Thread: Your opinion on engine diagnostic

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Hi everyone, just wanted some opinions on what is going on with my 68 Coupe. First off its a 289, Holley 650, Edelbrock RPM manafold, milage unknown but receipts say it was rebuilt in 1991. I have some smoke out the breather tube and the exhaust under acceleration. Otherwise it runs great. I have set the valves, carb. and put in new plugs.

Vacuum reads 18 steady.
Compression reads,
1 120 lbs. (150 with a teaspoon of oil)
2 135 lbs.
3 145 lbs.
4 145 lbs.
5 135 lbs.
6 130 lbs.
7 125 lbs.
8 135 lbs.

I am thinking that #1 and maybe # 7 piston has bad rings. Your thoughts?

Like lotsa smoke? Your compression is not bad, 120 might be lower than the others, but that's not bad. It'll run there anyway, and should run fairly well.

Is it running bad? Or are you just concerned about the compression readings? I mean it sounds like it's got some miles on it, but it sounds like it should run for awhile.

You need to run a cylinder leak down test
that will determine if it's rings or valves, you for sure have a problem with 1 & 7, although it is slight .......

I thought is was a slight drop also, I have heard of guys running theirs in the 80's. I only get smoke under acceleration but it feels like it should have a bit more power then it does.

I am thinking of running it through the summer and maybe having a rebuild next winter.

Thanks for your help.

the compression reading will depend on pistom dome or dish and the combustion chamber size. Rule of thumb is no more than 20 percent of your highest reading..
But The cylinder leak down test will pinpoint the leak and tell ya how bad its leaking.......

Originally posted by Blue68Coupe
Hi everyone, just wanted some opinions on what is going on with my 68 Coupe. First off its a 289, Holley 650, Edelbrock RPM manafold, milage unknown but receipts say it was rebuilt in 1991. I have some smoke out the breather tube and the exhaust under acceleration. Otherwise it runs great. I have set the valves, carb. and put in new plugs.

Vacuum reads 18 steady.
Compression reads,
1 120 lbs. (150 with a teaspoon of oil)
2 135 lbs.
3 145 lbs.
4 145 lbs.
5 135 lbs.
6 130 lbs.
7 125 lbs.
8 135 lbs.

I am thinking that #1 and maybe # 7 piston has bad rings. Your thoughts?

the wet test you did shows some ring ware, but if its not missing keep on driving it. as long as its not missing, dont use to much oil and drive ok, it dont make no dif what the comp is. JMO

Ok so my biggest issue until a rebuild is the amount of smoke out the breather tube. You smell like an exhaust pipe after a short trip.

I would think that these commpression numbers would be good enough to not blow-by that much. How can I tell if it's the valve seals?

make sure your pcv valve is working properly, check the pcv hose at the carb. and make sure its open, other wise thats about it. if you dont have a pcv system you need to hook one up.

http://www.clubhotrod.com/forums/att...&postid=100112

PCV works fine but the smoke is pouring out the breather on the drivers side.

I am thinking of replacing the valve seals so that I can drive it this summer and rebuild it on a winter project.

valve seals dont normally smoke that bad. i guess they could thought. most of the time valve seals smoke show up out of the tail pipe, smoke out of the valve cover shows blow-by which is rings.

is it just smokestacking like crazy out of the oil fill hole when you open it up??
even though the pvc valve is working??
either check for plugged hose or too much blow by.
i had a old ihc scout 304 that did the same thing to the point of being goofy. comp was ok and power was fine but still stunk and smoked.
my cure was install two pvcs on it. went to the wrecker and got another pvc assy(cheap) put a t in the back of the pv pickup in the manifold and hooked both up.
worked ok stopped the blowby it even burned less oil for some reason
just a idea to get you by till rebuild time. may be worth trying.

hey denny did 68s have pvc valves ??my 66 289 doesnt have one. when did they start putting them in the fords.

Don't think it's original and the carb is a Holley 650.

Actualy I have been running it with 2 PCV valves. Not bad, better then being covered in smoke.

I think I will just have to nurse it until rebuild time.

Thanks for your help.

Heh, you smell like smoke too when you get out? I started noticing the same thing with mine but no smoke out of the breather, only behind the middle of the rear of the intake manifold. Just tell everyone it's the new smell these days. This thread is interesting to me too, I want to see what your problem is, let me know what you find out, I am curious!