carb questions

[old blue 75]

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.

[Kenth]

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.

[old cars]

Kenth. Is this the tube your referring to. Could you explain how that works? And did all marine quadrajets  use this? Thanks

[Kenth]

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.

[Cliff Ruggles]

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

[old blue 75]

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.

[Cliff Ruggles]

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?.......

[old blue 75]

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.

[Cliff Ruggles]

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......

[old blue 75]

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.

[Cliff Ruggles]

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

[old blue 75]

Is that a 60's carb with that vent set up?

[old blue 75]

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.

[Cliff Ruggles]

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........ 

[old blue 75]

Why do you not like doing it? Is it to thin or the seal seat?