Timing on TFS Twisted Wedge (or other new alloy) Heads

[C0V3R]

I have been tuning my new 5.0 roller motor for a while and am wondering how much timing I should use on Twisted wedge heads. I know the old iron heads like as much timing as you can give them before pinging. Are the new aluminium heads the same? I read in a few places that the improved combustion chamber shape on some heads require less timing than the older design. I have also read that aluminium heads can run more timing than iron. Consequently I am a bit confused.


At the moment I am running around 15-16deg initial for 34 total. It feels a little flat in the bottom end and doesnt seem to want to break the tyres loose. Feels very good at the top end. I am thinking a little more timing could help down the bottom.


How much timing are you running on your TW or modern aluminium head setup?

 

[ForceFed70]

There's alot more to the equation than just the heads. Compression ratio, fuel octane, and cam design also play big rolls in timing.

As a general rule of thumb, you can get away with 1 or 2* more timing than the same heads made out of iron.

For you, it sounds like your total timing is about right. Have you thought about changing the springs(lighter spring) in your mechanical advance so that it "comes in sooner"?

 

[C0V3R]

True, heres some more info.

CR - about 9:1
Cam - TFS stage 1
Fuel - 98 octane
Intake - single plane wieand 7515 (probably losing some tq here)
Exhaust - try ys
Ignition - full msd
Carb - edelbrock 600cfm

I had the same exhaust/intake/carb/ignition on another motor that was on its way out that seemed to be able to break the tyres loose alot easier. That old motor was no where near as good in the top end and would only rev to 4500.

I have already moved the ignition curve in so it should be all in by 3200. I might try moving it in a bit further.

 

[bnickel]

well the comp. ratio is a little low for an alum head engine running 98 octane. with those heads i'd be running at least 10:1 compression maybe even 10.5:1. that said i think you can easily get away with more timing provided that's what the engine wants, say in the 38-40 degree range. i'd bump it up to 38 total and see how the engine responds, if it likes 38 then try 40, i wouldn't go any more than 42 total though. if the engine needs that much timing you really need to reconsider the comp ratio or a cam with a tighter LCA at least to help build some dynamic compression.

 

[Bullitt]

i ran 14 initial and 36 total on my combo which wasn't too different from yours:

Lunati cam - 218/228 w/ .536 lift
TFS Heads
Performer RPM
Edelbrock 750
9.6:1 compression
1 5/8" longtubes
MSD distributor/ignition

did 325 HP / 317 TQ to the wheels.

If you look at the TW install documents they recommend between 32 and 36 total advance. I had my ignition set so all of the ignition was in by like 2500 RPM (I can't remember which springs that was on the dist.) and it worked pretty well.

You're running way too much octane for that engine though. You should be able to run 89 with 14 initial and 9:1 compression with no problems and definetaly have no problems with 93. Octane makes the flame burn slower and may kill some of the responsiveness.

 

[C0V3R]

We cant even get 89 octane here The lowest I think is 91 or 93.

I might give the lower fuels a try - cant hurt to save AU 10c per liter (or say US 25c/gal for you guys)

 

[Bullitt]

although you'd have to tear into the engine to do it, you might look into getting the heads shaved to bump the compression. i got my TW heads cut 0.020 and that raised the compression from 9.6:1 to 10:1. Still not quite enough compression to need higher octane than 93, but does make things a little snappier.