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1969 Opel Gt 1.9 Automatic
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Discussion Starter · #1 ·
Hi guys so my grandpa and I have been working on the GT. It is not running right when you put it in drive and just idle along. Also just have it in park and just idling, it idles very low and doesn't sound right. My grandpa thinks that we should get a new distributor that has only one diaphragm instead of two. My grandpa says it works better and it gives better performance. My grandpa has a MG ad he says that all the MG racing guys have only one diaphragm distributors. What distributor should I use and have you guys tried this set up?

Thanks Sam
 

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You can also just eliminate the retard canister on your current distributor. If you’re looking at the other ones try this link to help you decide also it will help you identify the distributor you have by the stamped numbers on the side of your distributor. The 1972 distributor on my GT only had the one advance canister. I’d give Gil a call at OGTS he more than likely would have some good used distributors and you would get set up right in the process. I’d think anything between 71’-73’ should work fine.
It’s all about limiting the total mechanical advance if you want more advancement at idle. 28-32° is where I’d be looking for starters. The 1975 distributor is probably the best in that department but offers no vacuum advance therefore I scratch it off my list. Unless you run side drafts with a performance cam which I do not have. They are also more rare and a bit difficult to find. I apologize if I’ve lost you with too much information. I certainly had no idea what all this stuff meant when I was younger.

Certainly no harm in acquiring another good distributor, it’s always good to have a spare. No matter where you end up it’s money well spent.

I just modified my current distributor so I can get more advancement at idle. I suggest this to everyone, perhaps your grandpa has one already, it pays to have a timing light with an adjustable advance. This might be more than what you want to get into right now depending on how much you want to learn or have time to learn put another way.
That said I used to just leave the distributor bolt a little loose when I was younger and stomped on the gas in 4th gear at 2,000 rpms advanced it until it didn’t like it, either by hearing a pinging noise and dialing it back a bit (honestly with my 1972 low compression engine I never heard) so I did it for best performance. It’s a tough engine and you’re not going to hurt it very easily.

If you haven’t already. Check out the cranking compression it’ll tell you how far you can go with tuning. 120 low side 150 would be a good number looking preferably for a 10% or less difference between cylinders. That’s where I always started. That way you don’t spin your wheels trying to get more than you ever will from what you realistically have in your engine.

Maybe someone on the site has a spare distributor they can offer you.
 

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1969 Opel Gt 1.9 Automatic
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Discussion Starter · #3 ·
You can also just eliminate the retard canister on your current distributor. If you’re looking at the other ones try this link to help you decide also it will help you identify the distributor you have by the stamped numbers on the side of your distributor. The 1972 distributor on my GT only had the one advance canister. I’d give Gil a call at OGTS he more than likely would have some good used distributors and you would get set up right in the process. I’d think anything between 71’-73’ should work fine.
It’s all about limiting the total mechanical advance if you want more advancement at idle. 28-32° is where I’d be looking for starters. The 1975 distributor is probably the best in that department but offers no vacuum advance therefore I scratch it off my list. Unless you run side drafts with a performance cam which I do not have. They are also more rare and a bit difficult to find. I apologize if I’ve lost you with too much information. I certainly had no idea what all this stuff meant when I was younger.

Certainly no harm in acquiring another good distributor, it’s always good to have a spare. No matter where you end up it’s money well spent.

I just modified my current distributor so I can get more advancement at idle. I suggest this to everyone, perhaps your grandpa has one already, it pays to have a timing light with an adjustable advance. This might be more than what you want to get into right now depending on how much you want to learn or have time to learn put another way.
That said I used to just leave the distributor bolt a little loose when I was younger and stomped on the gas in 4th gear at 2,000 rpms advanced it until it didn’t like it, either by hearing a pinging noise and dialing it back a bit (honestly with my 1972 low compression engine I never heard) so I did it for best performance. It’s a tough engine and you’re not going to hurt it very easily.

If you haven’t already. Check out the cranking compression it’ll tell you how far you can go with tuning. 120 low side 150 would be a good number looking preferably for a 10% or less difference between cylinders. That’s where I always started. That way you don’t spin your wheels trying to get more than you ever will from what you realistically have in your engine.

Maybe someone on the site has a spare distributor they can offer you.
Thanks for the help. The compression is around 80-90 psi. My grandpa says this is decent and it runs pretty good.
 

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Opeler
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Thanks for the help. The compression is around 80-90 psi. My grandpa says this is decent and it runs pretty good.
Glad you checked it. However, that’s not “decent” at least not for our motors. The 120 mark that was suggested is on the very low end of the acceptable range. If anyone sees 110, that means it’s a worn out engine. 80-90...I’m not surprised to hear it isn’t running well, either in idle or in gear. I don’t think the main issue is the distributor, in fact, it’s probably towards the tail end of the problem. Compression, fuel/spark, vacuum leaks and timing are what I’d suggest tackling.
 

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Can Opeler
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3,462 Posts
The dual canister distributor is fine. It has similar specs to the later models. You won’t notice a difference in performance from swapping unless the diaphragms are leaking. In fact the dual canister model have the most aggressive timing curve I believe. It should give better performance than the later ones technically.

80-90psi should be barely running on GT. Did you make sure the carburetor throttle plates and choke were FULLY open when cranking? 110psi is about the minimum that will drive well.
 

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Über Genius
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9,354 Posts
vacuum canisters don't affect idle.
 
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Discussion Starter · #8 ·
Thanks for all the help. I will have do the compression again.
 

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This engine had been setting up a long time it may take a while of running (1800 rpms not at idle) at temperature to reseat the rings to the cylinder walls and valves to the valve seats. Then retest with a good compression gauge (screw-in-type).
Everyone says 28 to 32 degs. for dist. but that is for a high performance engine (10+ compression ratio) not an everyday a driver you should be fine with your unit just check vacuum advance unit. HTH
John
 

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You might be fortunate, as I was when I first tested the compression after I acquired my '71 GT that has a '69 engine. I had one cylinder that was quite low and found the valves in that cylinder to be too tight. Adjusted, the cylinder came in at the mid-point of the 120-150 spec, in line with the other three cylinders. Check the valve adjustments before you do the compression test.

A major problem with these cars is vacuum leaks.

The dual-canister distributor will not by itself affect the idle except if one or both vacuum lines are leaking. The vacuum advance side connects to a nipple on the carburetor while the retard canister connects to a nipple down by the vacuum "tree" that screws into the intake manifold. Looking down at the distributor, with the condenser at the bottom of the circle, the advance canister is to the left and the retard canister to the right.

Many people cut the retard canister out of the circuit simply by unhooking it and plugging the vacuum line, with no effect on the operating capabilities of the engine.

Because you have an automatic transmission, there will be a vacuum line from that vacuum tree to the transmission modulator valve. If the line is missing or deteriorated, you will have a significant vacuum leak if you find the motor burning transmission fluid, it will be because the modulator has failed.

As many here will tell you, one source of vacuum leaks lies with the intake manifold gasket and the carburetor gaskets, including the spacer.

Not sure if you are aware of this website, but Mr. Wesson at Opel GT Source has put together a really helpful series of instructions for various things to look for.
 
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