Stuttering/surging

[ossieoz]

!02 HP will lose high speed power if the timing is set over 18 advanced.

It’s going OK at 13 and OK at above 18

So this is weird


1961 Greenbrier, 1962 Rampside and 1964 Monza cab.

[terribleted]

Check the clocking of the distributor. Are you positive it is installed correctly?? If it is not in the correct orientation it is possible that the timing you are reading is not correct.

[ossieoz]

Hmmm 102 should not have a balancer on it. What about improperly clocked distributor?

What do you mean by this? I’m not an expert on all terms... but surely if i can adjust the distributor so it gives me an advance of 13 or 16 and the engine idles at around 550 or 600 then everything is ok with the distributor? Or?

When I advanced above 18, idle went all the way up to around 1000rpm


1961 Greenbrier, 1962 Rampside and 1964 Monza cab.

[ossieoz]

Could it more than likely be just a bad valve spring some where?

Maybe I should go to a 1/2 or 3/4 turns from zero lash (just to see what happens)? Is this a pointless or stupid idea?


1961 Greenbrier, 1962 Rampside and 1964 Monza cab.

[ossieoz]

As you seem to have just proven, the car needs more timing advance. But not just static initial advance, it needs timing advance at slow engine speeds (provided by vacuum advance) and then it transitions to more advance at high engine speeds (as the vacuum advance disengages due to low levels of vacuum at the carburetor vertical spark port at open throttle) with higher RPM — as the centrifugal advance takes over.

"ossieoz" Fri Jun 08, 2018 1:56 pm

Jerry Whitt wrote:
An idea. Try advancing the spark more. Additional timing advance may give better performance. Let us know what happens

Tried this and the 102hp went like a ‘rocket’... probably advanced to at least 30/36 with some testing... is this possible to advance this much and still go well?

However the jolting is still there :(

If the vacuum advance canister is faulty, the diaphragm may not be opening consistently and smoothly in response to carburetor spark port vacuum. This could be caused by a leaky vacuum hose, or a faulty vacuum advance diaphragm mechanism that could be intermittently advancing the timing and then dropping out. If this is happening you may still feel a jerky surge of power as the vacuum advance kicks in and then drops out cyclically even as you dialed in more static initial timing. Try disconnecting and plugging the vacuum advance hose, and see if the jolting disappears. If it does, check the hose for leaks or try replacing the vacuum advance unit.

Just to confirm, your vacuum advance is connected to the spark port (vertical) and not the choke vacuum break port (horizontal)?

I’ve swapped to 3 different vacuum advances and there is no difference in engine response... there’s always judder. When i rev the engine i can see that the vacuum advances seem to work correctly.

All vacuum tubes are in the correct places.


1961 Greenbrier, 1962 Rampside and 1964 Monza cab.

[64powerglide]

Put your timing light on & set it to 18 then adjust your idle back to 550 - 600 RPM. My 62 Monza only went to 16 but the Chevy dealer mechanic said to set it at the right side of the timing marks block & that would be 18.

[Jerry Whitt]

If your crank pulley is only one piece, it is known as a crank pulley. If it has a rubber insert, it is a harmonic balancer.

Please take a good look and let us know.

[ossieoz]

If your crank pulley is only one piece, it is known as a crank pulley. If it has a rubber insert, it is a harmonic balancer.

Please take a good look and let us know.

Jerry, it’s a crank pulley not a harmonic balancer. I have harmonic balancers on both my 110hp. I know all about failing harmonic balancers... while checking out my Monza 110 hp engine (just a few hours after buying it last summer) something flew up and hit me on my forehead... looked down and saw a very wobbly harmonic balancer. Lucky that bit of rubber didn’t take my eye out and the HB didn’t totally fall to bits.

I’ve read in a few places that the 102hp engine didn’t/doesn’t need a harmonic balancer? Even if it was a harmonic balancer that was ‘failing’ wouldn’t my problem just be that i was having problems with setting the the correct timing of 13 BTDC for a 102hp?




1961 Greenbrier, 1962 Rampside and 1964 Monza cab.

[ossieoz]

Put your timing light on & set it to 18 then adjust your idle back to 550 - 600 RPM. My 62 Monza only went to 16 but the Chevy dealer mechanic said to set it at the right side of the timing marks block & that would be 18.

I’ll try that 64powerglide, mine also only shows to 16. So when I said ‘30 plus’ i was only estimating on how far BTDC I could move it.

I think I’ll have to make a video of this and put up a link.


1961 Greenbrier, 1962 Rampside and 1964 Monza cab.

[bbodie52]

I don't believe you ever mentioned performing a cylinder compression test or that you posted the results of all cylinders. Has this ever been done on this engine?

[Yellow]

Jerry Whitt wrote:
An idea. Try advancing the spark more. Additional timing advance may give better performance. Let us know what happens

by ossieoz » Fri Jun 08, 2018 5:56 pm
"Tried this and the 102hp went like a ‘rocket’"

OFF TOPIC: I agree with this!

[ossieoz]

I don't believe you ever mentioned performing a cylinder compression test or that you posted the results of all cylinders. Has this ever been done on this engine?

I had done a compression test after i had just started the 102hp engine... all cylinders were around the 140/145 mark. As it was a totally renovated engine I presumed that after a while it could only get better.

Thanks for the good tip Brad and I haven’t double checked on how compression since that... I’ll do that and get back to you :)


1961 Greenbrier, 1962 Rampside and 1964 Monza cab.

[ossieoz]

I don't believe you ever mentioned performing a cylinder compression test or that you posted the results of all cylinders. Has this ever been done on this engine?

OK... I’ve done a compression test and here’s the results of my 102hp #1-150, #3-152, #5-160, #2-152, #4-168, #6-160

Test was done with all spark plugs out and throttle fully open.

As far as i can see from this result is that it has a little too good compression in #4 but overall within range. Or am I wrong?

This is at least a good result and I don’t have a bad cylinder that’s giving the jult/stutter :)


1961 Greenbrier, 1962 Rampside and 1964 Monza cab.

[ossieoz]

All spark plugs looked good, they all looked ‘even’ and correct


1961 Greenbrier, 1962 Rampside and 1964 Monza cab.

[bbodie52]

Just trying to backtrack a bit to see if anybody missed anything. With compression readings like those it does not appear that mechanical fault is at the root of your troubles.

OK... I’ve done a compression test and here’s the results of my 102hp #1-150, #3-152, #5-160, #2-152, #4-168, #6-160

The overall numbers are consistently higher than the factory standard, but that could be attributed to the differences in test instrument calibration. The readings are all solid and within a maximum variation of 20 psi between cylinders, as specified in the shop manual. (We should all be so lucky!)

Stuttering/surging
Post by ossieoz » Fri Jun 08, 2018 7:57 am

OK, I've put the 102hp engine into my Greenbrier and have had a few problems. Had a weird vacuum leak that is now solved :)

The only problem I have now is a stuttering/juddering/surging when I just cruise at low speed. I’ve near enough checked and changed everything and I’m pretty sure everything is balanced and correct. While accelerating it does seem to have a little miss but nothing consistent and it accelerates well... driving up hills go fine. On the motorway it goes well even at ‘high’ speeds.

Can you define the "weird vacuum leak" and how it was solved?

Also, you didn't happen to stick that Harvey Aluminium flywheel in the Greenbrier, did you?

[ossieoz]

Just trying to backtrack a bit to see if anybody missed anything. With compression readings like those it does not appear that mechanical fault is at the root of your troubles.

OK... I’ve done a compression test and here’s the results of my 102hp #1-150, #3-152, #5-160, #2-152, #4-168, #6-160

The overall numbers are consistently higher than the factory standard, but that could be attributed to the differences in test instrument calibration. The readings are all solid and within a maximum variation of 20 psi between cylinders, as specified in the shop manual. (We should all be so lucky!)

Stuttering/surging
Post by ossieoz » Fri Jun 08, 2018 7:57 am

OK, I've put the 102hp engine into my Greenbrier and have had a few problems. Had a weird vacuum leak that is now solved :)

The only problem I have now is a stuttering/juddering/surging when I just cruise at low speed. I’ve near enough checked and changed everything and I’m pretty sure everything is balanced and correct. While accelerating it does seem to have a little miss but nothing consistent and it accelerates well... driving up hills go fine. On the motorway it goes well even at ‘high’ speeds.

Can you define the "weird vacuum leak" and how it was solved?

Also, you didn't happen to stick that Harvey Aluminium flywheel in the Greenbrier, did you?

‘Weird vacuum leak’ was at the metal tube coming out of the heads that attach to the vacuum balance tube.

Didn’t dare putting the Harvey flywheel in.


1961 Greenbrier, 1962 Rampside and 1964 Monza cab.