67 Tripower jetting

[c4c5specialist]

Hi there,

Looking for the ACCURATE jet number for the main circuit on the center carb.

I have 66s on this one for both sides and I get massive spark knock and AF ratio is very lean.

Carbs are completely clean and correctly set per service manual guidelines. Ignition timing is correct both static, vacuum and mechanical advance.

Intake manifold gaskets are being done at the same time.


Allthebest, c4c5

 

[Hib Halverson]

Before you change jetting, make sure the power enrichment circuit is working properly. Check the power valve and the power valve channel. If that circuit is not working, you can have the proper jets but the engine will detonate and the engine will be lean.

 

[JohnZ]

Original factory jetting for the center carb was #64's for the 435hp, and #62's for the 400hp.

If you haven't done so already, it'll run a lot better, have a more stable idle, better throttle response, improved idle/low-speed cooling, and fuel economy if you relocate the distributor vacuum line from the original "ported" vacuum nipple in the base of the center carb to the hose from the front of the center carb base to the choke pull-off diaphragm, which is a full manifold vacuum source. Cap the original nipple and use a tee in the choke pull-off hose.

 

[Hib Halverson]

I agree with what JohnZ says about going from ported to manifold vacuum. As for the engine running lean, again, check the power enrichment circuit as, based on JohnZ's factory jetting and that you say the center carb now has 66es in it, you should be running anything but lean.

Make sure some moron hasn't replaced the power valve with a plug. If the valve is there, make sure its the correct value and make sure the valve is not leaking and that the power valve channel is free of debris and has no leaks.

 

[c4c5specialist]

HI there,

The power valve was there, not ruptured and the channel clean.

64, ok, so that means this HAS been changed, to be RICHER????!!!!!!!

This is an NCRS, BG car, so everything is OEM.

OK< now, my next concern is that this is something that even using my 5 gas analyzer, no matter how I changed the idle mixture, it was lean.

I will now looking for the jet charts for this. But the powervalve value eludes me, I see NO values on the valve itself, or the replacement in the overhaul kit.

Thank you in advance, I love learning new stuff.

Allthebest, c4c5

 

[jims427400]

JohnZ,
I'd like to try your vacuum line idea on both of my tripowers. Do you have a diagram or a picture of how you routed your lines.
Jim

 

[JohnZ]

JohnZ,
I'd like to try your vacuum line idea on both of my tripowers. Do you have a diagram or a picture of how you routed your lines.
Jim

It only takes about two minutes - all you need is a rubber cap and a plastic vacuum hose tee. As shown in the photos below, just cap the existing nipple on the base of the carb, cut the hose from the front of the carb base to the choke pull-off diaphragm and insert the tee, and connect the line from the vacuum advance to the open nipple on the tee.

This will deploy the vacuum advance at idle, and the idle speed will increase somewhat - just re-adjust the idle rpm, and touch up the idle mixture screws for highest steady vacuum. That's all there is to it.

 

[jims427400]

Thanks John.. looks quite simple. Wonder why they didn't do that from factory. Question.. like your surprised.. I got my mightyvac, to touch up my idle mixture, can I use the Mvac and what vac line would I hook it up to to determine highest steady vacuum? I'll take a guess.. the line coming off the distributor??
thanks JohnZ

 

[c4c5specialist]

Ok, so now, HTH do I tell which power valve I am supposed to have ??????

The one that came out did NOT have any numbers, I have been shipped 3 different types.
Different springs, different hole designs and IM BETTING THE FARM that someone half-assed this overhaul before I got it.

So, I have NO idea what is what on this and there is no documentation that I can find to confirm what I SHOULD have.

Any further ideas ?????

And to answer, this is a 435 horse car.

Allthebest, c4c5

 

[Hib Halverson]

I'm not enough of an expert on the 3x2bbl system to know the proper valve, but determining a power valve selection is fairly easy.

The power enrichment in a carb works very much the same as power enrichment with EFI.

At a given MAP, the power valve opens, allowing more fuel to flow and (hopefully) bringing the air/fuel mix to about 12.5:1.

I'd install a 6.5 power valve and see how the car runs. A 6.5 is what I find in Holley documentaion I have on the 2300 2bbl carb. The Holley PN is 125-65.

 

[NORTY]

Since the engine is still lean, have you replaced ALL the vacuum lines? If any are original, then they are old enough to leak whilst looking "ok."

Manifold crack?
Gaskets?

 

[c4c5specialist]

HI there,

Well, after dye testing the carb airhorn, found a crack, the length of the venturi between the barrel and the plate.

The residual particles clogged up the main circuit completely.

Well, now I have to find a new body. Thats not going to be fun.

Power valve was totally wrong, and noone else at the local carb shops knew what was going on. After making some calls and dye testing the casting, I found the crack.

So, that being said, it should be better. Thanks for the assists on the carb jets
its all fixed now, just gotta get the horn.

Allthebest, c4c5

 

[JohnZ]

Thanks John.. looks quite simple. Wonder why they didn't do that from factory. Question.. like your surprised.. I got my mightyvac, to touch up my idle mixture, can I use the Mvac and what vac line would I hook it up to to determine highest steady vacuum? I'll take a guess.. the line coming off the distributor??
thanks JohnZ

The best spot is the existing vacuum fitting boss that's used for power brakes or Powerglide or A/C, near the rear of the intake on the passenger side. In the photo below, note the square-head plug directly below the vacuum diaphragm on the rear carburetor - that's where the fitting goes; just put a rubber cap on it when you're not using it, or replace the fitting with the plug when you're done tuning.

 

[ratman]

carb vacume lines

switching vacumes works as per johnz big differerance on my 66 L72 ratman

 

[jims427400]

All I can say is wow!!! This car has never run so well. Especially after I switched the vac lines per JohnZ. Big difference.
C4C5 good luck with your tripower and thanks for the thread..
Thanks to you both.

 

[1967L71]

Wheres the pictures lol?

It only takes about two minutes - all you need is a rubber cap and a plastic vacuum hose tee. As shown in the photos below, just cap the existing nipple on the base of the carb, cut the hose from the front of the carb base to the choke pull-off diaphragm and insert the tee, and connect the line from the vacuum advance to the open nipple on the tee.

This will deploy the vacuum advance at idle, and the idle speed will increase somewhat - just re-adjust the idle rpm, and touch up the idle mixture screws for highest steady vacuum. That's all there is to it.

Im having the same issues with mine, Cant figure out the correct vacuum routing to eliminate cooling issues when its idling

 

[JohnZ]

Im having the same issues with mine, Cant figure out the correct vacuum routing to eliminate cooling issues when its idling

Just do as I noted in my earlier posts; connect the distributor vacuum line to a tee inserted in the center carb choke pull-off diaphragm hose, and put a cap on the nipple it's connected to now in the baseplate of the center carburetor. I've done this to about a dozen L-71's.