Author Topic: 68 KR tuning issue  (Read 1208 times)

Bill

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Re: 68 KR tuning issue
« Reply #15 on: March 31, 2022, 08:34:18 AM »
Engine builder got back in contact and confirmed 10.5 compression ratio and suggested 38 degrees on the timing. Initial is at 6 BTC.

Made the carburetor changes yesterday but was unable to take for a test drive. The changes were that I installed a 5.5 power valve and changed primary jets to #78's. Increased primary nozzle to #37 and secondary nozzle to #35. Not sure if the weather is going to cooperate today as we are bracing for some bad thunderstorms moving into Central Florida.

Don
gt350bp

Don,

   Do you have a vacuum gauge hooked up for bench tuning?
How are you data-logging your timing while driving?
Has the carb been rebuilt, or is it new out of the box?

I ask, as an engine under load will behave differently than an engine being tuned in the garage, at rest so to speak.

Finally, any chance you can get it on a chassis dyno for real world tuning purposes? I learned quite a bit after a good friend bought a chassis dyno and used one of my old Cobra replicas (427 sideoiler) as a benchmark for tuning of the car and different carb configurations (IE: 7 or 8 different carbs, and as you, power valves, jets, etc).

Bill
Instead of being part of the problem, be part of a successful solution.
Current: 70 2642, SPF 289 roadster replica, ERA-FIA replica
Previous: 68-2623, 69-2177, 69-1584 the partial remains of 68-03278

corbins

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Re: 68 KR tuning issue
« Reply #16 on: March 31, 2022, 10:16:16 AM »
Not near enough initial..... bump it to 12* and see how she does.

Rukiddin

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Re: 68 KR tuning issue
« Reply #17 on: March 31, 2022, 10:54:45 AM »
+1!  I agree,it needs more initial (12-16) but keep total around 36.

gt350bp

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Re: 68 KR tuning issue
« Reply #18 on: March 31, 2022, 01:11:23 PM »
Want to be sure that the initial suggested is 12 degrees and then 26 degrees of advance for total 38 degrees? Factory setting is 6 degrees BTDC.

Thank you.

Don

corbins

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Re: 68 KR tuning issue
« Reply #19 on: March 31, 2022, 03:40:01 PM »
Thats what I would try...FEs love some initial timing, 12*-16* and 36*-38* total all in around 2500-2800 seems to be a sweet spot for street driving.

gt350bp

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Re: 68 KR tuning issue
« Reply #20 on: April 04, 2022, 06:30:23 PM »
Put the recommended #78 jets in the primary metering block as well as changed the power valve to a 5.5. Increased the primary accelerator pump nozzle to a #37. Set timing at 36 degrees total and 13 degrees initial in the mechanical advance MSD Pro Billet distributor. (Green spacer) Can finally pull out of the driveway without upsetting the neighbors! Still have a slight bog and surge just above idle at 25 to 30 mph.

Ordered a #40 accelerator nozzle for the next change.

Thanks for the recommendations and help, as I'm going in the right direction on the changes.

Don
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