I know this was covered before, just can't find it.

Anyone have details / pics of Tripower full vac advance, link to choke pulloff, etc?

Thanks.

 

Yes. That (and the rest of the carb/choke system) is covered in detail in the Chevrolet Chassis Service Manual, for that model year, in the "Fuel" section. There is no other document that even comes close to the info in that manual.

 

Choke Link:


Vac to pods:


Disclaimer:
The vac Tee is supposed to be a simple 3 port Tee (3906664).
Seen is a 4 port Tee that I use for a vacuum gage during setup etc.

 

Tom,
Have you ever made any adjustments to your diaphragms on your tripowers to allow them to kick in sooner than normal? I've heard that holley makes different tension springs that can be switched out.

 

There are differences of opinion on this one. Some folks like to feel a "kick in the pants" when the outboard carbs open, others say nay. My experience has been that the kick should be "gradual" but hard. I.E.- put you back in the seat but not wrench your neck or spill your Dr Pepper if the carbs are set up as intended. This is a "subjective" sensation so don't quote me on it. I got the most kick in the pants when there was a slight "bog" and then the engine came back to life... so this is not the best situation. Your ET suffers. Consequently, I have always left the springs as the General gave 'em to me and I have been very satisfied with that arrangement.

I believe the idea was that the engine will operate on a 2-Barrel carb when you're putzing around town but when you put your foot in it you get the added fuel... which is essentially "metered" by the amount of air passing through the center carb venturi. That's where the port is that controls the secondaries. So... in theory.. if GM got it right... the engine will only get as much fuel as is honestly needed. The 435HP engines (rectangular port) and the 400HP engines (oval port) all used the same springs in the secondaries.

Having said that, be aware that the BB TriPower housings do not use the same spring as the more common Holley housings. The Holley part number for the TriPower spring is 38R-477 and you can compare that to the smaller, more common spring, for example the R-3367 1966 carb with a 38R-597 spring. You have to use the correct diameter spring for the housing to function properly.

That's a start... general over-view. Perhaps some of our friends here who actually have track time with the TriPower setup will chime in. I have driven mine only on the street.

 

I've just installed the next lighter spring (forget color) in my '69, L-71. Since it is a little snowy out yet, no testing. I am at Denver altitude and that affects the vacuum signal. I have tried the paper clip trick on the secondary linkage and am not sure mine were opening. We'll see.

I've always heard that if you can feel it, they are not operating properly.

Ralph

 

Do a thorough search of the C3 and C2 forums and you will find HOURS of reading regarding tripower. I'm getting ready to dial in my secondaries which I have tied closed and disconnected while I was dealing with center carb, distributor, etc tuning and was amazed on what info I found

 

Hi Ralph:

When I drove the car Oct last year in Beijing, it stumbled quite a bit when I step on it. So I think the secondaries were opening up way too early. FYI Beijing is at sea level and weather was cool.

Just got around to changing the springs today. You had the lightest white springs on the car. I changed to 3 steps firmer purple springs. Will test the car when weather cools down in 3 months. Mean while I'm wondering is there any particular reason you ended up using the white springs when you had the car?

Regards,

Wayne

 

Hi Tom:

Do you know what is the spring color GM used from factory?

And regarding the correct tri power springs, do you know the dimensions? I'd like to double check what I have in hand are the correct tri power springs not the 4 barrel springs.

Regards,
Wayne

 

I changed to the lighter spring because of the Denver altitude, which would be a lot different than you at sea level. Also using the paper clip method on the actuator rod, I could not see any movement on the clip indicating opening. I would think you would need to do some experimenting since you are at lease 5000' lower in altitude.
Best regards. Ralph

 

38R-477 was supposedly brown.... I can't verify that though.

https://centralhp.com/38r-477-second...rs_hol-38r-477

I pulled a vacuum pod apart and measured the OEM spring...

The small end snaps onto a stub protruding from the pod cover... 5/16" ID.

The large end fits into the "cup" of the diaphragm... 1-1/16" OD.

The free length of this "worn" OEM spring is 1-3/4".

 

Thanks Ralph. So did you get movement on the paper clip test after you put in the white springs?

 

Thanks very much Tom! I have a whole bunch of springs in each color. And there seem to be 2 distinct free lengths. I'll check them later to see what size they are.

 

Tom -
I used your first photo above in a tech answer I provided on this Forum - I gave you credit for the photo - hope you don't mind!

Lars

 

It's all good Lars. That's why we're here.... to share information.