Thread: 3.9V8 Tuning Help Needed (aka I still hate V8s - but they do sound good ;))

Originally Posted by isuzurover

I guess there is no easy way to check which cam it has??? I am pretty sure the receipts that came with the county just say "reco 3.9 short motor".

If you have the receipt .... You could grab the engine block number & try ringing up ..... and seeing they if they have records of "How it was recon'd" .... IE Which cam??

Mike

[QUOTE=isuzurover;1190956]Bojan has hidden the timing light, so I can't measure it - Bojan???

QUOTE]

... Pretty sure its in the brown county - passenger front seat.

You say its ok up to about 1500 that means its working right kind of lol

Did the injectors get dirty while they where out or is the fuel line pinched or leaking
Either would cause this problem because the fuel cant keep up with the engine

If you think you did everything right then look for the simplest fix

if it worked before it will be something very simple

Are you running carb heads with EFI? If so, did the heads get the little cut out ground into the intake ports for the injectors to fire into?

I'd start by hooking the vacuum line direct to the manifold - there's no need for ported vacuum. Set your timing by filling up with low grade fuel and slowly advance the dizzy bit by bit untill you get pinging at around 2000 rpm whilst under heavy load and wide open throttle (do this on a hot day and you'll be safe). You may have to comprimise between this setting and idle quality. Running the vac advance direct to the manifold will help with this, but it will always be a comprimise with dizzies - they are old fashioned rubbish. The initial 6dbtdc as marked on the balancer doesn't mean much, just use it as an initial starting point, nothing more.
Have fun

(all above assumes the fuel system is ok)

Originally Posted by BigJon

Are you running carb heads with EFI? If so, did the heads get the little cut out ground into the intake ports for the injectors to fire into?

Good call worth a check
that is a good point
i didnt pick that up till i read it again

3.5 Carb heads on a 3.9 no dimples for the injectors and its just hitting the head and dribbling

Originally Posted by BigJon

Are you running carb heads with EFI? If so, did the heads get the little cut out ground into the intake ports for the injectors to fire into?

Originally Posted by steve_35

Good call worth a check
that is a good point
i didnt pick that up till i read it again

3.5 Carb heads on a 3.9 no dimples for the injectors and its just hitting the head and dribbling

It's running carb heads with EFI and as far as I know the intake ports didn't get any cutouts.

The EFI was running well for about 5 minutes (possibly without the airflow meter connected - Ben?). Given that the engine ran well, how likely is it that the divets alone are the cause of the misfire?