Billet jet plates from Promax ?

[biomedtechguy]

Who is using them? Motor mods you have (if any)? Jet size that works best for you? I have a set of TTi 2"primaries headers on the way with a 2 1/2" exhaust system , and I am thinking that may be conducive to some outboard carb rejetting. Also is anyone using their metering block? Other options? My V code 440 has a hydraulic purple stripe cam (not sure which one) 4 speed and a 3.54 Dana 60.

 

[uwss]

i have a 6 pack and use Promax. You can send your carb to them and they will dyno it for you. That what you will get the best results.

 

[lewtot184]

the quick fuel plates are cheaper. i bought some quick fuels thinking of doing some jetting changes. in the end i didn't use. just thought they were more gimmick than substance. i tried .093" main metering orifices in the end carbs (440, small solid cam, 2"tti's, 3" exhaust) and thought that was a little fat. personally, i don't think there's a lot to be had on jetting up the end carbs. i found that fuel delivery and opening rate made more of a difference.

 

[biomedtechguy]

the quick fuel plates are cheaper. i bought some quick fuels thinking of doing some jetting changes. in the end i didn't use. just thought they were more gimmick than substance. i tried .093" main metering orifices in the end carbs (440, small solid cam, 2"tti's, 3" exhaust) and thought that was a little fat. personally, i don't think there's a lot to be had on jetting up the end carbs. i found that fuel delivery and opening rate made more of a difference.

Fuel delivery? Can you elaborate? As far as opening rate goes, aren't the diaphragm springs the main controlling factor in that regard? Thanks a lot for the replies! I am also going to install an air/fuel O2 sensor stand alone gauge to see how the a/f looks through the rpm range.

 

[lewtot184]

i've gotten more from my engines by paying close attention to fuel volume/pressure than end carb jetting. the springs are the primary control on opening the end carbs, but i've juggled vacuum tee sizes and kill bleeds (which i've learned not to mess with) and the vacuum orifice in the center carb play a part in opening. for me, the promax stuff isn't worth throwing money at. the idle circuts and the main metering in the center carb are the problem areas and are fairly simple to resolve. the edelbrock manifolds themselves are a problem but people get get their minds around the fact that edelbrock has always screwed the intakes up with bad machining.

 

[biomedtechguy]

"... the edelbrock manifolds themselves are a problem but people get get their minds around the fact that edelbrock has always screwed the intakes up with bad machining."...

I will be pulling the driver's side cylinder head off to have an engine shop drill out a broken exhaust stud (I got the car that way) before the TTi s go on. I am going to have the intake (aluminum Chrysler /Edelbrock) media blasted to remove the paint and run it raw aluminum. Is there anything I should look for or have "cleaned up" on the intake while it is off?

 

[JRL]

If you are going upgrade your carbs, I would recommend buying from someone other than Promax. Just opened a 1000$ package from them and I'm really dissapointed. Their machining sucks.
The bore on the throttle base is .040 off. The throttle plates will not even fit...

Ok, got a bit carried away there, but I'm really pissed off.

 

[68 HEMI GTS]

If you are going upgrade your carbs, I would recommend buying from someone other than Promax. Just opened a 1000$ package from them and I'm really dissapointed. Their machining sucks.
The bore on the throttle base is .040 off. The throttle plates will not even fit...

Ok, got a bit carried away there, but I'm really pissed off.

id be calling them back, they seem like a decent company. i would expect them to make it right.

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just for the nay sayers, the six pack outboards do respond to bigger jetting.

 

[biomedtechguy]

I have read a couple of articles on 440s that were built to various levels of performance, as well as a "modern 4 bbl vs. 3x2 bbl. performance (including dyno results). I ABSOLUTELY will be sticking with the 3x2bbl arrangement, and I have a popular book on the 3x2bbl 340/440, but with my upcoming headers, I am looking for a way to tune the a/f ratio and have more flexibility with the setup (3x2bbl) to maximize its capabilities to perform, even when the time comes to build a stroker. Thanks for the replies

 

[Meep-Meep]

The six pack is just plain miserable if it's not right, and getting it right is also a miserable task. You want to rejet the center carb?? Be prepared to pull the rear carb and break the fuel line connections in a strategic way to not box yourself into a corner. I too have a six pack that I'm bound and determined to make work and have it live on my 69 RR (not A12 car) so as time goes on I'll be cussing at it until it's right.

So far in my own experience I found the EGT for #3 cyl and I believe #6 to be high and the result burned the paint off those header primaries during cam break in. This indicates those cylinders are very rich so clearly I'm having fuel distribution problems. The idle mixture settings on the out board carbs are also critical.

Recently I have been in contact with Bob Karakashian (Mr. Six Pack) and he gave me the following BASIC settings to start out with:

Use either #65 or #66 jets on the center carb. Use #82 jets on the pass. side front and rear carb. Use #84 jets on the driver side front and rear carb. These are starting points. Use a 3.5 or 4.5 power valve and if the car wants to idle with the center carb butterflys past the idle transfer slots, you probably will have to drill a small hole, .090-.110, in each butterfly in the center carb. This assumes billet jet plates in the outboard carbs.

My cars don't idle past the transfer slots so no issue there, but I'll add if you have that problem you need to first check and/or correct your initial timing. Timing in the tail pipe will cause you to crank open the idle speed screw.

The opening rate of the out board carbs is also controlled by a bleed off orifice in the out board carbs. The internal passage is teed with one port going to the vac diaphragm and the other to the main venturi. I have seen two sizes of this bleed orifice - .067"-ish and I believe .043". The smaller bleed orifice will allow a stronger signal to the vacuum diaphragm and vice versa. On one of my sets of factory carbs the bleed orifice is .067" on one carb and .043" on the other. WTF??? I drilled my currently running outboard carbs to the larger size and put the black spring. This made a huge difference and believe is a step in the right direction. Also I will note that the opening rate is not linear. I watched them open under load on a dyno and what I found was the initial opening was very quick to about half throttle then very slow after that to not fully open depending on what springs are installed. I think I would prefer the opposite.

FYI: The Ford Tri Power carbs had a progressive linkage and were mechanical. You drive on the center as you'd expect then as you lean on the throttle the front tips in first and finally about 1/3rd to 1/2 throttle of the front carb opening the rear comes in. I thought for a minute with my old factory set with different size orifices front and rear that the opening would function like the Ford but then decided that's impossible because the safety linkage ties them together.

 

[biomedtechguy]

Thanks Meep-Meep

 

[66Satellite47]

.

"So far in my own experience I found the EGT for #3 cyl and I believe #6 to be high and the result burned the paint off those header primaries during cam break in. This indicates those cylinders are very rich so clearly I'm having fuel distribution problems. The idle mixture settings on the out board carbs are also critical."

Gee, I thought the burned header paint was from being lean. Isn't the excessive fuel, "rich", causing the gas coming from the chamber to be cooler? I sure could be wrong. The end carb idle mixture adjustments make a huge difference. Having an adjustable bleed on the vacum lines to end carbs is very convenient. I had 3 different sets of carbs from '69's to 71's, they all seemed to have a little different metering & vacum orifice sizes. Stock metering plates in the end carbs worked pretty well in both the '69 & '70 carbs.

 

[uwss]

I had great results from Promax; service was great. Parts I ordered were right on. I guess every company can have a hiccup once in a while.

 

[biomedtechguy]

.

"So far in my own experience I found the EGT for #3 cyl and I believe #6 to be high and the result burned the paint off those header primaries during cam break in. This indicates those cylinders are very rich so clearly I'm having fuel distribution problems. The idle mixture settings on the out board carbs are also critical."

Gee, I thought the burned header paint was from being lean. Isn't the excessive fuel, "rich", causing the gas coming from the chamber to be cooler? I sure could be wrong. The end carb idle mixture adjustments make a huge difference. Having an adjustable bleed on the vacum lines to end carbs is very convenient. I had 3 different sets of carbs from '69's to 71's, they all seemed to have a little different metering & vacum orifice sizes. Stock metering plates in the end carbs worked pretty well in both the '69 & '70 carbs.

Ditto re: too lean =excessive heat. Good replies from all. Thanks

 

[SUPERSTOCKRACER]

I like quickfuels!

 

[Meep-Meep]

.

"So far in my own experience I found the EGT for #3 cyl and I believe #6 to be high and the result burned the paint off those header primaries during cam break in. This indicates those cylinders are very rich so clearly I'm having fuel distribution problems. The idle mixture settings on the out board carbs are also critical."

Gee, I thought the burned header paint was from being lean. Isn't the excessive fuel, "rich", causing the gas coming from the chamber to be cooler? I sure could be wrong. The end carb idle mixture adjustments make a huge difference. Having an adjustable bleed on the vacum lines to end carbs is very convenient. I had 3 different sets of carbs from '69's to 71's, they all seemed to have a little different metering & vacum orifice sizes. Stock metering plates in the end carbs worked pretty well in both the '69 & '70 carbs.

A very lean mixture will cause lower EGT's but so will a very rich mixture. In my case I believe the mixture to be rich enough to cause higher EGT because there is more fuel being burned but not to the point of excessive fuel providing cooling. I'm also beginning to foul a plug and that's typically a rich condition.

 

[biomedtechguy]

Foul a plug? Are you sure that the intake is thoroughly sealed at the valley pan gasket? If not, oil can be suked in to the intake.

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I like quickfuels!

I will check that out. Thanks

 

[68 HEMI GTS]

I like quickfuels!

like these :icon_cool:

 

[JRL]

Nice!

 

[62MAX]

Nice!

And 1/3 the price and you can get their cast plates for even less !