Blow Thru Carbs

[supergass]

What is the story on these carbs and there performance. I have a 565 Chevy that I want to use with a D-3 Procharger on the street. I do understand carberators well but I just didnt want to spend all the money to buy one of these carbs only to find out they didnt work well at all. Thanks!

[jmarkaudio]

The trick with a street blow thru is getting the PV calibration right. It is a bit tricky, you need a properly built carb, an O2 sensor, and time to make final tuning yourself. It needs adjustable restrictions to the PV cavity from both the boost side and the vacuum side to balance where it opens.

[supergass]

The trick with a street blow thru is getting the PV calibration right. It is a bit tricky, you need a properly built carb, an O2 sensor, and time to make final tuning yourself. It needs adjustable restrictions to the PV cavity from both the boost side and the vacuum side to balance where it opens.

Ok I see what you mean. So you think they work good once they are right?? I just didnt want to wish I had spent that money on the EFI. I believe with the 565, 10-12 lbs of boost would be nice easy big power. First time building anything forced induction.

[user-23911]

Waste of time when EFI is so cheap and infinitely better in every way.

[dave brode]

https://www.theturboforums.com/forums/c ... tions.223/

[turbotater]

i have done several . built my own carbs. i was driving one of the cars back and forth to work last week. in my worthless opinion if you are putting together a 500-800 hp combo blow thru works fine. any more than that and what it costs to get decent data logging information and street manners is equal or more than a basic efi setup.

[supergass]

i have done several . built my own carbs. i was driving one of the cars back and forth to work last week. in my worthless opinion if you are putting together a 500-800 hp combo blow thru works fine. any more than that and what it costs to get decent data logging information and street manners is equal or more than a basic efi setup.

Yes I am sure that since there are so many manufacturers getting into EFI that the cost will come down, and already has I am sure.

[user-23911]

The megasquirt EFI is the best value for money, it's open source, all the required info is online to DIY.
All the sensors and other bits you can get from the junkyard.

What more would you want?

[user-23911]

https://www.diyautotune.com/product/meg ... lack-case/
For bringing an old technology car up to modern standards.

http://www.jegs.com/p/Demon-Carburetion ... 7/10002/-1
For Fred Flintstone.

[Pro-SeriesFab]

I agree with what's been posted . . . having gone down the blow-thru route with a junker 650 holley converted to BRPV, vent tube extensions, etc I did all that to realize I was way ahead starting with megasquirt.

Car ran better than it ever did with a carb and also got a lot better mileage.

Not saying it can't be done but I am saying it's like running mechanical fuel injection on the street . . . you're going to have alot of trial and error and pulling parts.

[Frankshaft]

I have used no less than a dozen quick fuel blow thru carbs, specifically designed for blow thru applications. They all have worked awesome. Idle, drivability, power mileage, simplicity. Street cars, street/strip stuff and marine. As high as 1160hp. 548 BBC, procharged, hydraulic roller marine engines. If you convert a carb, I can see it working ok, but a dedicated purpose built carb, can and will work great. Csu, dual needle and seats, with big volume bowls for anything over about 1200.

Mega squirt is a cool set up for sure. Also, the fi tech units work surprisingly well if you want efi and simplicity.

[jmarkaudio]

Info on boost referencing the PV

http://racingfuelsystems.myfunforum.org ... f=28&t=517

A little more on a blow thru.

http://racingfuelsystems.myfunforum.org ... f=25&t=502

[Tuner]

Posts in this thread, specifically on page 5, describe dialing in the BRPV bleeds and hitting the sweet spot for the particular engine, turbocharged 514 Cadillac, blow-through 850 Holley, video of 10.93 120mph pass, '71 C10 Chevy PU.

http://racingfuelsystems.myfunforum.org ... 7&start=40

[dave brode]

That was my struggle with the 850. I tried and tried to address a lean spike. I was worried about rattling the head gaskets out. Mark and Tuner [and others] held my hand along the way. Finally, blocking the MABs did the trick. I suspect that at my power level, a smaller venturi carb [650-750] might have worked ok w/o blocking them .Tuner's BRPV setup is so slick, and quickly adjustable.

Note that I had it adjusted for quick PV opening for the dragstrip pass. On the street, the AFR is more mileage happy. It actually was not bad at all on gas.

Dave

[user-23911]

Once you've got boost, you also need ignition.
A carburettor is only half the story.
You need knock control too.The megasquirt (most EFI) can do knock control but needs add on bits.
It can do ignition too. Distributor, wasted spark or COP.

So with a carburettor you're going to go with MSD?
As in my spark's disappeared.