Simple L98 timing questions
Thread Starter
Large Impressive Member
Joined: Jul 2003
Posts: 65,811
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Simple L98 timing questions
'88 L98 w/ 6 speed conversion, otherwise totally stock. I'm wondering where's the best place to set initial timing and what to look for, for total advance. Also thinking of putting a curve kit in it. The owner just wants a little more pep. Thanks.
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
Unless you hook up a scanner and go for a run, you'll never be able to see what the equivalent of "total" is. I would just start making runs and adding 2° until it quits improving, and then back to the previous best. I ended up with a base of 14° BTDC that way. Most people end up with 8° to 10°.
RACE ON!!!
RACE ON!!!
Thread Starter
Large Impressive Member
Joined: Jul 2003
Posts: 65,811
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Interesting. I hadn't looked under the cap yet but was assuming that all of the big distributors still had mechanical advance. So I guess when the precipitation stops here, I'll just take it out and play with it! 
Thanks for the tips, fellas. 
Thanks for the tips, fellas.
Former Vendor
Joined: Jun 2001
Posts: 7,204
Likes: 6
From: St Marys PA
Originally Posted by Morley
Stock TPI, 6* BTDC. A "curve kit" won't work, the spark curve is controlled by the ECM via the programming in the prom chip.
Run what timing the motor runs best at. Do not shoot for a specific number. You are using a stock pointer that may or may not be dead on at 0* (TDC).
Go to a track or dyno - run the car at various timings and see what produces the best numbers. I usually start out conservative and then keep adding timing till my MPH drops off at the track. Back the timing up and lock it down where it ran the best MPH. Best MPH = Most power.
Thread Starter
Large Impressive Member
Joined: Jul 2003
Posts: 65,811
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Originally Posted by ski_dwn_it
Run what timing the motor runs best at. Do not shoot for a specific number. You are using a stock pointer that may or may not be dead on at 0* (TDC).
Go to a track or dyno - run the car at various timings and see what produces the best numbers. I usually start out conservative and then keep adding timing till my MPH drops off at the track. Back the timing up and lock it down where it ran the best MPH. Best MPH = Most power.
Go to a track or dyno - run the car at various timings and see what produces the best numbers. I usually start out conservative and then keep adding timing till my MPH drops off at the track. Back the timing up and lock it down where it ran the best MPH. Best MPH = Most power.
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Melting Slicks
Joined: Aug 2003
Posts: 3,399
Likes: 395
From: Lakeville MI
The "total advance" for an 88 L98 in the high rpm/high load area is between 32 and 35.9 degrees. A couple of excerpts from the ABTR table. Spark vs rpm vs load.
Load = 192
4000 rpm 32
4400 rpm 33
4800 rpm 35.9
Load = 208
4000 rpm 28.8
4400 rpm 32.0
4800 rpm 35.9
Advancing the base a couple of degrees from 6 may help here, but will push you kind of high above 4800 rpm. (not really a problem for a stock L98)
Load = 192
4000 rpm 32
4400 rpm 33
4800 rpm 35.9
Load = 208
4000 rpm 28.8
4400 rpm 32.0
4800 rpm 35.9
Advancing the base a couple of degrees from 6 may help here, but will push you kind of high above 4800 rpm. (not really a problem for a stock L98)
Pro
Joined: Jan 2002
Posts: 718
Likes: 0
From: W.V.C. Utah
Originally Posted by CFI-EFI
Unless you hook up a scanner and go for a run, you'll never be able to see what the equivalent of "total" is. I would just start making runs and adding 2° until it quits improving, and then back to the previous best. I ended up with a base of 14° BTDC that way. Most people end up with 8° to 10°.
RACE ON!!!
RACE ON!!!
Pro
Joined: Jan 2002
Posts: 718
Likes: 0
From: W.V.C. Utah
Originally Posted by CFI-EFI
That is iron headed like mine, isn't it? I use 85 octame gasoline, exclusively. I am sure my compression ratio is lower than yours.
RACE ON!!!
RACE ON!!!
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
I ended up at 8 on my 87, I've always believed in the -set it where it runs best. Hey Kid, I grew up with those engines too, mech and vac.
I actually liked toying with weights, springs etc.But, I too like the electronics of our engines-except when there's a problem.
I actually liked toying with weights, springs etc.But, I too like the electronics of our engines-except when there's a problem.
