sethj78

Hey guys I got this roller 455 going and had some questions about carb and timing. I posted a timing question when I was tuning a 403 and I got that the timing is suppose to be like 32 degrees advanced, the 403 had throttle hesitation and advancing the timing fixed it but is 32 degrees advanced correct for a big block or does my memory fail me???

And the carb question is how close is my carb for a .30 over 455 with medium cam duration .520 intake and .530 exhaust lift, heads were ported to very large runners and even went into the water jacket on an intake port, 2.07 intake valve (i think) normal big exhaust valve, headers, auto trans, 3.42 gear??

carb is 3310 750 holly, vacuum secondary's, electric choke with #72 jets in front block and #79 jets in rear, front power valve is soft and rear is harder.... is this enough info to have an idea????

Thank you

oldcutlass

You can keep bumping your timing 2 degrees at a time to the point it pings and then drop it back down 2.

The carb sounds ok. Thats one of those items that you need to feed it what it will eat and make it happy.

cutlassefi

If you want to increase the chance of blowing up your motor then do it that way. Otherwise do it the way intelligent civilized people do it, buy a timing light and see what your initial, centrifigal and vacuum advance gets you in the way of a total and when it comes in. Then go from there.

Carb jetting will depend more on head flow and duration than lift. Start with what you have and read the plugs from there.

Jmo.

oldcutlass

He did it the civilized way and now he's trying to tweak it. The normal of getting around 34-36 at 3000 gets you really close! Then you need to get the last drop out of it! The object here with timing and carb jetting is to make the motor happy. Every motor is different.

sethj78

I set timing with an old stand up roll around oscilloscope, it was really close when i hooked it up so set at 32. the scope has an exhaust analyzer but not sure how accurate, I am about to look at that and ignition, I feel a bump that feels like a miss at 1800rpm to 2500 light throttle, heavy throttle is just scarey but smooth....Thanks guys.....any tips for advance curve? motor has 13-16 vacuum and doesn't have much curve now, will that be the same way, just cut and try or do olds like a certain thing??

oldcutlass

They were really cool, I had an old Sun machine from the 60's. But then someone made me a really stupid offer back in the 80's, so it found a new home.

What was nice is you could fine tune each cylinder!

sethj78

with the carb I just wondered if it sounded way outta whak, got it from a guy that was talking about racing a big dodge....charger or something

sethj78

My dad had an old blueish gray Sun machine that was 7 or so foot long and like 6 foot tall maybe, it was great but don't remember if had an exhaust analyzer this one is like that but much smaller...3 1/2 x 5 foot

oldcutlass

Mine was the size of yours, no exhaust analyzer. The carb should be fine if it idles well, with no bog off the line, and feeds fuel all the way through whatever rpm you run without falling on it's face. If you really want to dial it in right get it on a dyno or go to a test and tune at the track.

sethj78

Is the dyno test expensive?? Probably less expensive than driving it when it gets 4 or 5 miles a gallon...Went to get my little girl from school yesterday and a mid 2000's camero kept giving my side ways glances so when we came to the end of the school zone i stuck my foot in it and holy crap did this thing take off, I have a beefed up 700r4 behind it that I haven't got to shift right so it down shifted when I hit the throttle but up shifted before the motor got to 2500 rpm but wow it took off...camero would catch back up afterI'm impressed!!!!!

sethj78

I have to be careful when running this thing hard, it has the stock rearend (I think) with an auburn gear posi diff in it and not to sure how much it will take...I know of a turnpike service road I was gonna tune it on so may try a couple runs and look at plugs

oldcutlass

Check with some of the local car clubs, they usually would book the machine for a day and take turns!

Rickman48

First thing I'd do or get done is adjust the trans cable correctly - it'll toast the trans immediatly as the cable designates line pressure to the clutches - low pressure = slipping clutches!!
I'd also get some bigger jets for the rear - 88's or larger!
The tuning kit for that carb will give you different cams for the accelerator pump - eliminate the flat spot! And different springs for the secondaries!
Going up 2-3 sizes on the squirters will help, too.
I had a 396 and went through the 3310 VS 780 about 5 times - mid 13's @ 110 mph and got 15-17 mph with 3:55 gears, and stock converter!

sethj78

I will check to see if I can find any car clubs, shouldn't b hard, my step dad has a 750hp twin turbo 1991 300zx that i think he did the same thing because he was telling me the blowen big block guys that were there were a little green when he got up there

Yes...I need to find out the correct sweep for shift cable, it has a long sweep on the holly, to long I think! It shifts long and hard under light throttle and short and soft under heavy throttle, I put a corvette servo in it, that seemed to help stiffen the shift but like you said cable isn't right...any idea where I can find 700r4 specs??