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I only know it was way to open when I started. Probably I can open a little bit more without nozzledrop. I am going to work with this during the weekend.


Hi again. Getting a pretty god idle now. The trick was to change a little bit here and there.

Opened up the the bypass a little more. Raised the timing a few degrees. I get a better idle when using manifold vacuum, good or bad I dont know. Opened up the idle fuel a little bit but then I think it is going a little bit rich of idle. I think I will reverse that.

Called up MaximumTorqueSpecialities in California and talked about the camshaft and low vacuum. The guy at MTS sad that 10 hg was around the expected value with this cam.

Thanks for help and all the tips.

Erik Olsson
Diagnose a Quadrajet carburetor problem / Re: Dual quads
« Last post by chance on October 17, 2017, 10:51:06 AM »
The 400 block I have is a 71, the car originally came with a 301. the guy i got the car from didn't know anything about the car or engines so someone put it in there before he got it. So is there an N cast into the crank I should  be looking for or a special number to Identify the crank?

Take care!!
God Bless!!!
Diagnose a Quadrajet carburetor problem / Re: idle bypass question
« Last post by wannabemachinist on October 16, 2017, 07:41:34 PM »
I checked  the carb today as you suggested and found no dribbling from the boosters
Backed out the adjusting screws, the idle became slightly worse
Turned the idle screws completely in and pretty much stopped the motor
Removed the carb and checked the transfer slot. It was exposed close to 3/32 or .092 and when the idle speed screw was backed off completely it was exposed slightly over 1/32
My idle screws are backed out about 2 1/2 turns and showing about 15 inches of vacuum at about 725 RPM
Initially I felt I was not getting anything when turning the screws in, even with a coil removed from the spring but today I did. Definitely not a huge change when backing them out though
When it starts cold and the choke is on and I completely close the flap it will die if left
Could all this be improved upon? (besides the cam at this point :))
You mentioned the jets and rod being lean also. What would you recommend
Diagnose a Quadrajet carburetor problem / Re: Dual quads
« Last post by Cliff Ruggles on October 16, 2017, 09:39:51 AM »
The early "N" cranks are tough as nails and you can turn them clear down to BBC or even SBC journal sizes if needed.

I avoid the later "PMI" cranks as they are just not that tough and have seen enough issues with them to avoid them altogether, same with the 1975 and later 400 blocks unless it was a T/A 4 speed.....Cliff
Diagnose a Quadrajet carburetor problem / Re: Dual quads
« Last post by chance on October 16, 2017, 08:43:27 AM »
Ok, Thanks! How far can you turn one of those cast cranks safely? If my 400 crank was forged I turn it and use it. I've turned my Mopar cranks as much as .050 on the mains and turned them 6500 rpm and never had a problem. Like I said before I don't know Pontiac's.....Yet....LOL. You're going to fix that right??
Thanks again for your time my friend.
Take care!!
God Bless!!!

P. S. How are those grand kids doing?
Quadrajet Carb Talk and Tips / Re: vacuum at WOT
« Last post by Cliff Ruggles on October 16, 2017, 03:04:49 AM »
The "hybrid" set-up works well on that cam because it is an older design.  Tight lashing the HIPPO solid roller lifters simply takes the hydraulic action out of the equation, pretty much like have a true anti pump-up hydraulic lifter in there.  It's a great set-up and trouble free now for many years, and the quietest valve train I've ever had on one of these engines.

I'd go this route again w/o hesitation.  It's a little bit of a PITA to lash the valves on my car as the wiper motor is in the way of removing the drivers side valve cover and getting in there to set the valves, but worth the extra effort.....IMHO......Cliff
Lobby / recommendations for a tow vehicle.
« Last post by omaha on October 15, 2017, 11:08:24 PM »
I have kind of been looking around for a pickup. 2 wheel drive and at least a 3/4 ton. Was looking today at a '92 chevy ext. cab long box automatic trans. Not in too bad of shape, has the normal rust in the cab corners and minor dents. Nice interior. It has the 5.7 with the throttle body injection. 14 bolt rearend, not sure of the gear ratio. I went for a test drive and was only mildly impressed. Of course with 170,000 miles I'm sure the engine was somewhat tired. not a lot of power. the trans shifted wonderfully. Is this truck capable of towing a car trailer on a regular basis with somewhat heavier loads. 5000 lbs for example.  The guy wants 1400 dollars obo. [did I mention I don't have a lot to spend]. Need advice cause I am not real "hip" with the GM pickups. [hard to find a dodge out here that's not a 4wd]. I also found a real nice 86 chevy 3/4 ton for the same price but it has the truck manual trans. 4 speed. Is the small block chevy good for a tow vehicle.
Quadrajet Carb Talk and Tips / Re: vacuum at WOT
« Last post by Miles on October 15, 2017, 05:16:17 AM »
I understand about the rockers and metal in the oil as that is what I now have, but I'm wondering if you chose the hydraulic cam and solid lifters as you already had the camshaft installed? Would you use a solid camshaft if you were starting over or is there an advantage using the OF camshaft with the solid roller lifters over a solid grind?
Diagnose a Quadrajet carburetor problem / Re: Dual quads
« Last post by Cliff Ruggles on October 15, 2017, 04:00:41 AM »
The cranks are only the same for dimensions, they 350 would have used lighter pistons so unlikely it's balanced the same as a 400 crank.  Not a big deal if you are getting the spinning assembly balanced but something to keep in mind when using a 350 crank in a 400 build.......
Diagnose a Quadrajet carburetor problem / Re: idle bypass question
« Last post by Cliff Ruggles on October 15, 2017, 03:59:01 AM »
Address the idle issue first.  Take a gander into the carburetor at idle and verify that there is no fuel dribbling from the boosters.

If not you may already have enough idle fuel but lack control of it because too much transfer slot is exposed.

Remove the carburetor and turn it over (make sure the stop is against the idle speed screws) and see how much transfer slot is exposed.  If you see a lot of transfer slot exposed adding bypass air will lower the throttle angle and degrease the amount of idle fuel it's getting there and may restore some response to the idle mixture screws.

Before you do that I would however back the idle screws out quite a few turns and see if it goes way rich at idle, indicating that at least you have plenty of idle fuel right to start with.

I would also full seat the idle screws (remove the springs from them since you opened up the holes under them) and see if you have any control at all of idle fuel at or close to seated.  If you see some control doing this (engine slows down) and no nozzle drip then your idle tuning may be over.

I've tuned a good many engines brought here using that particular camshaft and not overly impressed with it.  Idle was "quirky" and although it throws some power at you right off idle and initially "feels" pretty responsive it's not overly impressive otherwise and how could it be as it's 12 degrees less seat timing that a stock replacement cam and tighter LSA......FWIW......Cliff
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