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Incurable Opelitus
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203 Posts
Now that I have had a chance to drive the car some, I have found that I need to check the electric choke operation, carburetor jetting, and possibly tweak the mixture / idle screws. I experienced some stalling / hesitation from a cold start. Once the car warmed up everything was great and the "seat of the pants" test still indicates some extra power out on the highway at speed. This Sprint manifold was treated with a heat shielding coating and that may be affecting the current "tune" as the under hood heat dynamics have changed.
Matt,
I'll be very interested in learning what you have to change in the carb settings, as I have the same problem since changing out to a Sprint manifold, and don't know what I should try first. Although it feels like I have increased power, my gas mileage has fallen way off (although some of that could be attributed to a little more "lead" in my foot as I "test" the car out), from 18mpg just after adjusting my valves a couple months ago, to 13.5mpg on my last tank. I also have a lot more problems when cold, like the engine wanting to die when coming to a stop light (only in the first few minutes of running), hesitation on acceleration, slight backfiring on deceleration (more of just a kind of rumbling than actual backfiring, and I actually kind of like the sound). One other change I made in the last few weeks was adding a Magnaflow 11365 2 and 1/4" muffler (no resonator tips yet), but the headpipe is still the stock 1 and 5/8" diameter (using a new Bosal unit courtesy our friend Bob Legere).
Randy
 

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'72 Opel GT (Sara)
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2,119 Posts
Discussion Starter · #242 · (Edited)
Matt,
I'll be very interested in learning what you have to change in the carb settings, as I have the same problem since changing out to a Sprint manifold, and don't know what I should try first...

Randy
On my way out the door for a test drive after making some adjustments. I'll edit this post when I get back (hopefully :lmao:)...

OK, I'm back and in one piece :veryhappy. The car is running much better both at idle and at all types of driving - from a stop, cruising, hard acceleration, and higher speeds. It is raining here so I had to limit my high speed driving as my tires are not the best in the rain. I would say the only place I notice maybe some further room for improvement is the transition from the Primary to the Secondary when you push the pedal right to the floor. There is a very slight "pause" there before she kicks in and then it's very quick. Using a more gradual approach results in a smoother acceleration. Here is what I did post-Sprint install:

  • Right after the install, my idle RPMs jumped considerably. John adjusted that for me before I left for home from the meet. Warm idle was at about 1K RPM and that is where it remains after the changes below.
  • After having cold start and idle issues until the car was fully warmed up, I adjusted the electric choke. I ended up rotating the choke 3/4" counter-clockwise from its prior setting to keep the choke closed longer. Choke now opens fully when coolant temperature is at full normal operating temperature (third mark from the left) and oil temperature is 50 degrees Celsius. Maybe the choke should open a little sooner? It seems fine to me.
  • With the idle issue resolved, I next looked at the jets. My only change here was to take the Primary Air from 170 down to 160. If I understand the jetting correctly, this made the Primary mix richer (less air to fuel in the mixture). My configuration is: Primary 135 Main / 160 Air, Secondary 140 Main / 160 Air. I think this matches Otto's configuration from the "All These Jets" thread which I have now read in it's entirety :boggled:.
I did NOT have to change the mixture screw or the idle screw at any time once it had been adjusted immediately after the Sprint install (i.e., changing the choke and jetting did not necessitate a change in these two screws).

Finally, My fuel economy BEFORE the Sprint install was averaging ~ 22 MPG in mostly city driving. I haven't checked MPG post install as I haven't driven the car enough. Seeing how the Opel gets the best gas mileage of all four of my cars, I am not too concerned about MPG - I would trade lower fuel economy for even better performance.

HTH...

Matt
 

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'72 Opel GT (Sara)
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2,119 Posts
Discussion Starter · #244 · (Edited)
Very nice work Matt
Next you'll be telling how to tweak the A/F and timing in and all the new spark plugs you went through.
:biggthump
I doubt I'll get that far but I'm learning - Thanks! :D

BTW, there is still a slight idle issue. I had a stall condition on the drive into work today. Everything else was fine so I think I do need to go back and look at the idle mixture and idle set screws again. Maybe dial the choke back a little too. I won't get to the car again until Sunday with the holiday this week...

UPDATE: Roads dried out here and so I was really able to open her up. An issue I had noted prior to the Sprint install was a complete loss of power in third gear above 4,500 RPM or so. That issue is gone. In fact - more power in all gears up to and slightly beyond 5,000 RPM (the furthest I was willing to push it).


Matt
 

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UPDATE: Roads dried out here and so I was really able to open her up. An issue I had noted prior to the Sprint install was a complete loss of power in third gear above 4,500 RPM or so. That issue is gone. In fact - more power in all gears up to and slightly beyond 5,000 RPM (the furthest I was willing to push it).


Matt
Matt
With the heat of the exhaust manifold gone your going to have some cold driveabilty problems.
As you noted the trade off is well worth the effort. And your CAI helps .

You might find that you'll have a summer and winter choke setting along with the changing fuel in Ga. even the spark timing can/or will change.

Yep it won't be long before your reading the plugs. :D
 

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Matt ,
You will have winter and summer settings and now the fun begins .
Dan , Matt will be reading plugs :yup:
 

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......oops
 

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'72 Opel GT (Sara)
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2,119 Posts
Discussion Starter · #249 ·
Absolutely beautiful restoration, and fascinating thread. Very inspiring!

I confess that though I read the whole resto thread, I did not read all of the comments. I have just one question. Is the right rear bumper not straight, and if so, why?

Thanks,

Jim :cool:
Thanks! Yes, there is a slight slope to the right rear bumper. When I first got the car back in 1986, I accidently backed the GT out of the garage and right into my Dad's Buick which was parked in the drive directly behind. While the Buick wasn't even scratched, the Opel took a major hit there and the rear panel was dented in pretty severely. My Dad and I did our best to fix it up and bump it out and it remained that way until the restoration at which time it was improved upon. However, if you look closely, you can still detect a slope to the bumper in that area even though all the dents and other damage was repaired.
 

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'72 Opel GT (Sara)
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2,119 Posts
Discussion Starter · #251 ·
Thanks! I hope you were not offended. The car is incredible, and the work done and shared, will be extremely valuable to maqny others, myself included.

I hope one day to be able to meet you, and see your beautiful car in person!

Jim :cool:
No offense taken - I appreciate your kind words. Actually, you must have a pretty keen eye because you are only the second person to notice. You have to be looking at the back end at eye level and compare the two sides to really tell so it doesn't bother me at all. Hopefully we'll meet up at a future gathering of Opels.

Matt
 

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'72 Opel GT (Sara)
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2,119 Posts
Discussion Starter · #252 ·
Just like old times...

Hey Keith - I know I've been pestering you for photos. Thanks for posting an update on progress in the Restoration thread. I miss my Opel terribly :sigh:. I guess I've been a little tough on the brakes... :dunno:

Matt
 

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'72 Opel GT (Sara)
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2,119 Posts
Discussion Starter · #255 · (Edited)
It'll be nice to see a restored car with and without the lowering spring, makes my decision easier. Intermediate spring I assume?
There was some confusion on my part as to how much drop you got in the front with the sport springs available and which to go with. However, this thread contains some great discussion after which I settled on the spring with the most drop (results in a 2" drop in the front I believe) and the 1.5" drop in the rear (If I now have my measurements correct).

Matt
 

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Sick with Opelitus
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1,374 Posts
Mat, I thought you would clean it up a little before the photo shoot:ugh:
 

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'72 Opel GT (Sara)
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2,119 Posts
Discussion Starter · #257 ·
Mat, I thought you would clean it up a little before the photo shoot:ugh:
I noticed it's looking pretty messy under there too. Keith must be going out for joy rides :haha:. Actually, it's probably still a mess from the drive up from Atlanta. I drove the car up there on 02/13 and there was ice and snow the whole way combined with that sand they throw all over the highway. Keith washed it down as soon as I got there but the undercarriage is still quite nasty.
 

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'72 Opel GT (Sara)
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2,119 Posts
Discussion Starter · #258 ·
Front suspension done...

That is exactly the look I was hoping to achieve! I love the spacing in the wheel well now and we are getting the center of gravity even lower on the car. As a bonus, my shocks even have a decal on them! I like decals... :yup:

Matt
 

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Driver
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987 Posts
Perfect ride height now and it will handle GREAT!:haha: Make sure and keep those decals nice and clean. You will be happy with the results. (not the clean decals but the handling)
 

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Driver
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987 Posts
Looks good. I want to do that brake upgrade myself. I am guessing you just have not installed the battery hold down yet right???:confused:
 
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