Almost there , another timing question
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Almost there , another timing question
Actually my 352 is runnin pretty good now, thanks to Bear, but I do have another question, My dizzy is set to the 10L mark and The spring combination gets full advance at right around 2600 rpm, I have run both ways
without vacum advance timing set at 22 BTDC / motor runs very agressive chirps the tires and goes like heck.gas milage is around 6 city 12 highway.
with vacum advance 12-14 * BTDC / motor runs well ,frankly like a nice well mannored stock truck motor, gas milage is within .25 mpg more
From everything I have herd on the forum here I should be running Vacum advance to get better milage, but the .25 miles im getting is not that big of an inprovement.
The trany is a 3 speed/overdrive manual so I rarely see 3000 rpm. shift point are usaly around 2500 - 2700 rpm and she cruses on the freeway at 65mph at 2000 rpm.
Why should I be running vacum advance ? the motor seems to run better with out it and more base timing, iv tried playing with the adjustment in the diaphram ( it is a new one and adjustabull ) but im not seeing 2 or 3 mpg gain with it.
Thanks
without vacum advance timing set at 22 BTDC / motor runs very agressive chirps the tires and goes like heck.gas milage is around 6 city 12 highway.
with vacum advance 12-14 * BTDC / motor runs well ,frankly like a nice well mannored stock truck motor, gas milage is within .25 mpg more
From everything I have herd on the forum here I should be running Vacum advance to get better milage, but the .25 miles im getting is not that big of an inprovement.
The trany is a 3 speed/overdrive manual so I rarely see 3000 rpm. shift point are usaly around 2500 - 2700 rpm and she cruses on the freeway at 65mph at 2000 rpm.
Why should I be running vacum advance ? the motor seems to run better with out it and more base timing, iv tried playing with the adjustment in the diaphram ( it is a new one and adjustabull ) but im not seeing 2 or 3 mpg gain with it.
Thanks
Last edited by jav409; May 24, 2005 at 01:12 AM.
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From: Long Island USA
Does the engine start right up, or do you get a "wrr, wrr, wrr" type cranking sound? At 22 BTDC static, it'll be hard to start when hot unless it's really low compression.
That's about the only reason for a vacuum advance... other than that "stock" type of drivability.
In my case, with my 11:1 390, I had to use a vacuum advance, but it was really a vacuum retard, I had it setup totally backwards.
What kind of cam are you using? Big lopey, RV, stock, what?
art k.
That's about the only reason for a vacuum advance... other than that "stock" type of drivability.
In my case, with my 11:1 390, I had to use a vacuum advance, but it was really a vacuum retard, I had it setup totally backwards.
What kind of cam are you using? Big lopey, RV, stock, what?
art k.
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From: Union, Washington
Originally Posted by krewat
Does the engine start right up, or do you get a "wrr, wrr, wrr" type cranking sound? At 22 BTDC static, it'll be hard to start when hot unless it's really low compression.
That's about the only reason for a vacuum advance... other than that "stock" type of drivability.
In my case, with my 11:1 390, I had to use a vacuum advance, but it was really a vacuum retard, I had it setup totally backwards.
What kind of cam are you using? Big lopey, RV, stock, what?
art k.
That's about the only reason for a vacuum advance... other than that "stock" type of drivability.
In my case, with my 11:1 390, I had to use a vacuum advance, but it was really a vacuum retard, I had it setup totally backwards.
What kind of cam are you using? Big lopey, RV, stock, what?
art k.
jav409, Are you saying your total mechanical advance is 22 degrees? Total mechanical advance should be around 30 to 35, vacuum disconnected.
Vacuum advance is there it improve fuel economy and your's should be better than it is, at least city thai is. Unless you are heavy footing the thing in town. Highway is not to bad.
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From: Long Island USA
Uh, and I quote:
without vacum advance timing set at 22 BTDC / motor runs very agressive chirps the tires and goes like heck.gas milage is around 6 city 12 highway.
I take that as initial/static is 22BTDC... I DO NOT see anywhere that he mentioned 10BTDC initial. That's "10L" remark, I take it, means he has the centrifugal advance in the dizzy on the 10L notch.
As to the "vacuum retard" comment - hook the vacuum advance to manifold vacuum, retime for about 16BTDC at idle (big cam) and you'll see what I mean. Lots of initial advance for good vacuum (big cam again), but when cranking it's not anywhere near 16BTDC. And, hit the gas about halfway and the timing drops to keep from pinging. That's in an 11:1 390 with 93 octane street gas. Anyway, I digress.
without vacum advance timing set at 22 BTDC / motor runs very agressive chirps the tires and goes like heck.gas milage is around 6 city 12 highway.
I take that as initial/static is 22BTDC... I DO NOT see anywhere that he mentioned 10BTDC initial. That's "10L" remark, I take it, means he has the centrifugal advance in the dizzy on the 10L notch.
As to the "vacuum retard" comment - hook the vacuum advance to manifold vacuum, retime for about 16BTDC at idle (big cam) and you'll see what I mean. Lots of initial advance for good vacuum (big cam again), but when cranking it's not anywhere near 16BTDC. And, hit the gas about halfway and the timing drops to keep from pinging. That's in an 11:1 390 with 93 octane street gas. Anyway, I digress.
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From: Union, Washington
Originally Posted by krewat
Uh, and I quote:
without vacum advance timing set at 22 BTDC / motor runs very agressive chirps the tires and goes like heck.gas milage is around 6 city 12 highway.
I take that as initial/static is 22BTDC... I DO NOT see anywhere that he mentioned 10BTDC initial. That's "10L" remark, I take it, means he has the centrifugal advance in the dizzy on the 10L notch.
As to the "vacuum retard" comment - hook the vacuum advance to manifold vacuum, retime for about 16BTDC at idle (big cam) and you'll see what I mean. Lots of initial advance for good vacuum (big cam again), but when cranking it's not anywhere near 16BTDC. And, hit the gas about halfway and the timing drops to keep from pinging. That's in an 11:1 390 with 93 octane street gas. Anyway, I digress.
without vacum advance timing set at 22 BTDC / motor runs very agressive chirps the tires and goes like heck.gas milage is around 6 city 12 highway.
I take that as initial/static is 22BTDC... I DO NOT see anywhere that he mentioned 10BTDC initial. That's "10L" remark, I take it, means he has the centrifugal advance in the dizzy on the 10L notch.
As to the "vacuum retard" comment - hook the vacuum advance to manifold vacuum, retime for about 16BTDC at idle (big cam) and you'll see what I mean. Lots of initial advance for good vacuum (big cam again), but when cranking it's not anywhere near 16BTDC. And, hit the gas about halfway and the timing drops to keep from pinging. That's in an 11:1 390 with 93 octane street gas. Anyway, I digress.
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From: Iowa
Originally Posted by krewat
As to the "vacuum retard" comment - hook the vacuum advance to manifold vacuum, retime for about 16BTDC at idle (big cam) and you'll see what I mean. Lots of initial advance for good vacuum (big cam again), but when cranking it's not anywhere near 16BTDC. And, hit the gas about halfway and the timing drops to keep from pinging. That's in an 11:1 390 with 93 octane street gas. Anyway, I digress.
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From: Long Island USA
WAY OF TOPIC
An 11:1 390? with the cam advanced 4 degrees... 16 was about where it would start giving me problems. Keeping the initial down around 6 was a good place for it to start right up ...
To have only 10 in the dizzy, there'd have to be a "5L" slot in there
Thanks rusty70f100
Originally Posted by Bear 45/70
So you are using the vacuum unit to advance your idle timing, then when you stomp on it it drops out. But even with an aggressive advance curve and short advance (say 10 in dist and 20 at the crank) initial can still be 16 with your engine and you still shouldn't have any start problems. At least I never did in the true hey day of the FE's, the 60's.
To have only 10 in the dizzy, there'd have to be a "5L" slot in there
Thanks rusty70f100
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Hi guys, Thanks for the responce, the 10L is set in the disto to give a total of 20* total mech advance if I time it to 22* BTDC without The vacume advance it runs realy good, if I add the vacum it's to much and I get some missing, now if I lower the vacum advance when it's set like this I have to lower it a lot, not enough to see much differance, so without it's 22 + 20 = 42 total avance at 2600 RPM
The other way is set the base to 12 BTDC add the vacum ( about 10* ) and it runs fine so 12 + 20 + 10 = 42*
Se what I mean eather way it ends up at 42* but the first was has way more "off the line" power.
as for MPG it runs between 6 and 7 around town but their are lots of hill's and stuff here.
it's a Stock 352 rebuilt about 26k ago I think, it was 22k when I bought it dont know what kind of cam but I never have gotten any ping.
The other way is set the base to 12 BTDC add the vacum ( about 10* ) and it runs fine so 12 + 20 + 10 = 42*
Se what I mean eather way it ends up at 42* but the first was has way more "off the line" power.
as for MPG it runs between 6 and 7 around town but their are lots of hill's and stuff here.
it's a Stock 352 rebuilt about 26k ago I think, it was 22k when I bought it dont know what kind of cam but I never have gotten any ping.
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Post Fiend
Joined: Mar 2004
Posts: 6,056
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From: Union, Washington
Originally Posted by krewat
WAY OF TOPIC
An 11:1 390? with the cam advanced 4 degrees... 16 was about where it would start giving me problems. Keeping the initial down around 6 was a good place for it to start right up ...
To have only 10 in the dizzy, there'd have to be a "5L" slot in there
Thanks rusty70f100
An 11:1 390? with the cam advanced 4 degrees... 16 was about where it would start giving me problems. Keeping the initial down around 6 was a good place for it to start right up ...
To have only 10 in the dizzy, there'd have to be a "5L" slot in there
Thanks rusty70f100
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Joined: Jul 2002
Posts: 42,561
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From: Long Island USA
Originally Posted by Bear 45/70
I ran 11:1 428 CJ's and never had a problem. Any engine that kicks back at 10 or 12 degrees initial has something else going on regardless of compression. And ten in the dist. would give you 20 at the crank, last time I check the the dist turn at half crank speed.
I retimed as I described and everything came together at once, so I could be way off.
I'm going to have to start saying "crank timing" and "cam timing" ...
Post Fiend
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From: Union, Washington
First off, 22 is way to much initial for any engine and 42 is to much total advance, even for a racing FE. Unless you are running premium fuel you are pinging your engine and just not hearing it. With regular gas a total advance of 32 to a max of 35 is all you can run. The vacuum advance is not your problem, the 10 extra degrees of initial advance are. Back off initial to 12 degrees for a total advance of 32 and hook up your vacuum advance. The engine will run better, get better gas mileage and live a whole lot longer.