Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Which choke? 7044240 Buick qjet

<< < (3/4) > >>

Glutenfreecarbs:
Trans Am, I'm selling a freshly-rebuilt 17083226 that might be a great fit for your truck. Chevy-style throttle/trans linkage, side fuel inlet, electric choke, etc. It's not pretty or re-plated, but it's got Cliff's SR Rebuild kit and runs great; I actually drove it to work Monday through Wednesday of last week.

http://ebay.us/NvvgsP?cmpnId=5338273189

Trans Am:

--- Quote from: Glutenfreecarbs on May 22, 2021, 10:49:23 AM ---Trans Am, I'm selling a freshly-rebuilt 17083226 that might be a great fit for your truck. Chevy-style throttle/trans linkage, side fuel inlet, electric choke, etc. It's not pretty or re-plated, but it's got Cliff's SR Rebuild kit and runs great; I actually drove it to work Monday through Wednesday of last week.

http://ebay.us/NvvgsP?cmpnId=5338273189
--- End quote ---
No thanks man, looking for more DIY.

Cliff Ruggles:
"I was told the engine was rebuilt but I have NO idea if it was a stock rebuild or what. I don't know the bore size if it was changed. I don't know the cam if it was changed."

Not really a big deal, if it isn't hammering really loud and the County is trying to hire you to kill mosquitoes this summer from the burned oil smoke it's probably OK!

At a minimum I would do a vacuum test at idle speed and a compression test in all cylinders. 

The vacuum will give you a relative idea as to how much camshaft was installed during the "rebuild".  A cranking compression test will also let you know if the cam was well chosen for the compression ratio and at the same time how well the rings are sealing up.

Knowing the vacuum produced at idle, idle quality and cranking pressure also helps me when choosing tuning parts and how to set up the carbs idle system so it will work perfectly once placed in service.

Big Block Chevy engines sadly were really "low" compression in those years.  They also had crappy cams in them and late cam timing.  All that was done to please the EPA, not the end user.  They are however excellent otherwise, just sitting their waiting to be exploited.

I've helped quite a few later model 454 "truck" engines by improving the "squeeze" in them a tad, tighter squish, well chosen cam and they literally pick up 100hp and an least that much torque!  No need to spend a lot of money on them either, the "truck" heads are more than adequate for the task.  They just need higher compression and improved cam timing.  Even the "flat" iron intakes are excellent even though folks have labeled them "door stops" and been tossing them in scrap piles for decades.

Recently had a customer do a "stock appearing" 1970 Chevelle SS.  I supplied the carb for his 454 (bored and stroked to 496).  The engine "builder" targeted 560-580hp and under his breath told the owner that the POS stock iron intake and Q-jet would NEVER "feed his engine". 

I get a call on dyno day and it isn't making chit for power, around 425hp and DONE at 4500rpm's.  I tried to help the engine builder/dyno operator with some questions and such but he was so focused on bad-mouthing the intake and carb it was difficult.  Finally I got around to asking about the timing and distributor.  He told me he installed a Pertronix and timed the engine right at 36 degrees total for dyno pulls.  I told him to remove the Pertronix and put points back in it as I've seen GOBS of those modules not work well in recent years.

Reluctantly he put the points back in it and went back to dyno testing.  I get a call about an hour later from the owner that it made 565hp/587tq on the very next pull!  So don't think for a minute the stock intakes and carbs are not adequate for you average 396-454 engine build....FWIW.....Cliff

Trans Am:
OK I'll try and complete those tests in the next two days, simple enough

Trans Am:
Compression was an even 140-145 for all cylinders. Vacuum gauge appeared to stick so I'll get another one but If I tapped the gauge it would react. Vacuum read was ~15 at 600rpm, it wouldn't get to 18 nless it revved to about 900 or so.
It seems to idle rough, timing was set at 12º BTDC.


I can't imagine the farmer who owned it would have asked for a mild cam--of all things-- to be installed, just sounds very silly. But who knows....vacuum gauge is definitely not in good condition but honestly the thing idles way rough for what I'd think is correct for stock.....but again, the thought of a farmer installing a lopey idle cam is just silly....
I'd also like to clarify that I was told the engine was rebuild long ago, but everything is clean around the engine. At speed it runs very smooth, just idle is lopey. Get it to 1000rpm and it sounds perfectly smooth and stock.

Navigation

[0] Message Index

[#] Next page

[*] Previous page