My engine sure seems to want more jetting

[Lil Demon]

Ok I’m about to pull the carburetor off. Meanwhile I’ve replaced the spark plugs and noticing that on both sides the plugs indicate richer at front cylinders vs back, each plug looking cleaner towards rear cylinders. Is that a fuel distribution problem with these Edelbrock RPM Airgap intakes? I verified intake bolts and they are all well tightened. Sorry not the greatest lighting in the picture

 

[TT5.9mag]

Ok I’m about to pull the carburetor off. Meanwhile I’ve replaced the spark plugs and noticing that on both sides the plugs indicate richer at front cylinders vs back, each plug looking cleaner towards rear cylinders. Is that a fuel distribution problem with these Edelbrock RPM Airgap intakes? I verified intake bolts and they are all well tightened. Sorry not the greatest lighting in the picture

View attachment 1716482865

Haven’t noticed that on my magnum with the rpm air gap. Do you have a spacer on it or is the divider cut down?

 

[Lil Demon]

I got a 1 inch phenolic spacer but the carburetor was loose. I guess I just snugged them down and forgot to tighten yesterday.

 

[Illahe]

Ok I’m about to pull the carburetor off. Meanwhile I’ve replaced the spark plugs and noticing that on both sides the plugs indicate richer at front cylinders vs back, each plug looking cleaner towards rear cylinders. Is that a fuel distribution problem with these Edelbrock RPM Airgap intakes? I verified intake bolts and they are all well tightened. Sorry not the greatest lighting in the picture

View attachment 1716482865

Your carburetor is equipped with 4 corner idle circuits, correct? Are your butterflies set equally at idle?

 

[Lil Demon]

4 corner idle, idle screws and throttle plates equally set, carburetor was loose.

 

[Lil Demon]

Looks like I’m going to have to drill if I want to tune the emulsion package?

 

[MobileCustoms]

well, now you know why I suggested checking all the basics for sources of vacuum leaks, etc. Pretty hard to tune with a loose carburetor! I'd try a set of even smaller jets in the front primaries, like 68... if it were me. Then get some new vacuum readings at various cruise speeds and at idle, and write them all down.

 

[Lil Demon]

I get it but the carb has been off multiple times during this discussion and the only time it was loose was for my drive home yesterday which was not being vacuum tested so it takes that problem out of the equation.

 

[fishmens67]

Looks like I’m going to have to drill if I want to tune the emulsion package?

View attachment 1716482885

I wouldn't monkey with the emulsions at this time, just another rabbit hole at this point.

 

[fishmens67]

1 inch phenolic spacer

Have you tried it without the spacer.

 

[Lil Demon]

Not recently, I figured we’d be skipping messing with emulsion so I slapped it back together with 68 primary and the 6.5pv just to see what it did. I also opened up the transition slots a bit and brought initial timing down to 18. Plugs are white and bucking returned, not as bad but returned. It was happier with the last setup. Like I mentioned it was almost completely solved. I had to make it leave really soft and shift super early (1700) to make it buck. Under normal driving (2200 shifts) it was virtually solved. With that being said I will go back to 70 primaries, and mess with the 7.5-8.5 PV. My engine lives below 10 inches of vacuum given the gearing, so I don’t think I want the PV fueling all the time. So I think I need to stick to tuning in that vacuum range to make it best. I’m going to call it a day and mess with it again when I get that 7.5pv.

You all have a Happy Thanksgiving!!

 

[fishmens67]

Are you running vacuum advance, is it ported vacuum or full, where is your full mechanical advance set. mechanical would have decreased with your latest initial setting.

 

[Newbomb Turk]

Looks like I’m going to have to drill if I want to tune the emulsion package?

View attachment 1716482885

You NEED to close that middle hole off. You don’t need three emulsion holes open.

How big are the holes now? If they are bigger than .028 you need to use a 6-32 brass set screw and drill an .028 hole in it.

Thread the holes in the metering block to 6-32.

Do you see the brass restrictors on each side of the power valve? You need to measure those holes too.

Those holes for a 650 don’t need to be any bigger than .028 and then you start with an .070 idle air bleed and tune from there.

That extra emulsion with a carb that small will cause slugging. That’s what happens when you pull a “slug” of fuel and then a “slug” of air.

You can usually see it on the a/f meter most of the time.

You need to correct that first.

 

[fishmens67]

You need to correct that first.

He needs to correct his timing curve first

 

[MobileCustoms]

24 initial seemed a little high and going all the way to 18 seems a little low. Maybe bump it up to 20 or 22 and see if that makes any difference before changing jets again. The biggest rule for me in fine tuning is to only change one thing at a time to see how each thing affects it. You'll get there with a little patience!

 

[Lil Demon]

Are you running vacuum advance, is it ported vacuum or full, where is your full mechanical advance set. mechanical would have decreased with your latest initi

No vacuum advance. Mechanical advance is limited to 12 degrees. So with the 18 initial, I had 30 total.

This engine has always felt better with 22-24 initial. Quicker starts, happier idle and more responsive.

 

[mopowers]

Nothing wrong with 22-24 initial if that's what it wants.

 

[Illahe]

Looks like I’m going to have to drill if I want to tune the emulsion package?

View attachment 1716482885

No vacuum advance. Mechanical advance is limited to 12 degrees. So with the 18 initial, I had 30 total.

This engine has always felt better with 22-24 initial. Quicker starts, happier idle and more responsive.

Why only 30* total?

 

[Lil Demon]

Why only 30* total?

Cause I lowered base timing and didn’t feel like disassembling the distributor to increase mechanical. I normally run 36 total

 

[Illahe]

Just wondering, I ran a mechanical Mallory unilite in my 340 for years.

 

[Lil Demon]

Just wondering, I ran a mechanical Mallory unilite in my 340 for years.

I love Mallory Unilite. This is a Pertronix and it’s a bit more involved to change the mechanical advance

 

[TT5.9mag]

Looks like I’m going to have to drill if I want to tune the emulsion package?

View attachment 1716482885

I just wanted to see if you had 5 hole blocks and what was open. You have 3 hole blocks (good) and do like Newbomb said below.

You NEED to close that middle hole off. You don’t need three emulsion holes open.

How big are the holes now? If they are bigger than .028 you need to use a 6-32 brass set screw and drill an .028 hole in it.

Thread the holes in the metering block to 6-32.

Do you see the brass restrictors on each side of the power valve? You need to measure those holes too.

Those holes for a 650 don’t need to be any bigger than .028 and then you start with an .070 idle air bleed and tune from there.

That extra emulsion with a carb that small will cause slugging. That’s what happens when you pull a “slug” of fuel and then a “slug” of air.

You can usually see it on the a/f meter most of the time.

You need to correct that first.

I came to say just that. Thanks

 

[crackedback]

Is the factory jet spread 6 or 7? Last thing I saw was you have a 4 spread primary to secondary.

That needs to be that 6-8 number to balance things. Unless you went way down on the PVCR.

 

[Lil Demon]

Is the factory jet spread 6 or 7? Last thing I saw was you have a 4 spread primary to secondary.

That needs to be that 6-8 number to balance things. Unless you went way down on the PVCR.

Factory spread was 4 70/74

 

[TT5.9mag]

Factory spread was 4 70/74

The chart you posted said the jets were 86/93