[Zimtok]

I have been trying to get my engine to idle at a lower RPM but cant seem to get there without the engine dying.

I have a 421 with an unknown cam.
I have my 66 tripower on it and I can't get it to idle below about 1100rpm without dying.

I also notice that the end carbs have air flow into them with the throttle plates closed. the rear one has more air flow then the front one.
Is it normal to have air flow into the end carbs before they are engaged?


.

[carbking]

You will need to get the end carbs throttle plates to almost seal before you will be able to get a decent idle.

Jon.

[Zimtok]

Originally Posted by carbking

You will need to get the end carbs throttle plates to almost seal before you will be able to get a decent idle.

Jon.

I have checked them and they seem to be sealing fine.
I held the plates up to a light and don't see any light coming through.
Is there any other way the air could be pulled through the carb or around the plates?

I did notice that the throttle plates have a tiny hole in them on the front carb but not on the rear carb.
The extra carbs I have also have these tiny holes.

[Kenth]

If the throttleplates are fully closed and are sealing fine there will be NO airflow past them.
The tiny .029" fixed bypass holes are standard and will NOT cause the symptoms you´re experiencing.
Check for correct flange gaskets?

Also check vacuum signal in intake, both in "N" and "D".

You MAY have a too lean idle circuit for that unknown camshaft?

[Zimtok]

If one of the problems is the idle circuit being too lean how can I rectify this problem?

Can I modify the center carb to have a richer idle circuit?


.

[Zimtok]

I changed the throttle plate assembly and checked the gaskets.
The gaskets are the same as on the front carb, the spare throttle plate assembly has the small holes like the front, when the plates are closed there is no sign of a gap.

But it still is pulling in air.

The front carb seems to be fine.

I'm taking a break and getting some lunch, time to think on it a little.

.

[PRC]

There is a black sealant that can be used on the throttle plates on the end carbs. It has worked well on mine so far. Mike Wasson at pontiactripower.com sells it and there are probably other sources too.

[carbking]

This may help:

http://www.thecarburetorshop.com/Tripowertuning.htm

As to the DAG-213 sealant: If you would like an opinion rendered by a extremely well-respected GM engineer that specialized in Pontiacs, call me.

Jon.

[Zimtok]

Well after my phone conversation with Jon (I learned a lot) I managed to get the center carb to idle down to about 800rpm and stay running.
My manifold vacuum is low because of the cam so I don't think I'll get it any lower. It is currently at 8 on my vacuum gauge at idle.

Kenth was correct that the idle circuit was too lean. Jon explained how to make it richer.
I had to pull the venturi cluster out and enlarge the idle tube orifices to allow more fuel into the mix.

I still need to get the choke working on the center carb and install the front and rear carbs. But once it warms up it runs and idles great on the center carb.

Thanks to all of your suggestions and guidance.


.

[Tom Vaught]

I read thru the "Tri-Power Tuning Tips" by Jon H.

Some very good points made there.

Tom Vaught

[ho421]

Originally Posted by carbking

This may help:

http://www.thecarburetorshop.com/Tripowertuning.htm

As to the DAG-213 sealant: If you would like an opinion rendered by a extremely well-respected GM engineer that specialized in Pontiacs, call me.

Jon.

Jon, thanks for posting this link. informative.