1965 421 Tri-power
 

What is the easiest way to tell if my tri-power is running rich at idle. I have been suspecting it is for a while now. I do smell something odd while at idle. If it is do I correct by adjusting the idle screws or do I need to change out something else.
THe tripower was restored several years ago by Mike Wasson. I put it in a 421 that Butler Performance bored and stroked to 453. They put a comp roller cam in and they got 491 HP out of it.

What do the plugs look like? What does the oil smell like? Are the plugs black? Does the oil smell like gas?

I am not sure. I will pull a plug tomorrow. I will pull the dip stick and see if the oil smells like gas.

Also check the oil level to see if it has gone up.

Talk to Mike he will set you straight.

Does the engine idle smoothly? If do, I'd leave it alone. You may improve things by tweaking the idle mixture screws, but the odor will not go away. I have never seen a carbureted engine that didn't smell rich at idle, two barrel, four barrel, or Tripower.

If anyone disagrees or has suggestions, please post.

If the idle circuit is not adjusted/modified for the current intake vacuum signal you WILL have the throttle blades opened too far.
This causes the dreaded nozzle drip from main circuit and engine run-on at shutoff.
The nozzle drip is fuel that goes right thru the combustion chamber un-ignited and instead dumped out the exhaust tearing eyes and makes your clothes stink for a weak if standing behind the car at idle.
In this scenario the "condition" of the carb is actually lean, not rich.

Kenth,

You're right about the idle circuit needing to be tailored to the CID, cam, compression, etc. so there is the correct amount of fuel/air mixture delivered at idle. I do this with every Tripower I restore.

However, even at optimum settings and orifice sizes, our carbureted engines emit odor at idle. Modern fuel injected cars do, too, but not as noticeable as carbureted engines.

Best tip--run the engine with the garage doors open or run it outside! No problem!

Agree, What is your idle vacuum at with the roller camshaft?

If it is different from the factory vacuum setting you may need to talk to Dick B about trimming the Power Piston Spring length.

Tom V.

Yep, those guys are correct. Cam changes vacuum parameters. Again, read the plugs. They will tell a lot.

Hi guys, sorry for not responding before now but I have been out of pocket for several days. I did pull a plug and it is all black. I am going to try and attach a picture.

I do have run on when I shut down especially when engine is hot. Engine idles at about 800 RPM. It is a little rough but I thought that was from the performance cam.
I believe my vacuum at idle is around 10”. It was low enough that I had to add a vacuum pump for my power brakes. Power brakes were borderline. I was told by Butler that the vacuum would be borderline for power brakes.
Please advise what I should do next.
Thanks for your help.

10" of vacuum tells me you need the venturi cluster modified and the power valve spring trimmed by about 5 turns. I can do that for you if you send the cluster or carb to me. Or, you can do it yourself if you have a .039" (or about) drill and a .052" drill (or about), a sidecutters, and a .072" drill (or about). I can coach you over the phone or text. Call or text 920-450-1040.

Mike Wasson, restored my Tripower and set it for a 421 performance cam. I will get the modification he made this evening and post them.

Ok what I found:
Jets are 74 - 64 - 74
Idle mixture orffice = .076
Idle mixture tubes = .038
He didn’t say anything about cutting the spring.
Paper work did say for a 421 aggressive roller cam.

I will put vacuum gage on tomorrow and see exactly what the vacuum is. It may have been 12” now that I think about it.

10 or 12 is low compared to the upper teens with a closer to stock cam. Fixing the idle circuit will eliminate nozzle drip and keep your plugs from fouling. Also need to know what main jets are in the center carb.

Mike Wasson restored it with the following:
Jets are 74 - 64 - 74
Idle mixture orffice = .076
Idle mixture tubes = .038
Is this what you are asking for?

We need to know the idle downchannel restrictions too.
Standard for 389 is around .046" and for a 421 around .049".
For your engine with hotter than standard camshaft, i would suggest .052"-.055" idle channel restrictions. Start small.
Jets, idle tubes, needle holes are fine.

Yes. I would begin with .052" idle bypass restrictors.

Just keep in mind---A cam that has more overlap and lift than stock will result in odor at idle. More unburned fuel is wasted due to the later intake closing. We try to minimize this with proper idle circuit flow.