idle issues 70 gt help please = )

[danktank]

ok so here is the skinny. its a 1970 opel gt as you may have read in my other thread. it is the 1.9 with high compression pistons. it now has a iskenderian combination cam from opel gt source and the weber downdraft. i started with a 60 idle jet and have now gone to a 65 thinking that would be my problem. but it still wont idle correctly without me turning the idle screw way up and if i do that i cant properly set lean idle mix. i have been racking my brain on this for a week now. i got some carb cleaner and started spraying around and didnt find anything. took all the vac lines off and capped their ports and still nothing. then i took carb cleaner to the manifold and sprayed all around on the top of the manifold. not any difference. then around the bottom and it made a little change in idle. it dropped. so i suspect maybe manifold gasket on the bottom? maybe my torque wrench is off and i didnt get the head down tight enough? that would explain the slight amount of blue smoke i get. i dont know im runnin low on ideas. so i turn to the opel experts that populate this site. id like to get this thing finished soon so i can take it to a meet. please help me my friends. and thanks so much in advance for your help!

[Tru-Craft]

Need more info about carb......38dges?
Jet sizes?
Idle vacuum?
Lyle

[opelnut10]

If you are getting a change when spraying at the bottom of the intake that is where I would start looking. Do you have a ("sprint") FI Exhaust manifold? if so is the cast hump on the center port still there? if so then in some cases that hump interferes with the intake manifold pulling up tight on the head. The hump needs to be ground down or ground off when being used with a carbureted stock intake manifold. Hope that helps and you find the problem and fix it.

[bigjim5551212]

check the intake manifold hanging up on the exhaust first. If that is happening, you should have an idle that is not steady.

But...camshafts tend to make the idle run lean. The reason for this is that the intake and exhaust valves are open for a longer time than normal and more of the unburned fuel goes out the exhaust before it is burned. Then you have to run a big idle. We have 70 idles in stock. One thing else, when we see larger engines, like Toyota 22R (2400 cc) with cam and headers, a 32/36 DGV is too small the idle speed screw has to be open too far and the idle jet needs to be too large. A 38 DGAS might be better for you over all. You have 2 idle jets and 2 synchronous (open together) throttle plates to admit air. Its easier tuning as well, because you are making both barrels the same.

[hrcollinsjr]

Originally Posted by bigjim5551212 But...camshafts tend to make the idle run lean. (snipped) Then you have to run a big idle. We have 70 idles in stock.

I did a 2 liter for a friend with a mild cam and we had to use a size 80 primary idle jet to get it within recommended specs of 1 1/2 to 2 turns.

Harold

[danktank]

as i said i started with a 60 jet and moved to 65. still wont idle. its a weber 32-36. its what opel gtsource sells as the most common kit so they told me. i dont have a vac gauge so i cant tell you what the vac is at idle. but it sure does run for ass at idle and fine above it. it burns a little bit o oil too so could it be stuck rings from sitting? i wouldnt think that would cause an idle issue tho. i called opel gts again today and although they are usually helpfull they didnt give me much to go on except that a 65 idle jet is the largest they have ever had to use. you really think i may have to ramp it up that much? i mean i will if you all think it will help but a 65 should suffice. anything else it could be? i eliminated any vac leaks outside the carb mount and manifold by removing them and capping them. cracked manifold maybe?

[Tru-Craft]

So many things it could be!
I would get a vacuum gauge & a compression gauge, very handy cheap tools.
Brake booster leaking?
Timing at idle?
Stock distributor?
Intake manifold flanges not the same height as exh manifold?
Basic tune-up is always a good start for idle problems.
Do the simple stuff first.
Most times the carb is not the problem, a new one from OGTS should be perfect as is.
?
Lyle

[danktank]

well to eliminate the possibility of brake booster and dizzy i unhooked all 3 vac lines coming off the manifold and carb. and capped them all and it still behaves the same way. to get it to idle i have to crank the idle adjust screw really far in. like the spring on it is all the way compressed. i tried spraying carb cleaner on the flange for the intake mani and that didnt alter anything. ill try loosening all the manifold bolts and try to even them both up but there are guide pins so i dont know how much it will help. but ill get that torqued down again and see if it does anything. im sort of running out of ideas lol. im also going to try some marvel mystery oil down in the cyls. since the engine sat for a while im thinking maybe the rings are locked up and the marvel may get em loose. hopefully that will clear it up but i have no idea. ill get a compression test done soon here and try to get a vac reading. but i know there is alot of vac at idle so yeah. but thats what i have so far. the vac leak if any has to be in carb manifold flange or head. all the externals have really been eliminated.

[wrench459]

Originally Posted by danktank to get it to idle i have to crank the idle adjust screw really far in. like the spring on it is all the way compressed. ill get a compression test done soon here and try to get a vac reading..

When you turn the idle screw that far your uncovering the idle slot and going into the transfer slots. Your right about the compression test and what valve lash are you using?

[bigjim5551212]

was this car sitting around? sounds like the idle system is not working at all. I think there is a blockage in the idle system

[danktank]

the car was sitting for quite some time i believe however the carb itself is brand new. when i took the origional idle jet out there was a blockage in the new jet. i cleaned it and it did nothing. maybe a problem with the casting of the carb? ill try running a small wire through it and see if that helps. a compression test i still need to do to determine if its rings or something else causing the oil burn. and i did the lash to the zero spec as per the instructions i got with the hydraulic lifters i put in when doing the head. new valves, seats, lifters, cam, and cam bearings. also new stem seals.

[bigjim5551212]

do you have someone that you know nearby that has a weber that does work? it can be from anything like a Datsun BMW, Toyota, whatever. even formula ford race car.

I dont think its in the casting. I think there is a buildup of mung in the passages

[Anonymous D]

"..to get it to idle i have to crank the idle adjust screw really far in. like the spring on it is all the way compressed..."

That is the classic symptom, of a major vacuum leak. I suggest cleaning the mount areas beneath the carb (including the heat shield, if you're using one), then using a thick carb base gasket (NOT the stock or the weber type) and using Permatex Hi-Tack gasket sealer on all surfaces (although, I warn you, you might also encounter a differing point of view here concerning the use of sealer).

Web links for downloads on this, from the June 2006 Blitz, are at:
www.opelclub.com/TuneUpPart1bJune2006.pdf

[danktank]

so permatex the carb base? i have heard from many many ppl thats bad. and yeah the gasket im using is the stock weber one. i sprayed carb cleaner all over it and it didnt change a thing. anyone know where i can get a new base gasket that would be better?

[Tru-Craft]

OGTS has them, might want to get a rebuild kit while your at it.
Check to make sure your carb base is flat, sand it on a piece of glass with 320# in a figure 8 pattern.
I just use my finger to smear on a "very thin" layer of permatex on the carb gaskets.

[danktank]

its a brand new carb. if i have to rebuild it then im sending that bitch back. new carb new gasket new fuel filter. ill try the permatex thing here in a few days when the new waterpump comes. the guy at ogts said that it could leak vaccum through the valve cover. however unlikely i would think that would be im going to attempt to investigate it. and i did run the engine and spray carb cleaner all around the base of the carb and it showed no change in idle up or down.

[Tru-Craft]

*If the carb is new and the idle passages are open, then the carb should be OK.
*If the carb spray didn't change idle rpm then the gasket should be fine.
*If the vacuum port to the valve cover is plugged and not leaking, then the valve cover is not the problem.

Can't help you much without checking the basics, compression, vacuum, intial timing/advance curve.
Most cars will run OK above idle, even when the above things are off.
But not at idle!

[Anonymous D]

"its a brand new carb. if i have to rebuild it then im sending that bitch back."

Most problems with a new Weber are caused by improper installation.
You've already been informed that you are experiencing the most common
symptoms of a major vacuum leak, and that one remedy is installation of
a thick base gasket with a layer of permatex sealer. It's a deductive process,
so why consider the most expensive solution (when the alternative is less than
$10)?

[danktank]

ill try pulling the gasket off and throwing some permatex on there and see what that does for me. its a new gasket with like less than 2 hrs run time on it so ill post up what that does for me. thanks for all the help guys i do apriciate it and im sorry if i seemed a bit testy this car is just getting to me. lol

[Anonymous D]

Just to say it again, the permatex sealer remedy
is best used with a (3/8"-1/4") thick carb base gasket
(not the "stock" Weber gasket, which is much thinner).

[hrcollinsjr]

Originally Posted by Anonymous D Just to say it again, the permatex sealer remedy is best used with a (3/8"-1/4") thick carb base gasket (not the "stock" Weber gasket, which is much thinner).

I've probably installed or re-installed a dozen Webers and I've always used the THICK gasket. It's the best way I know of to eliminate vacuum leaks.

Harold

[BDD]

The thick gasket made a BIG difference for my car. I would consider it a must. Then you can look for other vacuum leaks.