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#26 | |
Fabricate till you "puke"
Join Date: Jun 2002
Location: Ill
Posts: 9,403
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Re: vacuum advance issues
Quote:
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69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears.... |
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#27 |
*** That's interesting ***
Join Date: Oct 2008
Location: Pittsburgh, PA
Posts: 2,772
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Re: vacuum advance issues
Right. Basically you start at some value, I suggested 8 degrees as an initial timing value at idle. Some SBCs can tolerate more, but usually no more than 14 degrees. As you rev the engine, the weights and springs under the distributor rotor "fly out" and advance the timing until it hits the stops. Once it hits the stops, it will stop advancing. Whatever timing reading you get here is your "total" mechanical timing. Most SBCs like 28-32, but some can go as high as 36 here.
If yours likes 35 total, that's fine. You have your "all in" value. But what concerns me is your initial value when you have it set for 35. And you said it was 19 (which is too much IMO). Subtract the two and you get 16 degrees. So that means that your weights and springs are only allowing 16 degrees of travel. I don't like that. You need a weight and spring setup that gives you at least 20-24 degrees of travel to get the best curve for a street vehicle. So....... next step is to pop off the cap and rotor and study the weights and springs underneath. You may even have "stop bushings" installed on on the pins that the weights hit to control their swing. A good picture of your weights and springs may help us help you. Longhorn was saying that you may need to change these out, which is VERY common to do to solve these problems. Even just changing the weights may give you more travel because there are different weights you can buy or pull from a junk car that is shaped differently and allows more travel. The weight and spring kits they sell sometimes come with different size stop bushings which can also limit the travel of the weights. This might be why this distributor was for sale............. You could always swap the weights and springs from your old distributor. That alone might give you better range. I have the opposite problem with the last MSD Streetfire I bought. It had too much range in the weights and springs and caused bad pinging. Using the weights from an old MSD distributor solved that. Did the car this came off of have a radical cam? Some cams like a ton of initial timing so a 16 degree spread might be perfect for something with a radical cam. But no good for a stockish engine...
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Tom ![]() Chevy by day... 1969 Chevy C30 Rollback Tow Truck -- 383 stroker, 4L80E 2011 Chevy Caprice PPV 9C3 6.0L 1995 Chevy Caprice 9C1 1994 Chevy Caprice 9C1 #3 1995 Chevy Caprice Wagon #2 1995 Chevy Impala SS Mopar by night... 1969 Dodge Charger 1972 Chrysler Newport 2dr Hardtop (27K miles) Plus others... Last edited by storm9c1; 04-14-2016 at 10:12 PM. |
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#28 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,641
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Re: vacuum advance issues
Maybe this link will help him figure it out storm.
http://www.crankshaftcoalition.com/w...EI_distributor |
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#29 | |
Fabricate till you "puke"
Join Date: Jun 2002
Location: Ill
Posts: 9,403
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Re: vacuum advance issues
Quote:
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69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears.... |
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#30 |
Registered User
Join Date: Nov 2015
Location: Marrero, Louisiana
Posts: 47
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Re: vacuum advance issues
Sorry for the delay, internet issues .... Here is a pic of my distributor. My best way to describe the springs is that there is not much resistance when moving the arm's that are stamped (60) by hand, don't know how they should be but these seem kind of loose.
I decreased my total to 34*, no change with initial nor did it change performance, my 350 is primarily stock, I'm assuming the cam may be slightly above stock. Don't know much about it as I purchased it this way. It seems to be running fine as far as I know but how will I know if its running at optimal timing or not? What indicates where initial timing should be set as the starting point? Do I keep adjusting initial/total until it begins running poorly then adjust back until it runs good? When I connect vacuum advance what change should I expect to notice? Last edited by Erratic67; 04-17-2016 at 10:32 PM. |
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#31 |
Fabricate till you "puke"
Join Date: Jun 2002
Location: Ill
Posts: 9,403
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Re: vacuum advance issues
I have read the the... Page,... and, feel that if the weights/pins are loose,or sticky... you have issues. shoot for the 3'4 to 1 ton weights/centerplate(best curve). Understand that the HEI will kickobout 20 degrees on mechanical....I would suggest 14 initial, to hit a 34 total....after that, a 8-10 degree vac advance, but you might do 12 (cam issuies)? You have my PM.....I can talk faster than I type
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69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears.... |
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#32 |
*** That's interesting ***
Join Date: Oct 2008
Location: Pittsburgh, PA
Posts: 2,772
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Re: vacuum advance issues
OK, those are GM weights and center plate. That helps. What are the numbers? I can read the #60 on the weights. But what's the center plate? #406 or #408 or what? Having this info, we might be able to research the timing curve this combo should produce. Either way, I think you need to pull that all apart and get all that rust off. With the way it looks now, it may not operate smoothly.
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Tom ![]() Chevy by day... 1969 Chevy C30 Rollback Tow Truck -- 383 stroker, 4L80E 2011 Chevy Caprice PPV 9C3 6.0L 1995 Chevy Caprice 9C1 1994 Chevy Caprice 9C1 #3 1995 Chevy Caprice Wagon #2 1995 Chevy Impala SS Mopar by night... 1969 Dodge Charger 1972 Chrysler Newport 2dr Hardtop (27K miles) Plus others... |
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#33 |
Fabricate till you "puke"
Join Date: Jun 2002
Location: Ill
Posts: 9,403
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Re: vacuum advance issues
Dave, was the ign guru, that new the numbers on the weights....but basically, he said pull em ..from a 3/4 ton truck, what you will get, is a far better curve, than you will see on a car dizzy. Me & that old man butted heads pretty hard......but he knew his ****! Not too bad in my spot....the last tune on my 383....(beat up old junk dist/750 edel, went 12.9, in my bros truck@ the track. I cost him 1500 bones, to get that 12.5 ride....IMHO, not to bad, for a street ride? street/ tune @ 12.9....longhorn
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69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears.... |
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#34 |
Registered User
Join Date: Nov 2015
Location: Marrero, Louisiana
Posts: 47
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Re: vacuum advance issues
The center plate is #406 ....
Where can I purchase the weights, center plate and springs and what type, size and spring tension I need? |
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#35 |
Fabricate till you "puke"
Join Date: Jun 2002
Location: Ill
Posts: 9,403
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Re: vacuum advance issues
Bone yard , on the weights/center plate.....I would go Crane on the canister/springs. Understand, that the 3/4-1 ton trucks had a better curve, than the 1/2 tons ,or cars had.....the big trucks , just were not fitted with emission parts (76-79 3/4 or 1 ton), for the best weight set. do not try to play with aftermarket "lite weights", on the HEI.....they flat wont work, been there, tried that! I can explain it better.....pm me, I will give you my cell ...as I said, I can talk faster than I can type.. Longhorn
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69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears.... |
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#36 |
Registered User
Join Date: Nov 2015
Location: Marrero, Louisiana
Posts: 47
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Re: vacuum advance issues
I could be wrong, I'm pretty sure it's #408 .... Will it hurt anything for me to drive the truck as is until I receive the distributor parts, cause it seems fine without any issues?
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#37 |
*** That's interesting ***
Join Date: Oct 2008
Location: Pittsburgh, PA
Posts: 2,772
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Re: vacuum advance issues
I don't think it will hurt. Just listen for pinging since you have a ton of initial timing. When it gets hot, you may get some "kickback" on the starter with too much initial timing and that can break the starter. So keep an eye out for that.
You can keep the vacuum advance disconnected for now. Your MPG will suffer, and your truck won't be the "greenest" truck on the planet emissions-wise. But it should feel normal otherwise. Keep an eye on your temp gauge while cruising the first time if you do any highway driving. The extra timing from the canister also helps it run a little bit cooler. Let's not touch the canister until you get the weights and springs sorted out first. If Longhorn is offering his advice over the phone, I'd take him up on it. ![]()
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Tom ![]() Chevy by day... 1969 Chevy C30 Rollback Tow Truck -- 383 stroker, 4L80E 2011 Chevy Caprice PPV 9C3 6.0L 1995 Chevy Caprice 9C1 1994 Chevy Caprice 9C1 #3 1995 Chevy Caprice Wagon #2 1995 Chevy Impala SS Mopar by night... 1969 Dodge Charger 1972 Chrysler Newport 2dr Hardtop (27K miles) Plus others... |
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#38 |
Registered User
Join Date: Nov 2015
Location: Marrero, Louisiana
Posts: 47
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Re: vacuum advance issues
Longhorn .... sent u a pm, need some info regarding springs/weights. At your convenience, give me a buzz.
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#39 |
Fabricate till you "puke"
Join Date: Jun 2002
Location: Ill
Posts: 9,403
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Re: vacuum advance issues
The Crane canister/spring set , that I was referring to....Crane # 99600-1 or jegs # 270-99600-1 (for GM HEI). It is listed for $38.50, & while you may find some a tad cheaper, they do not offer the springs & limit plate
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69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears.... |
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#40 | |
Fabricate till you "puke"
Join Date: Jun 2002
Location: Ill
Posts: 9,403
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Re: vacuum advance issues
Quote:
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69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears.... |
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#41 |
Registered User
Join Date: Nov 2015
Location: Marrero, Louisiana
Posts: 47
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Re: vacuum advance issues
Longhorn ..... Thanks for taking the time out of your schedule to contact me and explain in detail, possible issues and resolutions to my problems.
Soon as I receive the springs/canister and have them installed, I will set my timing again. I'll keep y'all informed as to how it goes. Wish me luck. Does the term "all in" refer to ..... When my timing stops advancing at that given RPM? |
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#42 | |
Fabricate till you "puke"
Join Date: Jun 2002
Location: Ill
Posts: 9,403
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Re: vacuum advance issues
Quote:
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69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears.... |
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#43 |
Registered User
Join Date: Nov 2015
Location: Marrero, Louisiana
Posts: 47
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Re: vacuum advance issues
Sorry for the delay but finally got around to working on my truck again .....
Cleaned all the weights, plate and springs rust free. Set initial @ 8* BTDC, 3000 RPM,s "all in" @ 26* ..... Advanced timing to "all in" @ 30*, initial now at 14*. I have the different springs and weights but did not change them as of yet, until I received advice from y'all. What should my next move be? |
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#44 | |
Senior Car Nut
![]() Join Date: Jan 2008
Location: shellman bluff, GA
Posts: 1,411
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Re: vacuum advance issues
Quote:
the latest info re-affirms what you have been saying all along. your current combo of springs/centerplate/weights gives you 16 degrees of mechanical advance. as the guys have said, you probably want more like 20-24. if you bought a kit it should have come with a chart of what amount of advance the different combinations of springs will give at what rpm. - pick a spring combo that doesn't start advancing 'til after idle speed (important) and gives the desired max at 3000. - if you want, if you can post a picture of the chart we can point out which combo we think will get you the desired results
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Larry |
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#45 |
Registered User
Join Date: Nov 2015
Location: Marrero, Louisiana
Posts: 47
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Re: vacuum advance issues
Here's the chart, hope this helps
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#46 |
Registered User
Join Date: Nov 2015
Location: Marrero, Louisiana
Posts: 47
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Re: vacuum advance issues
Heres another
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#47 |
Senior Car Nut
![]() Join Date: Jan 2008
Location: shellman bluff, GA
Posts: 1,411
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Re: vacuum advance issues
those help me a lot, Erratic. especially the 2nd photo 'cause I was having trouble reading the stop bushing colors on the first photo
![]() if you want 20 degrees @ 3000 it looks to me like you'd go with curve "D" (2 blue light springs) with the blue or purple stop bushings. I think if you use this combo and set your total at 34 you'll end up with 14 initial EDIT: I just realized that the kit you bought is apparently the MSD kit for their distributors. I'm not familiar with stop bushings, the MSD kit I have for my GM distributor (http://www.summitracing.com/parts/msd-8428/overview/) didn't have them. I'm guessing that the bushings don't work on the original GM. this is what my curve looks like: http://static.summitracing.com/globa...8_frm28648.pdf if I use 1 light spring and 1 medium spring my curve is about right (in between using 2 lights or using 2 mediums)
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Larry Last edited by fleetsidelarry; 05-07-2016 at 09:32 AM. |
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#48 |
Registered User
Join Date: Nov 2015
Location: Marrero, Louisiana
Posts: 47
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Re: vacuum advance issues
I changed my stock springs to the blue ones but there is no bushings that fit in my weights, without the bushings they do have some play and feel pretty loose. With that said, I set my initial at 7* BTDC and at 3000 RPM's "all in @ 27* ..... Advanced distributor to 34* and initial increased to 18*
Maybe I should try installing the aftermarket weights & backplate that came with the bushings to see how that works out, what do you suggest? Another question I have is how does that backplate come off? |
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#49 | |
Senior Car Nut
![]() Join Date: Jan 2008
Location: shellman bluff, GA
Posts: 1,411
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Re: vacuum advance issues
Quote:
the advance "curves" shown in those charts you posted are a product of the shape of the scroll plate (what you're calling the backing plate I think), the shape and weight of the weights, AND the springs. how much advance (16 degrees in your case) is based on the shape (see note **). the RATE that the distributor advances (how quickly it reaches those 16 degrees) depends on the springs. changing only the springs changed only how quickly you got to 16 degrees. (**the springs CAN affect the total if they are too heavy to allow full travel of the weights at a given RPM or too light to allow the weights to fully retract at idle, don't worry about that just now) you should be checking your initial at the same idle speed each time, preferably fairly low 6-700 rpm in order to change your total you need to swap in the new plate and weights. the plate is held in by "e" clips on the posts that hold the inner loop of the springs. take those e-clips off and the plate should pry right up and off. only thing that would interfere would be rust on those posts
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Larry Last edited by fleetsidelarry; 05-13-2016 at 08:57 AM. |
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#50 |
Registered User
Join Date: Nov 2015
Location: Marrero, Louisiana
Posts: 47
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Re: vacuum advance issues
okay thanks ... umma remove that back plate and replace everything with the new parts in the kit. I have been told that aftermarket weights / back plate does not work as well as stock but what will it hurt to try, i'll post my results when done. Thanks again
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