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470 conversation tuning

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Trying to get the carb on my 470 conversion dialed in. It has a two barrel Holley. #88 jets and a I believe a 4.5 power valve.
Seems to run pretty good, I'm happy with how it runs. But seems like in my research everyone seems to be running smaller jets then this, and I think im burning more gass then I should.

PXL_20240721_163728505.jpgStbd bank top. Left is rear. Threads are a bit oily on the rear. Dry on the others.

PXL_20240721_163214884.jpg
Port bank top. Right is rear. Same thing just the rear has oily threads.
Ngk ab-6. We put quite a bit of hours on it this weekend, between light load frogging and higher load ridding.

How do these plugs look?

The port bank I had to replace the piston in the middle cylinder because it had a bad intake boot before it and ran lean. I should have done all 3 while I had it apart. I have a suspicion the rear cylinder also needs rings and it's leaking oil. But I might use one quart for a tank, 25-30 gallons.
 
John Fenner said:
Put in a power valve plug, #88 jets are way too fat, go to #78 a new set of top plugs and while heated up do a full run up with little to no idle time, plugs should have a slight tan color.
Click to expand...
I should be able to do a pull on the trailer to fine tune jets right?

Other then one less thing to fail, why don't these engines benefit from a properly sized power valve? Is it the low RPM?
 
John Fenner said:
Power valve is for fuel economy in a car or truck, not needed in this application.
A run up on trailer is fine.
Click to expand...
I purchased a jet kit and a power valve plug.
If it opens under high load, wouldnt it be open on a sticky trail, yet burning less fuel while cruising?
 
If you play the vacuum tuning game.
Think of it this way, there are no bracket race cars with power valves to keep it consistent timing and response.
My 220 has a secondary plate from a 750 AED carb no power valve provision on a 500 Holley, runs great.
 
Installed a power valve plug and 78 jets.
Throttle response seemed slower. It came up to temp significantly faster.
Little bit of idling, few minutes at 2000-2500 then about a minute at wot and shut down.
Stbd bank. One with the socket is the rear.
PXL_20240728_191748179.jpg
Port
Socket is rear.
PXL_20240728_191347757.jpg

Looking lean?
 
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Also once it warmed up I was getting about 14 of vacuum at idle and it was about the same at 2200
 
He told you multiple times what to do, and to ditch the power valve, yet you still do it your way, so additional help might be un-likely.
And as an aside, you had a genuine expert giving you advice.
 
Alaska viking said:
He told you multiple times what to do, and to ditch the power valve, yet you still do it your way, so additional help might be un-likely.
And as an aside, you had a genuine expert giving you advice.
Click to expand...
Reading comprehension must not be your strong suit
 
I have the squirter on its way.
Is it normal for the vacuum to be similar at idle and 2200 on these engines?
Just checking, could the design of my manifold be giving me any issues?IMG_20240729_202319.jpg
 
As far as the vacuum goes, gotta keep in mind this is a big bore engine with the proper cfm carb to feed it so I'd say yes.
The intake plenum looks very well built, I see absolutely nothing wrong with it.
 
A thought crossed my mind amongst all the other s#¡t running through it, you need to open up the pilot jets a size, this will give a fatter idle mixture adjustment and off idle transfer as well.
They are located on either side of the now power valve plug, brass inserts.
 
John Fenner said:
A thought crossed my mind amongst all the other s#¡t running through it, you need to open up the pilot jets a size, this will give a fatter idle mixture adjustment and off idle transfer as well.
They are located on either side of the now power valve plug, brass inserts.
Click to expand...
Do those get opened up with a small drill?
 
Put the #32 on. It had a 28.
Reamed out those holes.
Went to remove the brass filter and found a wasp in the barb. Must have snuck in the fuel line when I had the carb off.

I didn't have the trailer hooked up, so I couldn't really get on it but it felt much better.
What are some symptoms to look for when I take it out if it's running lean?
 
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