I've been working on a friends truck and there is a miss I can't pin down and I was looking for help.
The truck is 94 12v 5 speed.
Upgrades:3,000 gsk
370 marine injectors
#4 TST plate full foreward.
AFC Spring
High flow delivery valves
ATS Hybrid Turbo HX-35 14cm
Scotty II
4" Jannetty Racing Exhaust
Pump timing set at 15.8 degrees
South Bend con ofe clutch

The truck runs really strong but at 2700 to 2800 rpm's there is a very noticable miss. I'm not really familiar with the 12 valves and I can't figure it out. Could someone please help me? My 24 valve got a miss when I did some sled pulling and had an ez stacked with a Powermax 3 comp. I pulled the ez when sled pulling and the miss went away. Is 15.8 to 16 degrees too much timing?
Please advise.

Meacham Evins

 

Do you think it could be the valves floating?

 

My truck started doing the same thing after the timming slipped. Funny thing was that with the 4000K gov. springs I could pull through it and the miss would go away in the upper rpm range?

I'd check the timing and then go from there if the problem is not cured.

 

Rebel,
We just set the timing 15.8 degrees and the miss is still there. The truck will also stall out at traffic lights. The accelerator has to be pumped to restart the truck but it starts right up.

Meacham Evins

 

I sure hope not... Im running about 21*
I would definately say the problem is timing. Every truck is different so you will have to play with it a while to get it (timing) right, but after all thats half the fun .
For example: With my truck I had the same miss, except it was at about 2300. After setting reseting and then re-re-setting ( and I think a few more times after that) I finally got the miss to go away. I started at 16* and went up a degree at a time untill I got my truck to except the timing. No problems since.
BTW: Make sure to re check the timing after you have set it. When tightening the inj. pump nut the timing tends to retard itself. Also make sure to torque that nut down good'n tight so to avoid future slipping.
Good luck.
Scott

 

dsljunkie,
Thanks for the reply. I will recheck the timing and go up until the miss goes away. Someone else told me this evening that I might not have enough timing. I'll try your method and see if the miss will go away.

Meacham Evins

 

It needs more timing, the little pumps like a bit more timing to cure that....try 1 degree more if it just has a slight pop on the topend.

Jim

 

Thanks Jim!


Meacham Evins

 

You need 17* timing and the DV's could be the miss. To me this truck is short on air for all the fuel available. Is this hybrid turbo and HX35 with the HX40 compressor housing and 60cm pinwheel? Also with the plate full forward the plate is beyond rack travel and you are most likely over fuled at that point. Bring the plate back to where the rack is traveling on the plate and that should help.
Bruce

 

Stupid as this may sound,
Adjust on the star wheel. The AFC Spring kit has attendencie on my truck the change the upper end behavior. I have a Bad injector, and if i turn the wheel back some it has a lower end miss 2000-3000, and if i turn it up its from about 2700-3000, the miss gets worse unless you have the star wheel just right, guess i could put new injectors in hmmm lol