Ignition retarding at high rpm

[Dave-R]

This one Adam?

My thinking is you are too rich at the start and getting leaner as you progress. A rich mixture effectively retards the ignition - requiring more ignition timing.
A lean mixture effectively advances timing - requiring less ignition timing.

I would put money on it.

[Pete]

The problem is that I am leaving the line at about 5000rpm and well on the main jets by then, so few options to do anything with mixture....

[Dave-R]

Is the engine getting flooded a little at the start line after burnout etc? Fuel pooling anywhere? Pump shots dumping fuel in when you raise the rpms up?

Then at the top end it is drying out? Fuel bowl levels dropping?

As I have said. Until you record what is actually happening you are just guessing.

What is the difference between the engine at 5000-7000rpm at the start of the track to 5000-7000 at the other end?

[Pete]

Is the engine getting flooded a little at the start line after burnout etc? Fuel pooling anywhere? Pump shots dumping fuel in when you raise the rpms up?

- Yes, but the car has a huge cam and huge ports, so not surprising. The motor needs huge shooters to stop it bogging. Mashing a 1050 on the line creates a BIG drop in vacuum.


Then at the top end it is drying out? Fuel bowl levels dropping?

- No, the fuel pressure is fine at the top end at 6900rpm.


As I have said. Until you record what is actually happening you are just guessing.

- Probably, but need to start some where...Adam did a great job of analysing the plugs and recommended more timing and more fuel.


What is the difference between the engine at 5000-7000rpm at the start of the track to 5000-7000 at the other end?

- Different load? Therefore the need for different timing???

Thanks for your help

[Anonymous]

This one Adam?

My thinking is you are too rich at the start and getting leaner as you progress. A rich mixture effectively retards the ignition - requiring more ignition timing.
A lean mixture effectively advances timing - requiring less ignition timing.

I would put money on it.

That.s the one.

[Pete]

If that is the case, then how does one get a "variable" fuel mixture?

These Holleys are pretty crude.

I do not disagree with you, I am thinking of using the timing as a "workaround" to fix the fuel issue. Unless I fit FI then I will always have this problem.

I would think the problem will be WORSE next season as the motor will be 400 "B" based with the same heads, plus a Tunnel Ram with 2 x 750 DP's; so I am trying to solve the problem whilst it is still "simple" with a single carb.

Thanks for your continued input.

[Anonymous]

What quench you running Pete?

[Dave-R]

Well there you go. You are dumping a ton of fuel in on the start line (which needs more timing) and then as it "dries out" it is going leaner (which needs less timing).

So the way you are delivering fuel is the problem.

I would use less pump shot and bring the rpms up before launch rather than mashing the throttle.

Use a trans brake.

[Pete]

Don't get technical with me.

I have no idea....

[Ian Z]

FI it Pete, and use a BT laptop..

[Pete]

FI it Pete, and use a BT laptop..

Nope.

Old school look

[AllKiller]

FI it Pete, and use a BT laptop..

Nope.

Old school look

Carb type throttle body...looks like a Domi...thats old school look

[Pete]

Errr, Tunnel Ram

[AllKiller]

Steve , back off the lash & i bet it picks up some.

Have you stopped grittin yer teeth?

Adam, i guess you think i never play with the car in the 30 odd years ive had it
engine built 8 years ago
Cams and associated tuning 4
Engines blown , None,
Faster, yes every year
Major rebuilds None
performance adders, 1 Nos 150 shot.
engine damage/ melted none
|C16 running Gas and C12 without
only this year i had lost my N02 so ran it C16 no Gas, and went quicker than C12 no Gas

Teeth Grittin None

Why would MSD/Mallory Build in HIGH speed retards if it was nt useful ?????

Sorry for the Hi jack Pete

[AllKiller]

Errr, Tunnel Ram

ERR 2 then ???????????