RT930turbo

The squirters are 31's, I'm going to pull the carb, check everything over AGAIN, then reset the timing, and go from there. I will report back...

Thanks again all.

3mthunder

I had an idle problem similar to yours I put a new base plate on and it worked great . There must have been a small leak I could not find.I also increased my squirters to I think #45 and my hesitation went away.

mcollinstn

The cam is a little on the hot side with a pretty narrow lobe center for a 468" boat motor.

but, you still have some carb problems.

1) Make sure the throttle plates are centered up on the screws and are facing the right direction. Best way to do this is back out all of the throttle stops and let them close all the way. Then, loosen all the throttle plate screws and then barely snug em. Flip the throttles open and closed a few times, and tighten the screws. This way, you're starting off with all of the venturis balanced with each other.

2) Make sure your accel pump cam starts bringin in the squirt right off idle.

Don't set your secondaries open, leave them where they pretty much shut.

Now, you've mentioned you're using a LOT of idle mix screw (lots of turns out) and LOTS of idle stop screw (in, to open plates) in order to get your 750rpm idle.

This KILLS the transition circuit.

You need to start drilling holes in the primary throttle plates and trying it. Generally a little bit goes a long way. Start small and test. Each time adjust idle mix for best vacuum. Keep upsizing the holes one drill size at a time until you're in "normal" idle stop and idle mix screw positions.

Your powervalve at 2.5 is low enough to not be a factor for these tests (assuming the diaphragm isn't ruptured - be certain about that).

This ought to get you into a range where things behave more like you expect them to. You should be more familiar with the fine tuning procedures once you get some bleed air thru the butterfly holes...

MC

Griff

I agree with mcollinstn, the cam is definately on the large side for a 468. It probably won't make peak power until close to 6000rpms. It is part of the issue and probably causing the low vacuum readings.

Strip Poker 388

try going up in squirter,iv even drilled them out on the smaller ones .Ive been up to 60 on my Chevelle,still no stumble.

or the nozzel style

Hey guys what about a 4hole spacer to get more responce/signal out of the carb?

mcollinstn

Performer RPM already has a divided plenum. Going to a 4-hole shouldn't really do anything unless he is currently running an open spacer (is he?).

JJONES

just curious. when did this problem start? is this a new carb for the engine? have you changed ANYTHING and then found the carb none adjustable? is anything new on the motor? did the cough just start on its own? I think you need to start all over from the beginning and figure out when this problem first occured. Holleys are pretty simple and old school technology so im guessing when the first instince happened you will probably get the answers.

RT930turbo

Spent quite a bit of time in the shop tonight, didn't make it to the water, but certainly will tomorrow.

Awesome advice, this will be my starting point tomorrow morning! Also pulled and checked the power valves tonight, all good.

I know the cam is on the large side, the boat runs best when it's proped for 6k RPM. The power really comes on between 5100 and 6000.

It currently has a 4 hole spacer, forgot to mention that.

I haveve some larger squiters, I'll bump them up and see what gives.

The problem really manifested whn I changed props. I've only had the boat for about a year, and it came with a cleaver that really had no bite down low. When I switched to a mirage plus, the problems really became apparent. It has been acting up since I've owned it, thats part of the reason I'm having trouble getting a base line.

I owe you guys some cold ones! I'll let you know how it goes tomorrow...

RT930turbo

Got everything in order, changed squiters to 50's, reset everything in the carb, and cracked the secondaries a little more. Put fresh gaskets on it, and ran on the trailer. We are definately getting closer, headed to the lake now to see how she does.

Mbam

You need to open up the idle feed restrictors. Take a look at that Holley book and find out which of the passages they are. Get a set of small number drills and a pin vise (this is a holder so you can twist the drills by hand). Go .005 at a time (with testing in between). Your goal is to have a stable idle with the mixture screws open about 3/4. You will know if you have it right when you keep opening the screws and the rpm falls off. Listen to MC on drilling the throttle plates.