vacuum advance issue, weber installed... trust me i searched...

I recently replaced the mikuni with a rebuilt weber, checked for vacuum leaks, installed an electric fuel pump, checked the timing marks on the engine and distributor according to this site's info, and have 2 vacuum lines on my engine (1. brake booster 2.vacuum advance)

when accelerating everythign is fine unless i go over half throttle; after that it stalls and acts like its going to die, unless i let off, then i can start accelerating. Also i can run the engine upto roughly 3500-4000rpms this way(no tach), but it seems like there is no top end.
I pinched off the vacuum advance while the truck was idling and the idle dropped; this tells me its getting advanced right from the bottom of the rpm range. No amount of moving the distributor around will seem to fix this.

Do I need a new distributor?(vacuum diaphram? maybe something different that requires more vacuum to actuate it?)

This truck never had any amount of power in stock form, but after i replaced the fuel pump(electric: made my own circuit complete with fuse), carburetor(weber), de-smogged, fuel pressure regulator, dropped the gas tank, replaced fuel and vacuum lines, checked every wire on the harness, and BANGED MY HEAD OFF THE WALL!

I have no idea what else to do, short of replacing the vacuum diaphram or modding it in some way???

it also seems to be running rich, but i think that is just part of the timing issue

thanks,
Dustin

you have the vacuum advance hooked to manifold vacuum , not ported vacuum. Use a port that is above the throttle plate. This could also be causing the fall flat issue.

i have it hooked to the vacuum nipple on the side of the carb... do you know at about what RPM the advance should start moving?

Which fitting is it attached to? the front one or the one closer to firewall. There is one with a flat head screw in it on the drivers side carb, take that out, insert hose there and cap off the one next to it that is closer to firewall side of carb.

I switched ports as you suggested. I would never have thought to remove that screw.
The last two webers I have used were on isuzu engines, and they just used manifold vacuum.

The truck was idling better, but I didnt have time to take it out and hook up the timing light. I will let you know the results I come up with.

-Dustin

its running the same as it did, seems to have a bit more getup but still falls in its face when you put more than half throttle into it, and there still seems to be an early limit on the rpms...
I am going to check all my timing marks and spark plug gaps again, if that don't change anything, im going to play with the vacuum diaphragm and see if maybe one of the toyota or isuzu diaphragms make any difference..
-Dustin

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Originally Posted by Dustinicus

its running the same as it did, seems to have a bit more getup but still falls in its face when you put more than half throttle into it, and there still seems to be an early limit on the rpms...
I am going to check all my timing marks and spark plug gaps again, if that don't change anything, im going to play with the vacuum diaphragm and see if maybe one of the toyota or isuzu diaphragms make any difference..
-Dustin

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I cannot speak regarding a 1st Gen. I have no experience or reference material for a 1st Gen, only an '89 FSM.

The parts to rebuild the distributor for an '88 2.6 are still available, but they have to come from from Japan and they take a month to get here.

The 2nd Gen 'A's ('87-'89) have two different distributors- the 2.0s have a 'Denso type' and the 2.6 have the 'Mitsubishi type'.

Really high mileage 2.6s can also have worn timing gears and chains. With the distributor fully advanced, I can only get a max advance of 4ATDC or -4TDC.

I think if you rebuilt the distributor to 'as new' specs you'll fix your problem I think. If you have over 350k, do that and new timing chain and gears.

All that said, I'm not a 1st Gen guru, but a 2nd Gen 'A' guru. ;)

I ordered a jet kit.It's the only thing that i haven't changed. I went with the jets that were in it when i got it, after that i will see if there is a difference, then move onto the distributor. The engine doesn't have allot of original miles and everything in the distributor seen till be in good writing order

Did you ever find a fix I have the same problem with my truck any info would help

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Originally Posted by Ram 50

Did you ever find a fix I have the same problem with my truck any info would help

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The 32/36 Weber isn't jetted for the G63B out of the box (selecting the correct jet sizes will make a noticeable improvement in power and economy). The Weber generates more vacuum than the Mikuni and as a consequence will over advance the distributor. It takes trial and error to get the engine running at an acceptable tune but if you either delete the advance (use a distributor off a 4G64 maybe?) or have the existing distributor re-curved you will make a ton of response out of it.