1971 383 red headers
Thread Starter
Safety Car
Joined: Jan 2008
Posts: 3,795
Likes: 435
From: Aarhus, Denmark
1971 383 red headers
Hi,
In our garage we have a 1971 Corvette that after 2 min in idle, are getting red headers.
The car setup is:
383 with trick flow alu kit, roller, alu intake, Holley EFI, 1 5/8" SS headers, TH400
HEI and new chain/gear set, push rods 7.3"
We startet the car after a new chain set with 14 degrees timing, headers got red, then 10 degrees, headers got red, now 5 degrees, and still red headers. (after 2 min)
The engine starts VERY FAST with 5 degrees.
Any idea what our issue is?
Thanks,
John
In our garage we have a 1971 Corvette that after 2 min in idle, are getting red headers.
The car setup is:
383 with trick flow alu kit, roller, alu intake, Holley EFI, 1 5/8" SS headers, TH400
HEI and new chain/gear set, push rods 7.3"
We startet the car after a new chain set with 14 degrees timing, headers got red, then 10 degrees, headers got red, now 5 degrees, and still red headers. (after 2 min)
The engine starts VERY FAST with 5 degrees.
Any idea what our issue is?
Thanks,
John
Race Director
Joined: Mar 2017
Posts: 11,949
Likes: 4,507
From: Virginia
The more you retard the timing, the hotter it gets!
I guess this is news to you.
Advance the timing, such that the max mechanical advance is 36 degrees or so, and make sure you are using a proper vacuum advance can. Between idle and vac, you will likely have 25 to degrees at idle, and not cook your headers.
Email @lars to get a copy of his timing papers, and distributor setup papers.
I guess this is news to you.
Advance the timing, such that the max mechanical advance is 36 degrees or so, and make sure you are using a proper vacuum advance can. Between idle and vac, you will likely have 25 to degrees at idle, and not cook your headers.
Email @lars to get a copy of his timing papers, and distributor setup papers.
Race Director
Joined: Nov 2006
Posts: 13,229
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From: Sunshine Coast, Queensland, Australia
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Cruise-In VIII Veteran
Idle timing should be around 18 degrees, PLUS vacuum advance timing of another 12 degrees or so.
retarding the timing will definitely make heat!
your going the wrong way with your timing!
retarding the timing will definitely make heat!
your going the wrong way with your timing!
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Have you checked to see if the heat riser valve on the RH side is stuck CLOSED. If so, RH exhaust manifold will get super hot and gasses will try to flow under the carb to the LH side.
If that's not the problem, you have a SERIOUS issue with retarded ignition timing (ie, no vacuum advance at idle).
If that's not the problem, you have a SERIOUS issue with retarded ignition timing (ie, no vacuum advance at idle).
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
c3 dk,
My money is on one big clue:
New Timing Chain Set installed.
You installed it a notch retarded. Its firing closer to the exhaust stroke than the compression stroke.
Sorry, but you need to check the crank degrees position. And may have to do the timing chain crank & cam sprockets alignment over again.
Another slight possibility is, you set the valve lash way too tight and it's firing out the open exhaust valves. However, the Intake valves would be too tight also. Popping up through the carb?
My money is on one big clue:
New Timing Chain Set installed.
You installed it a notch retarded. Its firing closer to the exhaust stroke than the compression stroke.
Sorry, but you need to check the crank degrees position. And may have to do the timing chain crank & cam sprockets alignment over again.
Another slight possibility is, you set the valve lash way too tight and it's firing out the open exhaust valves. However, the Intake valves would be too tight also. Popping up through the carb?
Last edited by HeadsU.P.; Apr 11, 2025 at 07:47 PM.
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