Hesitation at high rpm on Rochester 2bl

[nitrosteve]

My first trip out after the engine swap and I noticed for the first 15 min just tooling around at 3000 rpm everything seemed good. But after further acceleration past 4000rpm the engine will run up like everything is fine then start to sputter then begin dropping rpm rapidly. If I pump the gas it will sometimes come back for a moment but then almost immediately drop rpm again till it dies. But if I pull the throttle back it will idle. If I leave it floored it will die. Here is what Ive done so far checked timing, checked fuel pump filter,took gas cap off to allow the tank to vent better. From WOT to hesitation is roughly 20 seconds. So whats next in your opinion....

 

[Alpheus]

Re: Hesitation at high rpm on Rochester 2bl

Check your fuel pressure. Ease up on taking your motor up that high with this problem. Sounds like its leaning out at WOT and you dont want to detonate your new engine....

 

[Quadruplecccc]

Re: Hesitation at high rpm on Rochester 2bl

check your primary float level. sounds like its starving for fuel.

 

[nitrosteve]

Re: Hesitation at high rpm on Rochester 2bl

check your primary float level. sounds like its starving for fuel.

How would I go about that?

 

[nitrosteve]

Re: Hesitation at high rpm on Rochester 2bl

Could this be the result of a vacuum leak under the carb. This carb was just put on maybe the gasket isn't right. I hear some serious sucking going on when I try to accelerate. What do you think?

 

[crestflite165]

Re: Hesitation at high rpm on Rochester 2bl

you know i got a gm 3.7 l that does the same thing but mine is from idle to full open r's that it will stumble. i also have a 2 bar rochester and i hear sucking sounds even at idle!! i might have to put a good ole 4 barrel on her!!check your timing and your mains to make sure eveything is open. doest sound like a acceleration pump issue just a main jet clogged?

 

[nitrosteve]

Re: Hesitation at high rpm on Rochester 2bl

After replacing the fuel filter in the pump and the carb I decided to swap carbs with an older one I had laying around I also found out my newer carb that wasnt working was a mercarb. So I put the Rochester on it and it runs great. But I did notice the Rochester has much smaller butterfly on the underside I wonder how much this will effect performance.... I may just rebuild the mercarb