I know this isnt the carb board.

I'm helping a guy build a drag car for his son and I told him I'd ask around to see what the poop was in the drag sceen on predator carbs. This is a little chevy II car he picked up with a beefed up "13:1" so the builder said 350/glide/4.56 combo. The speed shop told him not to use one and reccomended a 750 DP which I think is way to much. This car will never see the street so I think the predator might be a better choice for a race only carb.

 

I've seen a few but it's not a common carb to use, especially for drag racing. The majority use Holley/Barry Grant or a Q-jet, Edelbrock, Carter AFB style. They're easier to tune and get parts for than a Predator.

You're going to want a minimum of a 750 DP on a drag car even for a 350. Don't go by the carb formulas for an engine. They're for street cars. Drag cars can easily use larger carbs since you use it at WOT where the volumetric efficiency is a lot higher. I ran an 850 on a 383 just fine. I also used it on my 469 but have just upgraded to two 850's.

A 13:1 engine is going to need race gas. That's a little out of reach for normal premium blends. VP C12 would do fine.

 

Personally never seen one on a drag car but had a buddy that used to compete in mud runs that tried one on his 396. He tried for a soild month to get it tuned, but always seemed to have a low end lag that he could never work through so he sold it and went with a 850DP, problem solved.

Like Stephen said the 750 will not be too small and would be the minimum starting point imo. I'm running the 950HP on my 388 with great results, I have many other posts regarding the MANY cfm sizes I used on my old 355 over the 2 yrs I raced it, that 355 was a very mild 9.3:1, 230/230, .480/.480 cam with 305 heads-street motor the whole way. Started with a 600VS, 650DP, 750VS, 700DP, 830DP, then the 950HP-in that order. The car got consistently quicker/faster with each jump in carb until I went from the 830 to the 950. After doing some research found the 950HP only wet flows 830cfm so it explained the same et/mph as what the original 830DP had to offer, biggest change was consistency came around to what I'd call deadly after I installed the 950HP.

 

The 950HP is actually and 850 sized body with a 750 sized baseplate so the number confuses many people. For many people it works well but no 2 engines are the same.

 

That's why I was very upset once I found out, after the fact of course Otherwise I would've just gone 850 and been done, but overall being a street/strip set-up, the 950HP has proven to be a very versitile carb on more motors than just the 2 I've had, many of our Mod. racers here at home swear by this carb and it's running on 327's to 496's with more than not seeing street/strip duty and ET's from very low 10's to high 12's/low 13's.

Just unfortunate it costs so much txperiment by buying/borrowing carbs and logging passes to see the difference, and paying for dyno time is not cheap either and your kind of limited by what carbs that particular shop has on the bench for testing anyways.

I would still not run anything smaller than a 750 in this case, that's my story and I'm stickin to it

 

Thanks for the input, I'll tell him not to get a pred.

Another question, how much would a 650DP limit this car? His son is running in the high school class and is use to a low/mid 14 second BB GTX. He doesent want his son to jump from a 14 second car to somthing that will scare the crap out of him. This little nova doesent need too much to be very quick it's already very light and I'm thinking if the engine is built like the prevoius owner said it will run low 11's even at this altitude.

 

Once you get the jetting right it will slow down the high rpm top end charge since it can only take in so much cfm. Just an off the hip guesstimate I would imagine only using a 650DP would slow it down maybe .2 or .3, kind of hard to say since there are soo many variables, but it will be slower with the smaller carb period.

 

Engine is an air pump. It draws in an air/fuel mixture to burn which produces power. No matter what size the carb is, they all need to be jetted to achieve a proper 14.7:1 or so air fuel mixture. The larger the carb, the more air/fuel can be sucked into the engine. There comes a point when the carb just gets too big and the increased volume of air/fuel is too much for the engine. 2 small 600's on a tunnel ram is better than one large 1200 dominator however it takes more tuning to get multiple carbs working properly.

The engine's ability to draw in air/fuel plus things like cam specs and compression ratio all factor into how big a carb is enough. Even a mild street SBC will gain from having a 750. I've also seen some 350's at the track run faster with a 650.

If you could read the plugs after every run, use a EGT to see what the exhaust temperature is and use an o2 sensor to watch the mixture, you could probably figure out what carb works best.