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Still screwing around with the Holley 390
https://slantsix.org/forum/viewtopic.php?t=36652		 Page 2 of 3
Author:  DusterIdiot [ Mon Aug 10, 2009 5:27 am ]
Post subject:  Uh...
Are you running points or EI?
Author:  wjajr [ Mon Aug 10, 2009 7:38 am ]
Post subject: 
orange box

Me quoting me from first entry this post:
Quote:
Any hints on getting rid of the rolling rpm? Would a GM HEI up grade over the orange box help this condition?
Author:  ceej [ Mon Aug 10, 2009 8:06 am ]
Post subject: 
It sounds like your light spring is too light. The hop out is too close to idle speed.

IIRC the mechanical shouldn't start coming in till ~1200-1500 rpm. Having the spring perch a tad tighter to load the spring slightly may help that. Are you seeing timing bounce at idle?

CJ
Author:  wjajr [ Mon Aug 10, 2009 11:57 am ]
Post subject: 
Ceej:
Quote:
It sounds like your light spring is too light
Ceej I think you are on to something. I conducted yet another study, curve of mechanical advance: rpm; degrees advanced; vacuum; and idle quality.

Small red spring & long black/green spring with 11-R governor, vacuum advance disconnected and its port sealed off at carburetor, transmission in park:

900 rpm +10* steady 8" Hg. rough lope
1000 rpm +12*-15* 9"-10" Hg. lope
1500 rpm +23* 14" Hg. smooth
2000 rpm +23* 15" Hg.
2500 rpm +27* 14" Hg.
Quote:
IIRC the mechanical shouldn't start coming in till ~1200-1500 rpm.
As one can see, mechanical advance is starting to roll in just above 900 rpm and is fluttering around+/- 3* just where I need idle set.

Now that initial timing is lower, previously +15*-17* at idle, vacuum reading has fallen from 12"-13" Hg. at 1000 rpm to 9"-10" Hg. Previously 2500 rpm made 16"-17" Engine now has flat spot under light throttle up off of idle up to 2200 rpm, after that not so noticeable.
Author:  Aggressive Ted [ Mon Aug 10, 2009 2:39 pm ]
Post subject: 
wjajr,

An HEI is not going to magically fix what your experiencing.

You still need to get the right primary spring installed or the spring post cranked around to to tighten the spring your running so the advance weight doesn't prematurely pop out giving you the variance your seeing. You will need to try a stiffer primary MOPAR spring. The secondary spring won't help much at this rpm.

I have been hoping you would experience this and be able to measure what is going on with the timing before you do any more carb tuning. Good work!

Fix one variable at a time and document it. That's my motto, then move to the next item. Eventually you will get back to carb tuning.

When your recurve is nailed you will have a good solid launch once your accelerator pump shot is strong enough to match it.
Author:  wjajr [ Mon Aug 10, 2009 7:52 pm ]
Post subject: 
Ted,
Quote:
need to get the right primary spring installed
Kind'ah figured that after Ceej proposed there should be no advance until 12-1500 rpm. Also explains the unsteady or fluttering initial timing setting, and what I thought was a problem with the distributor hold down clamp walking the timing up.

No punch off the line is because of too early timing advance?

Before me, I have a print out I found on Dutra.org titled; "Adjustable Vacuum Advance Kit". First test it recommends; is to check for full throttle spark knock with vacuum advance source disconnected and plugged before going any further. If audible spark knock occurs at stock, two or four degrees advance from stock timing specs your centrifugal advance curve is correct for your application. What would be considered stock timing setting on my engine? FM lists 225 @ TDC with C.A.P., what ever C.A.P. is.

I'll perform this test tomorrow. I don't recall the engine ever producing spark knock, not that one could hear it over the turbo mufflers...
Quote:
spring post cranked around to tighten the spring
Are all spring posts on an eccentric, or just select governors have this capability to adjust spring travel?

So I need to put out an APB for a stiffer MOPAR Primary Spring... Which spring do I need, I'm not fluent in MOPAR distributor springs.
Author:  Aggressive Ted [ Mon Aug 10, 2009 9:48 pm ]
Post subject: 
wjajr,
Quote:
What would be considered stock timing setting on my engine? FM lists 225 @ TDC
My 74 calls for zero degrees timing as well, but that was with all the smog control equipment such as the EGR gasses being fed back in. After the engine rebuild the EGR port was blocked off, etc......no more vacuum hoses, timers etc.
You can see the pictures on the red link below my name the engine layout.
Double click on the picture when it first comes up to put it into full screen slide show mode. I am only running the PCV and the charcoal canister.

I am running 12 degrees initial, 20 mechanical and 22 degrees vacuum advance at 2500 rpm. I have never heard my engine ping either........
Quote:
No punch off the line is because of too early timing advance?
You need a pretty healthy pump shot to match allot of initial. When you get the balance right you will get the rear to bust loose.
Quote:
Are all spring posts on an eccentric, or just select governors have this capability to adjust spring travel?
The electronic ignition distributors have the adjustable spring posts from about 73 on up to where they went to the Lean Burn Computer system. The Lean burn distributor design is totally different.
Quote:
So I need to put out an APB for a stiffer MOPAR Primary Spring... Which spring do I need, I'm not fluent in MOPAR distributor springs.
Read page 4 of Doug's recurve document. It tells you the colors and what to use. I can resend it if you need it, just need your email.
Author:  wjajr [ Tue Aug 11, 2009 7:27 am ]
Post subject: 
Ted:
Quote:
Read page 4 of Doug's recurve document.
I'm looking at it, lists three colors all starting advance rpm of 800. Orange has the highest full advance rpm, so is that the one I'm looking for? Also the red spring I have, could be orange it is rather crusty and faded.

Looking around the net I found these Mr. Gasket distributor advance kits provide full advance between 2,000 and 2,800 rpm. Would one of these springs work. I don't have any spare springs to play with.

Now to recap for me to better understand what the goal is:
1. Need to have initial advance of +10* to 14*
2. No mechanical advance before; say 1500 rpm.
3. Mechanical advance high 20's Mine is R-11 = 22*.
4. Vacuum advance tip in after 1500 rpm, and what ever it takes to get total advance at cruising rpm to between 45 & 55 degrees.

Here is presently what I think I have:
10* initial
22* mechanical
14* vacuum
Total of 46*

Looks as if I need a bit more initial timing.
Author:  Aggressive Ted [ Tue Aug 11, 2009 1:54 pm ]
Post subject:  Distributor recurve instructions
wjajr,

Your right on track.......

I have used the MR. Gasket springs and they are very, very light for drag racing only to be used with a governor that has short slots to limit over all timing to 30 degrees. They just come on like gang busters and your spinning out of control. It's fun for awhile, but not for an everyday street car.

The early 340 distributors and 400, 440 distributors have the heavier primary spring. Or you can use your current spring and rotate the spring post out all the way to create more tension.
Author:  wjajr [ Tue Aug 11, 2009 5:20 pm ]
Post subject: 
Hey Ted,

I gave that spring post a twist, ran her down the road less vacuum advance with no pinking with initial set at +12*. Idles in park about 900 to 950 rpm timing floating around +/- 1 degree. and in gear 550 to 600 rpm with steady timing. Got my kick back at shut-down back.

I'm going to have to find a stronger spring to settle it down

Anybody out there in slant land that has an extra 340, 400-440 heavy primary spring, PM me, I could use one.
Author:  DusterIdiot [ Tue Aug 11, 2009 6:20 pm ]
Post subject:  Wrong kit...
Quote:
I have used the MR. Gasket springs and they are very, very light for drag racing only to be used with a governor that has short slots to limit over all timing to 30 degrees.
The colors in Doc's article correspond to a set of Crane springs that are no longer available(mopar primary springs come in various lengths/coil windings and I have seen each color from blue to white depending on year and application you pulled it from). MR.Gasket 925B and D are too light as Ted says, but there is more 'room' to play when you use the 928G GM set... heavy vehicles I set for slotted spring with the eccentric cammed out a bit and the 'silver' spring... the bronze springs are just too heavy for any thing... the black ones can be 'adjusted' a bit for performance and mileage.

Good luck recurving,

-D.Idiot
Author:  wjajr [ Wed Aug 12, 2009 5:54 am ]
Post subject: 
D.I.,

Are you recommending use of the sliver spring by its self for the primary, or using the pair in place of my MOPAR long black & primary?
Quote:
heavy vehicles I set for slotted spring with the eccentric cammed out a bit and the 'silver' spring
???

This is not clear here. Are you saying for heavy vehicles, or this is a heavy vehicle GM set? Sorry to be so thick...
Author:  Aggressive Ted [ Wed Aug 12, 2009 11:03 am ]
Post subject: 
wjajr,
Quote:
I gave that spring post a twist, ran her down the road less vacuum advance with no pinking with initial set at +12*. Idles in park about 900 to 950 rpm timing floating around +/- 1 degree. and in gear 550 to 600 rpm with steady timing. Got my kick back at shut-down back.
Excellent, sounds like your making good progress and are pretty close, at least you have some steady numbers. You certainly have enough initial timing. You have done everything right so far and are right on track!

On the kick back issue......, it could be related to valve lash. It would be nice to know what cam you have, however, the typical .010 and .020 may not work well for your engine. Your cam may require a much larger lash to get the valves shut. If they don't shut all the way or for very long it will reduce low end torque and produce the kick back at shut off.

Do you have any idea what your compression ratio might be?
If it is around 10 to 1 and with 10 degrees initial timing it should shut right off like turning off a light, providing the lash is set right for the cam.

You may have to loosen up the intake lash. Try .016. This is pure guess work and trial and error at this point. Not knowing the cam duration and lift, it's a shot in the dark. However, I would encourage you to try it since you are so close.

Well done!
Quote:
928G GM set... heavy vehicles
I think DI is referring to the heavier spring set in his comment. Should read "928G GM set for heavy vehicles".

I would stick with the MOPAR springs if you can. Leave your big secondary spring on there and only change the primary spring to the silver spring from the set.
Author:  wjajr [ Wed Aug 12, 2009 1:21 pm ]
Post subject: 
Ted,
Quote:
It would be nice to know what cam you have
Dream sequence:
If I had 10 bucks for every time someone has said that here....

Sometime back several months ago, I had this same conversation with Doc over valve lash. Presently have set intake at, (crap I didn't write it down) I believe; 0.016", and exhaust at 0.024".

Compression ratio per online calculator is 9.5:1. Josh S helped me through the head shave and those calculations this spring. Cylinder pressure is about 150 psi each.

Posted a "Spring APB" on the "Parts Wanted Board" last night; someone is checking their spring stash, and hopefully will have a nice MOPAR unit that I can have. Plan "B" is to get the GM after market selection.
Quote:
Leave your big secondary spring on there and only change the primary spring to the silver spring from the set
I thought that is what DI's drift was, but had to double check.
Author:  DusterIdiot [ Wed Aug 12, 2009 6:54 pm ]
Post subject:  Ok -review
928G- GM spring set

Come with 2 of each color: black/Silver/Bronze

Take dizzy, leave heavy looped stock spring in place... rotate cam to furthest out....
Pull your stock light spring... put silver spring in... time it and test drive and see what happens...

Black is a bit lighter and nice for the lighter cars (like yours, but with less compression).

Silver is good for heavy cars/trucks, but slows the advance so high compression/ rattling/ needs slower advance works a bit better

Bronze- I'm not sure what GM has for this spring...I put one in and got no advance up to 3500 engine rpm.... must be for a 307 powered Chevy longbed heavy duty dump truck...


-D.Idiot
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