Carb prep for blowthrough setup?
 

I'm a pretty fair way through my build and was not aware that my carb may not hold up to being boosted. I have searched and searched to find a thread covering my issue, but was unsuccessful. I have a Holley 600, single feed, vacuum secondaries, jetted for an SP 12a, fitted with a nipple for the omp.

1. Is it necessary to mod my carb if I'm only running about 7psi?

2. What modifications need to be made to the carb to handle boost?

3. Am I better off going with a webber set up?

Thanks in advance for your help.

Here, this should help get you started: http://www.hangar18fabrication.com/blowthru.html

One problem you will run into is the fact that your carb has vacuum secondaries. These don't normally work in a blow-through setup. It may be possible to mod the carb so that you can still use it, but you may have to get a mechanical secondary carb. I don't know.

Webers are dead simple to prep and tune, but there's a lot more info on blow-through Holleys out there, and you can actually buy pre-made carb hats for Holley style carbs. So, take your pick.

Either way, http://www.theturboforums.com/ will be a great resource for you, especially if you go the Holley route.

Hey, thanks for the help! awesome info in those links.

I've been back and forth for a while about whether to stick with the Holley set up, or go with the dual Webers. I've heard much more + feedback about the Webers. I have a carb hat for my set up and may be buying a turbo prepped carb from a member here on the forum.

Any idea on what size ida Weber would work best for a low boost, blowthrough set up?

I'd avoid dual carbs, personally. Blow-through setups are tricky enough with just one. For the Weber route, use a single 48 IDA. Great carb, very flexible. You'll have to ask someone who's run one on a 12A what size venturis would be appropriate.

Bear in mind, though, that for the cost of even a used 48 IDA and manifold, you could buy a brand new boost-prepped Holley from any of a number of sources (granted, it won't have fittings for the OMP lines). Since you already have the manifold and carb hat for the Holley... eh, if it was me I'd just go with that. Your choice, though.

bad83 can boost prep a stock nikki. Probably other carbs to, I've never asked him.

:icon_tup: :icon_tup::icon_tup:

I really do want to stick with the Holley set up. The cost of a Weber set up is what led me to go with a Holley in the first place. I know that a Holley can work great on a rotary when they're jetted and tuned properly. I'm sure that it's no different with one that's prepped for a turbo set up. I'm really hoping to get the prepped carb that's for sale on here.

if its a 600 duble pumper/ mec. secondaries it will work the vacume secondaries is where you run into problems.

poost preping a holley is not hard at all. if thats the rute you go let me know i can hellp you with jetting ect. to get you started.

fyi. im running a holley 600 dp, bnr stage1 s4 turbo, 3" exaust, s4 tii rad. & fd e-fan upgrade under way.

The one that I currently have is a single feed 600 with, what I believe to be, vacuum secondaries.

I'm waiting for word on a 650 dp that is already boost prepped. If that doesn't go through, I'll let you know. How well does your carb work with your set up? Are you using a rising rate fpr? Also, what fuel pump did you go with?

You definitely want a double pumper. Vacuum secondaries wont work, and holley's don't like to ghetto rig mechanical secondaries like the Nikki does.

Follow Hanger. Start smaller on the bit size and slowely work up on the boost. Once you over drill, your metering block is done.

Thanks for the help, guys.

When I started my build, I never planned on boosting it. I had the carb before the decision to go with a turbo. I would be done and driving by now if I didn't take this, $2,000+ detour that's added an extra year or so on my project. I'm just glad that I went with the 3rd gen corner seal springs when it was rebuilt and ported.

I have a 3" Griffin radiator, with a ford e-fan and a Mazdaspeed 6qt. oil pan with twin 3" fans on the oil cooler to, hopefully cut down on the extra heat that's going to be generated.

Hey I'm like you. When I started this I never planned to turbo it, anyway. I was gung-ho for Camden. I'll still start with a Camden, to see what I can get out of it, but I feel turbo is the right way to go.

PercentSevenC or anyone else that might know, I've got an RB Holley 600 I'd like to boost prep. I'm not too clear about specific changes RB makes to these carbs to get them to run on a separate runner manifold. I'm wondering whether these changes will hinder boost prepping. Any thoughts?

turbo is the way to go.i had a camden for a year i got bored real quick..+ with a turbo the blow off valve sounds so cool......a top end is good 2

Yes. I might have access to an FD engine. I wonder if that will fit?

how u are talking....it will fit with a little work:bigthumb:...back to the holley. boost prepping iz easy .start off with hp series. send the base plate to customcarbs.com they will prep it..get a new base plate gasket .nylon gaskit kit...four orings 4 ldle screws make thing eazy get quick jet bowls.............and block off power valve

Ok, I've sold the old single feed and now have a 650 dp. I'm wanting to do the prep myself by following the hangar thread. Does anyone know if a Barry Grant rebuild kit would be sufficient for what I'm doing?