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#1449925 Fri Apr 29 2022 10:35 PM
Joined: Nov 2021
Posts: 307
F
'Bolter
The engine in my 66 C10 started and ran in the fall. Idled well, no smoke. Plugs were horrible when I pulled the old ones.

Assumed things would be good with it. Lugnutz convinced me to do a leakdown test. Just got done the even side and I don't think there is a point to do the odd side, but I will in the morning.

Here the numbers, Percent of loss

Cyl 2 35% Cyl 4 45% Cyl 6 and 8 70%

I am amazed it ran as well as it did when I got it started in September.


Now the decision to be made. Rebuild or Repower?


1966 C-10 Step Side. 283, 4spd, 3.73 gear. 60K miles prior to restoration. 507 Paint Code. Currently in 10,000 pieces.
Transmission is done! Rear Suspension is done! Wheels are done! Bed bodywork is done! Soon to order a 383 crate.



Joined: May 2005
Posts: 8,817
B
Sir Searchalot
Can't answer without context and info. When did Lugnuts recommend? What was the issue? What other tests have you done? What is the history of this post question?
Leak down is not enough. It depends on where it is leaking. Depends what it needs to be tight so as to estimate cost vs replace. It depends on input pressure. It depends if the test was done correctly. Depends if the tool is a quality two gauge tool. Depends on the compression numbers.

Your numbers are so high and in all cylinders as to be very suspicious. I wouldn't go off hog wild right away. A motor would not run good with those numbers, maybe not run at all. (compression is one of the criteria for a motor to run). It sounds like it was running fairly good? It my mind it was a testing problem until I hear the story.


Watch out for careful drivers!!!
I'm away on an ego trip. Will be back on Feb 30.
I'm not an Auto Mechanic, but I play one on TV.
I charge $0.02 for every opinion and I take Paypal.
Plan B is always better than plan A, by definition.
"We have no time for comment, every man will make his own. LET IT BE MADE WITH POWDER AND BALL!!!"
I recommend invoking MIL-T-FP41c when machining and fabricating
I used to think beer was bad for me, so I gave up thinking.
Sometimes no nonsense makes sense, in a sense.
You can't teach a new dog old tricks.
Honk if you're Amish


Joined: May 2015
Posts: 5,464
Housekeeping (Moderator) Making a Stovebolt Bed & Paint and Body Shop Forums
What Bartamos said. Start with a compression test, then go to leakdown to determine where the compression loss (if any) is coming from (rings or valves). A leakdown test needs a decent set of ears, not just a gauge.


Kevin
Newest Project - 51 Chevy 3100 work truck. Photos [flickr.com]
#2 - '29 Ford pickup restored from the ground up.
First car '29 Ford Special Coupe
Busting rust since the mid-60's
Joined: Feb 2004
Posts: 24,558
H
Kettle Custodian (pot stirrer)
Where are the leaks going- - - -intake, exhaust, or crankcase? Leakdown testing is FAR better than checking compression, because you can tell where the pressure loss is actually happening. Were you using an air regulator set to 100 PSI with no flow through the hose as a baseline? There's a running testing method known as a "cylinder balance test" that is also more effective than compression testing. All it requires is a tachometer and a vacuum gauge. PM, email, or call for more info, if you like.
Jerry


"Freedom's just another word for nothing left to lose"
Kris Kristofferson

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!

WAG MORE- - - - - -BARK LESS!
Joined: May 2005
Posts: 8,817
B
Sir Searchalot
No one said it wasn't better or worse. We just said you ALWAYS do a compression test and would like to know the results. So that it can all be put together to answer his question. No need to invent controversy.


Watch out for careful drivers!!!
I'm away on an ego trip. Will be back on Feb 30.
I'm not an Auto Mechanic, but I play one on TV.
I charge $0.02 for every opinion and I take Paypal.
Plan B is always better than plan A, by definition.
"We have no time for comment, every man will make his own. LET IT BE MADE WITH POWDER AND BALL!!!"
I recommend invoking MIL-T-FP41c when machining and fabricating
I used to think beer was bad for me, so I gave up thinking.
Sometimes no nonsense makes sense, in a sense.
You can't teach a new dog old tricks.
Honk if you're Amish


Joined: Nov 2021
Posts: 307
F
'Bolter
I didn't do a compression test while it was in the truck because I was dumb and it ran so well when I tried to start it. I started it by pulling plugs, putting MMO in the cylinders, and rotating by hand. Next day rotated again, threw new plugs in, fuel in the bowl and it fired and idled perfect.

Engine is out and Lugnutz suggested I do the leak down which seemed reasonable. I was wanting to check for a head gasket leak without going to deep into the motor. Little to no crud and sludge in the tin.

I pulled plugs, rotated rockers off he springs, put some MMO into the even side and rotated the engine a few times by hand.

Started with #2. Put 100 lbs into it and the gauge, to my horror, on the hold side is at 55 lbs! WTH? I came inside watched a couple videos to make sure I was doing it correctly. One of the suggestions was to tap the spring to make sure valve is seated well. I went back out and did this and it went up to 65lbs. Hmmm still not good.

Off to #4. 100lbs in and it's at 40. Tapping the exhaust brings it up to 45.

#6 and #8 got 100 lbs in and were at 30 lbs regardless of what I did with the spring.

There is some coming out the exhaust on 2 and 4. Enough to feel it. I can stop it with my hand but it does not change the gauge.
Nothing comes out the intake. I tapped an intake spring and it pushed the towels I have in the intake out immediately.
Its mostly coming out into the crankcase. The MMO drips out when I put air to it.

Last edited by Ferris Bueller; Sat Apr 30 2022 11:51 AM.

1966 C-10 Step Side. 283, 4spd, 3.73 gear. 60K miles prior to restoration. 507 Paint Code. Currently in 10,000 pieces.
Transmission is done! Rear Suspension is done! Wheels are done! Bed bodywork is done! Soon to order a 383 crate.



Joined: Nov 2021
Posts: 307
F
'Bolter
Your numbers are so high and in all cylinders as to be very suspicious. I wouldn't go off hog wild right away. A motor would not run good with those numbers, maybe not run at all. (compression is one of the criteria for a motor to run). It sounds like it was running fairly good? It my mind it was a testing problem until I hear the story.[/quote]

I hope I screwed up with the test, but I don't think so. I agree with your thoughts. It idled and ran so well just putting fuel in the bowl I am a little baffled.


1966 C-10 Step Side. 283, 4spd, 3.73 gear. 60K miles prior to restoration. 507 Paint Code. Currently in 10,000 pieces.
Transmission is done! Rear Suspension is done! Wheels are done! Bed bodywork is done! Soon to order a 383 crate.



Joined: Nov 2021
Posts: 307
F
'Bolter
Originally Posted by Hotrod Lincoln
Were you using an air regulator set to 100 PSI with no flow through the hose as a baseline?
Jerry

Not quite. But I will redo the test this morning like you just said. I hooked it up, and turned my air on. Adjusted the regulator on the gauge to 100. not much different, but different enough as another reason to redo the test.


1966 C-10 Step Side. 283, 4spd, 3.73 gear. 60K miles prior to restoration. 507 Paint Code. Currently in 10,000 pieces.
Transmission is done! Rear Suspension is done! Wheels are done! Bed bodywork is done! Soon to order a 383 crate.



Joined: Feb 2000
Posts: 4,464
J
'Bolter
Can you get it running again? If so, let it run while you adjust the rpm up and down and get the block hot. Then do a test on it. It could be a simple matter of stuck rings or dirty valve seats. While its running, hold the rpm up and dribble water down the carburetor, it will steam clean the cylinders. With no load on the flywheel, you start and run an engine setting in tire or on blocks of wood.

Joined: Nov 2021
Posts: 307
F
'Bolter
Ok. Just got done redoing the test.

Giving numbers with 100psi to start and then 100 while testing

Cyl number, PSI in start, PSI in while testing, PSI in cyl

1 100 Dropped to 90 while testing 65 Nothing out int or exh. All out into CC
1 100 78
2 100 Dropped to 90 while testing 50 Exh and CC leaking
2 100 55
3 100 Dropped to 92 while testing 70 Nothing out int or exh. All out into CC
3 100 75
4 100 Dropped to 90 while testing 45 Exh and CC leaking
4 100 55
5 100 Dropped to 92 while testing 60 Nothing out int or exh. All out into CC
5 100 65
6 100 Dropped to 90 while testing 45 Nothing out int or exh. All out into CC
6 100 30
7 100 Dropped to 90 while testing 30 Nothing out int or exh. All out into CC
7 100 30
8 100 Dropped to 90 while testing 45 Nothing out int or exh. All out into CC
8 100 50

I had it all spaced nicely for ease of reading, but it took my spacing away? None of this is looking good.

Last edited by Ferris Bueller; Sat Apr 30 2022 01:44 PM.

1966 C-10 Step Side. 283, 4spd, 3.73 gear. 60K miles prior to restoration. 507 Paint Code. Currently in 10,000 pieces.
Transmission is done! Rear Suspension is done! Wheels are done! Bed bodywork is done! Soon to order a 383 crate.



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