Carb jetting

I’m rebuilding a carb for Kayse’s 440 Dart.

What’s a good starting point for jetting for a Holley 830 double pumper.

The combo is 9.5 to 1, 509 cam, Torker intake, headers.

The carb was an old Carb Shop carb that had the power valves eliminated and 90 jets on the primaries.

I have to replace the metering blocks due to the parts that hold the jets being broken so I got new metering locks.

What’s a good starting point on the jets?

Look up the original specs for the list # on the carb as it came from Holley. You gotta start somewhere (as I've been told myself more than once).

Did you get hold of some billet adjustable metering blocks?

They're not billet, but these are the ones that I bought.

What brand are those?

EDIT: If those are Speedmaster/Procomp, you'll be better off getting your $ back and using old Holley blocks.

What's wrong with the speedmaster/procomp blocks?

Brad - It sounds like the main jet threads are stripped. See top post. Not much depth for a helicoil or insert. Suppose it might be worth a try.


I suspect one thing Brad's looking at is the emulsion and idle feed restriction. Easiest and most straightforward tuning will be setup like an old school Holley. This keeps the fuel most consistant.

You can make the blocks you purchased similar to the original blocks.
Some useful references and explanations here:
https://www.tapatalk.com/groups/racingfuelsystems/stickies-f31/

in particular the ones titled
Relocating the Holley Idle Jet
Emulsion Tuning
Numerical Listing

I’d set it up 100% per original settings, then tune from there. I’ve always felt that if you have to go much off the original jetting spec with a basically stock Holley carb, then there’s likely issues elsewhere that need to be found and addressed. I’d start questioning anything more than 4 jet sizes off spec., personally.

Look like chinese crap and would steer away from those as I've tossed a few in the trash for having issues..........

To quote Dominic, who has certainly had his hands on more carbs than I have: "... chinese crap and would steer away from those as I've tossed a few in the trash for having issues..."

Even the fancier billet version isn't a good product. More examples of cheap offshore copies that aren't even GOOD copies.

I think Mark Whitener commented that by the time you've checked and corrected all the passage sizes with these things, you would have wished you'd bought better parts to start with.

I wasn't trying to suggest that the OP use the old damaged blocks, but to get set of standard Holley blocks before he starts trying to tune it. Sorry for any misunderstanding.

If u need good quality BLP blocks, I can set a pr. up for ya and ship em............

^ that is probably the best route...

Well I read more into it than you intended. No biggy. Everything posted is relevant and should be helpful.

Thanks for the replies.

What I had on it were Carb Shop metering blocks like this.









They are designed to be able to change the jets without taking off the fuel bowl.

My problem is that one of the jet holders is broken in half.
Those are the brass hex's you see going in on an angle on the top of the metering block.
This means the jet isn't in the proper place and fuel gets by it that isn't metered by the jet.

Since apparently they went out of business in 1996 and parts aren't available that's why I'm changing the metering blocks.

I've got a buddies 850 double pumper on the car right now and it has 82 jets in it.

I'm going to start with 78's on the primaries and 80's on the secondaries and see how that works on my carb.

Might be worth posting something on the RFS forum.
Its not a high volume of activity there, but higher than normal percentage 'collect' interesting things like that.

In fact there's a couple of threads there about the Carb Shop and Rapidjet blocks. BLP made a version very recently. Troy Patterson was always promoting the Weber version, although I hate suggesting contacting him.
Before doing that, see if with some collective knowledge, we can determine which if any of the metering tube/jet holders interchange.

Mark and a couple of others also have some insight into their pecularieties during high flow. I think they are pretty neat idea, and the carb shop's version was close to the same thickness as an original Holley block. Pretty slick IMO.

All that lazy fancy stuff is just that and a basic good ol holley with normal blocks(billet being best) have out shined those gimmicks forever...........