LT-1 engine in ZR-1 and non-ZR-1 cars

[J W.]

Are LT-1 engines in ZR-1 cars any different than LT-1 engines in non-ZR-1 cars?

[Joe L.]

Re: LT-1 engine in ZR-1 and non-ZR-1 cars

Are LT-1 engines in ZR-1 cars any different than LT-1 engines in non-ZR-1 cars?

J. Michael------


The primary difference is that most non ZR-1 with LT-1 used a "5 quart" oil pan (except early 1970 LT-1 without P/S) whereas all ZR-1 are equipped with a "6 quart" oil pan.

The ZR-1 LT-1 engine was scheduled to receive a cast iron balancer pulley instead of the stamped steel pulley used for other LT-1. However, I don't know that any apparently original 1970-72 ZR-1 have ever been found equipped with this pulley.

[J W.]

Re: LT-1 engine in ZR-1 and non-ZR-1 cars

Thanks Joe

What would be the advantage of a cast iron balancer pulley over a stamped steel pulley?

[Dan P.]

Re: LT-1 engine in ZR-1 and non-ZR-1 cars

The LT1 & ZR1/LT1 engines are the same internally and externally with these exceptions:

ZR1 Features
1) HD starter - high-torque and used a different nose to accomodate the ....
2) L88 smaller diameter Lightweight flywheel

Otherwise - the engines were identical. The ZR1 used the 436 HD aluminum/L88 style radiator w/overflow bottle and steel (base motor) fans shroud in 1970 and '71. 1972 ZR1's used NO fan shroud. Those would be the only other cue under the hood to let you know an LT1 was really a ZR1. Finally, Joe mentioned the pulley - and he's right; they say ZR1's used a cast pulley, but all documented ZR1's I'm aware of have stamped units, mine included.

i believe the oil pans were the same for LT1's regardless of ZR1 status; 6 quart in 1970, and 5qt in 71 & 72.

[Joe L.]

Re: LT-1 engine in ZR-1 and non-ZR-1 cars

The LT1 & ZR1/LT1 engines are the same internally and externally with these exceptions:

ZR1 Features
1) HD starter - high-torque and used a different nose to accomodate the ....
2) L88 smaller diameter Lightweight flywheel

Otherwise - the engines were identical. The ZR1 used the 436 HD aluminum/L88 style radiator w/overflow bottle and steel (base motor) fans shroud in 1970 and '71. 1972 ZR1's used NO fan shroud. Those would be the only other cue under the hood to let you know an LT1 was really a ZR1. Finally, Joe mentioned the pulley - and he's right; they say ZR1's used a cast pulley, but all documented ZR1's I'm aware of have stamped units, mine included.

i believe the oil pans were the same for LT1's regardless of ZR1 status; 6 quart in 1970, and 5qt in 71 & 72.

Dan------

As far as I know, all ZR-1 LT-1's were equipped with "6 quart" oil pans. Non ZR-1 LT's were "5 quart" (except early 1970 without P/S)

[Joe L.]

Re: LT-1 engine in ZR-1 and non-ZR-1 cars

Thanks Joe

What would be the advantage of a cast iron balancer pulley over a stamped steel pulley?

J. Michael------

I don't know. However, most (but not all) 1965-71 SHP big blocks used a cast iron balancer pulley. These pulleys were more expensive than stamped steel so, presumably, there was some sort of performance advantage.

[Larry M.]

Re: LT-1 engine in ZR-1 and non-ZR-1 cars

Admittedly I'm splitting hairs here, but since the question asked about non-ZR-1 applications, the LT-1 engines in Z-28s had different air cleaners, distributors and exhaust manifolds (and probably other items as well).

[Dan P.]

Re: LT-1 engine in ZR-1 and non-ZR-1 cars

The LT1 platform for Camaro and Corvette were the same. The difference in horsepower rating was equated to the difference in exhaust restriction between the two models. Block, Intake, heads, crank, cam and pistons all were identical. There may have been a difference in carb jetting. Also, not if all all camaro z28's were K66 - so that may be another difference.

[Kenneth B.]

Re: LT-1 engine in ZR-1 and non-ZR-1 cars

The LT1 platform for Camaro and Corvette were the same. The difference in horsepower rating was equated to the difference in exhaust restriction between the two models. Block, Intake, heads, crank, cam and pistons all were identical. There may have been a difference in carb jetting. Also, not if all all camaro z28's were K66 - so that may be another difference.

Also Camaro's cost a lot less than Corvettes. GM played with the #'S to make sure you got more HP in a Corvette.

[Ron G.]

Re: LT-1 engine in ZR-1 and non-ZR-1 cars

I had a 70 Z28 when I was 19, many years ago. I believe not only was it a marketing ploy, but also the Z28 exhaust pipes go over the rear axle making for a little more back pressure as opposed to the Corvette's rear pipes that exit straight out with an inward bend.

[Joe L.]

Re: LT-1 engine in ZR-1 and non-ZR-1 cars

I had a 70 Z28 when I was 19, many years ago. I believe not only was it a marketing ploy, but also the Z28 exhaust pipes go over the rear axle making for a little more back pressure as opposed to the Corvette's rear pipes that exit straight out with an inward bend.

Ron-----


Z-28 LT-1's use log type exhaust manifolds whereas Corvette LT-1's use "ram's horn" style manifolds. The "ram's horn" style flows better.

Corvettes small blocks have always used "ram's horn" style exhaust manifolds, from 1955 right through 1996. No Corvette ever used a log style manifold.

[Ron G.]

Re: LT-1 engine in ZR-1 and non-ZR-1 cars

Joe -

I wasn't referring to hte exhaust manifolds. I was referring to the rear exhust pipes confuguration. However, now that you mentioned it, that too would have an impact on the 10 extra h.p.

[Mike E.]

Re: LT-1 engine in ZR-1 and non-ZR-1 cars

I thought that prior to 1972 all horsepower ratings were in SAE Gross HP meaning horsepower was measured at the flywheel, but with no accessories and only absolute essentials attached to it. Nothing more than a carb, fuel pump, oil pump, and water pump.


Mike

[Ron G.]

Re: LT-1 engine in ZR-1 and non-ZR-1 cars

Mike,

I and believe and think Joe Lucia was only referring to the 1970 model year when LT-1 Corvettes and Z28's was rated at a difference of 10 h.p. 71 and 72 LT-1 Corvettes and Z28's were rated the same h.p.

[Joe L.]

Re: LT-1 engine in ZR-1 and non-ZR-1 cars

Joe -

I wasn't referring to hte exhaust manifolds. I was referring to the rear exhust pipes confuguration. However, now that you mentioned it, that too would have an impact on the 10 extra h.p.

Ron-----


Yes, I realize you were referring to rear exhaust configuration. However, I think the difference in exhaust manifolds had more to do with the lower rating than the exhaust pipes.

I don't know why the 1971 and 1972 Z-28 and Corvette LT-1's were rated at the same HP.