WHERE'S THE "PING" THRESHOLD?
Thread Starter
Drifting
Joined: Sep 1999
Posts: 1,970
Likes: 91
WHERE'S THE "PING" THRESHOLD?
Started the fresh rebuild with the stock 8*. After reading all the timing threads I figured I'd see how high I could go before the pinging started.
Well I'm up to 19* initial, total around 41* in by 2400. No ping, seems to run fine. Something must be wrong. Numbers don't seem right
Taking to a shop for valve adjusting in the morning. (can't seem to get the right side to stop clacking). See if he has an opinion.
Well I'm up to 19* initial, total around 41* in by 2400. No ping, seems to run fine. Something must be wrong. Numbers don't seem right
Taking to a shop for valve adjusting in the morning. (can't seem to get the right side to stop clacking). See if he has an opinion.
Burning Brakes
Joined: Jul 2000
Posts: 1,162
Likes: 2
From: Beaverton, OR
How are you testing for knocking/pinging? I normally find a hill and accelerate very hard (WOT if possible) up the hill from a rolling start of about 20MPH or more. A freeway is a good place for the test, get on the onramp and floor it. . .
I would expect knocking with that much advance myself with most engines. . .
I would expect knocking with that much advance myself with most engines. . .
Safety Car
Joined: Feb 1999
Posts: 3,631
Likes: 14
From: Fountain Hills AZ
Originally Posted by dennis
Started the fresh rebuild with the stock 8*. After reading all the timing threads I figured I'd see how high I could go before the pinging started.
Well I'm up to 19* initial, total around 41* in by 2400. No ping, seems to run fine. Something must be wrong. Numbers don't seem right
Taking to a shop for valve adjusting in the morning. (can't seem to get the right side to stop clacking). See if he has an opinion.
Well I'm up to 19* initial, total around 41* in by 2400. No ping, seems to run fine. Something must be wrong. Numbers don't seem right
Taking to a shop for valve adjusting in the morning. (can't seem to get the right side to stop clacking). See if he has an opinion.
Thread Starter
Drifting
Joined: Sep 1999
Posts: 1,970
Likes: 91
Should mention there is no vacuum advance until 3rd and 4th gear. Dam TCS system. Thinking of getting rid of it and going 4* with vac advance like the 69 version.
Gone up hills, high way on/ off ramps. Mechanics place is up a long hill. Check on that in the morning. Backing off to 16* though.
Its a 70 350 HP 11to1. Stock with comp roller tip 1:52 to 1, MSD dist & 6al box. Compression is 160 in all cylinders. Vacuum is 10-11 steady. (*always was low).Funny thing is, before this rebuild, my compression was up around 190. Wouldn't run on anything but 100LL av fuel without pinging like crazy. Think my intake oil leak may be back too. All this with about 50 miles on the engine! Not to mention the carb won't idle until it warms up. Thats what I get for doing a clutch and not resisting the "while I'm at it's". Sure wish I had that last NJ Lars spot.
Tempted to pull it and build that 383 out of the 4 bolt block I kept from my pick up.
Gone up hills, high way on/ off ramps. Mechanics place is up a long hill. Check on that in the morning. Backing off to 16* though.
Its a 70 350 HP 11to1. Stock with comp roller tip 1:52 to 1, MSD dist & 6al box. Compression is 160 in all cylinders. Vacuum is 10-11 steady. (*always was low).Funny thing is, before this rebuild, my compression was up around 190. Wouldn't run on anything but 100LL av fuel without pinging like crazy. Think my intake oil leak may be back too. All this with about 50 miles on the engine! Not to mention the carb won't idle until it warms up. Thats what I get for doing a clutch and not resisting the "while I'm at it's". Sure wish I had that last NJ Lars spot.
Tempted to pull it and build that 383 out of the 4 bolt block I kept from my pick up.
Burning Brakes
Joined: Jul 2000
Posts: 1,162
Likes: 2
From: Beaverton, OR
Who did build your engine??? That compression also sounds a little on the low side to me, although I don't really know what it should be as that always seems somewhat like a black-magic kind of number. My 10:1 383 is about 195 psi on most cylinders (bit over on some, bit under on one).
Could also be the balancer slipped, that's easy enough to check for and I would probably check that first. Lars wrote a good paper about finding TDC and checking that your balancer hasn't slipped once you've found it (assuming you don't already know a good technique to find exact TDC without using the balancer mark).
-dath
Pro
Joined: Jan 2004
Posts: 535
Likes: 1
From: Darwin, Australia NT
Originally Posted by dennis
Compression is 160 in all cylinders. Funny thing is, before this rebuild, my compression was up around 190. Wouldn't run on anything but 100LL av fuel without pinging like crazy.
Thread Starter
Drifting
Joined: Sep 1999
Posts: 1,970
Likes: 91
Lot of good advice.
Machine work was done by a pro engine builder. My assemblt.(Oh-Oh) No I think I've done enough engines, but I could have overlooked something.
I checked the timing mark with number 1 piston at TDC. The damper is right on. All parts are the same.
What would cause the drop in dynamic compression? I thought the oiled plugs were from an intake issue, but maybe its the rings.
Looks like a leakdown test. Getting out the timing wheel to check the cam timing. Hate to tear the thing down right now.
With all the little problems I can't understand why it runs so well.
Machine work was done by a pro engine builder. My assemblt.(Oh-Oh) No I think I've done enough engines, but I could have overlooked something.
I checked the timing mark with number 1 piston at TDC. The damper is right on. All parts are the same.
What would cause the drop in dynamic compression? I thought the oiled plugs were from an intake issue, but maybe its the rings.
Looks like a leakdown test. Getting out the timing wheel to check the cam timing. Hate to tear the thing down right now.
With all the little problems I can't understand why it runs so well.
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Pro
Joined: Dec 2002
Posts: 560
Likes: 1
From: Mooresville NC
If I read your comments correctly above, this seems like a fresh engine rebuild. If the cylinders were honed, I wouldn't expect the rings to set in for a couple of thousand miles. Maybe a little less if moly rings were installed and the correct honing stones were used. Also if you chnaged the cam to a different one used before, you may see a compression test difference.
Good Luck
Good Luck
Drifting
Joined: Nov 2001
Posts: 1,469
Likes: 6
From: 68 427 4.11s Roadster
I think your vacuum and idle will change later. Not sure but it may be your low vacuum is allowing this large advance, that and an artificaly low compression.
Might as well set normal and wait for breakin to be over. Then alot of the funnies will be gone.
Thread Starter
Drifting
Joined: Sep 1999
Posts: 1,970
Likes: 91
Originally Posted by Techno
I think your vacuum and idle will change later. Not sure but it may be your low vacuum is allowing this large advance, that and an artificaly low compression.
Might as well set normal and wait for breakin to be over. Then alot of the funnies will be gone.