unknown_host

iTrader: (1)

I would like to switch over to a carb on my street/strip L98. Current setup:

1989 L98
Vortec Heads
Stock Cam
9.5-10:1 compression
1 5/8" Hedman headers
1.6 comp magnum rockers
Summit Racing Dual Plane intake
2800 Stall Converter
2.77 gears


I am trying to decide on a carb for this, I would like to stay on a budget. I do plan on putting steeper gears in the car at some point in the future. A lot of the carbs I like are 600 cfm, is that enough CFM for this motor?

Most of the "budget" carbs are either 600 or 750 (Quick Fuel Slayer, Summit Racing, etc), and I worry a 750 would be too much carb with the stock cam.

Thoughts?

sofakingdom

iTrader: (1)

Holley 6210 (650 CFM man sec spreadbore)

Screw a bunch of "budget" carbs... you want your car to run right, OR WHAT? and of course, always remember we're talking about FUEL here... ya wanna cheeeeep out on the carb and PAY for it EVERY SINGLE TIME you stick a gas pump nozzle in your car? Are you REALLY capable of outsmarting your own self to that extent?

Do it right, do it once, enjoy it FOREVER.

Cheeep out, buy it again, pay for it over and over and over, hate it every minute you own it.

unknown_host

iTrader: (1)

Understood, so I like the idea of running a vacuum secondary carb since I will be running with numerically low gears for a while. The slayer series of carbs have a lot of nice features for the price and Quick Fuel is a great brand.

http://www.summitracing.com/parts/qf...s/media/images

I am just trying to decide between a 600 cfm VS carb and a 750 VS carb, I could get a Holley too I just don't want to go too big.

Then again, I have heard you can't really go too big on a VS carb since the secondaries open based on engine demand.

Thoughts?

novaderrik

a stock non electronic quadrajet from an early 80's pickup is the answer you are looking for.. normally i'd say to get one from a late 70's truck, but they won't have the proper linkage for the tv cable in a 700r4 trans..
get the carb and buy a rebuild kit, float, and a couple of cans of carb cleaner. pull it apart, clean it up, and put it back together. it will be damn near "perfect enough" with only adjustments to the choke and idle mixture screws..
with this carb, you will get a great idle, good throttle response, good economy, and as much power at WFO as any other carb once you dial in the secondary air door.

bwiencek

Given that you said street/strip and I'm going to guess that you're 99% street with the trip to the 'strip' is only going to be a couple of times per year... That said:

With the stock vortec heads and stock cam I would recommend a regular 600cfm vacuum secondary carb or the spread bore 650cfm if you're wanting to stay with a spread bore. If you plan on putting a bigger cam in there with more duration and swap to a little more performance oriented rear end ratio (say 3.73's or at least 3.55's) then I would put a 750VS on there as it will help in the future and you're right on when you say there is really no over-carburation worry with a vacuum secondary carb - or at least it's real hard to get it to the point where it's not going to work well.

If it was a 99% strip with only occasional trips down the street - then I'd go with the double-pumper...

bestracing

You do not want to get a 750 for that motor. Go with one that is rated 650 to 600.

novaderrik is right that a good quadra-jet is an excellent option but most used carb's I have come across needed to have the throttle shaft bushings replaced and/or the bowls were warped. Best to find one dirt cheap, use it for as a core to get a good rebuilt carb from a shop like Karb King.

bygddy

Do you wanna go fast? Then stop with the qjet's, and 600 spreadbores....both great for a nice driver with some snot, you said "street/strip" tho. If gears, and hopefully cam swap are in the near future, then 750DP, if just gears, then go 750vc. Trust me...you won't be dissapointed.

bestracing

With a safe maximum RPM's of 6700 and a volume efficiency off 100% you only need 678 cfm but no street car runs near 100% VE. More like 85 to 90 max which at max VE you only need 610 CFM.

The motor he has with a stock cam and small gears he doesn't need a 750. Yes your motor will only use what it needs but going too large is just as bad as too small. Been there, done that.

I wouldn't dismiss a Q-jet either. I've seen Q-jets run a hell of a lot better than a Holley and the other way around too. Holley is just easier, IMHO, to change jets in a hurry at the track with just 4 bolts holding the bowl.

bygddy

He did say it was getting gears, next......
Hey, just got mine up and running tonight, little 268h cam, 327 gear, 2400 converter, 750DP, no stumble, no bog, no rich smell, and no wondering how the secondaries are working.....oh and its fast.
Set up right, the DP always works well for a street/strip car

bestracing

No argument for the double pumper which you can get in smaller sizes.

I raced a 388 motor and it required more than a 750 according to the calculations. Dart "builders" heads, 2.08 intake, 506/519 lift 240/245@0.050 106LSA, 11:1 compression, PG, 4:88 gears. We had an 850 sitting around, put it on there and it worked good but wasn't as consistent as we would have liked. Swapped it out for a 800 (trade with a friend) and the car picked up in the mid rpm range and was more consistent in the quarter.

I just believe a 650cfm would be a better choice. They even offer a 700 double pumper which still would be better than putting a 750 on that motor.

http://www.holley.com/0-4778C.asp