Technical Holley Tunnel Ram 450 carb tuning

howdy All

After some tuning advice for a pair of Holley 0-9776 450 clear tunnel ram carbs.

As these carbs have jets in the front metering blocks and specific size fuel holes in the rear metering "plates", do the jets and metering plates need to be replaced in tandom to effect any increase in fuel?

I know you can get conversion kits to add metering blocks in the rear so you can have jets in the rear also, but want to know about the metering plates.

Is it worth adding primary jets without increasing the size of the secondary metering plates?

Cheers

 

You can just change the primary sides if you don't have to make that big of a change.

 

Those carbs respond very good to a pump cam change - they have mechanical secondaries and no accelerator pump (in the secondaries) so you want a cam that is still shooting fuel as the secondaries start to open to help cover the "hole" created when they open........as for your actual question.....if your not rich enough at wot after jetting up the primaries a few sizes, you can get a different secondary plate......much cheaper than converting to a secondary block

 

Or you use small diameter reamers to open up the holes a step er 2 bigger....

 

Thanks folks, we are pretty close but a only a tiny bit lean as we are 0.002 off a 10 second run, we are on the rolling road next weekend to dial in the timing so thinking to step up on one size on the primaries to get everything we can out of it.

I've read up on the cams but i'll get me head around that also as it should also help.

Thanks again

 

On mine I converted over to 50cc pump and cam kit, increased the shooter, also bumped up the jets and float level to mid sight level, ran like a ****d ape !

 

As mentioned , accelerator pump, cams is key a lot of the time on these carbs. The 50cc pumps is a nice upgrade for not alot of $. Increase shooters til it is rich and then back them down some. Throttle response should be very crisp.

 

Unless you turn the carbs sideways there's no room for metering blocks , you can buy metering plates that fit in the normal spot that use regular holley jets from AED , not terribly expensive... anoyher way to richen WOT is to increase the PVCR's...