L72 vs L71 which had a the stronger motor

[Danny P.]

Trying to find out some facts of L72 in a 1966 Corvette and the L71 1967 Corvette, which had the stronger motor ,

[Mark E.]

Re: L72 vs L71 which had the stronger motor

I'm sure the experts will chime in. Meanwhile, my understanding is they are identical except for intake and carburetoration. My guess is the 3x2 set up is harder to tune, less reliable and offers little if any performance advantage.

[Duke W.]

Re: L72 vs L71 which had the stronger motor

Other than slightly different spark advance maps and air cleaner systems, the ONLY difference between L-72 and L-71 is the induction system. The 3x2 carb induction system was purely MARKETING, not engineering driven, and this was confirmed by the late John Hinckley here long ago.

You can find in the archives claims that the 3 x 2 carbs flowed over 1300 CFM. Few knew, but I pointed out that 2-bbl. carbs are flow rated at 3" Hg depression versus 1.5" Hg for four barrel carbs, and since flow is proportional to the square root of depression, 3" depression flow can be easily converted to 1.5" depression flow, which is 906 CFM for trips versus 800 for the 4-bbl. Holley.

Advantage (marginal) trips, but the problem is that the trips manifold is not very efficient. The 4-bbl carb manifold is more efficient, and this is the reason L-88 and ZL-1 had a single 850 CFM Holley 4-bbl on the same L-72 manifold despite that carb "flowing less" than the trips system.

Also my hunch is that the 3 x 14" open element cellulose L-72 air filter is actually less restrictive than the Mickey Mouse short triangular polyurethane element on L-71 that won't filter our anything much smaller than a mosquito.

I'll gladly make an even odds bet that with OE air filters and the same optimized spark advance map the L-72 induction system on blueprinted L-72/71 long block will make equal or GREATER peak power than the L-71 trips system.

Beyond that the only bigger PIA than one Holley is THREE HOLLEYS!!!

Recall that the late Dale Pearman (MIT engineering grad and '62 C1/AFB fan) described Holleys as a "packaged leak".

Duk

[Danny P.]

Re: L72 vs L71 which had the stronger motor

Your very correct Duke , the tri power was just for show and appealing to see, if the Tri-power was a better system they would of put on the L88 the single Holley made more power, but the early 1966 L72 450/425 Hp was pretty close to the L88 HP power range.

[Owen L.]

Re: L72 vs L71 which had the stronger motor

There's a direct comparison with the 1967 L-36 and the L-68. Both use the same components except for the intake and carb(s). If there were a significant difference in tri-power performance Chevrolet didn't report it as such - 10hp isn't much to brag about. The 390hp carb is something around 585cfm... if the tri-power was adding usable air, it sure wasn't much given such a small hp increase.

[Steve B.]

Re: L72 vs L71 which had the stronger motor

With the stock manifolds, yes the L72 was close in power to an L88 since the cam on an L88 was designed to run with open exhaust. Once that happened the difference in power was significant. L88s also had 12.5 to 1 compression and aluminum heads with larger valves. L88s also had a larger 850 cfm carb plus material was machined away inside the intake of the L88s to give more top end HP.

As for L71 vs L72, it would come down to which is in a better state of tune at that time. As far as looks goes, I'll take an L71 any day of the week.

[Larry E.]

Re: L72 vs L71 which had a the stronger motor

FWIW>Jerry Macneish (Camaro/NHRA) expert pulled 480 HP on his dyno with a "Stone Stock L72".
NASCAR learned years ago that a 4 BBL Carb will pull more horsepower then any Multi-Carb setup.
JMHO_Larry

[Danny P.]

Re: L72 vs L71 which had a the stronger motor

FWIW>Jerry Macneish (Camaro/NHRA) expert pulled 480 HP on his dyno with a "Stone Stock L72".
NASCAR learned years ago that a 4 BBL Carb will pull more horsepower then any Multi-Carb setup.
JMHO_Larry

Very interesting, lets step back in late 1965 Chevrolet introduced the first 427/450/425 hp in the 1966 Corvette L72 one year only it must of been a strong car to beat on the streets with all the other competitors out there, 1966 Corvette L72 has to be one of the rarest Corvette out there along with the L71 and L88 which lasted a few years longer, then the HP went down hill from there.

[Michael J.]

Re: L72 vs L71 which had a the stronger motor

382440583_10220653090152148_3425414449316721985_n.jpgI would agree multi-carb engines are for show, not go. I have a '62 409 dual quad and a '60 Chrysler 300 413 dual quad with ram induction, and neither are as quick and fast as my single carb '65 GT350, or my '63 fuelie. But they sure do impress people when you open the hood......

[Mark L.]

Re: L72 vs L71 which had a the stronger motor

I've owned both a 66 425 and a 67 435. Both rebuilt to stock with.030 over. The 66 was run on a dyno and got 467 Ft-LB and 443 hp at 5676 rpm. Never had the 435 on the dyno. Both cars had 4:11. My seat of the pants test tells me the 66 was a bit more of a beast.

[Danny P.]

Re: L72 vs L71 which had a the stronger motor

I've owned both a 66 425 and a 67 435. Both rebuilt to stock with.030 over. The 66 was run on a dyno and got 467 Ft-LB and 443 hp at 5676 rpm. Never had the 435 on the dyno. Both cars had 4:11. My seat of the pants test tells me the 66 was a bit more of a beast.

Just amazing , and only one year only and 5000 L72 unit build , I bet alot of L72 engineering went into the L88 program.

[Mike E.]

Re: L72 vs L71 which had a the stronger motor

Very interesting, lets step back in late 1965 Chevrolet introduced the first 427/450/425 hp in the 1966 Corvette L72 one year only it must of been a strong car to beat on the streets with all the other competitors out there, 1966 Corvette L72 has to be one of the rarest Corvette out there along with the L71 and L88 which lasted a few years longer, then the HP went down hill from there.

[Danny P.]

Re: L72 vs L71 which had a the stronger motor

71 LS6’s were 425 hp rating and only 188 were made, so don’t forget to include them when talking horsepower and rarity.

Yes for sure , 71 LS6 was very rare i wonder how many still around Mike, I know in 72 the LS5 took a big hit with only 270 HP everything went down hill from there, so looking back in 1966 L72 must of been a big hit for the racers turn key race car in the C2 .

[Mike E.]

Re: L72 vs L71 which had a the stronger motor

Yes for sure , 71 LS6 was very rare i wonder how many still around Mike, I know in 72 the LS5 took a big hit with only 270 HP everything went down from there, so looking back in 1966 L72 must of been a big hit for the racers turn key race car in the C2 .

Our NCRS survey, begun in 1993, knows of about 85 for sure, and another handful not well-enough documented to be in the survey. Of those 85, 28 are convertibles.

[Larry E.]

Re: L72 vs L71 which had a the stronger motor

Just amazing , and only one year only and 5000 L72 unit build , I bet alot of L72 engineering went into the L88 program.

Danny:Not so. One must remember the vast majority of the COPO Camaro's/Chevelles engines where all L72's. Also there was a fair
share of RPO's in the Full size Chevrolets that where L72"s. So if you add all the availability of the L72's from the factory
there was more then you think. Thanks>Larry