Flat spot under light throttle application.

[azriel_strife]

anyway. I'm pretty sure this is fuel related. can anyone else recommend good needles for a 2.9 stroker build with a free flowing exhaust?

[Captain Obvious]

The SM needles should run richer than stock and there's no reason you should be running lean with them. They should be capable of delivering more than enough fuel for your motor.

Can you get your hands on a wideband to help nail down if it's a fuel problem or not?

[siteunseen]

Could it be the cam's power band, or lack of?

[azriel_strife]

I would have to buy a wideband, I don't know of anyone that will loan me one.

If i remember correctly the cam is a factory n42 cam, making it an "a" grind. I want to get a stage 2 cam for this car if i can't find a turbo motor, but I dont want to spend that money if there's some other underlying issue.

[Captain Obvious]

Well the symptoms say "lean miss", but the SM needles say "richer than necessary" at almost all points. Only place they are leaner is way way up by the shank. I would expect that you're above that area at pretty much any spot except maybe idle?

In your original post, you said that you "seated the needles against the seats". What do you mean by that?

[azriel_strife]

the z thereapy dvd says to set the needles against the jets (at zero turns out) by holding up on the choke plunger and pushing the slide down until it stops, then completely tighten the needle set screw. basically it ensures the the needles are set perfectly on the slides. once this is done you set at 2.5 turns out and go from there.

not sure if i explained that clearly?

[azriel_strife]

I've been reading and it seems that this flat top block and n42 head bump the compression up too much for a stock cam, this might be my issue, as the mechanical advance maxes out around 3000rpm where i start to see this lack of power appear.

thoughts?

[madkaw]

What makes your engine a stroker--crank? What compression are you running? I don't buy the stock cam is the culprit.

[madkaw]

A stumble at cruise SU's and timing

I'm still talking ignition:)

Edited August 30, 2014 by madkaw

[azriel_strife]

What makes your engine a stroker--crank? What compression are you running? I don't buy the stock cam is the culprit.

it has an LD crank in it. it's definitely a stroker motor.

A stumble at cruise SU's and timing

I'm still talking ignition:)

wish i could nail it down, advancing or retarding timing doesnt seem to have any effect on the flat spot. but retarding does kill my torque and idle.

[madkaw]

Wasn't sure but did you say you do or do not run with vac advance?

Have you experimented with float adjustments?

Spark plug gap?

[azriel_strife]

floats have been rechecked twice, they are exactly on spec. plug gap is at .35 across the board, i run with no vac advance