Hi all!

I have a 1972 Delta 88, 350 2bbl. I'm thing about converting to a 4bbl intake to wake it up a little bit and I have some questions?

-What years will fit correctly without having to reconfigure vacuum, etc?
-Will I need to change anything else in the motor? I'm not building a race car, just looking for a bit more power.
-Is my current 350 suited for the 4bbl conversion, or am I just looking for trouble here.
-I was looking at using a rochester carb, thoughts?
-Lastly, who's got one for sale!!! I'm in Pittsburgh, Pa, but willing to pay shipping if need be.

THANKS FOR ANY ADVICE!!!

Have a great weekend.

 

fairly straight swap - stay with a pre-emission manifold (no EGR) and you'll need to obtain a 4bbl throttle cable along with the proper bracket for it (both are available used or repro). I personally would suggest you source an aftermarket aluminum manifold - will save a lot of weight - the Edelbrock Performer p/n 2711 is a great street performance choice - I did this same swap when building my 72 350 and installed a performance-built 800cfm Qjet with electric choke. Your engine timing will need to be reset as the 4bbl motors typically needed more initial timing than the 2bbl.

 

Question: What is the HP gain with that intake swap? Aren't 350 2bbl low compression motors?

 

If you want a factory iron manifold, get a 1970-72 designed to use a carb with an integral choke. The correct Qjet will be a better choice than any aftermarket carb and will also avoid the need to cobble the accelerator linkage. Any intake and carb change will likely require some mods to vacuum hoses. This isn't a big deal. The stock timing assumes you are using 1972-vintage gasoline in a stock engine. In 1972 the 2bbl and 4bbl 350 cars used the same distributor and the same 8 deg initial timing. With today's ethanol-laced cat urine, find the best initial timing by trial and error. The factory spec is only a starting point.

 

Good question. How would compression be affected here?

 

All 1972 motors are low-compression motors. You'll still get a 15-20 HP gain, and frankly the small primaries on the Qjet will actually provide better gas mileage - when driven the same.

 

Arguably minimal performance increase just by itself - I think the 'official' increase range was something like 10-15 hp. But the difference is noticeable in terms of more spirited off-idle acceleration performance, especially if you have a well-dialed Qjet and properly set timing. In my case, I'm running 15 degrees initial timing and if I recall correctly 34 degrees all in. That's with an MSD electronic ignition distributor (p/n 8529).

 

Like I said above, 20 HP difference from the L33 to L34 motors, and both had 8.5:1 CR. Dual exhaust bumped the 2bbl motor from 160 to 175 and the 4bbl motor from 180 to 200, so that also shows the benefit of matching the engine components to improve breathing on both the inlet and exhaust sides.

 

Gain a little more performance and reliability by replacing the timing chain and gears at the same time.

Good luck!!!

 

Yeah, that's how I usually MIGHTASWELL myself into a body-off resto.

 

ALL GREAT ADVICE, thanks all!!

I already had a nice dual exhaust system put on, so I'm good there!

 

I've never messed with advancing the timing. It's got 61k OG miles, so I don't think any internals are worn enough to need it. But in the name of performance I suppose I could look at it. I always thought you could end up running hot with advanced timing. I don't want that issue.

 

😂🤣..thats the damn truth right there!

 

THAT'S what I'm trying to NOT do. And I have a brand new Kent State bill that agrees...

 

the '72 350 motors call for 12 degrees initial timing on 4bbl motors, 8 degrees on the 2 bbl. I would try 12 as your baseline once swap completed. In my case 15 degrees worked best for my combo, which was fully rebuilt to include cam, flat-top pistons and a bump in compression to 9.5. As to running hotter,you probably won't see any significant difference in your operating temps as long as you don't increase timing to the point where your motor pings/detonates on moderate or greater acceleration. Suggestible to replace your thermostat while you're at the swap - get a good 180 degree performance t-stat.

 

I believe the opposite is true. That is why timing is retarded sometimes to induce a quick warm up.

 

Actually, you're correct for the AT motors. I stopped reading at the QD, QE motors in the table in the CSM Tune Up section. Those MT motors used 8 deg with 4bbl, but the QJ, QK, QP motors with AT and 4bbl used 12 deg initial. Sorry for the mis-information. I still stand by my statement that the factory spec is only a starting point. Modern gas, amount of carbon in the cylinders, and whether or not the TCS is connected will alter the optimum initial timing from the factory spec.