'69 Tri-power

[John M.]

I have ridden in and driven a friends' '67 Tripower BB and when you step on it there is a distinctive "surge" when the secondaries cut in. My '69 does not have this surge but it realy goes after about 2500-3000 rpm. The secondaries are cutting in to some degree because I had some high rpm idle problems after acceleration before I got the linkage properly adjusted. What's normal? Should I expect a sharp surge? Thanks for any help.

[Tom Buddie]

Re: '69 Tri-power

Mine is currently off the car, I am re-bushing the throttle shaft bores, but when I was driving it, it ran as you described... no major surge... a smooth transition- but noticeable, 2500-3000 as designed. The surge you describe could be from different diaphragm springs, or because the secondaries on the other car are momentarily sticking before they open up. Mine is a 400HP oval port... don't know of any design differences between the 435 and the 400 (carbs). The adjustment, as you already know, is critical.

Is the other car stock? I have run across these setups where a bigger cam was installed, the carbs re-jetted (re-metered) and small holes drilled in the carb throttle plates to compensate for the cam. These run a bit more "unrefined" than the stock setup. Just another possibility.

[Tom Buddie]

Re: '69 Tri-power

Mine is currently off the car, I am re-bushing the throttle shaft bores, but when I was driving it, it ran as you described... no major surge... a smooth transition- but noticeable, 2500-3000 as designed. The surge you describe could be from different diaphragm springs, or because the secondaries on the other car are momentarily sticking before they open up. Mine is a 400HP oval port... don't know of any design differences between the 435 and the 400 (carbs). The adjustment, as you already know, is critical.

Is the other car stock? I have run across these setups where a bigger cam was installed, the carbs re-jetted (re-metered) and small holes drilled in the carb throttle plates to compensate for the cam. These run a bit more "unrefined" than the stock setup. Just another possibility.

[Dick W.]

Re: '69 Tri-power

John, the "surge" that you refer to is sometimes actually a very brief stumble that occurs when the secondaries open a little too quick. Sure you should feel an increase in power when the end carbs open, but it should be smooth.

[Dick W.]

Re: '69 Tri-power

John, the "surge" that you refer to is sometimes actually a very brief stumble that occurs when the secondaries open a little too quick. Sure you should feel an increase in power when the end carbs open, but it should be smooth.

[John M.]

Re: '69 Tri-power

Thanks for the replys. You guys sure make troubleshooting and diagnosis a lot easier.

[John M.]

Re: '69 Tri-power

Thanks for the replys. You guys sure make troubleshooting and diagnosis a lot easier.