30 psi no. 5

-
rigger3006

rigger3006

Well-Known Member
Joined
Aug 6, 2013
Messages
866
Reaction score
249
Location
north america
just did compression test on my smoking 318, 30 psi on 5, the rest averaged 120, 284/ 484 cam, while testing other cylinders oil was flying out of no. 5, added oil to cylinder and still 30 psi , rings?
 
this came about from a 7000 rpm burnout, both pushrods through rockers on no 2, and serious smoke coming out of breathers
 
Remove #5 plug. With your finger in the hole, have someone bump the engine until you feel compression just begin to blow against your finger. Then, use a long this screwdriver and place it against the piston. Bring the engine on around by hand until that piston is all the way UP as far as it will go. If you feel it JUST begin to go back down, that's ok. You have just gotten #5 up on the compression stroke and closed both valves on that cylinder.

Now get a compression tester hose and screw into #5 plug hole. Then attach a live air hose to it. If you hear escaping from the carburetor #5 intake valve is not seating. If air escapes from the tail pipe, #5 exhaust valve is not seating. If air escapes from the valve cover breather, you have a broken ring or a hole in that piston. I am betting on a burned exhaust valve. Wherever air escapes, you WILL know it.

You make get a small amount of air in other areas, but wherever the problem is, will be very obvious.
 
RustyRatRod said:
Remove #5 plug. With your finger in the hole, have someone bump the engine until you feel compression just begin to blow against your finger. Then, use a long this screwdriver and place it against the piston. Bring the engine on around by hand until that piston is all the way UP as far as it will go. If you feel it JUST begin to go back down, that's ok. You have just gotten #5 up on the compression stroke and closed both valves on that cylinder.

Now get a compression tester hose and screw into #5 plug hole. Then attach a live air hose to it. If you hear escaping from the carburetor #5 intake valve is not seating. If air escapes from the tail pipe, #5 exhaust valve is not seating. If air escapes from the valve cover breather, you have a broken ring or a hole in that piston. I am betting on a burned exhaust valve. Wherever air escapes, you WILL know it.

You make get a small amount of air in other areas, but wherever the problem is, will be very obvious.
Click to expand...

Or........yank the valve gear off that side so the valves are closed and apply air.........
 
67Dart273 said:
Or........yank the valve gear off that side so the valves are closed and apply air.........
Click to expand...

I would have said that, however I have made the recommendation before and was told that it was "too much work".
 
^^^X2 RRR...diagnose correctly and succinctly so you can determine your required action.
 
j par said:
I'm not seeing any way you're not going to be pulling the head ??
Click to expand...

Absolutely correct. But why not diagnose it correctly, actually find out what it IS through proper diagnosis and learn sumffin all at the same time? I never "just tear into" anything without proper diagnosis.
 
You'd feel pretty stupid to find out it was something like a broken valve spring or seized rocker arm. Hey it's happened, and "we" didn't have to pull the heads, either.
 
Yes. ^^^^^

Perhaps the best reason to remove the valve cover. But, as I said. LOL
 
Blown head gasket? I did a high rpm burnout on one of my 340's years ago and blew the top of the head gasket into the lifter valley, sucked oil into that cylinder and I had oil coming out the tail pipe, no bent pushrods though.
 
all good ideas, rain storm last night, couldnt get at it, head is definitely coming off, but for sure i need to know the problem first.thanks guys
 
had a similar problem once, a leak down test would hold good but had oil in cyl /blow by/low compression a wrist pin came out and put a nice machined groove in the cylinder wall hope this is not the case.
 
gts dude, exact same thing! thanks guys, had the air compressor beside the car , fitting in cylinder,pulled rockers, could see head gasket hanging in the lifter valley, i was worried i had just screwed my newly worked 302s
 
Glad to hear it will be a (relatively) easy fix. I didn't expect you to go willy-nilly pulling the head off without do proses as some would've suggested. Again, I didn't see a way it was going to get fixed without the head coming off. I was actually giving you enough credit to check the springs and rockers before removing the head.
I myself recently had oil in the number one in intake runner and I was told pulled ahead and take it to a shop. This forum has a lot of good advice coming from a lot of different sources and I think that's why we participate with it. again, we can't go run off all willy nilly when there's a simple fix like resealing the manifold and stopping a leak (my case). We do have to take process and take everybody's good intentions into consideration and use these as tools for help when we need it. Again I'm very happy that it's looking up !!
 
j par said:
Glad to hear it will be a (relatively) easy fix. I didn't expect you to go willy-nilly pulling the head off without do proses as some would've suggested.
Click to expand...

I made no such implication. I merely suggested that it's better to diagnose. You always read an insult into everything and then turn around and put you little digs in. I simply suggested it was better to diagnose. Period. You inferred the rest and quite incorrectly. You really do assume too much. No one is out to insult you or make you look bad. Honestly, I don't know how to extend the olive branch any harder to you than I have been lately. For you to continue on with your little digs and innuendo just shows it is you that's not willing to accept it. That's cool too.
 
^^^ I refuse to do this with you triple-R on this posters tread - on to my Festivus. please carry on with this thread as I will not go there.
 
120 is too low but that can be remedied by advancing the cam timing, once proper repairs have been made.
 
it used to be high 140s with 340 cam, 86 318 roller block, heads cut 010, thin head gaskets 021 or 025 cant remember!
 
The 340 cam was a much better match, but if you advance that 484 enough after you fix the problems with the engine, you can get it right back up there.
 
RustyRatRod said:
The 340 cam was a much better match, but if you advance that 484 enough after you fix the problems with the engine, you can get it right back up there.
Click to expand...


Rob, that is something you should address in your hot rodding thread, a little info about cams, cam degrees, cam timing etc.

As much as I read about it, I still have a difficult time wrapping my head around it. I need it in see spot run lingo, lol.
 
You must log in or register to reply here.
-

Back
Top