How does a ignition system react to Overdrive
Thread Starter
Teching In
Joined: Mar 2007
Posts: 10
Likes: 0
From: Shawnee, ks
How does a ignition system react to Overdrive This is for the old school out there. I am curious to know how you set up a carburated engine with Hei for overdrive that does 2350rpm at 70 miles an hour.
Pontiac 400
I am set up at 34 degrees all in at 3100 rpm. and I get 11.5 miles to the gallon mechanical comes in a 25-2600 rpm.
Speedometer has been checked and double checked
I have used ported and full manifold vacuum
I have used 730 Quick fuel and 670 holley avenger.
2004r with 3.73 final 2.499:1
What happens to timing at partial throttle at 2350 rpm going down the highway?
I am not sure this makes sense. But give it a try.
Thanks
Greg
Pontiac 400
I am set up at 34 degrees all in at 3100 rpm. and I get 11.5 miles to the gallon mechanical comes in a 25-2600 rpm.
Speedometer has been checked and double checked
I have used ported and full manifold vacuum
I have used 730 Quick fuel and 670 holley avenger.
2004r with 3.73 final 2.499:1
What happens to timing at partial throttle at 2350 rpm going down the highway?
I am not sure this makes sense. But give it a try.
Thanks
Greg
Thread Starter
Teching In
Joined: Mar 2007
Posts: 10
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From: Shawnee, ks
Using vacuum advance will give you much more timing while cruising. 40+ which will help mileage. I have a 73 vette with a Vortec 350, 700r4, Holley 600, and hei that gets 25mpg at 80.
Thread Starter
Teching In
Joined: Mar 2007
Posts: 10
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From: Shawnee, ks
what is your intial and mechanical timing?
Thanks
TECH Junkie
Joined: Dec 2012
Posts: 3,621
Likes: 1,335
From: Iowa
vacuum advance distributor will help increase timing under light load (high vacuum) thus improving highway mileage.
what's the tire size. What's done to the engine? What fuel?
are you using the torque converter lockup function?
what's the tire size. What's done to the engine? What fuel?
are you using the torque converter lockup function?
Thread Starter
Teching In
Joined: Mar 2007
Posts: 10
Likes: 0
From: Shawnee, ks
pontiac 400 bored .040
Crower cam 421 and 446 lift
8.75:1 compression
2004r transmission
3.73:1 rearend
28" tires
gets 10 mile mpg in town and 10 mpg cruising at 70
It cruises at 2350 and I dont think I am getting any advance while cruising.
Thanks
Crower cam 421 and 446 lift
8.75:1 compression
2004r transmission
3.73:1 rearend
28" tires
gets 10 mile mpg in town and 10 mpg cruising at 70
It cruises at 2350 and I dont think I am getting any advance while cruising.
Thanks
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TECH Junkie
Joined: Jun 2008
Posts: 3,204
Likes: 1,391
From: Nitro Alley
Are you trying to burn premium gasoline with only 8.75:1 static compression ratio and 34 degrees of total ignition advance?
If you are... I would strongly consider moving to a lower octane (faster burning fuel) or increasing the total ignition advance up towards 40 degrees.
If you are... I would strongly consider moving to a lower octane (faster burning fuel) or increasing the total ignition advance up towards 40 degrees.
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