I just recently put my new 406 in and iv changed the wires,cap and rotor. and nothing, i put the plugs from the 305 in it because they were brand new. but i dont know what to check anymore. if i have it idleing and i rev it up, its fine, but between say 1500-2500 you can easily tell it has a dead skip on one cylinder. anyone have any idea's what this could be? i had 2 coils i swapped each onto it and it didnt make a difference. when the car is warmer it seems to not do it so much.the only possibilities i think could be a bad plug, i doubt its the fuel filter but maybe, defective new wires, i was thinking the cam didnt brake in good enough but if that happened it would skip idleing as well. anybody have any ideas, this is really starting to tic me off! lol

 

What cyl. is skipping and do you have a hand held tach or timming light to find out if it a spark problem or fuel?

 

i cant tell which cylinder, it only does it under load, like just driving it. but yes i do have a timing light.

 

can you duplicate it in park?

 

i was trying today, but when it warms up it doesnt do it as much, but id ont want to slip the clutch at 2-2500k rpm. im going to get a new fuel filter for it tomorrow, it needs one anyways. because sometimes its ***** to the wall then sometimes it feels kinda like my 305 cause it skips.

 

what type of fuel system?

 

Q-jet with performer intake for now.

 

new or used q-jet? That can be your problem. they are great carbs but they have ti be dialed in first.

 

stock 85 q-jet off the car, its a messed up carb anyways, idles fine but hessitations ect.

 

My vote is the qudrajunk is the source of your problem. Did you re jet it for the 406?

 

Q- jets are good carbs much better than holley and edelbrock for reliability. but you have to know how to tune them in. They are tricky. Talk to a local speed shop and i bet you someone will know how to tweak it for your application

 

no i didnt rejet it at all, just put the carb on. maybe ill put my cousins 800 double pumper on. but maybe ill just wait for my LT1 intake/TPI system to go on. also i dont have my charcoal canister hooked up and theres quite a bit of suction in the gas tank, i doubt thatll do it but, im just trying to give idea's

 

#1 vent the tank if it sucks in you will regret it. wait for the tpi.

 

My Car had a Similar Problem in its V6 days...

Would Idle Fine...
Would Navigate the Parking Lot Fine...
When You went to take Off would fall on its face until the RPM's had a chance to build up to around 2500...
And it would do better the warmer it was.

If its the same issue mine was it will just get worse and worse over time.

When it first started it was just as you described it, sounded like it wasn't firing on one or two cyl's.

Mine was the Rear Intake Manifold Gasket. There was a small gap in it, and when it was cold I was losing Vacuum pressure.. and oil... but when it warmed up I guess the seal would make good, or at least better than when it was cold.

A lot of the engines didn't use Rubber seals on the intake valleys, they just used black rtv, which is more prone to that problem than the rubber seals, but my grandfather (45 years with buick dealership) said it was a common problem with cars in the 80's.

May not have anything to do with your problem, but its something fairly easy to check to eliminate.

 

i understand what you mean, im going to go out tomorrow and tighten all the bolts down on the intake because i know they have to be loosened from the fresh rebuild. thanks for the input! ill see if it helps

 

i tightened all the engine bolts down, like 2 of the intakebolts were pretty loose, and the others were alright,but now it seems to run fine. its very odd.

 

The Way it Was Explained to me, both the Vacuum Advance and Carburator Need a Reliable Vacuum, and if the seal is broken in any way, then the Vacuum will fluxuate, causing said problems...

Anyway, Like I said, its a cheap check, and if it solves the issues, move on to other issues...

 

i just bought a used set of SLP headers, and one header is 1 3/4 and one is 1 5/8ths, is this a factory defect or did someone try screwing me?

 

?????Someone screwed you..they should be the same size.

 

yeah i measured, one is 1 5/8ths and one is 1 3/4, im going to request partial money back for them. i mean, they'll work, but idont know i keep getting crapped on. lol oh, i also hit a deer yesterday, its nothing bad.