Cliff's Quadrajet Parts and Rebuild Kits
General Category => Quadrajet Carb Talk and Tips => Topic started by: old blue 75 on June 24, 2021, 06:38:09 PM
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Hey guys I have a carb i'm working on and need some info on it.
The number is 17059288. In the book there is no 88.
From what i can tell it is from a boat. It has the look of a 1975 and older(chevy side in let.) but has
a 1979 date. There is no pcv valve port on the front, divorced choke.
Being a 1979 will this have a apt or not?
I would like to add the port for the pcv, it has a flat spot for it so i'm thinking of tapping it for
1/8" npt for a nipple. I work in a machine shop so adding the npt hole is no big deal.
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You´ve got a 4MV Quadrajet for Marine usage.
No vacuum ports or APT. Fuel overflow tube from "passenger" side primary venturi.
Better left for the seaside guys.
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Kenth. Is this the tube your referring to. Could you explain how that works? And did all marine quadrajets use this? Thanks
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Marine pumps have a double diaphragm. When the first one breaks, it will leak fuel into the cavity where the small hose port is and send it to the carburetor instead of the bilge.
Also, marine units rarely, if ever, use fast idle cams.
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Marine Q-jets come in two flavors, Volvo Penta and basically everything else. With that said there are a few exceptions to that rule as Q-jets were used on some rare 4 cylinder Ford Marine engines and "odd" applications in very late years of production. So you may on occasion run into a Marine unit that is side inlet (Chevy style) but also electric choke.
Volvo Penta units were built from Oldsmobile style (early) hot air units, many are electric choke.
OMC, Mercruiser, Crusader, etc will be Chevy style side inlet units with divorced chokes.
Most Marine units did not use PCV or vacuum advance, or fast idle parts but the cams are often in place just not parts on the primary shaft. They may have done this just for the weight to help with divorced choke operation.
In any case I do not recommend using a Marine carburetor for automotive and truck use. They have special calibrations and castings because Marine engines were heavily loaded most of their lives. They aren't emission calibrated either, so pretty generous for fuel delivery.
Marine carburetors also take different rebuild parts, which are NOT supplied in currently available rebuild kits unless you get them here.
I rebuild hundreds of Marine units and well known for doing them. In the last 20 years it is rare to see one show up here with the correct N/S assembly and accl pump. Even if they have the short pump in them it will use the "soft" blue seal and have already failed or failing as they are not compatible with this new fuel.
So basically Marine Q-jets REQUIRE high flow N/S assemblies to keep them bowl under heavy load and high RPM's. The accl pumps are short for a reason. If you are cruising on a plain enough throttle is used up there will be little or no pump shot left if you move the Morse controls ahead to speed up. Without some pump shot in that scenario you may experience a stumble or bog due to a momentary lean condition.
So outfitting Marine units with automotive parts, or the wrong parts is a recipe for disaster before you even get started. Hope this helps some......Cliff
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That carb was rebuilt about 12 to 15 years ago with a parts store kit and has been on my truck ever since. It's been parked for the last 5 years for a body rebuild.
I have a 7045214 carb available to use that has the same linkage set up.
I will have to see if it is missing any parts.
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Overall it will be a better choice having provisions for PCV, vacuum advance, and vacuum for accessories, etc.
No mention of what engine or what has been done to it?.......
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Engine 355 sbc flat top pistons, 441 heads 1.94/1.50 valves bowl blend, crane hr-260-2-12
hyd. roller cam (lift .429 I .452 E dur 260 270 dur @.050 204 214 112 lca), stock gm gjet intake
(aluminum version egr removed) 1 5/8" headers, hei dist.
It is in a 1986 short box chevy 4x4, 700r4 trans. crappy 3.08 gears, stock 235/75/15 tires.
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Nice engine build, should work very well for what you are doing. I actually had a near identical engine in one of my 1970 GMC pick-up trucks decades ago. 441 heads, .020" shim head gaskets, flat top pistons .015" in the holes at TDC, Crane 288 Blazer camshaft, 1.6 ratio rockers, stock iron intake, factory Q-jet. It was backed by a TH350 and Dana 60 with 4.10 gears. I ran that truck for many years and it was pretty impressive for towing and pretty darned quick on the street for what it was.
441 heads are at the top of the pile for the 1970 and later large chamber SBC offerings. They still had the good ports left over from the good 1960's heads but used a larger combustion chamber for lower compression/emissions. That head is actually quite a "sleeper" as the larger chambers unshrouded the valves a bit for good breathing. They were actually quite sought after and still are for some circle track racing classes that require a "stock" iron head but larger combustion chamber.
3.08 gears actually do pretty good with a 700R4 as it has a pretty tall first gear.
What are you doing for a choke? The later EGR intakes were either hot-air or electric, none were set up for divorced choke carburetors that I know of......
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Thanks for the compliments on the engine build.
I too used a .020 shim gasket but my pistons were a little farther in the hole.
I ended up at .044 piston to deck. I would have liked .038-.040 but was not
worth another deck job.
I had the same thinking on the 441 head plus the fact it is one of the heavy castings not the thin 77 and later crack prone castings. I also had hardened seats put in for reliability.
After your comment on the choke I went out and looked.
I have casting number 14007378. It must be a hot air intake.
https://cimg7.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/2000x1504/img_0219_6d2241e78a83913d6d06f1b21937ee395b4c9416.jpg
I made a mount out of aluminum for the choke thermostats spring and made linkage to work.
Even in 0 deg. weather it seemed to work fine.
Does it sound like the 7045214 carb will work ok. I know it is the older version with less available parts selection.
Thanks for the input.
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All of the Chevy 1970-1976 divorced choke units are pretty much equal from a performance standpoint. They will have large MAB's, side inlet (with a few exceptions) and divorced choke. If you can use a divorced choke carburetor it will work fine for what you are doing.
It's going to need a little help in a few areas being emission calibrated, but nothing dramatic needs to be done to it.
I can supply a kit with tuning parts to take the guesswork out of the equation if you decide you can use it. It will have a PCV port, and at least one manifold vacuum and one ported vacuum port for the distributor......Cliff
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Is that a 60's carb with that vent set up?
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Bad news.
The 7045214 carb has bad inlet threads. Some one put a self tapper in it.
Looks like I will have to try and find a helicoil kit.
The way that the fitting seals at the bottom does the bottom of the tap need to be
ground off so there are full threads at the bottom.
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You will not find that to be an easy operation. I don't like doing the later carbs with the 1"-20 threads and I'm set up for it.
Might want to look for another carb or main casting.
Not sure what year the pic above is, probably a 1969........
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Why do you not like doing it? Is it to thin or the seal seat?
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The operation involves EXACT precision. If you are off any at all the seal will not fit evening against the seat at the bottom of the threads and it will leak.
I have genuine heli-coil taps for both 7/8"-20 and 1"-20 threads and have installed thousands of heli-coils into Quadrajet and 2-Jet castings.
It is actually pretty rare to see the 1"-20 (1972-up) Quadrajets stripped out. That only happens when someone cross-threads the fuel filter housing. Attempts to install self-tapping fittings may remove needed material required for the heli-coil tapping operation.
I'd have to see the carb to know if it can be repaired or not?....
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Have you ever made or thought of making a new fitting and tapping it 1 1/16-20?
I spent 8 years standing in front of a lathe so making a new fitting isn't the end of the world.
My thinking is to tap it 1 1/16-20 then at the same time take a 1" end mill and re face the seal
surface square to the threads (.003 to .005 thousands).
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I suppose with enough effort anything is possible.
Unless it were a really valuable Ram Air, HO, Super Duty, Stage 1, W-30, Cobra Jet or something difficult if not near impossible to replace I would just walk to the core pile and get another casting vs spending many hours on that type of repair.
Machining a fitting wouldn't be that difficult until you got to the inverted flare deal. I'd most likely at that point just tap it for NPT threads and install an adapter fitting.
I have the equipment and skill sets, Military trained and I used to make parts when we needed them in the machine shop on board ship when were on deployment, thousands of miles from port and no hardware or parts stores floating around out there anyplace. Where I typically fell short on those sort of jobs wasn't making the part, it was the heat treating if/when needed........
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Cliff thank you very much for your service. Yes I would agree aboard ship It would be tough to heat treat any thing. About the only thing I can think of would be small parts made from o-1 with a torch
and oil.
I under stand it would be easier to use a different carb but Here in Michigan the junk yards ran out of vehicles with carbs on them many years ago. And with the covid crap swap meets have been few
and far between. I will have to think on this while I work on other parts of the truck.
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Another .040ish in the hole SBC. Rebuilders flat tops. I’m not alone.
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Yup you have to pay attention we ordering pistons. Stock sbc 350 is 1.560 pin height, there are 1.540 and 1.550 pistons out there. I figured this out to late.
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Finally got back to this carb.
I found a 1 1/16"- 20 tap on ebay and made a replacement fitting ( and made a inverted flare cutting tool to finish the fitting). Taped the casting and refaced the seal seat. I did a pressure test with a plugged seat and air hose hooked to a short piece of fuel line. At 20 psi did not see bubbles in my soapy water. Is this a good enough test or is there a better way?
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20 psi and no bubbles/leaks it will be fine...
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Ok cool.
Moving on, I have the primary shafts bushed but will need screws.
I measured the primary metering rods and they seam to be the 74 back
long style. The part number says 1975. Was 1975 a transition year?
The primary rods have flat spots worn on them, I did not see them on
your site do you not have them?
Here is info on the carb.
Idle tube .044
Idle down channel .053
Upper idle air bleed .092
lower idle air bleed .063
Idle bypass .097
mixture screw hole .074
Air bleed main body .119
Air bleed air horn .120
main jet .071
primary rod .026
secondary air bleed .026
Secondary air flap 1.390
Accelerator discharge holes .053
Secondary accelerator wells .034
J hanger CP rods
Also what is the life expectancy on choke pull offs.
The one I took off is good but I have had it sitting on the
shelf for 10 yrs plus and who knows how long it was on there
before I got it?
Thanks
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7045214 is a 350 HD Truck 4M Quadrajet.
This unit have 39B primary rods from factory.
Only M4M uses the shorter primary rods.
Check the "accelerator discharge holes" or secondary POE again, the restriction is located a bit in from the .053" exit.
SB Chevy Qjets uses .042" restrictions, most BB and some HD SB units uses .035".
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Ok rechecked the discharge holes you are correct it is a .042.
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I stock primary metering rods for all q-jets, plus have close to 10,000 #3-48 black plated screws for the primary shaft. If you don't see what you are looking for on the site best call to place an order. I'm here 7am-4pm M-F EST. Call volume is heavy, so if I don't pick up leave a good number and I'll call you back.......tks....
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Ok will do.
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Cliff what tuning modifications should I do to this carb?
Or would you rather discuss it when I order a kit?
I for sure need new idle tubes, kind of mangled them
getting them out.
Thanks.
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I'm here 7am-4pm M-F EST. Call me when you get a moment, saves a lot of typing....tks..
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Hi Cliff I got my kit in the mail(thanks).
I was re reading the book and looking at the carb. I have.
My engine being identical the the example on page 94 LH column,
my idle channel and idle air bleeds are different. Are they far enough
off I need to fix them or will it be ok as is. Also it looks like I should drill
out the mixture screw holes.
In my kit i received new jets and primary rods, same size as stock(71 jet, .040 rod).
With this being a large air bleed carb do i need to go up in jet and rod size?
Looking at example 3 on page 98.
Page 106 it shows drilling the secondary air bleeds to .036.
Is this some thing I should also do?
Not sure how many of these changes I should make and or what to leave stock.
Thanks in advance.
Carb as it sits.
Idle tube .044 (new ones in the kit .036)
Idle down channel .053
Upper idle air bleed .092
lower idle air bleed .063
Idle bypass .097
mixture screw hole .074
Air bleed main body .119
Air bleed air horn .120
main jet .071
primary rod .040 tip .026
secondary air bleed .026
Secondary air flap 1.390
Accelerator discharge holes(poe) .042
Secondary accelerator wells(poe) .034
J hanger CP rods
Engine and vehicle.
Engine 355 sbc flat top pistons (.020 gasket .024 piston to deck.), 441 heads 1.94/1.50 valves bowl blend, crane hr-260-2-12 hyd. roller cam (lift .429 I .452 E dur 260 270 dur @.050 204 214 112 lca), stock gm gjet intake (aluminum version egr removed) 1 5/8" headers, hei dist.
It is in a 1986 short box chevy 4x4, 700r4 trans. crappy 3.08 gears, stock 235/75/15 tires.
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I suggest installing .050" main air bleed inserts in airhorn and float bowl, use .067"-.068" main jets with yours 40B rods and a set of DA secondary rods.