[Hurst65]

Guys,
I need some help with my tri-power. The exhaust stinks really bad! It's almost to the point that I can't stand even starting it up. It get in my clothes, my hair, my nose, and my eyes. It stinks! Yuck! I hate that nasty exhaust smell. Once you've been around it you have to take a hot shower to get it off. Ugh!

I tried messing around with it today but, I still can't get rid of it. So, if you guys don't mind, I need some help. I'm ok at tuning but, I'm by no means great.

The engine is a 400 (.040" over), 11:1 compression, zero decked, with a Crower 60243 cam. Nice cam, BTW!

The tri-power is a correct '65 tri-power set up.
I think the jets are 72-66-72. (It's been a while.... I'm not totally positive)
The idle tubes were drilled out several years ago when I had the Comp XE-284 cam (barf!). I think I drilled them out to something like .035".
The idle/air mixture screws are turned out 3 turns. If I turn them in to less than 1 turn, the engine wants to die.
I'm pulling about 11" of vac. at idle (with the vac. advance disconnected)
I clipped 3 or 4 coils off of the power valve spring.

I'm running a stock type distributor with a Summit box. The points are just a trigger.

The car runs good. It idles at about 950-1000 RPM. It pulls good through the RPM range.

I'm out of ideas....

Thanks!
Eric

[Schurkey]

Misfire from any cause. Cylinderload of un-burned fuel goes out the tailpipe. The fuel is the stink.

If a rich mixture burns, the exhaust CO goes up, but CO is colorless and odorless. Doesn't stink.

Often, a too-lean mixture lean-misfires, the exhaust "smells rich" and the guy leans the mixture even more.

[old66tiger]

Been there and done that. You need to go back to basics. Take the center apart and make sure that the float is set correct and that you don't have fuel creep past the float. Make up some block off plates for the end carbs and try running off just the center. If the smell goes away and it runs fine, chances are that your end carbs are leaking and causing the car to run rich. You will need to address ill-fitting throttle blades on the ends. If the throttle blades on the ends are leaking, you will pull some fuel out of the end carbs, making the damn thing run rich. Have you pulled plugs??? If you had a wide band O2 sensor fit in the exhaust, it would also tell you which way you need to go. With out that, it is trial and error.

[geeteeohguy]

To me, it sounds like you modified the carb(s) for a cam you are no longer using. That means your combination is no longer calibrated. I would reconnect the vacuum advance, and re-check vacuum. Should be 16-20" at idle depending on what cam you have. Much less if a large cam is being used. Stinging eyes and stink IS unburned fuel....either by misfire (ignition) or just waaaay too rich. If it's not misfiring, it's too rich. My bet is that the carbs need to be put back to stock ;for a baseline and you can go from there. My '65 GTO stinks at idle too...it's due to a large, antique SIg Erson Cam that's in place. No misfire....just too much fuel at idle. I try not to idle it much!!

[old66tiger]

Tri-powers are tough to get perfect. I screwed with mine forever to get it running right on my old 455. The ends leaked and I tried the aftermarket bases that Charlie from Vintage Speed. They are a work of art, but the close tolerances of the bases made then get tight when the engine heated up.

I had Mike Wasson seal my originals with the epoxy that GM used to use back in the olden days. That helped a lot. However, I could not get the idle circuit to respond well to the big cube engine and it suffered from pretty bad nozzle drip. In the end, I built a Q-Jet that worked well and then migrated to EFI which is the cat's pajamas.

[geeteeohguy]

I've been really lucky...the tripower on my '65 was installed by Pontiac, and I overhauled the carbs in 1982 when I bought the car. Haven't touched it since. No issues, no problems. I have a '66 unit that I bought for $120 back in the '70's....I rebuilt it in '79 and haven't touched it since. I use it from time to time, and keep it bagged on the shelf. Never had an issue with it, either. I think reliability has a lot to do with how much something has been monkeyed with, and with carbs, that's critical. I also think if the carbs were left out in the elements, that would cause serious degradation. Stripped out jets, broken/buggered castings, warped airhorns from over tightening, and buggered up "upgraded" throttle shafts. The fact that the Trips on my '65 have been on the road and full of fuel from 1965 to present may have something to do with their reliability. The carbs had rebuild kits installed way back when, but were never modified or horsed up. I don't know. Again, maybe I'm just lucky. A lot of folks out there seem to have multiple issues with tripower set-ups....mine have been rock reliable forever. Ugly and dirty, but reliable.

[zeebo]

im doing some research into how the 60's carbs were calibrated vs. the 70s carbs for emissions. i know without taking them apart that 60's carbs both 2 and 4bbl rochesters were way more generous on the fuel calibrations than the later carbs--almost to the point of not having to modify them much to get them to run good with larger cams. im going to get a baseline by measuring a factroy stock 66 pontiac 2gc and a 67 pontiac qjet for my future carb calibrations.

[mario65]

I tell everyone the same thing. Just get an O2 sensor. I swear I hate guessing and pulling my hair out also. Its about 160.00 and especially with a tripower and all the stages you can know exactly what you are doing. No more guessing.
My Holley 800 stunk until I got the O2 sensor. I run vacuum advance and have around 28 degrees with vacuum at idle. I then adjusted my carb to 14.5 to 1 in and out of gear and it is within the parameters for the highest vacuum. I pull 14 to 15" vacuum in park and 11" in gear. Having more timing will enable you to run it leaner at all stages. Most people have a low timing which yields low vacuum which requires a rich idle for it to run well.

No way I would run what I have without it and especially no way I'd run a tripower and its complexities without it. You want it right, get the ignition right then install the O2 and then tune it to the O2 and enjoy.
Got it on ebay for 155 or so and its a joke to install.
http://www.innovatemotorsports.com/products/MTXL.php

[Hurst65]

Thanks, guys!
All the input helps. I'm trying to get myself motivated to start working on the car again. Getting help on here helps a lot!

I feel like I covered all the basics several years ago. I feel pretty confident that the end carbs are sealing. The only way they could seal any better is if I get some of the DAG sealer from Mike Wasson... or if I used some J.B. Weld on them. Lol. I'm sure it's possible that the throttle shafts have a little wear in them and that could be a source of a small vac. leak. But short of sending all the carbs in to be totally 100% restored, I think they are about as good as they're going to get. ... maybe I'm wrong...??

I feel like I'm at the point of guessing when it comes to jets sizes, idle tube size, and the spring tension on the power valve. I hate guessing!Ugh! Maybe I should get a good O2 sensor and do it right.

Is the Innovate set-up the best one to get? How accurate is it? Are the sensors readily available at a local parts place - ie: NAPA or Autozone?

[mario65]

I have had many different O2's on turbo GM cars and trucks. I like this one because it way too easy to install and Ive noticed it being very consistent. There are some good old plug readers out there but how do you know that every stage idle, light accell, heavy accell and WOT is where you want it except with an O2? The smallest turn on my Holley idle screw can move me from 12 to 1 to 15 to 1. Thats alot of plug pulling and hoping you got it right.

The innovate mx-l is on ebay at around 156 and it lists for 199. Its the besy price I could find.

Heres the one I got Id buy this since I know its genuine and its a fast ship.
http://www.ebay.com/itm/130810873834...84.m1497.l2649

[Hurst65]

Update-

I picked up one of these and I'm working on getting it installed. I decided to go with this one because it will match my existing oil press. and water temp gauges.

http://www.autometer.com/cat_gaugede...gid=4332&sid=7

I'm thinking about installing the O2 sensor in the right side down pipe, coming off of the Ram Air manifolds, just a little bit aft of the oil filter. Does that sound like a good spot for it?

Any other tips on the install??

Thanks!

[old66tiger]

It needs to be welded anywhere from 9:00 to 3:00 to keep moisture from ruining the sensor. I install mine in the 10:00 or 2:00 position an no problem to date.

[carbking]

If the idle tubes were drilled out, and the large cam is now a small cam; then three turns on the idle mixture control screws is WAAAAY too much.

Would suggest what others have, back to square one. Square one on a tripower with issues is to remove the two outer carbs, install block-off plates, and tune the center carb ONLY. Tuning is basically eliminating unknowns. And the two ends do nothing positive at idle, so they are unknowns.

Once the calibration is correct on the center, reintroduce the ends to the system, one at a time. An end carb without issues should NOT change the calibration of the center carb at idle.

And remember......95 percent of ALL carburetor issues are ignition!

Jon.

[Hurst65]

Originally Posted by old66tiger

It needs to be welded anywhere from 9:00 to 3:00 to keep moisture from ruining the sensor. I install mine in the 10:00 or 2:00 position an no problem to date.

Yep. I had the fitting welded in today. It's in the right side pipe at about the 1 o'clock position. ...looks good and should be in a good location for any future maintenance.

[Hurst65]

Originally Posted by carbking

If the idle tubes were drilled out, and the large cam is now a small cam; then three turns on the idle mixture control screws is WAAAAY too much.

Would suggest what others have, back to square one. Square one on a tripower with issues is to remove the two outer carbs, install block-off plates, and tune the center carb ONLY. Tuning is basically eliminating unknowns. And the two ends do nothing positive at idle, so they are unknowns.

Once the calibration is correct on the center, reintroduce the ends to the system, one at a time. An end carb without issues should NOT change the calibration of the center carb at idle.

And remember......95 percent of ALL carburetor issues are ignition!

Jon.

Thanks for the response, Jon! All points will be well taken. Once I get finished with the install of the wideband gauge the real tuning will begin. I hope you'll stick around for that. I'm sure I'll have other questions.

BTW, do you still have those kits with the different power valve springs? I may be contacting you soon.

Thanks!
Eric

[Hurst65]

I finished installing the wideband gauge this morning and started to do a little tuning.

The idle was pig rich! Jon, you were right! The gauge was reading between 12.12 & 12.5:1 at idle. So, I turned the mixture screws in all the way and then back out 1 turn. That proved way too lean-- the car wouldn't idle well and the gauge was pegged out. I then went another turn out, for a total of two turns. That was a close but, a little too rich. Right now, I'm at 1.75 turns on the mixture screws and the gauge is reading about 14.5:1.
I never knew that the mixture screws were that sensitive. The slightest little turn makes a big difference!

I think I'm okay with the idle. It idles real nice at a steady 900 RPM, w/15 degrees of timing, pulling 11" of vacuum, and the wideband gauge reading 14.5:1. The idle is really smooth-- almost stockish.

Ok.... so, then I went for a short drive. The mains are pig rich too! The gauge was reading about 11:1 to 11.5:1, in any gear, at 2500 RPM. How much of a jet change do you guys think I need to make?

Thanks!

[Schurkey]

Originally Posted by Hurst65

I finished installing the wideband gauge this morning and started to do a little tuning.

The idle was pig rich! Jon, you were right! The gauge was reading between 12.12 & 12.5:1 at idle. So, I turned the mixture screws in all the way and then back out 1 turn. That proved way too lean-- the car wouldn't idle well and the gauge was pegged out. I then went another turn out, for a total of two turns. That was a close but, a little too rich. Right now, I'm at 1.75 turns on the mixture screws and the gauge is reading about 14.5:1.
I never knew that the mixture screws were that sensitive. The slightest little turn makes a big difference!

I think I'm okay with the idle. It idles real nice at a steady 900 RPM, w/15 degrees of timing, pulling 11" of vacuum, and the wideband gauge reading 14.5:1. The idle is really smooth-- almost stockish.

Ok.... so, then I went for a short drive. The mains are pig rich too! The gauge was reading about 11:1 to 11.5:1, in any gear, at 2500 RPM. How much of a jet change do you guys think I need to make?

Thanks!

What happens if the idle speed is more reasonable? 900 is kinda high.

Is that 11" of vacuum at idle the most the engine will make at that throttle position? Does changing the idle mixture screws increase the vacuum from there?

[Hurst65]

Originally Posted by Schurkey

What happens if the idle speed is more reasonable? 900 is kinda high.

Is that 11" of vacuum at idle the most the engine will make at that throttle position? Does changing the idle mixture screws increase the vacuum from there?

Great question. Okay, so I wanted to see the same thing. Here's what I found out--
1.) I can go down to 750 RPM but, the engine doesn't seem to like it. It kinda starts to lug and it's just not very smooth. I brought it up to 800 RPM and that seems like a good compromise.

2.) I was able to eek out about 12" of vacuum after some further tinkering. Not a big change in vac. readings.... maybe + or - 1" of vacuum either way with the screws. But a tiny turn of the screws, one way or the other, really makes a big difference on the wideband gauge.

I opened up all 3 carbs this afternoon to verify my baseline.

Center carb - Idle tubes are at .0355", .066 Jets (waaaayy toooo fat!)
End carbs - .072 Jets

I switched the end carb jets to .070 while I had them open.
I was going to put smaller jets in the center but, I don't have any. I'll have to order some. I'm not sure where to start, thou. I'm thinking .063's. ??

Overall, I think I'm going in the right direction. I just need to get some smaller jets for the center carb and go from there.

[old66tiger]

I think the stock center is 62's. Call Mike Wasson and he will have what you need for jets. pontiactripower.com . The power valve is a wild card here. Too much spring pressure and the valve will be open and it will be sucking more fuel. I am not sure what too little spring pressure will do. Hang the valve?

[Hurst65]

Yeah, I'm wondering about that power valve. I've noticed that when I take off from a stop and right after a gear change it goes way rich. The gauge will dip down to around 10:1 and then come back up to around 11.5:1. I'm thinking I better get my center jets dialed in before I start with the power valve, thou.

I'll try to get some jets on the way tomorrow.

Here's a question for you guys, regarding "the stink". I think I'm making progress in getting rid of the stink at idle. However, it's really hard to tell. Once it's in your nose and on your clothes it hard to notice any improvement. Ok, so, is it possible that the car is building up this "stink" while driving and then it hits you when you stop? Does that make sense?