Timing Mech vs Vac advance Good Read

A

Anonymous

Guest
Glad it helped you :D if your caddy engine happens post for caddyguy on this board or check out Terrys caddy powered Bu Wagon and Ford PU also caddy powered at petersonracing.com great guys :!: They have a nice site and message board to boot tell them I said hello. :lol:
 

Got Torque

Top Fueler
Oct 29, 2003
2,776
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Stockholm, Sweden
Will do!

Thank's for the links.

I'll let everyone interested know if i buy the engine or not.
 

HellCamino

Dragway Regular
Dec 13, 2003
980
0
0
The Dog House
Vacuum cans

:shock: yup that was a bit of a read :shock:
Look'in like a fish.

OK, so you say the vacuum advance is best for a street car.
I would agree,if I could find a can that would work with lots of initial advance and a good curve.

I run a MSD distributor with one medium spring and one heavy spring,full advance at 3000(I think), 18 degrees mechanical advance,and 14 initial,this makes 32 total.Currently without vacuum advance.

I run pump premuim gas.

I have used a stock 18 degree can, a stock 15 degree can,a stock 10 degree can from a Vette, and a Accel adjustable can.None of them have worked without making the engine ping.
The guy who owns and operates the local performance shop in town is the one that suggested the Vette can.He said that it came in at a low Hg point.
Should I try the Echlin#VC-1810 -15 degree can mentioned in the first post?

Whenever I tried to use a advance can I had to retard the initial timing
wich hurt the 60's.I finally used the adjustable Accel can but I had to have the screw so far in that it really had no effect since it only adjusts the total amount of advance added and not the Hg starting point or rate..
If I had known that I would not have bought it.

Is there a master listing of vacuum cans that shows the Hg starting point and their advance rate with Hg loads?

My 79 EL runs a SB350.The combo is 10.2:1,CamDynamics HYD cam 278 221 467 110,Performer RPM,Holley 650DP,S/R Torkers 202/160 Mildly Pocket Ported,1 3/4 inch headers,2 1/2 inch exhaust,MSD distributor,6-A box,Blaster 3 coil,TH-350,Trans-GO Stage II shift kit,TCI 11inch 2400 stall,3.42 possi,26tall tires.

I think this combo might just have too much compression to be able to use more advance at light throttle acceleration during passing, hills and such.
 
A

Anonymous

Guest
It sounds like you have tied several combos to date I had some of the same problems a few yrs ago. After trying all the options I personally went to a locked dist MSD setup. I just changed to EFI last winter and was able to go to ECU control. Post this question on main Fourm Drivetrain Tech for some of our sharper tuners :D shouls be able to answer your questions. Glad to have you on board someone will be able to help you.
 

Canadian-T-Bone

Dragway Regular
May 25, 2003
1,147
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Abbotsford,B.C.
All I know is that the more I read ,the more I need to do to my Malibu !
Soooo much time so little $
 

Mezmorized

Dragway Regular
Nov 7, 2003
1,398
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Carleton Place, Ontario, Canada
That's going to take me a while to read... LOL I have the attention span of a gerbil!! :shock: :shock: :shock:
 

wadedog

Pro Stocker
May 21, 2003
1,927
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southern ohio y'all
thanks fred, that was a good read.
i wonder what conditions then should a guy run the echlin can, how do you know if you need it?
How about some info from you guys that have swapped springs and weights in your street cars with HEI.
what site did that come from fred, sounds like you know some good sites.
how about some site names buddy,lol.
 
A

Anonymous

Guest
Wade I can't remember where I found that at it was on one of the racing boards that it came from. I've slept sense then, wish I knew who the author was I would give them credit for it.
 

WEBBER

Pro Stocker
Apr 25, 2004
1,828
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80 miles west of Joliet IL.
Vacum advance ported or manifold

I've been arguing with people for years,on this topic. What a great article.
THANKS!!!!!
 
A

Anonymous

Guest
thanks for all the info

my question is I have a BBC with a 254-260 660-666 solid roller cam that will make barly any vacum so is it worth me running vacum advance or not?
 

Norm Peterson

Amateur Racer
Oct 18, 2003
251
0
0
state of confusion
Little Red Wagon said:
This is a reprint from another board author unknown but wanted to share this with the group as there has been some recent discussions on this.
. . .
For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum. Absolutely. Positively. Don't ask Summit or Jeg's about it – they don’t understand it, they're on commission, and they want to sell "race car" parts.
Thanks for reposting this article, Fred.

I saw later on in this thread mention of an ECU, and I'll say right now that you absolutely need to understand all of that stuff if you ever get into tuning EFI ignition maps. But when you do understand it, EFI ignition tuning is pretty simple and at the same time gives you far greater control over the shapes of the "curves".

I wonder if the member who still had pinging issues regardless of which vacuum can he was using was encountering partial blockage in the vacuum line or if the canister itself wouldn't let the air back into it at enough of a flow rate to kill the vacuum advance fast enough? I'd look for debris in the lines, damaged fitting(s), perhaps a hose being collapsed shut or even being too small, and things like the hose connection at the can being too small for his specific combination or the vacuum can return mechanisms too soft for the can-related problems.

IOW, anything that could restrict or limit the airflow back into the canister needs to be investigated. Apparently his combination wants the vacuum advance "all gone, right now", and something (or several things) is not letting that happen.

Norm
 
A

Anonymous

Guest
Norm tuning is still hard for this old man but last year I finally switched to a crank trigger for my MSD setup. It is easier to control the spark for me with it than my other setup and more precise than the other was.
 
A

Anonymous

Guest
I too Have a cam I don't think is going to make much Vacuum. What would be the minimum amount required to operate the lowest start HG. canister?
 

Excelerater

MalibuRacing Junkie
May 22, 2003
6,799
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Memphis,TN
I have neither

My distrub is locked at 38 degrees

:p
 

SEVNT 9

Dragway Regular
i have a question regarding this as well

i have a 355 with milled vortec heads 10.5:1 crane cam .454 .480 216/228 @ .050 i set timing durring break in to 30 total at 3000 with vac. adv. unplugged (i was told to go to 32 but i have also heard vortecs perfer 28-30 i was fearing spark knock durring break in with all the extra heat so i played it safe ) i havent changed the position yet my readings on the timming light jumped all the way to 60 (balancer at 0 @ 3000)with vac plugged in. i have the line ran to the port that the instructions say to place timmed spark source is this ported or manifold vac. and should i go to 32 deg. with this combo.............. is more info needed?
 
A

Anonymous

Guest
my question is I have a BBC with a 254-260 660-666 solid roller cam that will make barly any vacum so is it worth me running vacum advance or not?
Personally with your combo, and I'm "assuming" it's not regularly street driven, more of a weekend warrior, then I'd lock out the dist.

I've been running the wagon like that for 2 years with NO problems and great driveability.
 

Dom87SS

Pro Stocker
Jun 6, 2003
1,659
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Lake Villa, IL
www.stroked57.com
the only question i have is about the weights and springs. is there somewhere or way to tell what the weight of the weight you are using is. and which you should, or would be better to use for a certain application. and spring rates, i know there are several different rates being soft, medium, and stiff. but how do you know whcih is for you. as someone mentioned they were using 2 different types of springs. i have a stock HEI housing, shaft, and cam gear. but all new pertronix everything else except the bushing and wires which are both MSD. i had gotten a cheapy aftermarket spring/weight kit and dont really know what to be using. i ditched the stock weights a while ago for whatever can in the package, and just put medium springs in i belive. ive never been able to get normal timing read outs. probably cause its a stock balancer and it most likely has moved. but when set the mech timing was about 14 and advanced read 45. which seemed weird (cause i had never done anything with it before) but that is where it seemed to run best so i left it. anyone have any idea?
 
A

Anonymous

Guest
this is hard to answer, it depends on how soon you want total timing. which depends rear end ratio, how much cam, headers or not (less exhaust gas in the fresh charge) the weight of the car, and on and on. What and why one combination of springs works for me and not for someone else, depends on too many things. Best thing to do is first as you mentioned make sure your vibration dampener is correct, you can sometimes use measurements based on the keyway. If thats right, with a timing light and a tach see what RPM the timing starts to move and what RPM it is at total. A good place to start is around 2500, the carb will be in the high circuit, and don't forget to do this with the vac.advance disconnected, and the port pluged. After that if it is too soon you need to start switching springs. Once you have a baseline test and tune night at you local track, if you want can help dial it in for whats best for you. Keep notes on what the timing is at diferent RPM and as you make changes you can track them.
 
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