High Advance needed for acceptable idle?

[hrcollinsjr]

Scenario:

Opel GT 1.9 with single side draft manifold and Weber 40 DCOE. New plugs and Pertonix ignition. This car ran okay when I got it. It sat for awhile ( 6 yrs.). I drained the old gas and replaced with fresh. The car doesn't start very well and the idle isn't much better. When I advance the timing enough to make it idle at a decent speed it wants to diesel when I turn it off. It also doesn't respond very well to the throttle. With the side draft carb and header I haven't been able to get a reading with my timing light. I haven't marked the front pulley yet to try to get a reading there.

Questions or suggestions welcome. I really need to get this car running right so I can return it and move on to projects for me.

Please help!

Thanks,

Harold

[wrench459]

Lets find true TDC first and go from there.

[West Coast GT]

I agree, find your TDC first.
_____________
Then set the spark timing statically.
Then replace all of your vacuum hoses, including the brake boost.

Once all that is complete, increase the idle speed adjustment until the engine will run on its own.
Adjust your idle mixture.
Once that's done, slow your idle speed down to the speed you prefer.

[hrcollinsjr]

Opelspyder had already suggested a vacuum leak. Guess I'll pull the vacuum line and do a check on it to see if it or the booster are leaking. I'll need to mark the front pulley. I static timed the engine and it barely idled at 500RPM at best. I'm not sure that I actually got it to start at 0 degrees. When I advanced it slightly it idled poorly but improved as I advanced it further. I'd bet it was in the range of 20 degrees and idled at 900 RPM. The idle speed screw is bottomed out!

Harold

[yellaopelgt]

Did you clean the carb? Needs a rebuild at least........not enough information on what you all did...
Joe

[hrcollinsjr]

Originally Posted by yellaopelgt Did you clean the carb? Needs a rebuild at least........not enough information on what you all did... Joe

You just HAD to say the "R" word didn't you? Yes, it could/would probably benefit from a good going over. I may wind up ordering a kit for it if I don't find anything else wrong.

Harold

[wrench459]

You might be able to hook up the timing light on number four cylinder and still get the right timing reading.

[hrcollinsjr]

Originally Posted by wrench459 You might be able to hook up the timing light on number four cylinder and still get the right timing reading.

The only way I've been able to static time the engine is to hold a pen light behind the carburetor and look through a small gap between the pipes on the header.

Harold

[wrench459]

Harold
Look closly at the gaps between the primary and secondary gaps
yes there very close like around .039 but you can see them

[hrcollinsjr]

Originally Posted by wrench459 Harold Look closly at the gaps between the primary and secondary gaps yes there very close like around .039 but you can see them

Are you speaking of the gaps between the exhaust pipes? If so when I get the timing light in position then there isn't room for my eyeball to line up with the slot plus you have the light reflecting off of the pipes.

Harold

[wrench459]

I'm being Bad sorry

[wrench459]

One way to make a piston stop is by drilling out a spark plug.

[wrench459]

What Cam is in this sucker BTW?

[hrcollinsjr]

Originally Posted by wrench459 What Cam is in this sucker?

Unknown! I'll try to do a compression check soon. I was told the compression was rather high, in the order of 180 PSI. If this is the case I would assume the cam is probably stock.

Sleep on it, I'm going to!

Harold

[wrench459]

Oh the LSA is around 114 or more
your going after bottom end torque

[wrench459]

Are you going with a short rod motor?
How stock is it?
The 180 psi cranking compression is not stock by any means.
More questions ??? and more and more.
I'll put my butt out here just to learn more.

[GTJIM]

You can never get a carb tuned correctly until the spark is right.

Have you ckecked that the advance mechanisim inside the distributor is working correctly? Reads to me like you are not getting any auto advance.

Carbs get blamed for most everything that does not allow propper idle - but are usually the last thing that needs checking ...

Correct spark and cam timing plus correct valve gap adjustment and elimination of all vacuum leaks MUST be put right first.

[hrcollinsjr]

Originally Posted by GTJIM You can never get a carb tuned correctly until the spark is right. Have you ckecked that the advance mechanisim inside the distributor is working correctly? Reads to me like you are not getting any auto advance. Carbs get blamed for most everything that does not allow propper idle - but are usually the last thing that needs checking ... Correct spark and cam timing plus correct valve gap adjustment and elimination of all vacuum leaks MUST be put right first.

The advance mechanism moves freely with some spring tension. No vacuum hooked up to the distributor, wasn't when I received the car and still isn't.

When I first tried started the car I removed the carb top to discover there wasn't any gas in it so I poured a little in, it helped but still didn't work. The plugs where fouled so I installed new plugs. This seemed to help but didn't "fix" the problem. I advanced the timing like it was before I messed with it. It turned over a lot easier when static timed but would't start.

I will try with a vacuum pump to establish whether I have a leak in the braking system or not.

Harold

[blancojp]

Originally Posted by hrcollinsjr Scenario: Opel GT 1.9 with single side draft manifold and Weber 40 DCOE. New plugs and Pertonix ignition. This car ran okay when I got it. It sat for awhile ( 6 yrs.). I drained the old gas and replaced with fresh. The car doesn't start very well and the idle isn't much better. When I advance the timing enough to make it idle at a decent speed it wants to diesel when I turn it off. It also doesn't respond very well to the throttle. With the side draft carb and header I haven't been able to get a reading with my timing light. I haven't marked the front pulley yet to try to get a reading there. Questions or suggestions welcome. I really need to get this car running right so I can return it and move on to projects for me. Please help! Thanks, Harold

This sounds almost like the same problem Rick had with his GT. I found a few things like dirt in the carb and so on, but ignition was the main problem. My experience with Petronix has always been that timing changes from stock so setting factory timming will not wortk right.

I would get do the following:
1) First check the impedance on your coil and make sure it is over 2.85 ohms. The Petronix tends to saturate on increasing Rpm's if your coil resistance is lees than 2.00 ohms.
2) Check your timming and set to 0 degrees by factory specs. Try to get the car to idle with all vacuum connections plugged.
3) Connect an external Rpm gauge and set Rpms' to roughtly 700. Don't worry if the engine runs rough for now.
4) Install a vacuum gauge and adjust carb to highest value possible. Stop the engine, wait a few minutes and re-check or re-adjust for max value at 700RPM.
5) Loosen distributor and set idle speed to 2500 Rpm. With the vacuum gauge installed, rotate the distributor slightly to obtain maximum vacuum once again. Rpm's will increase 2-300 if all goes well.
6) Perform step 5 several times and at the last attempt, turn the distributor to back down the vacuum 1 point lees the max value obtained.
7) Stop engine, lock the distributor down and re-set the idle to 700Rpm's.

Hook vacuum lines to distributor only and re-start engine, should idle properly at a slightly higher Rpm than set. If OK, then attach the remainder of the vacuum lines and check again. If there is a problem with any of the vacuum circuits, then you just isolated the area to look at.

An engine with 180psi of compresion is not stock and probably running a modified cam. If this is true, the above will tune in very close to what is required. If the engine still idles rough, Then I would start to investigate individual sections of the engine until the problem is resolved.

[hrcollinsjr]

Originally Posted by blancojp An engine with 180psi of compresion is not stock and probably running a modified cam. If this is true, the above will tune in very close to what is required. If the engine still idles rough, Then I would start to investigate individual sections of the engine until the problem is resolved.

Several have picked up on the alleged 180 PSI, I haven't confirmed this and highly doubt that it is that high. If it is I would assume the camshaft would have to be a short duration cam since I can see the piston tops and they are flat.

There is some trash in the carb bowl so I'm not going to get out of removing and cleaning the carb.

Harold

[hrcollinsjr]

Compression update:

Warmed engine up for test, removed spark plugs and opened throttle.

Cyl. # 1 150 psi
Cyl. # 2 175 psi
Cyl. # 3 175 psi
Cyl. # 4 175 psi

They came up to 150 psi rather quickly and took several more spins to reach their max. of 175 psi.

I'm going to pull the valve cover and check valve adjustment at least on #1 anyway.

No doubt the carb still needs to be gone through. Idle is low. When I bring the engine speed up, I'm guessing, to approx. 1500rpm the engine backfires through the carb and almost dies.

Harold

[hrcollinsjr]

Update:

When I pulled the valve cover I discovered Al spring retainers(?). Solid lifters in a four bearing head. I'm assuming this is correct and is an aftermarket cam. No specs so I pretended it was an Isky grind and tightened the valve lash to .018, a few were at this spec already.

I have not checked compression again. The difference in valve lash I seriously doubt would bring the pressure up 5 psi.

I marked the crank pulley to facilitate checking the timing.

Noticed the pertronix is wired directly to the aftermarket external resistor type coil, approx. 7.5V!!! I'll rewire for 12v and try again.

Harold