Exhaust manifold temperature variation

Talk about the E-Type Series 1

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Inspec Morse
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Joined: Thu Sep 01, 2016 3:46 pm
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#1 Exhaust manifold temperature variation

Post by Inspec Morse » Wed Apr 28, 2021 12:41 am

My 62 3.8L runs the original HD8’s on stock manifold. No matter what changes I make to carbs, the back three cylinders run around 600F and the front three in the 300 degree range. Back three plugs are carboned along with first cylinder. 2nd and third (from front) no carbon.
Setting jets down from bridge .060” backfired badly and finally smoothed out and pulled stronger at .140” down.
The needles are “U”. I believe stock needles are UM?
Have set all three based on undercut ring and measured to be same length. Butterfly’s were individually set, checked with velocity gage and linkage reattached and synced .
Timing was set with dial back to 32 degrees, vacuum disconnected and full mechanical advance (2500 rpm).
Valves have all been checked as well as compression.
I am at a loss. This does not seem normal and I am afraid 600-700F may be hard on valves.

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MarkRado
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#2 Re: Exhaust manifold temperature variation

Post by MarkRado » Wed Apr 28, 2021 4:37 am

I run mine with 0,042 down the bridge, sounds you have a massive air leak, maybe the brake vacuum tank check valve
https://www.sngbarratt.com/English/#/US ... ge=English
Mark
1963 OTS 880436

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PeterCrespin
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#3 Re: Exhaust manifold temperature variation

Post by PeterCrespin » Thu Apr 29, 2021 7:25 pm

What conditions are you measuring? Idle? Fast idle, medium load, high load?

Where exactly are you measuring?

What are you measuring with and how?

What kind of manifold (cast iron or tubular.

300F is impossibly cold
1E75339 UberLynx D-Type; 1R27190 70 FHC; 1E78478; 2001 Vanden Plas

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