340 Chugging instead of Reving

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1969GTS340 said:
I just brought it to TDC again with my finger over the spark plug hole. Felt the compression and watched as both valves closed and rotor is in #1 position. From there, I rotated the crank 180* and the exhaust was opening, intake was closed, per the picture I posted earlier.
Click to expand...

You need to rotate crank 360* after TDC compression stroke to get overlap, or look to #6 for equal overlap when #1 at TDC compression .
 
inertia said:
You need to rotate crank 360* after TDC compression stroke to get overlap, or look to #6 for equal overlap when #1 at TDC compression .
Click to expand...

Now that's releasing to hear because I continued to rotate 360* and both valves were open.
 
1969GTS340 said:
I just brought it to TDC again with my finger over the spark plug hole. Felt the compression and watched as both valves closed and rotor is in #1 position. From there, I rotated the crank 180* and the exhaust was opening, intake was closed, per the picture I posted earlier.
Click to expand...
Both valves do NOT close on overlap. Furthermore; the Exhaust is CLOSING while the Intake is OPENING.

If in fact the piston is at TDC inside the cylinder, with your valves that far out, I doubt it would start. But if it did, it would take a lotta lotta throttle to keep it running.

Have you done a compression test yet?

Here is something you can try;
With the #1piston on the overlap cycle; rotate the crank to where both valves are similarly far opened, the exhaust closing while the intake is just opening. Put a straightedge across the spring retainers, and jockey the crank back and forth until the straightedge is touching the two retainers in a total of four places, thus putting them at the same height. Now you are doggone close to Split overlap.
Now go read your timing tape.
you should be seeing from 4* retarded to 8* advanced. Anything outside that range is not gonna run right, especially at Idle and at LOW-rpm.
Here's another clue;
If it idles at ~700 with the throttles in the normal relationship to the Transfer slot, then I highly doubt that you have a cam-timing issue.
 
AJ/FormS said:
Both valves do NOT close on overlap. Furthermore; the Exhaust is CLOSING while the Intake is OPENING.

If in fact the piston is at TDC inside the cylinder, with your valves that far out, I doubt it would start. But if it did, it would take a lotta lotta throttle to keep it running.

Have you done a compression test yet?

Here is something you can try;
With the #1piston on the overlap cycle; rotate the crank to where both valves are similarly far opened, the exhaust closing while the intake is just opening. Put a straightedge across the spring retainers, and jockey the crank back and forth until the straightedge is touching the two retainers in a total of four places, thus putting them at the same height. Now you are doggone close to Split overlap.
Now go read your timing tape.
you should be seeing from 4* retarded to 8* advanced. Anything outside that range is not gonna run right, especially at Idle and at LOW-rpm.
Here's another clue;
If it idles at ~700 with the throttles in the normal relationship to the Transfer slot, then I highly doubt that you have a cam-timing issue.
Click to expand...

I can definitely measure the lift of both valves at that point. I was considering to use dial indicators to be more exact.
One correction to all of this is.. I was looking at overlap with the crank 180* from TDC. I understand that was in error, and it should be 360*. When I did that, both valves were lifted.
 
1969GTS340 said:
I can definitely measure the lift of both valves at that point. I was considering to use dial indicators to be more exact.
One correction to all of this is.. I was looking at overlap with the crank 180* from TDC. I understand that was in error, and it should be 360*. When I did that, both valves were lifted.
Click to expand...


Yeah, my bad. I said 180 degrees and I should have said 360. If both valves are off the seat at overlap it’s straight up.

If the timing light doesn’t quit blinking when you’re using it, it’s not the timing light.

The Mallory stuff is far less sensitive to timing lights than the MSD **** is.
 
Rat Bastid said:
Yeah, my bad. I said 180 degrees and I should have said 360. If both valves are off the seat at overlap it’s straight up.

If the timing light doesn’t quit blinking when you’re using it, it’s not the timing light.

The Mallory stuff is far less sensitive to timing lights than the MSD **** is.
Click to expand...

Not a problem on the deg. I learned more by doing it this way so it's still a win to me.

It's sounding more and more like things are pointing to ignition now.
 
If you think it’s ignition, you want to contact this guy and have him look at it for you. He is the guy who ran the R&D for Mallory for all the digital boxes. He’s retired now but he still does repairs for a decent price.

I don’t have any 685 boxes laying around or I’d send you one so you could test it.

[email protected]

Send Dave an email and he will hook you up.
 
I maintain your spark plugs are telling you it looks like one plane of the manifold is sucking oil, with probable vacuum leak.
The other runner, not so much.
That oil is coming from somewhere .
Perhaps put a vacuum guages on it .
My mentor had me read EVERY spark plug I took out, prob nearing a thousand.
They always tell a story .
Hope it helps
 
inertia said:
I maintain your spark plugs are telling you it looks like one plane of the manifold is sucking oil, with probable vacuum leak.
The other runner, not so much.
Perhaps put a vacuum guages on it .
My mentor had me read EVERY spark plug I took out, prob a thousand
They always tell a story .
Hope it helps
Click to expand...


Good mentor.
 
inertia said:
I maintain your spark plugs are telling you it looks like one plane of the manifold is sucking oil, with probable vacuum leak.
The other runner, not so much.
Perhaps put a vacuum guages on it .
My mentor had me read EVERY spark plug I took out, prob a thousand.
They always tell a story .
Hope it helps
Click to expand...

That does help and also reminds be that during initial start up, it started hard and wouldn't idle. Being a fresh build, I did t want to run it long under that condition but it was long enough to find a vacuum leak on both sides of the intake. When I replaced the gaskets I discovered that I had used LA intake gaskets and I should have used Magnum. There was just enough difference and more meat to seal them better. That partly answers to why the plugs look like that. I think I'll buy a new set so I have a fresh look at them. Also, I did a.vacuum check while adjust the carb and it appears good now. Pulling a steady 12 lbs which I thought was good with this cam.
 
Just for grins and giggles, put some new plugs in it, probably solve problem for a short while, then read the plugs again .
They may tell a different story .
If not, my asshole's sucking wind .


EDIT
 
Rat Bastid said:
If you think it’s ignition, you want to contact this guy and have him look at it for you. He is the guy who ran the R&D for Mallory for all the digital boxes. He’s retired now but he still does repairs for a decent price.

I don’t have any 685 boxes laying around or I’d send you one so you could test it.

[email protected]

Send Dave an email and he will hook you up.
Click to expand...

I really appreciate your passing that connection for Dave to me. I'll put everything back together and a fresh set of plugs
inertia said:
Just for grins and giggles, put some new plugs in it, probably solve problem for a short while, then read the plugs again .
They may tell a different story .
If not, my asshole's sucking wind .


EDIT
Click to expand...

Hahahaha..Hahaha.

Would you be able to recommend a plug that might help put this engine back on track? I don't think any of us want your asshole sucking wind lol
 
Ok so now we kinda know your cam timing is close. Have you tried locking out the distributor at some arbitrary number like 32 (because it will start, run, drive and be perfectly happy there for a test) to eliminate any kind of advance problem?
 
[1] Plugs should be NGK 5 heat range. Colder will foul like you have now.
[2] Unless the carb has been adjusted, I would expect a considerable amount of transfer slot showing below the pri throttle blades at idle....unless bypass air has been added. Too much slot showing causes a rich condition......& plug fouling.
 
inertia said:
I maintain your spark plugs are telling you it looks like one plane of the manifold is sucking oil, with probable vacuum leak.
The other runner, not so much.
That oil is coming from somewhere .
Perhaps put a vacuum guages on it .
My mentor had me read EVERY spark plug I took out, prob nearing a thousand.
They always tell a story .
Hope it helps
Click to expand...

THIS^^ I would also do a cylinder compression test.
 
TT5.9mag said:
Ok so now we kinda know your cam timing is close. Have you tried locking out the distributor at some arbitrary number like 32 (because it will start, run, drive and be perfectly happy there for a test) to eliminate any kind of advance problem?
Click to expand...

Later today I expect to have time to work on it again. Locking out the distributor seems to be a popular suggestion and I agree, it will remove another variable of the curve coming into effect. I have never locked a distributor before but when I disassembled it to set the mechanical advance, I see there are two set screws on the outer housing that seem to be used for locking the position. Since the current mechanical advance is set at 24, do I need to change that internally to 32, then lock it? Or can the lock screws be turned in and adjust the dist to 32 with a timing light.
 
Bewy said:
[1] Plugs should be NGK 5 heat range. Colder will foul like you have now.
[2] Unless the carb has been adjusted, I would expect a considerable amount of transfer slot showing below the pri throttle blades at idle....unless bypass air has been added. Too much slot showing causes a rich condition......& plug fouling.
Click to expand...

Thank you for the plug rrecommendation. I started with an Autolite plug that I found recommended with the Magnum heads.

2- I'll nend to ask my carb builder buddy the questions regarding the carb. He rebuilt it when I bought it used and made adjustments during this time of searching for why the engine was acting this way. He's been building Holleys for late modle and modified asphalt cars for 20+ years. Luckily I've known him since 5th grade so he comes as a.bargin lol
 
1969GTS340 said:
Thank you for the plug rrecommendation. I started with an Autolite plug that I found recommended with the Magnum heads.

2- I'll nend to ask my carb builder buddy the questions regarding the carb. He rebuilt it when I bought it used and made adjustments during this time of searching for why the engine was acting this way. He's been building Holleys for late modle and modified asphalt cars for 20+ years. Luckily I've known him since 5th grade so he comes as a.bargin lol
Click to expand...
Here this my help.
FBO Ignition - Home of the HRR688 - Spark Plug Reading
 
1969GTS340 said:
Later today I expect to have time to work on it again. Locking out the distributor seems to be a popular suggestion and I agree, it will remove another variable of the curve coming into effect. I have never locked a distributor before but when I disassembled it to set the mechanical advance, I see there are two set screws on the outer housing that seem to be used for locking the position. Since the current mechanical advance is set at 24, do I need to change that internally to 32, then lock it? Or can the lock screws be turned in and adjust the dist to 32 with a timing light.
Click to expand...


You dont have to lock it out if you don’t want to. Just turn a bunch of initial into it and see what happens. You can even drive but BE CAREFUL. You will also be adding to the total.

That way you don’t have to pull the distributor or anything. I like easy when I’m sorting stuff out and leaving the distributor in is easier. And less work.
 
1969GTS340 said:
Later today I expect to have time to work on it again. Locking out the distributor seems to be a popular suggestion and I agree, it will remove another variable of the curve coming into effect. I have never locked a distributor before but when I disassembled it to set the mechanical advance, I see there are two set screws on the outer housing that seem to be used for locking the position. Since the current mechanical advance is set at 24, do I need to change that internally to 32, then lock it? Or can the lock screws be turned in and adjust the dist to 32 with a timing light.
Click to expand...
When you lock it, you dont have to set anything. Just follow the directions Mallory has for locking that distributor. Then stab it and set the timing at 32 with a light. At any engine speed the timing should stay at 32.
 
TT5.9mag said:
When you lock it, you dont have to set anything. Just follow the directions Mallory has for locking that distributor. Then stab it and set the timing at 32 with a light. At any engine speed the timing should stay at 32.
Click to expand...


That’s true. And I forgot, he’s running a 685 box. If he wants to lock it out at 35 or even a bit more he can as that box has a built in start retard that he can activate and adjust. I think up to 20 degrees.
 
Rat Bastid said:
That’s true. And I forgot, he’s running a 685 box. If he wants to lock it out at 35 or even a bit more he can as that box has a built in start retard that he can activate and adjust. I think up to 20 degrees.
Click to expand...
Really it’s just for testing. I like a curve in a street car. But for a race car with a decent converter I dont see why anyone runs a curve. I’m not familiar with the Mallory magnetic pickup distributors though. I’ve only used their optical pickup distributors. @1969GTS340 do you have a part number on that distributor?
 
TT5.9mag said:
Really it’s just for testing. I like a curve in a street car. But for a race car with a decent converter I dont see why anyone runs a curve. I’m not familiar with the Mallory magnetic pickup distributors though. I’ve only used their optical pickup distributors. @1969GTS340 do you have a part number on that distributor?
Click to expand...


I even like a curve for a race engine. For what he’s doing he can lock it out about anywhere about 30 and get some kind of direction.

He’s got a really nice distributor.
 
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