Well, I desmogged with JimC's kit and installed a non-USA carb from City Racer. Fired right up and I tuned the timing and carb mixture. It runs well in the shop and the vacuum at idle has jumped from 14" at 7,400' ASL (17" seal level) to 16" at 7,400' ASL (19.5" at SL). In the shop, the engine now easily revs higher and sounds better without the air injection (AI) system. On the road, the secondary still only opens slightly (paper clip test) and still no pull above 2500 RPM.
fj60 no power above 2500rpm (1 Viewer)
- Thread starter jbeck53
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John McVicker
SILVER Star
What are your valves set at? I suggest 8 & 16.
fjc-man
SILVER Star
Read through the thread LandoNick started, loss of power,torque,deadspot,hesitation whatever you want to call It! I’ll bet your problem is too much advance-too soon. Caused by a missing centrifugal advance weight limiting stop. Assuming you’re still running the oem big cap distributor. Check it out.
I’ve always read idle vacuum drops 1inHg for every 1000’ above sea level. I’m at 5000’ and that rule holds true when I go up to 7000, 8000, 10000’, etc. What calculation are you doing? I’d be interested in knowing.
The correction factors are in this table. I happen to be a HVAC engineer and pilot that regularly uses these altitude adjustment factors. I use 0.82 as the factor for my altitude. These can also be use for compression checks at altitude and correcting the value to sea level.
In the aviation world, sea level has a standard air pressure of 29.92". At 7000' ASL the air pressure is around 25.4" hg. It is roughly an inch per 1000' (rule of thumb).
I hope this helps.
FJC-Man, I do have the large OEM distributor. How can I slow it down. I have the VTV in the primary distributor vacuum port line. I also have the high altitude distributor port hooked up to manifold pressure to advance the HAC 6 degrees.
Are there stops in the distributor that may be missing?
Would connecting the primary advance port vacuum to the HAC distributor port help? I would think less advance would occur, but not nessiarily slow the advance. Thoughts?
Are there stops in the distributor that may be missing?
Would connecting the primary advance port vacuum to the HAC distributor port help? I would think less advance would occur, but not nessiarily slow the advance. Thoughts?
John McVicker
SILVER Star
8 & 14 will be fine…but I would still verify. The prob lies in the fact that over time the valve setting becomes tighter…not looser. That’s why I set mine @ 8 & 16.
Recheck yours & if still @ 8 & 14, that’s not your issue. If tighter…it could be your issue.
This is great. Your knowledge definitely sounds more accurate than “stuff I’ve read on the internet”. So let’s say my idle vac reading at sea level is 21 … at 7000’ I multiply by 0.85 which means I should be at 17.85inHg, correct?
Or - in reverse - if my idle vacuum at 5000’ is 16.5inHg, I divide by 0.89 to find that my theoretical idle vac at sea level would be 18.5inHg. Yes?
The curve isn’t linear, but for truck purposes it seems to shake out to a loss of roughly 0.4inHg for every 1000’ of elevation. In an airplane at 30,000’+ the logarithmic nature of the curve would need to be factored in of course.
Do you have a table that goes to 12k’ or 13k’?
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fjc-man
SILVER Star
So I was trying to steer you to reading through “LandoNick’s” thread about this topic. Anyway, this is a picture of the stop pin with the travel limiting bushing missing.
surfpig
The Anti-Tech
Secondary throttle diaphragm? Is it new too?
Maybe check that the vacuum lines at the base of the carb are hooked up correctly. There might be three(?). And that little manifold on the carb. It's easy to mix all that up with those 30 miles of tubes.
Maybe check that the vacuum lines at the base of the carb are hooked up correctly. There might be three(?). And that little manifold on the carb. It's easy to mix all that up with those 30 miles of tubes.
The secondary diaphragm in my replaced (this week) USA carb was new as is my new non-USA carb just installed.
The non-USA carb only has a single advance port vacuum connection similar to my 1972 's carb. So I have the advance port connected to my distributor's primary port. I'll try it to the HAC port and see what happens.
That's for the thoughts. Keep'em coming.
The non-USA carb only has a single advance port vacuum connection similar to my 1972 's carb. So I have the advance port connected to my distributor's primary port. I'll try it to the HAC port and see what happens.
That's for the thoughts. Keep'em coming.
Concerning the valve adjustment…if you set the valves when the engine is cold then they will be tighter at operating temp. Setting the valves cold you could got 10 and 16 and still be fine. A little looser on the clearance is always better than over tight.
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