I am getting a car with a 305 with 350 crank in it, 350 transmission and no. 2 shift kit. the guy says it has a flat spot. I drove it and when I tried to leave from the stop sign the car would die. I barely push the gas. when I hit the gas a little harder I feel the slight pause or hesitation and then the car goes and is fine. he's sure it's the carb. what could cause this and how can I fix it? thanks

 

That's classic accelerator pump issues. They squirt a stream of fuel into the venturis when you snap the throttle open to prevent the exact type of bog you are describing.

Also, a 305 and a 350 crank are exactly the same stroke- 3.48". The counter-weighting is different but the stroke is the same. So if it's a 305 block then the motor is still a 305.

 

Sounds like the accelerato pump circuit not properly tuned. The parts are an accelerator Pump which can be 2 sizes (30cc and 50cc) 30cc is the most common and plenty for the 305. The next part is the Pump Cams on the side of the throttle shaft. They are colored to denote their 'profile' and can also be set a couple different positions. Then you have the Squirter which is where the fuel comes out at the top of the venturi. There is one front and one rear. Each supplies 2 streams of fuel to the respected venturis. The suirters are numbered (like 32 35 38 etc) to denote size. All the parts work in unison and can be mixed around to acheive the best result. Key is to get a good steady stream out the squirters for the accelerator stroke duration. The total fuel availible relies on the pump. A 30cc has less than a 50cc availible for each stroke. But again, your 305 setup shouldnt need that much ever. The cams are just like the one in your motor. In the respect they are a lobe that affects the movement of the pump action according to throttle input. Some cam lobes have a gradual profile which makes for a 'longer' shot of fuel and not too heavy right off. Some have a more heavier shot right off and then gets lighter. Next is the squirter. Its oriface size (denoted by the number....higher # the larger the holes) determines fuel velocity and duration as well. The smaller hole will restrict the shot. So if you have a gradual cam, then the shot will be steady and long. If you have a aggressive cam, and the same squirter, then the shot will strong right off but then fall weak. The larger squirter hole will allow for the most fuel. That squirter with a agressive cam will have a heavy but not as powerful shot right off. And with a gradual cam that squirter will have a medium stream overall. Its alot to play with as you can see. There are something like 8 cams that can be installed in at least 2 positions each. And a dozen squirter sizes also. I think most performance DP Holleys come with Pink cams in the #1 position and #32 Squirters. Cams and Squirters can be mixed and matched in the Primary and Secondary. Ill have to dig up my old tuning notes. I used to spend hours tuning the Holley DP on my 305. I changed its setup when I put it on the 355 I built and then again changed to a BF Demon later on.

 

thanks, the guy told us we could get the car. we told him we would come back today with the money and he said it was not a problem and he turns around and sold it to someone else without telling us.

 

For the sake of anyone else that may come across this thread:

All 305's have a "350" crank. They are the same stroke, same journal size. Slightly different balancing. If a crank that had been installed in a 350 was put in a 305, it would need to be rebalanced. And vice versa.

That's too low a number power valve, assuming the jetting and idle mixture are correct, and there aren't any vacuum leaks. The accelerator pump may contribute by not being adjusted properly, but not as likely.

Sorry to hear it was sold from under you. People like that really get my nose hairs standing on end.

 

thanks. I know I was really wanting the car. it was perfect for what I was wanting and we drove over an hour to see it. Oh well I guess I'm back to trying to get mine rebuilt and trying to find a hood. thanks

 

I have a feeling it's due to one thing that people always seem to get wrong, and I see it alot.

When setting up a holley accelerator pump linkage, there is a clearance setting, something like .015" or something like that. Anytime anyone rebuilds them, they assume that it is free play on the pump arm. That's wrong. It's the play available between the arm and diaphragm AT FULL THROTTLE. By setting this incorrectly, you generate a flat spot or stumble on tip-in since the extra fuel necessary is happening when the slack is taken out, ie..too late. The reason holley specified this clearance is so you don't squash the crap out of the diaphragm at full throttle.

sorry you missed the car. keep your eyes open and you will find something possibly even better!

 

Actually a 305 has smaller journals than a 350. You can still do a 350 crank in a 305.....same stroke but why? Now a 400 crank thats the same journal as a 350 crank in a 305 yes. It will require machining but gives more stroke. Like a 350 to a 383 the 305 can be increased to a 335.

 

journal sizes are the same, it's the couterweights that are different.

 

We are NOT going there on this forum. Stupid, stupid way to spend money, and has absolutely nothing to do with the topic of this thread.

 

i have a good steel hood for camaro....chattanooga

 

no the journal sizes are the same, just the balance is different due to the smaller slugs... edit someone beat me to it.. anyway to the orig poster sorry to hear he sold it out from under you, who knows though, it might have been a total pos, maybe he did you a favor. Something I've learned from experience, don't be impulsive with buying cars, look around. It seems every time I buy a car I see the same type of car in even better condition at a lower price a month or so later..

 

whats wrong with the car you have? I'm sure with all the knowledge and resources available here you can get her fixed and better than new!

 

Five7Kid I know your a mod but no need to thrust your authority about what can and cant be brought up on the topic of motor similaries. Your opinion is noted on stroking a 305. I thought about doing it myself B4 building the 355. Just seemed to cost the same and get less out of it, so I too am for building cubes from a better starting point. But nothing wrong with educating someone who might not know otherwise. Besides, I gave a lengthy post on the topic at hand and was willing to take the time to help out a fellow member. The topic changed and I explressed some more info based on that. If you want to move the motor-based post to the appropriate section, just start with your first post and go down from there. Enjoy

 

fuel filter change too maybe new fancy carb?