proform

thanks jack. but its not a backfire. there is too much fuel and not all is geting burned up so it passes into the mufflers and the heat of the mufflers sets off the fumes.I thought maybe someone has had the same problems with this swap.

Jack i have replaced the front jets with no luck. it just wont take gas. It stumbles untill you get wide open.

...forgot misajusted or stuck choke blades.

Paul........Question.

Is the backfire/stumble more when you try to accelerate hard from stop.... Reason I ask this is. If you carb accelerator pump is givng too small a shot (and if its a holly design could even be the pump cam is wrong), you could just be running way to lean. (ie. not nearly enought fuel with all that quick air).

I'd also add this. I've see folks setup the initial setting to the pump wrong, where basically its not even giving a "squirt".

Bob


Bob

Hey guys, thanks for all your help. i'm going through all of your suggestions. let me catch you guys up on all that has been done to my car. the engine has been rebuilt with all new parts. I've got about 600 miles on it and am just changing some parts for more power. this carb switch is just the main body of the carb. you use the base plate and the fuel bowls and metering blocks, this main body has no chock or air horn with high proformance downleg boosters. its also got adjustable scew in air bleeds. the car ran fine before the swap but now it wont take gas when you stomp on the gas. it just stumbles and almost dies. if you go slow it does fine. the idle is good. then after about 1500 rpm it wont take gas maybe its air adjustment im not doing right is there any good books on this? just let me know if you have any more ideas now that i've given you some more info. you guys are great thanks alot for your time and frendship, It means alot to have imput when your like me, stuck in a state with very few panteras. thanks Paul.....

NOW, it sounds like BoB has the right idea of it being the Accelerator Pump or Pumps, is it a 'Double Pumper'? Have you actually checked to see if you are getting a 'Good' squirt of fuel when you open the blades, both on the Primaries AND Secondaries? Are your squirter noozles big enough, or TOO big. As BoB suggested; are the Acc. Pump Cams correct and is the 'Spring' adjusted properly? You know, once in the past, years ago, I made the mistake of getting the METERING BLOCK Gasket (OLD design) in backwards, This will BLOCK the Accelerator Pump Passage. I have noticed that the NEW design gaskets now have the 'hole' on both sides of the gasket to make this mistake 'foolproof'. This last entry would be if the problem was NOT enough Gas. On the point of there being TOO much fuel going in: There are two possiblities, that you have one or two 'Power Valves' that are too weak, and are opening too soon, flooding the card(If your carb is a 'Race Only' then your secondaries have NO power valve and are delivering EXTRA fuel 100% of the time). Second: If you have mechanical Secondaries, they may be opening TOO soon. And if you have Vacuum Secondaries, the spring may be TOO weak, and is allowing the Sec's to open too soon. You might pick youself up one of the many books about Holley carbs, they all have a detailed troubleshooting section. Stick with it, you will find the problem!! Regards, Marlin.

Carburetors may be 90 yrs old but they are still a quite complex mechanical device. And 'just changing bodies' is not simple. There are a myriad of combinations of drillings & passages that must match up in the metering blocks, jet plates & bodies. In some carbs, only one passage being off in a metering block gasket can cause all sorts of problems, even with all the same mechanical parts. This's why carb shops get significant dollars for rebuilds, tuning etc. Your only hope is to clooect all the old stuff you removed, disasemble the carb as it now is, and begin chechimng every simngle drilling and passage. Once thats done, you can begin tuning.... or send the thing back & ask the maker to fix it. And as has been mentioned, it may not even be the carb. You get much the same symptoms for some types of ignition problems.Theres an entertaining article written by Chuck Melton of Nor-Cal Panteras on his carb rebuild [www.geocities.com/provamo72/index.html] .I believe it involved nearly 3 months of build-up, test, tear-down etc and was finally resolved as a whole series of problems with both carb bodies, some of which occurred while he he was trying to fix something else in the carb.

One thing that disturbs me a bit is that most tuning problems are low speed related, and the low speed system is not tunable on a Holley. Then most people start changing main jets as this are the only jets to change. Yes, they do affect low speed, but only to a small degree. The biggest change occur around 3000 rpm or so. The idle screws take care of the idle, but as soon as the blade leaves the idle, the transfer slot takes over. With NO adjustments.
Goran Malmberg

Yes! Goran the 'Transfer Slot' takes over, but the Idle curcuit remains active and continues to contribute to the overall system right up to and including 'Wide open Throttle'. And Paul! I ment to you, to try www.holley.com The site has a vast question and answer page, and troubleshooting. And you can print off exploded views of carbs. Also has an emense list of carb numbers. Check it out, you'll be impressed. Marlin.

...also, I was once told by an old racer friend, who really knew his holley carbs; he said "Whenever you take a well running carburetor apart, for any reason, and put it back together; you always take the risk of it NEVER performing correctly again!" Because ALL Holleys are inspected, checked, and flow tested before they ever leave the factory! Do We think that we know more than the Holley Technicians!? Regards, Marlin.

I would bet that some how your passage from the main jet's is blocked from getting into the venturi.

The metering block gasket does have a direction to it. You need to make sure it's facing the right way round and right side up.

You should be able to "blow" some air into the main jet passage and hear air coming out the venturi.

Good luck.

WOW thanks Guys for all your help. I got a hold of the teck. guy for proform and he said that my kit was incomplete. he asked if I changed the back air jets to the ones supplied. Of course I informed him that there was none. So to make a long story short they are sending me a set. I will try this as soon as they come in. Iwill keep you guys posted..... if it works like they say then it will be worth it. The car ran like mad with the big jets in it. but it could not recover from all the fuel, hope more air helps..... thanks Paul....

Paul can you post your results with the proform carb body? I am curious to see if you got any hp gains from it and your expierences in general. Thanks.

UPDATE. well i've installed the new air jets and it did make a differance. still got some poping in the mufflers but not as much. plus it does not stumble like before. called the tech. and he said to move the jets inward so i will. let you guys know hows its going. so far i can tell a differance in proformance. i will check back.

hey guys I've got it fixed. Mr. marlin was correct on his advice. It was the acc. pump cam. I had about 1/8 inch play in the arm and the cam. So I switched to a differant cam and that did the trick. As for the proform switch, It gave me more horsepower and the car feels like a street bike when you mat the gas or pass someone. it flat out flies. I would recomend this switch as long as you know that you will have to tune it in. Its not just a bolt on. Paul