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I-6 Engines For GMCs that came with the Inline 6 Engines

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  #21  
Old February 21st, 2017, 06:11 AM
Pops Pops is offline
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Default Re: inline six woes

Wow, it's been a long, long time. This was such a lengthy post I thought I'd take a minute and share what I did and what the status is now.
Misfires, shaky steering wheel on take off, vibration, whining noise, etc. are partially corrected.
Whining was related to rear end (of course). the seal at pinion was shot. The tiny spring around the seal was spun and broke. While removed, I also had the bearing changed (easy and cheap at that point) it was weak. also put a redi sleeve added to assure no more leak. Bal drive shaft and added u-joints. NO more noise.
Still have shakiness on take off; pretty smooth after that. exhaust is still stinky which leads me to think carb (rochester B). GMCDAC wrote about this. I have a remanned carb but that doesnt guarantee anything. Im wondering if the seal around mixture screw is crushed. When I set the carb it only requires about 1/4 turn to satisfy vacuum and idle. I was told if the inner seal is crushed it will probably run rich. Since my plugs carbon up quickly it sounds like a rich running engine.
Doug do you sell Roch 250? Esp rebuilt by you? If so, what is the process?
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  #22  
Old February 21st, 2017, 07:27 PM
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Default Re: inline six woes

Yeah the rochesters are junk, I tried rebuilding two and still had rich running or flooding issues. I got lucky with the reman I purchased for one of my 292's. It's a monojet 1 barrel. No issues thus far. I dumped the rochester on one of my 292's for an eddy 4 barrel. lol!

If you still have issues a common upgrade is the weber 32/36 2 barrel. Kind of a pain to tune, but you will get a nice mileage increase and a little increase in power once tuned.
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  #23  
Old February 21st, 2017, 07:46 PM
turbobill turbobill is offline
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Default Re: inline six woes

Quote:
Originally Posted by TJ's GMC View Post
Yeah the rochesters are junk,
No they aren't. People say the same thing about Q-Jets.

Just have to know what you're doing.
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  #24  
Old February 21st, 2017, 07:59 PM
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Default Re: inline six woes

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Originally Posted by turbobill View Post
No they aren't. People say the same thing about Q-Jets.

Just have to know what you're doing.
Might need to have a pro do one of mine then. Last rebuild I did I cleaned and replaced and set everything to stock specs. Still had problems, Ran much better than before though! Acted like it had a vacuum leak some where....had some hesitation when given throttle, couldn't find the leak. Replaced with a small 4 barrel and headers and never had any hesitation issues again.

Forgot to mention, I did not mean ALL are junk, just that particular line. All 3 of my 6's had problems with them, and all of us 250 and 292 enthusiasts have had the same common issues.
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1964 Chevy C20 292/SM420
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1977 Chevy C20 572 BBC/TH400
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Last edited by TJ's GMC; February 21st, 2017 at 08:12 PM.
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  #25  
Old February 22nd, 2017, 01:57 AM
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Default Re: inline six woes

I have had good luck with the Rochesters, the only reason I went from the Model B that was on my '55 GMC (mid 1960's 230 Chevy engine) was to get the "kick down" fast idle with the choke cable. I got 3 parted out Rochester Model M carbs and was able to build one out of the three.

Pops, the Model B I sold to a member on this site came from a '64 Chevy truck I parted out. I didn't build it but the carb had a fairly fresh rebuild. I put it on my 230 for awhile and it ran well. It sounds like it worked ok for the buyer. No I don't build carbs for anyone but myself.

DAC
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  #26  
Old February 23rd, 2017, 02:44 AM
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Default Re: inline six woes

thanks for feedback. I would prefer the Roch because linkage, air cleaner, man choke would all work. But, I am pretty much fed up wtih rich burn, exhaust smell, and mileage. and slight shaky on take off. I agree it acts like vacuum leak. Which opens up another posibility. My booster is a cardone with a 67 dual barrel master. I replaced check valve - no change. I sprayed around carb - no change. I change pcv - no change. I ran vacuum test and got a pretty steady needle +- 17 pnds. So I am back to carb which leaks at upper gasket around bowl.
Tj, why is weber 3236 diff to tune. and, does linkage and man choke need to be reorganized?
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  #27  
Old February 23rd, 2017, 06:11 AM
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Default Re: inline six woes

Quote:
Originally Posted by Pops View Post
Tj, why is weber 3236 diff to tune. and, does linkage and man choke need to be reorganized?
Jetting and fine tuning was the main pain for the last read up I did on it. Linkage I believe has to be redone, choke cable would be a matter of lengthening if needed. I'll search for the write up on it, been a year or so. lol Most of us convert to 4 barrels, but there are a few that convert to webers or holley 2 barrel carbs.
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1964 GMC 1500 305E/sm420 4 barrel intake mod and dual exhaust.
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1964 Chevy C20 292/SM420
1966 Chevy C10 292 hotrod 6/TKO600
1977 Chevy C20 572 BBC/TH400
1984 Chevy C30 292/SM465

My youtube channel aka Military Chevy:
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