i have been searching around for a new carb for my 91 camaro with a 350. right now i have a holley 600cfm vac sec. this one-- http://www.summitracing.com/parts/hl...57sa/overview/

here are my mods...

350 4 bolt,lunati cam 218 dur. 458 lift both sides 110lsa, trick flow 195cc heads 62 cc chambers 2.02, 1.6 valves, Edelbrock Performer RPM Intake 600cfm holley 1850 vac secondary hedman longtubes, dual exhaust with x-pipe, built 700r4 , 3.73 posi, k&n 14x3 filter

i cant remember exactly what size my stall is, i want to say it is 2400.

this car is not daily driven, only to have fun on the weekends and racing at the strip. i am thinking i need a 750 cfm. not sure if mech or vac sec. would be better or not.

any ideas?

 

Def a 750DP, you have enough gear and converter to warrant it, and the fact that its a weekend toy that sees the track often seals the deal. Try it box stock, with 16-18* initial timing and I suspect its going to be close out of the box.

 

yeah thats what i was thinking too. now to sift through all of the 750 DP versions of carbs...

 

http://www.summitracing.com/int/part...-750/overview/
I have used this on 2 builds and been very happy with it.

 

For what it's worth I have the holley 750 DP on mine, love it. There are plenty of good ones out there though

 

I don't see anything on your combo that warrants more than a 650DP or a 600. The cam is fairly mild and you wont be reving it up.

 

what RPM do you shift at?

 

thats a good question... i would say around 6000-6500. it has been 4 years since i raced it or have even driven it. i was stationed overseas.

 

Does that cam make any power that high? I would expect it to be dead by 5500.

 

good point... per summit - Basic Operating RPM Range: 1,500-5,200

and the range for my performer rpm intake is - Basic Operating RPM Range: 1,500-6,500

i will be upgrading the cam at sometime though. i was thinking one with around .500 or so lift.

 

also forgot to mention my heads are gasket matched and ported and polished.

do you guys think i would need anything more then a regular 750DP?

 

No, a 750DP can really throw the fuel to it, you should be fine. Just make sure you tune it well.

 

I think a 750 will be much more that you will ever need with that combo. A 750 should support a 500hp 383 no problem.

 

Im a big fan of AED
They are tailor made to your car, motor weight etc etc
Damn near perfect out of the box

What really impresses me is their service (in my case)2 yrs after the sale. Anything you need, question etc Jeff in sales will take care of you;that man knows carbs!
I could have saved $20 by buying a similar one at Summit or ebay glad I didnt;try returning a used carb lol
Once they got youre money youre on your own;that service stuff matters to me.

Call him up he will tell you whats best for your particular car may surprise you.
Many options, also.

 

i have a similar setup and the 750 4150 mechanical everything. i wanted that just because it seemed to me easier to know for sure whats going on with the secondary and choke because you can just watch it. i just wish it had jets you dont have to get gas all over to change. i might go for external adjustable metering blocks

 

well i have decided to just rebuild the carb i have, the 600 cfm vac secondary. worst case is i find out that i do need a bigger one and i will have a freshly rebuilt carb to sell instead of a leaking one.

thanks for all the help though guys!

 

Unless you put in a really wild cam your 600 will be fine. For your cam it is more than enough.

 

what would the definition of "wild" cam be? my next one will probably be around .500 or so lift

 

Lift has very little to do with things as it is only a partial category on cam profile. Your current cam and carb WILL hold you back on performance; especially on anything bigger than you've got now. Vacuum secondaries can be made to work well, but they'll never be as responsive as a mechanical secondaries simply because of the nature in design between the two.

You're leaving a ton of power on the table with that cam and those cylinder heads. You're honestly not even taking advantage of those ports until you hit .500 lift, preferably closer to .600 lift (and the other specs accordingly) provided the springs can handle it.

What cam is it, anyways? Hydraulic roller or is it a flat tappet? I'm assuming a flat tappet based on the lift numbers?


and for the record, if you're trying to make this a street warrior then that's fine... but that converter is majorly holding back your times at the strip as well. I only mention this because it's fairly critical that everything be matched accordingly. For your current combination it's more than adequate but you're going to see a big shift once you decide to start changing parts around.

 

it is this cam -- http://www.summitracing.com/parts/lu...16lk/overview/
it is hydraulic flat tappet.


so when i go to a bigger cam i will have to get a higher stall converter right? what size would you recommend?

 

The size of the stall will be based on the cam. Right now you have a mild cam that sound mean.

For something fairly wild you would want something like the XE284 or 292 but I would probably not run either on the street. IMHO the only time you need more than a 600 or 650 is when you spin over 6000 rpm or jump up to a 383

 

ok thanks for the help. it wont be on the street much. to and from races and to work once in a while.

 

Not necessarily, no. It depends on how the cam is ground, but if you want optimal 1/4 and 1/8 mile times, then YES a higher stall converter is necessary to make the gains you're asking for.

As far as cam recommendations, the sweet spot for those heads needs to lie in .540-.625 lift numbers with most likely a duration in the mid 230's to early 240's on the intake and exhaust. I do not recommend a hydraulic flat tappet for performance applications because they are severely limited compared to their solid flat tappet counterparts and hydraulic rollers.