Logic of the 250 Fuelie

[Mike M.]

Re: Logic of the 250 Fuelie

jim: you are absolutly correct. i should have noted in my cone spacing post that i was referring to the 4360 and 4520 in my two 57 FI's. regards,mike

[Duke W.]

Re: Logic of the 250 Fuelie

I can understand the Powerglide 250 HP Fuelie in the 57 to 59 cars. You cant drive a standard shift but want a Fuelie car. But after 59 when the 4 speed was manditory for all Fuelie cars why in your right mind would you pay the same $484.00 (a lot of cash in 1960 dollars) for less HP than the duel four barrel 469C engine in 1960 and the 468 engine in 1961.What was Chevrolet or the buyer thinking?

I wasn't aware that you couldn't order PG with the 250/275 HP FI engines after 1959. My question is why? Those engines used the same camshaft as the base 230 HP engine, which had a smooth 500 RPM idle in neutral with a manual and about 450 in Drive with PG.

Getting the FI systems to idle properly was always and issue, and even with the base camshaft idling in Drive was probably more of an issue than idling in neutral with a manual. Maybe that's the reason.

Does anyone else have any ideas why PG wasn't available with these engine after '59?

Regarding "CFM" for a given air meter/carburetor flow rating, a single plane manifold will usually yield better hi rev VE because each cylinder is drawing from the entire flow capacity rather than half as with a dual plane manifold. Also, a large plenun will further increase high rev VE.

As a rule of thumb the plenum volume should be at least equal to the engine displacement. This will yield poor low speed driveability and throttle response with carburation due to the huge wetted area and fuel distribution issues - think of a tunnel ram or the Trans-Am cross ram manifolds - but these are not issues when fuel is injected at each port.

Duke

[Clem Z.]

Re: Logic of the 250 Fuelie

I wasn't aware that you couldn't order PG with the 250/275 HP FI engines after 1959. My question is why? Those engines used the same camshaft as the base 230 HP engine, which had a smooth 500 RPM idle in neutral with a manual and about 450 in Drive with PG.

Getting the FI systems to idle properly was always and issue, and even with the base camshaft idling in Drive was probably more of an issue than idling in neutral with a manual. Maybe that's the reason.

Does anyone else have any ideas why PG wasn't available with these engine after '59?

Regarding "CFM" for a given air meter/carburetor flow rating, a single plane manifold will usually yield better hi rev VE because each cylinder is drawing from the entire flow capacity rather than half as with a dual plane manifold. Also, a large plenun will further increase high rev VE.

As a rule of thumb the plenum volume should be at least equal to the engine displacement. This will yield poor low speed driveability and throttle response with carburation due to the huge wetted area and fuel distribution issues - think of a tunnel ram or the Trans-Am cross ram manifolds - but these are not issues when fuel is injected at each port.

Duke

maybe the FI with a PG was not a big seller.

[Bill M.]

Re: Logic of the 250 Fuelie

the '62 air meters use a venturi cone that is open in the center. This revised cone greatly increases the air flow capability of the air meter.

This '62 air meter had the choke removed for use on a 327-powered sports racer (Echidna) in the early 60s

[Dennis O.]

Re: Logic of the 250 Fuelie

Someone above mentioned the insurance factor. I believe this may be so because, when I bought my original '67 L79, my insurance company had a strict "no cars under 10 lbs per HP" rule. They used 3005 as the shiping weight for a coupe, which meant they would insure a 300 HP car, but nothing larger. I seriously considered ordering a 300 HP car and upgrading it, but decided instead to order a 350 HP car and a 300 HP air cleaner sticker. Sure enough, about 3 weeks after I took delivery, my insurance company sent someone out to check the car out. I opened the hood and showed him my "300 HP" Corvette. He must not have been a Corvette guy, because he completely missed the finned aluminum valve covers and the higher redline tach. (I didn't think I could sneak a big block by this way, but in retrospect, I probably could have gotten a 390 HP car past that guy.)

Given that, I don't know how much a C1 weighs, but it might be such that a 250 HP car would qualify where a 270 or 283 wouldn't.

[Paul Y.]

Re: Logic of the 250 Fuelie

Here is a summary of FI advantages in the Chevy brochure that all early FI cars got:

exceptional smoothness even during warm-up
higher power and husky torque
quick engine starting even in severe weather
full power as soon as the engine starts
greater over-all fuel economy

And I can verify all of the above. Paul

[John D.]

Re: Logic of the 250 Fuelie

Mike, the '62 air meters use a venturi cone that is open in the center. This revised cone greatly increases the air flow capability of the air meter.


The increase in cfm is real but minor. The greater effect of spacing the venturi cone is to weaken the venturi signal which the fuel meter needs to control nozzle flow. As a result, the ratio lever stops would need to be adjusted to restore the proper air/fuel ratio.

Jim

Jim, Old Gail Parsons told me the same thing one time. He said spacing the air meter out a tad did't produce any noteworthy advantage on his test engine/dyno..
John

[Wayne M.]

Re: Logic of the 250 Fuelie

Here's a pic taken at Bloomington in 1977. You guys will probably be able to identify the model year of fuel injection this dealer (?) poster is referring to.

[Mike M.]

Re: Logic of the 250 Fuelie

early 57 4360 fi unit. note the first design air cleaner. i'm told that this dealer showroom poster is being reproduced, i think by howard baker. i'm certain that gary pronesti repo'd them several years ago. if i know howard, his will be perfect. mike