Timing?

[BigMo]

Hey guys whats a good timing to strart at on a 496 with an 871 blower? Right now its at 32* but the idle is to high and the idle screws a backed down all the way but it still idles about 1800???? Its a pump gas motor.
Mo

[Fiat48]

32 to 34. Less timing will create exhaust valve heat which you do not want. That high idle should not be a timing problem. Probably throttle plates not closing (especially secondary), mixture, sucking air, etc.

[Huffer]

I'm Running 496 1271 With Chiller 28 Deg With Pump Gas!

[Fiat48]

If you could read your exhaust temperature.....I bet you would see some pretty high temps.

[sleekcraft76]

what exhaust temp is to high,i was running 1400-1450 cruising and 1500 when on it hard is that ok?

[Fiat48]

That's the edge. I'd say 1400 is hot enough.

[steelcomp]

That's the edge. I'd say 1400 is hot enough.
Alum starts to melt right above 1300! 1400 IMO is pushing it. You'd be better off down in the 1300's for a non race deal.
Big Mo...I agree with Fiat...you probably have carb issues, but it's not your timing. :coffeycup

[kojac]

Big Mo,
I run a 572 cu inch, with a 8-71 bds, Two dominators with exhaust temps at 1350 to 1450 while cruising. Timing is set at 37 degrees at 3000 rpm's
any less timing causes the exhaust to rise and motor fouls up plugs. On 93 octane.
Hope this helps.
Kojac

[blowngas]

Timing is set at 37 degrees at 3000 rpm's
I would be more afraid of detenation killing the pistons and bearings with that much timing on pump gas----I get nervous at 35 with 118 race fuel----don't know what boost you're running, but seems that temps should come down with different air/ fuel ratio------larger or smaller jets-----sometimes too rich conditions leave fuel still burning going out the exhaust and causes high exhaust temps----

[steelcomp]

sometimes too rich conditions leave fuel still burning going out the exhaust and causes high exhaust temps----That's a BIG 10-4. More than one guy's thought he was running lean because of too high ex temps! More timing helps burn that fuel. Just keep a close eye on your plugs when you start messin around. :coffeycup

[Fiat48]

Especially alcohol. My highest exhaust temp ever was 2550 degrees. Never hurt a thing.

[kojac]

I would be more afraid of detenation killing the pistons and bearings with that much timing on pump gas----I get nervous at 35 with 118 race fuel----don't know what boost you're running, but seems that temps should come down with different air/ fuel ratio------larger or smaller jets-----sometimes too rich conditions leave fuel still burning going out the exhaust and causes high exhaust temps----
Running 94 jets in the 1150 dominators. 6#'s of Boost. Tried it with smaller jets and it backfired and coughed badly on the lake in the jetboat. On the dyno it seemed to like 98 jets for the most power. On exxon 93 octane with 11#'s of boost.
We tried the innercooler on the dyno and only made 18 more horsepower however I am not convinced that the dyno was set up to get the maximum horsepower with the innercooler. It was cold in the dyno room when the motor was initially set up and I wasn't convinced that the water pressure was adequate to the cooler to achieve maximum performance.
This is my first experience with blowers and had a hard time getting exhaust temperatures to come down initially. I thought that the boost was not allowing the intake valves to close properly. Went to a smaller cam.
I am only running 6#'s of boost until I get the pump and bottom setup near right and then I will go to 10 or 11#'s of boost.
After reading all the blower imput on the forums I am rethinking my setup.
Plugs look good though.
kojac