I have been fighting a problem with the tri power set up on the 327 SBC in my 'A' Roadster. I've read through the threads here and all kinds of stuff on the web but didn't see anything that addressed what I finally found. I may have missed it 'cause I'm an old guy. The problem was that the engine idle would speed up AND occasionally cylinders would lean out at idle making the exhaust hot enough to discolor the ceramic coating. Not a healthy situation. The set up is using the GM small base Rochester 2G carbs. The 'secondary' outboard carbs have been modified with the correct bases and thick throttle plates. I have been in them, cleaning up the plates in the bores. Additionally there was an intake gasket leak on the intake to head ports. That was addressed early on. Fuel pressure at 3.5 psig everything verified and would run great. I did then correlate throttle position and the rough idle with the two outboard carbs hanging slightly open. I could manually push them fully closed and all was well again. This happened after putting my foot all the way in it, which I came to avoid. I had spent time adjusting the throttle linkages to make sure they were all coordinated but to no avail. But what is the fun of having all those horses if you can't use them from time to time? Here is what I found today (I started down the path of adding additional return springs) Accelerator pump linkages not properly adjusted on two of the carbs . There geometry was wrong. Hint: the on the right is 'longer'. The one on the left is correct and allows the bell crank, on the throttle shaft, to rotate all the way to the shaft stop before the accelerator pump 'bottoms out' The other factor that plays in here is that the shafts have been changed out and the bell cranks are secured to the shaft ends with hex headed machine screws. They were just ever so slightly loose. The shaft would rotate slightly in relation to the bell crank and the throttle would not return back to its fully closed position. This condition would occur when the carbs were placed in a full throttle condition. The accelerator pump linkages are now all the correct length and the hardware tight on the throttle shafts. The results are promising. Hope that this may shed some light on someone else's problem solving process as they search for enlightenment into the world of tri power Larry
You will need to keep an eye on that. Once there is any slop between the shaft end, and the linkage plate, that allen might loosen again...especially with dual springs. one tidbit on factory tripower end carbs, is that the pump link is totally different shape comparing the front carb to the back carb. That was done to clear the original vacuum can servo. (just posting that in case someone bought an original set, and thought they bought wrong parts)
Yes, that would be good. One more thing about factory trips; the two outboard carbs always had their own throttle plate return springs, to help prevent plates not seating each time. >>I've seen 2 types: One has a mousetrap type coil spring wrapped around the passenger side of the throttle shaft. The other style has a small diameter pull spring mounted vertically on the passenger side. There is a long peg stuck in a hole, for the spring, then the bottom of the spring hooks to the plate on the throttle shaft. These factory springs really help, even if you have a single pull spring hooked to the pair of outboard carbs
Thanks for the reply. Here are some more shots Curb Side Road side Here is where the accelerator linkage is attached to the throttle shaft on the rear carb. This is the hardware that was tightened to the shaft to secure the bell crank.. It was you know, just the kind of loose that the bolt just 'popped' a little to tighten it a little more snug.
The outboard carbs have the mousetrap type springs. This is as good a photo that I could get with out the sun being up and the car outside. Thanks for the information, I really appreciate the feedback.
It's something I don't have to remember to push back in when the engine warms up Sent from my XT1254 using H.A.M.B. mobile app
Your center carb is leaking under the spacer, the spacer is wet. Possibly a vacuum leak as well. On some of the 2g and 2gc carbs I will use a spring under the accelerator pump to help close the end carbs. In your case you could put an additional stop on the linkage to push the end carbs closed as well.
...after looking at the pics....I would check to see that the rod that rides and is pulled by the center carb linkage fitting is not binding and sticking,that happened to me,...also I would disconnect the linkage from the front and back carbs,put a pull close extra spring on the front and back carbs,.. and then looking down inside them to the butter flies making sure there fully seated/closed and nothing come loose,then I would set the linkage rod length from the front to the back carb,...the other thing I would check is to see if the intake manifold gasket is leaking from the bottom of the intake which can not be seen,...I was told if the heads are milled the intake/head mating surfaces may not be the same plane which will cause a air leak from under the intake,...miller
Thanks but the gas in the photo was from all my messing with the accelerator linkages getting them set up with out the engine running. I'll clean it up and keep an eye on it but I had gas everywhere. Sent from my XT1254 using H.A.M.B. mobile app
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