Help! Are my tripowers working..

[jims427400]

I'm struggling trying to determine if my secondaries are functioning. First I drive the car aggressively and it doesn't seem to kick in like I'm used to on my 67 400hp. I then disconnect the vacuum lines to the front and rear carbs and then take it out and drive it the same way and dont notice any difference. What does that mean???
When at idle I oporate the front and rear manually and it revs as expected. Any suggestions how I can diognose this??
Thanks,
Jim

 

[JohnZ]

I'm struggling trying to determine if my secondaries are functioning. First I drive the car aggressively and it doesn't seem to kick in like I'm used to on my 67 400hp. I then disconnect the vacuum lines to the front and rear carbs and then take it out and drive it the same way and dont notice any difference. What does that mean???
When at idle I oporate the front and rear manually and it revs as expected. Any suggestions how I can diognose this??
Thanks,
Jim

If you're sure they're not opening, either their diaphragms aren't getting a venturi vacuum signal from the nipple on the center carb, there's a leak in the vacuum hoses, or the diaphragms are leaking or ruptured.

Pull the vacuum hose that feeds the diaphragms off the nipple on the center carb and connect it to a Mityvac tool, pump the handle, and see if the end carbs open.

 

[jims427400]

Thanks John,
Ordered my mityvac today, plan to try your ideas.
Question.. if I were only running on 1/3 of my carbs, wouldn't the car miss horribly when under a major load??

 

[Tom Bryant]

No. It will just be down on power.

 

[Kid_Again]

I haven't posted for a while but I'm always interested in tripower postings. I had some problems with the secondaries on my '66 and I looked all the hell over for a vacuum leak. The carbs were new from the outfit that Holley sent me to and all of a sudden, they didn't work correctly.

I started a long thread (may have been here), I Looked ALL OVER for a vacuum leak and I became JohnZ's penpal. The short version is that I used a cheap plastic tee to join the primary vacuum source hose to the secondary carb hoses. It developed a hairline crack which ONLY opened up under load. Drove me crazy until I found that problem. I now have a bigass 'ol brass tee which does look odd but I bury it below all the other hoses on that side of the manifold. Never see it.

Once I date stamp it, it will look JUST fine.otfl

 

[JohnZ]

Thanks John,
Ordered my mityvac today, plan to try your ideas.

I didn't mention it, as I figured you already knew, but the center carb needs to be held wide open when you do the vacuum check on the end carbs, as the mechanical return linkage on the driver's side will prevent the end carbs from opening if the center carb isn't wide open.

 

[jims427400]

Talked to my carb rebuilder yesterday and he said that if I send them back to him he'll plug something"don't remember what" and that will allow them to open at 3000rpm. he also said that the springs in the diaphram had nothing to do w/ it... not sure I agree with that but I shipped them off today for him to repair. Hope I'm doing the right thing.
Didn't see any leaks.
JohnZ, i appreciate the clarification as I didn't know, so when you say to have the center carb wide open AHHHH does that mean the car is running OR do I just hold the linkage open??

 

[JohnZ]

JohnZ, i appreciate the clarification as I didn't know, so when you say to have the center carb wide open AHHHH does that mean the car is running OR do I just hold the linkage open??

You do the vacuum check to verify operation of the end carbs with the engine OFF; just hold the accelerator rod to the center carb wide open while you apply the Mityvac.