Need some opinions on where to go from here...

[Dan the man]

A 1977 360. The bores should've been honed regardless, those bores are 48 years old, I wouldn't be surprised if it didn't need to be bored.

 

[mshred]

I would be making sure that #4 spark plug is firing cause that seems suspect to me.

Did you try running starter with valve covers off watching all the rocker arms?

I did back before first fire up, but I will check it again. Thanks for the suggestion!

smelling the oil will help to see if theres any kind of gas there

Oh it stinks man...

Connection issue. Clean the cables, posts, if they're clamp style ..loosen scrape and reclamp them and test again.

Yea that was going to be the plan, but the clamp itself is pretty nasty. Cheap old Chinese one, going to redo it with a better one with a stud for the other connections going to it.

So far every response to questions returns an answer of "I've already done that". Deja vu. lol
I think op will figure it out on his own the answer we all know.
What would have been a really good idea... is to have bore gauged the cylinders. The tapper and oor could be huge , like .007+

No man, not at all...I mean, I have done some of the things suggested, but maybe not looking for or doing it the ways suggested. Someone suggested finding the leak source, possibly head gasket, so I am going to try cylinder 6 again but with water in the block and rad. Someone suggested compression test with oil, never did that, so going to do that...Someone suggested cap and rotor, going to try that too.

Funny, I was actually going to buy a bore gauge when I had this motor apart...but I thought, let me be that guy who just SLAPS it all together from a visual and basic plastigauge checks, since a lot of low budget builds are done that way...and here we are! LOL

 

[mygasser]

i meant to mention before

A 1977 360. The bores should've been honed regardless, those bores are 48 years old, I wouldn't be surprised if it didn't need to be bored.

that was my first thought too dan, but then i noticed he reused the same piston/rings/rods so they're already matched/bedded to their respective bores.
neil.

 

[mshred]

A 1977 360. The bores should've been honed regardless, those bores are 48 years old, I wouldn't be surprised if it didn't need to be bored.

i meant to mention before

that was my first thought too dan, but then i noticed he reused the same piston/rings/rods so they're already matched/bedded to their respective bores.
neil.

Yes, the engine was rebuilt atleast once before I got it because on teardown I found it had .030" over pistons in the bores and the crank turned as well. The crosshatch in the cylinders was still excellent and I wanted to re-use the rings for each cylinder, so that's why I didn't bother with a hone

 

[SRT_DSTRHOLC]

Right now you're playing a guessing game that no one can really figure out without being there. Make a list of the suggested and just start checking it off before your to do list gets longer.

 

[SRT_DSTRHOLC]

Get back to us when you do all the things you can and then we can go from there, but make a list of everything setup and issue wise to further reduce the factors we don't know without being there like timing dizzy setup etc

 

[406dart]

You know cly 4 is missing. You know it has low compression. You even leak down tested it and it confirmed the compression test. Find where the air is going. My guess is thru a valve. Seen it often with speed master heads.

 

[Bewy]

The existing cap already has brass inserts. Make sure the spring leaf on the rotor contacts the carbon button in the cap. It has been making contact because there is some wear of the button, normal wear. You cam measure the resistance of the button. Under 1000 ohms is good; looks to be a performance cap because it is made of Rynite. Result of a new cap will be a lighter wallet...& nothing else.

 

[oldkimmer]

I’m afraid u got a real life lesson on using used rings over. Life is too short to gamble on them. They will be worn to the position they were in. Then when u re install then they will be rotated from the original position Not honing it is not a smart move also. I can’t see anyone being so dam cheap as not to buy new rings and hone the cylinders. Can u elaborate on why u did this? Kim

 

[mshred]

Get back to us when you do all the things you can and then we can go from there, but make a list of everything setup and issue wise to further reduce the factors we don't know without being there like timing dizzy setup etc

This is the plan. The last 2 evenings have been busy. Hoping to work on it tonight and tomorrow and have a clearer picture.

You know cly 4 is missing. You know it has low compression. You even leak down tested it and it confirmed the compression test. Find where the air is going. My guess is thru a valve. Seen it often with speed master heads.

Cylinder 4 had 2% leakdown though...

The existing cap already has brass inserts. Make sure the spring leaf on the rotor contacts the carbon button in the cap. It has been making contact because there is some wear of the button, normal wear. You cam measure the resistance of the button. Under 1000 ohms is good; looks to be a performance cap because it is made of Rynite. Result of a new cap will be a lighter wallet...& nothing else.

I was referring to the phasing of the rotor possibly being off from the wear on the brass inserts. Maybe a lighter wallet, but if there's a crack that I can't see, I don't mind ruling it out.

I’m afraid u got a real life lesson on using used rings over. Life is too short to gamble on them. They will be worn to the position they were in. Then when u re install then they will be rotated from the original position Not honing it is not a smart move also. I can’t see anyone being so dam cheap as not to buy new rings and hone the cylinders. Can u elaborate on why u did this? Kim

I mean, maybe...not even 100% sure it's the rings yet, but that said, LS guys and even some G3 guys will regap rings, put em back in the same hole with no hone, and run them HARD. So it's definitely not uncommon. Maybe I need to have 10psi huffing through it to help them seal right back up lol

Live and learn...I'm not angry, it is what it is

 

[92b]

Regarding the phasing on the cap. If you have a vac advance and it is not hooked up, that could account for the arcing on the side of the terminals. The vacuum can when applied will sweep the rotor across the terminals lining up the rotor with the cap. Hope that makes sense.

Also when retesting the leak down. Try listening more carefully without background noise. Put your ear to the tailpipe and the carburetor and the crankcase. Check adjacent cylinder spark plug holes and the radiator. If still leaking and no source can be found try tapping the top of the valve to dislodge any carbon or foreign material that may be stuck in the seat. Try the oil in the cylinder last. 70% is a lot of leakage. If it is leaking that bad you should be able to source where it is coming from.

 

[SRT_DSTRHOLC]

Regarding the phasing on the cap. If you have a vac advance and it is not hooked up, that could account for the arcing on the side of the terminals. The vacuum can when applied will sweep the rotor across the terminals lining up the rotor with the cap. Hope that makes sense.

Also when retesting the leak down. Try listening more carefully without background noise. Put your ear to the tailpipe and the carburetor and the crankcase. Check adjacent cylinder spark plug holes and the radiator. If still leaking and no source can be found try tapping the top of the valve to dislodge any carbon or foreign material that may be stuck in the seat. Try the oil in the cylinder last. 70% is a lot of leakage. If it is leaking that bad you should be able to source where it is coming from.

Do you think grabbing an inexpensive smoke machine would help? Filling the carb with smoke and then cylinder to see where it's escaping?

 

[oldkimmer]

This is the plan. The last 2 evenings have been busy. Hoping to work on it tonight and tomorrow and have a clearer picture.

Cylinder 4 had 2% leakdown though...

I was referring to the phasing of the rotor possibly being off from the wear on the brass inserts. Maybe a lighter wallet, but if there's a crack that I can't see, I don't mind ruling it out.

I mean, maybe...not even 100% sure it's the rings yet, but that said, LS guys and even some G3 guys will regap rings, put em back in the same hole with no hone, and run them HARD. So it's definitely not uncommon. Maybe I need to have 10psi huffing through it to help them seal right back up lol

Live and learn...I'm not angry, it is what it is

I wasn’t aware that anyone was installing used rings as I never have and never would. It just seems *** backwards to me. I’m like why go thru all that work and then have to do it over. You never by chance re installed the rings upside down did you?

 

[mshred]

Regarding the phasing on the cap. If you have a vac advance and it is not hooked up, that could account for the arcing on the side of the terminals. The vacuum can when applied will sweep the rotor across the terminals lining up the rotor with the cap. Hope that makes sense.

Also when retesting the leak down. Try listening more carefully without background noise. Put your ear to the tailpipe and the carburetor and the crankcase. Check adjacent cylinder spark plug holes and the radiator. If still leaking and no source can be found try tapping the top of the valve to dislodge any carbon or foreign material that may be stuck in the seat. Try the oil in the cylinder last. 70% is a lot of leakage. If it is leaking that bad you should be able to source where it is coming from.

Ah okay, I had no idea that could be the case regarding the Vacuum advance, and no, it was not hooked up, so that makes sense.

When I did the leak down, the shop door was closed, I had the rear axle on stands so I get under the mufflers with my ear right to them...Had all 4 throttle blades opened with my ear pressed to the throat of the carb...all plugs out, putting my thumb over neighboring spark plug holes, over the dipstick tube...I agree that it is a lot of leakage and found it weird I couldn't find its location. Water in the block and checking the rad will be one more thing for me to check.

Do you think grabbing an inexpensive smoke machine would help? Filling the carb with smoke and then cylinder to see where it's escaping?

Funny you mention that, I was actually thinking about doing that last night. If my current to do list of checks comes up short, im going to jump on amazon and see about that.

I wasn’t aware that anyone was installing used rings as I never have and never would. It just seems *** backwards to me. I’m like why go thru all that work and then have to do it over. You never by chance re installed the rings upside down did you?

I get it, but many wouldn't bat an eye to it if the engine is in good health originally. Rings are definitely installed correctly, I triple checked that, and judging by the fantastic leak down numbers on the other cylinders, I'm even more confident about that.

Hoping to have some clear direction from troubleshooting in the next couple of days.

 

[92b]

Do you think grabbing an inexpensive smoke machine would help? Filling the carb with smoke and then cylinder to see where it's escaping?

Maybe, I haven't ever tried that. I would put the smoke directly in the cylinder with both valves closed just like you would if you were doing a leak down test. But honestly I haven't ever had a cylinder leak at 70% that wasn't obvious where the leak was at. It will be interesting to see what the op finds when he gets to the bottom of this mystery.

 

[furrystump]

Ok, so I had that happen to me with the cap. I had a small flutter around 4000-5000 rpm. Not big, but annoying. Found the cap with the burn marks on the top of the terminal. Ignition is erratic depending on where it arcs upward. You need to lower the rotor in relation to the cap. I sanded the base of the rotor which allowed it to sit lower on the shaft. Stacked tolerances and old tooling and different manufactures.

 

[Spadman]

Sounds like you are like me. Not much time so sometimes you may rush. Any chance the excessive leak down test was the last of the session. If that happened to me I would go back to a good cylinder and repeat the test there to make sure my results were repeatable. I mean air could leak before it got in the cylinder, etc.

 

[mshred]

Alright, so back with an update...

First thing I did while waiting to borrow a good battery (here I was cleaning terminals, meanwhile it was a bad battery that would drop in voltage from 12.5 to 4 in under a minute after taking a charger off of it) was run another leak down test on cylinder number 6 a couple nights ago...As soon as I got it to top dead center, again using my small bore scope, I put the air to it, and it leaked less than 5% like all the other cylinders. So then I backed it up a bit to before TDC and the 70% leak was back....back to TDC and the leak was gone again...a bit past TDC, and it leaked. One more time right back, and all good at least then 5%. So then I added oil to the cylinder just to see what might happen, and readings based on piston position were EXACTLY the same as without the oil, literally made no difference- at TDC all good, just before or after and no bueno. When the leak was at 70% I left the rad cap off and had the cylinder filled for almost 10mins- zero bubbling of water in the rad. No sound out the exhaust, no air out the crankcase, no air out the intake/carb..It just seemed like air kinda at the valves is where the sound was..Also, since it was mentioned, when I did the initial leakdown test, I actually tested each cylinder twice and the numbers all repeated. Only cylinder 6 was the one I had trouble with, but now seems to be alright at TDC.

Today with the good battery in I ran a compression test on the engine, and just like the leakdown, with a completely cold engine. EVERY CYLINDER cranked 155-160psi. When the engine was hot, cylinder 4 was 20psi less, and I could swear the numbers were at 125psi, with cylinder 4 at 100psi, but stupid me, didn't write it down. This is a late 70s 360 with cast flat dish pistons down the hole about .110". With the thin MP head gaskets I'm running and the cylinder head chamber measurements, I'm right at aboit 8.9:1 compression, and with a 230/236 at .050" cam the cold compression numbers seem EXTRA healthy in my opinion. I did not bother to run a compression test with oil in the cylinders since honestly it seemed to me that it cranked awesome for what the build is.

Valve covers were off and I had the wife turning the key for the compression test so I could watch the test gauge and also watch the rockers. To the naked eye, valvetrain appears to be working alright, but really I don't think I'd spot anything unless something was very visibly bad. Lash on all the valves is set equal, and none required more or less adjustment, so that has me hopeful there is no bad lobes on the cam.

Here are my conclusions, and I'd like your opinions on whether you agree or think I should be checking something else...

It would seem to me that with the healthy numbers on the cold compression test, and finally getting cylinder 6 to leak down like the others, that my issue is either ignition related or valvetrain related (like possibly a bent push rod from the holes not being enlarged enough and making contact while it was running, or the contact of the pushrod in the hole hanging it up just enough to not allow the valves to open and close properly). Also thinking it could be a bad valve job or valve seals, since when the car was running the odd bank of cylinders had a lot of smoke out that side of the exhaust. Comparing my cold compression test numbers to what I recall the hot numbers were, it seems maybe because cylinder 4 wasn't firing as evidenced by the white plug, that maybe that's why it was down compared to the other cylinders that were all hot and seemed to be firing. I'm thinking the bottom end is sealing, and so are my head gaskets, and the bad leakdown on cylinder 6 was maybe carbon on the valves or just enough valve opening with the piston not perfectly at TDC to create a leak. Maybe the bottom end can stay together, but yanking the heads at this point to further enlarge the pushrod holes on all of them, as well as checking the valve seals and valve job, is a good idea? Gives me a chance to inspect the cam lobes as well to check if they wore in with lifters properly.

Interested to hear what you guys think. Appreciate the insight and patience reading my short saga here to help me out. Long day, pretty sure I'm not forgetting anything lol

 

[mshred]

Sounds like you are like me. Not much time so sometimes you may rush. Any chance the excessive leak down test was the last of the session. If that happened to me I would go back to a good cylinder and repeat the test there to make sure my results were repeatable. I mean air could leak before it got in the cylinder, etc.

You're right, I don't have a lot of time these days...BUT I actually won't touch the car unless I know I can carve out the time I need as I don't want to rush anything. When I did the leakdown the first time, I was out there for a couple hours running all the cylinders twice, and cylinder 6 probably 5 or 6 times....longest leakdown testing ever lol

 

[SRT_DSTRHOLC]

Try testing the plug wires and swapping those cylinders in question plugs to two other cylinders.

 

[Mean416]

I've had bad olug wires cause problems. Wires that by every Visual Indicator looked fine. Definitely worth trying new set.

 

[CRUZE 418]

The pushrods that you think are touching will have witness marks on them. Have you pulled the rocker shafts up to look at them? Having said that, don't think that is your problem. Rings can move around, you would probably need more run time for them to find their home. Again, they are not your problem. Keep looking at your ignition.

 

[mshred]

Try testing the plug wires and swapping those cylinders in question plugs to two other cylinders.

I've had bad olug wires cause problems. Wires that by every Visual Indicator looked fine. Definitely worth trying new set.

The pushrods that you think are touching will have witness marks on them. Have you pulled the rocker shafts up to look at them? Having said that, don't think that is your problem. Rings can move around, you would probably need more run time for them to find their home. Again, they are not your problem. Keep looking at your ignition.

I have decided I'm going to try and fire it up again, moving some plug wires and plugs around. Pushrods do have witness marks on them, unfortunately. That's how I know, because on the stand turning the motor over there appears to be clearance, but clearly after running the motor, there is not. All the test so far point to a healthy bottom end and head gaskets, so hopefully it's just ignition related, and something silly like wires or plugs. I'm running nice firecore wires from my old indy headed stroker, but I have another set I can try as well

 

[SRT_DSTRHOLC]

Report back

 

[B3422w5]

I've had bad olug wires cause problems. Wires that by every Visual Indicator looked fine. Definitely worth trying new set.

I just chased what ended up being a bad plug wire for couple weeks.
4 or 5 year old MSD wires that looked fine.
Swapped them out, high rpm miss gone.