Here's some more info.

It's the original engine and it has 151,000 miles on it. It's been well cared for all its life; never abused or overworked.

About two or three years ago however, it was severely overheated on a trip up to SF. This was caused by a fan clutch that went bad about half way into the trip. Fan clutch, radiator, hoses and thermostat were all replaced. Could this severe overheating be a factor?

Not sure how the compression was "adjusted"...whatever he did it ran much better afterwards, but as I mentioned, that only lasted about 900 miles.

 

Never heard of a compression adjustment. Maybe he tightened down the rocker on that cylinder and MAYBE that's what burned the valve. (??) There are many companies out there with rebuilt and/or built engines that will drop in. I'm with Saf on this....get yourself another mechanic no matter what you do. I would seriously consider a new engine but one from a trusted performance source or recommended by one.

 

Run and hide from any shop that say they "adjust" the compression.

And that will be your test for a new shop, tell them the same story and that they said they ["adjust" the compression] if they don't roll their eye and question it too. They arent to be trusted either as they will think they got a sucker on the line too.

Since your not handy with a wrench, buy a rebuilt engine with a warranty from a bigger name brand place, GM, Jasper, Summit, Classic, some place you know won't be fly by night and will be around well beyond the warranty life. And who also laughs when you say they ["adjust" the compression].

 

Those compression numbers are within specifications are they not?
A ticking sound and you guys have the poster buying a new or rebuilding the engine.
Sheeesh, again, I'm glad you're not my mechanics...
If it's a bad valve then it only requires pulling off the effected head.
151K is nothing, should be good for another 100k.
Valves can get really caked up and sticky.
Might want to seafoam it, or mist some water in the intake.

 

Mine overheated in Texas in 1999, then in 2006 or 2007 when we opened the pan, we saw how scored the bearings were, Andy. It only had 149,000 miles on it, in Texas. and 153,000 when we opened it up. At least mike the mains and rods.

 

I see your point Norm, but your statement suggests that even with bad bearings it's good for another 6 years. And who knows how many more miles. It was still running until you dropped a nut down the intake.

 

Would you rather have his mechanic, Andy??
Did you see the prices he was quoted for the work to be performed by the "compression adjuster"? Would you want him to work on your car?
Ordinarily I would agree with you, Andy, but I have a bad feeling about the mechanic and the prices he is giving out.
I didn't notice the numbers till you mentioned it and you are right...the spread is not good but manageable. Bottom line for me is....some people just don't know about cars. Open the hood and they are lost. THEN, enter the dishonest bad mechanic. By the time you deal with someone like that your car will probably STILL not run right and the cost will surpass a new rebuilt with warranty.

 

Glide-always, I'm with Andy on this one. FIND AH NEW WRENCH:2_thumbs_up_-_anima Their hastah be ah few good ones on the Left Coast that don't want your first born child every time they raise your hood Worst case iz that "down the road" you're forced to replace the engine. 150K isn't alotta miles to start talkin' replacement. Could be a stuck ring on that one cylinder too. Yah might try adding one qt. of ATF to your oil and take it out and try blowing the snot out of it You'd be supprised what that one qt. will loosen up, and it won't hurt nothin'! A rear main seal and or a timing cover seal iz a real PITA but $1200 iz ah tad stout too I think. You can add alotta oil for that kinda dough even if your tailgate does havta be wipped down after every trip. My '02 cents

 

I'm not sure what you think I'm suggesting, but I called out the mechanic on my first post. My question was tongue-in-cheek, like "ya right sure he adjusted" the compression.

And it seems you all are suggesting he should replace or rebuild the engine, with any real inspection or proper diagnosis. And I think that's just as irresponsible as the first mechanic.