454 timing
Mr. Floppy
36? This has stock heads for a 79, so just need to know.
CB
with dwell set at 32.
CB
Mr. Floppy <my73c...@takethisout.mailcc.com> wrote in message
news:eY8v6.693$MT2.2...@dfiatx1-snr1.gtei.net...
Mr. Floppy
news:24ov6.55282$cb.25...@typhoon.kc.rr.com...
> Are you talking advance or point dwell? Advance should be 10-15 degrees
> with dwell set at 32.
>
> CB
Total timing. Em said 34 was the spec for an LS6. This is not going to be
that much power. It's got stock heads, and about a 9.4 compression ratio,
so I would think it would take the 'standard' curve for a run of the mill
454.
--
Mr. Floppy
http://my73camaro.50megs.com/
Bigjfig
>From: "Mr. Floppy" my73c...@takethisout.mailcc.com
>Date: 3/25/01 3:15 PM Eastern Standard Time
>Message-id: <plsv6.2534$MT2.8...@dfiatx1-snr1.gtei.net>
An old Chilton or similar book for this 1979 Suburban will give you the stock
setting for the 454. That might be a good place to start and work from there.
Joe--ASE Certified Parts Specialist
'80 Carousel Red Turbo, 26k original-->http://www.0rdernet.com/Mean_Pont
'79 10th Ann. 400/4 speed, 57k original-->http://home.earthlink.net/~bryanan
'84 Olds Delta 88, 307 "Rocket" (lol), 137k and still going....
Carrell Hinton
news:eY8v6.693$MT2.2...@dfiatx1-snr1.gtei.net...
> 36? This has stock heads for a 79, so just need to know.
>
>
timing, just initial. I picked a few as examples.
1975, last year for 454 in Chevelle, and first year for electronic ignition.
Chilton specifies 16 degrees initial for automatic, no manual spec listed.
This engine had 8.15:1 compression and was rated at 215 hp @ 4000 and 350
lb/ft @ 2400.
A 1971 454/425 had a 9:1 compression ratio and called for 8 degrees with
manual trans and 12 with automatic. This one was 425 @ 5600 and 475 @ 4000.
The 1971 454/365 was 8.5:1 and called for 8 degrees manual or automatic.
If I were putting this engine together, I'd probably start with 34 total and
fine tune from there. You will not be far off. The open chamber BBC heads
tend to avoid detonation.
Good luck with it,
Carrell
http://members.home.com/carrellh/1972Camaro.htm
John Laferriere
recommendation is right on!) because it assumes you are using stock type
distributors, many of them with 36 degrees of potential mechanical
advance, with springs that would never see it except beyond their
recommended redline. You'll even see some of the smog years in the
Chilton with 0 degrees BTDC and a few -4's for some choked small
blocks. You'll also find in the Chilton that the LS-6 with 12 degrees
initial only had a 16 degree distributor, making it 28 total! WTF?
People had to advance that puppy to 20+ initial to get back to
advertised power.
But a bigger reason that historical numbers are a bad reference (if you
could find any useful ones) is that they refer to leaded gas. Unleaded
gas burns quicker and advance numbers should be reduced by 2 to as many
as 5 degrees. (O.K. guys, go ahead and flame away if you don't agree).
Some past documented work has shown numbers as high as 38-42 to work
well for performance big blocks, with the 42 deg only for 396 motors.
So, when you see numbers at 35, the main reason is for the unleaded gas.
In recent years, GM now states timing for many of the big-block crate
motors at total timing versus the typical 4 or 8 initial.
Look here at the bottom of the page:
http://www.sallee-chevrolet.com/ChevyBigBlockV8s/502ho.html
and you'll see:
Spark Timing: 36 degrees total advance at 3600 rpm (with
distributor vacuum advance line disconnected and plugged)
Can't get more clear than that. They tend to recommend 35 and 36
degrees between 3000 and 4000 rpm depending on the year of the parts
catalog and whether it is a Gen IV, V, or IV, with no consistent
difference between 454 and 502, except the 502's never have more or at a
lower RPM than 454's. However, I recall some of the more torque tow
motors have said numbers like 32 and 34 degrees.
Click some other links on the crate engine page:
http://www.sallee-chevrolet.com/Gm_Performance_Parts_Update/gmnew.html
The printed catalogs have more of this type of info, or at least a
collection of printed catalogs from the last several years have many
more combinations for you to read and reference. However, you'll find
that advance recommendations aren't entirely consistent.
In the GM power catalog (or whatever it is called, the one with the 60
degree V6 on the cover), you'll see the same advance recommendation
curve for 2.8L V6, 3.8L V6, SB, and BB, showing 36 degrees at 3000rpm
(linearly increasing with rpm, try that with your centrifugal advance
springs and weights, but that is another story...) The 454 peformance
stuff usually still follows Mk IV LS-6 heritage timing from catalogs
years ago as a simple "4 deg BTDC", which is entirely useless because a
SMOG EXEMPT motor with that cam will start, idle, drive better with
quite a bit more initial.
On my 10.2:1 454, I run 12-14 initial providing 34-36 final, all in
between 3000 and 3200 rpm, and add in about 10-12 degrees more of vacuum
from the timed port. This is for a manual transmission GM '65 A-body.
Recommendations for an EGR equipped vehicle is to add a few more degrees
of vacuum advance (14-16 degrees).
So my post is getting rather long so I'll offer 34 deg for torque/tow
motor maybe at 4000 rpm or possible 36 degrees for performance motor
possibly as low as 3000 rpm.
Hope this helps.
JL
Mr. Floppy
"John Laferriere" <john.la...@lmco.com> wrote in message
news:3AC0C209...@lmco.com...
> On my 10.2:1 454, I run 12-14 initial providing 34-36 final, all in
> between 3000 and 3200 rpm, and add in about 10-12 degrees more of vacuum
> from the timed port. This is for a manual transmission GM '65 A-body.
> Recommendations for an EGR equipped vehicle is to add a few more degrees
> of vacuum advance (14-16 degrees).
>
> So my post is getting rather long so I'll offer 34 deg for torque/tow
> motor maybe at 4000 rpm or possible 36 degrees for performance motor
> possibly as low as 3000 rpm.
> Hope this helps.
>
> JL
I am thinking the curve should come in quickly on this one. He doesn't plan
to run over 4000 RPM. So, I am going to stick it at 34, and work from
there. I know the stock HEI is going to be a pain in the ass to get right
for the curve.
Bigjfig
>From: "Carrell Hinton" carr...@home.com
>Date: 3/26/01 11:26 PM Eastern Standard Time
>Message-id: <VDUv6.503268$ge4.17...@news2.rdc2.tx.home.com>
Actually, 1974 GM cars had an option for HEI. My coworker's 74 Grand Prix has
HEI. Factory original. The parts books also confirm it.
75 does sound like the last year for the 454 in the Chevelle. 1976 usage (the
last year for the 454 in a car) is limited to the big B body cars in the Chevy
line as I recall.