possible T I issue

[Gary N.]

1966 427 425. starts runs excellent. idles 700-750. drives good, no misfire etc. after temperature exceeds 210-215 engine runs rough and dies at idle. will restart easily but idle now must be 900 -1000. tried new box, harness, coil, distributor pickup

[Leif A.]

Re: possible T I issue

It's the ethanol is today's gasoline which causes fuel percolation at high temps...especially at idle and restart after shutdown.. How long have you owned your '66?? How long have you been experiencing this issue??

[Duke W.]

Re: possible T I issue

...possible fuel percolation. Wire the heat riser open. If it has not already been done, convert the ported vacuum advance to full time. The original 360 12 VAC is okay as long as it works. Otherwise replace it with a B26, assuming it has an OE equivalent cam and not some high overlap hot rod cam. There is a recent thread on this subject and many in the archives.

The above changes should reduce temperatures in city traffic and reduce percolation to a tolerable level.

I recommend 900 idle speed for SHP big blocks, and it should pull about 14" Hg manifold vacuum at that speed.

Duke

[Timothy B.]

Re: possible T I issue

1966 427 425. starts runs excellent. idles 700-750. drives good, no misfire etc. after temperature exceeds 210-215 engine runs rough and dies at idle. will restart easily but idle now must be 900 -1000. tried new box, harness, coil, distributor pickup

Gary,

Sounds like you have eliminated the ignition, be careful with these reproduction coils FWIW.

Try lowering the float level two or three flats and see if that makes a difference.

Make sure the primary and secondary throttle plates are set correctly. The primary should allow no more than a little square of transfer slot exposed (and maybe less). The vacuum secondary can be adjusted by turning the stop screw if you turn the screw over in the base plate. On a vacuum secondary the secondary idle circuit is very rich so you can't open the secondary blades to much.