Best jet size, etc ?? 650 Holley 302 Ford crate

wtm442 · #1 (**permalink**) 10-18-2007, 12:18 PM

Kevin
As long as the kiss was on your forehead.

I was at a dyno shop with a bunch of Cobras a couple of years ago and the owner stopped a pull on one of the Cobras at about 4000 RPM. Just cheap $ pulls on a Sat morning with no tuning provided by the dyno shop owner. He said the motor was so lean, he did not want to chance blowing the motor. He told the Cobra owner to drive home, do not floor the gas pedal, and increase the jet sizes by 4 to 6 steps on primary and secondary.

FUNFER2 · #2 (**permalink**) 10-18-2007, 12:53 PM

Jerry- he is one of our sponsors on our sprint car so, $150 was cheaper for him. We don't overcharge our new customers. Because of that reason, we have four dyno nights per week. It brings in a lot of business. There is now way,......you can beat tuning on a chassis dyno ! You can even calibrate for weather conditions. If the operator can't tune your car for the street, you had better find a better one. There are some dyno shops out there that the operator is only a computer geek, not a mechanic.

Our Mustang dyno is a real world test, unlike the dynosport. The only changes after a dyno run you'll have to make is if the weather changes a great deal if you're racing or, a elevation change. We've had drag racers spend hours in the pits trying to find what the motor needs. They come to our shop for a dyno run and figure it out in one hour or less.

442- We also have a "dyno day" (the last was for all Mopars) and they were single runs for $50. It was a blast for all of us. Had pizza & soda (some had beer) Now, most want to come back to dial in their engines. That will be more $$$. We have all the jet's, spark plugs and distributer springs ect... to super tune most engines.

The dyno is good for our business as we don't over charge plus, "the word of mouth" for the dyno and our regular daily driver mechanic business is fantastic. We even put our sprint car on the dyno. Long story but, it was hilarious.

rdorman · #3 (**permalink**) 10-18-2007, 01:57 PM

Pick up a holley tuning book. Set the total timing according to manufacturers recomendations. Set your idle speed. Check your initial, should be in the 12-14 range with that cam so long as it starts after a hot soak. Many are not curved right. Take the carb off and check the transfer slot. it should be exposed 'square' to maybe twice that (the book will explain it), if not, get it right and adjust the secondary butterflys by the amount of the front (ie 1 turn close on the front, one open on the back). Set your float height (up till it drips, down till it stops, that is max, do down from their for tuning). Set your idle mixture, adjust your accelorator pumps. Call me in the morning

CobraEd · #4 (**permalink**) 10-18-2007, 02:01 PM

Quote:

Originally Posted by rdorman

Pick up a holley tuning book. Set the total timing according to manufacturers recomendations. Set your idle speed. Check your initial, should be in the 12-14 range with that cam so long as it starts after a hot soak. Many are not curved right. Take the carb off and check the transfer slot. it should be exposed 'square' to maybe twice that (the book will explain it), if not, get it right and adjust the secondary butterflys by the amount of the front (ie 1 turn close on the front, one open on the back). Set your float height (up till it drips, down till it stops, that is max, do down from their for tuning). Set your idle mixture, adjust your accelorator pumps. Call me in the morning

Uhhh how about the main jets???? They are the key element of performance tuning. All this other stuff is just carburators 101.

rdorman · #5 (**permalink**) 10-19-2007, 07:14 AM

Quote:

Originally Posted by CobraEd

Uhhh how about the main jets???? They are the key element of performance tuning. All this other stuff is just carburators 101.

Uhhh which is exactly what he needs to start with.

CobraEd · #6 (**permalink**) 10-19-2007, 07:25 AM

There was NO MENTION of main jets at all in what he wrote.

.

rdorman · #7 (**permalink**) 10-19-2007, 07:37 AM

Absolutely there was. But, he is starting in the wrong place. Carbs out of the box are generally very close on main jets. Some one else led him to the oem setting for jets for which he should return to if they have been changed. Jets are more dependent on the carb itself and atmospheric conditions then what is setting under it. He complained about drivability problems, said the plugs where a good color (althought reading plugs is an art so he probably is not seeing many things) and said that it had been a long time and he was rusty. Hence, as you put it, carb 101. What carbs and crate motors for that matter generally have against them out of the box is proper adjustment. Which is where I think he should start before trying some magical modifications only to see no improvement, run out and by another carb, and continue to be frustrated because the initial setup was still not done. Eliminate the simple and free stuff before he starts looking for a problem that may not exist.

You did bring up a very good point though. Once he does try and set up the main jets, he can't do it sitting in the driveway. Even the carb 101 that I gave him will need to be tested on the road and final adjustments made. But assuming the carb is not defective or in need of repair, if he carefully sets it up, I would be willing to bet he will be much happier then he is now.