LT1 Query

[Mad4slalom]

Hi all, hoping you all had a great xmas. Just browsing through vette stuff on you tube. When I bought my 72 over from the USA , the PO had told me that his son and he , had built the motor to as close to LT1 spec as they could. I always wondered why they fitted a hydraulic lifter/ cam set up and not a solid one . I presumed this was so they didnt have to bother with valve adjustments etc. I was surprised to learn from the guy presenting the video on you tube that the 1972 LT1 did in fact have a hydraulic cam/ lifter set up. Which is why you could spec A/c on the LT1 in 72. It was also fitted with the deep vee pulley’s but stock narrow belts so the belts stayed on at higher revs , albeit slightly less rpm than the 70/71’s. Interesting, and informative, I didnt realise either that only the LT1’s had the holley four barrel over the rochester quadrojet fitted to the base 350 ‘s. Nice to know that the build was thoughtfully done , starting with a correct 4bolt main block.
Anyone else out there with a Real72 LT1 that can confirm non solid lifters ? Just interested really.

 

[Oneball]

Can’t see why the type of lifter would affect the fitment of a/c??

 

[Mad4slalom]

Hi all, hoping you all had a great xmas. Just browsing through vette stuff on you tube. When I bought my 72 over from the USA , the PO had told me that his son and he , had built the motor to as close to LT1 spec as they could. I always wondered why they fitted a hydraulic lifter/ cam set up and not a solid one . I presumed this was so they didnt have to bother with valve adjustments etc. I was surprised to learn from the guy presenting the video on you tube that the 1972 LT1 did in fact have a hydraulic cam/ lifter set up. Which is why you could spec A/c on the LT1 in 72. It was also fitted with the deep vee pulley’s but stock narrow belts so the belts stayed on at higher revs , albeit slightly less rpm than the 70/71’s. Interesting, and informative, I didnt realise either that only the LT1’s had the holley four barrel over the rochester quadrojet fitted to the base 350 ‘s. Nice to know that the build was thoughtfully done , starting with a correct 4bolt main block.
Anyone else out there with a Real72 LT1 that can confirm non solid lifters ? Just interested really.

Now I am confused as cant find any other reference to any LT1 not having a solid lifter cam. I always thought the main thing with the LT1 was the solid lifters and higher rpm capability. Anyone shed light on this

 

[Mad4slalom]

Can’t see why the type of lifter would affect the fitment of a/c??

it was the higher engine revs that would spin the a/c belts off apparently .

 

[Roscobbc]

Can’t see why the type of lifter would affect the fitment of a/c??

Most serious hi-po optional engine options on 60's and 70's yanks always seemed to exclude the use of other options like power steering, air conditioning and power brakes. The first two (as mentioned previously) was due to the fear of belts flying-off at 6000+ rpm and presumably warranty claims for belts puncturing radiators and engines blowing from overheating.........no power brakes.......low vacumn response for power brakes......another insurance issue (didn't stip thenm supplying drum brakes though!)

 

[Mad4slalom]

Most serious hi-po optional engine options on 60's and 70's yanks always seemed to exclude the use of other options like power steering, air conditioning and power brakes. The first two (as mentioned previously) was due to the fear of belts flying-off at 6000+ rpm and presumably warranty claims for belts puncturing radiators and engines blowing from overheating.........no power brakes.......low vacumn response for power brakes......another insurance issue (didn't stip thenm supplying drum brakes though!)

Reading further , the 350ci /350hp L46 motor from 69-71 had 4bolt mains and hydraulic lifters, maybe this is what they started with. I will ask him when the snow melts in buffalo

 

[Roscobbc]

Reading further , the 350ci /350hp L46 motor from 69-71 had 4bolt mains and hydraulic lifters, maybe this is what they started with. I will ask him when the snow melts in buffalo

The early LT1 as described was effectively powered by a factory 'saturday night special' engine - definition of a saturday night special is effectively a low end race car for the street. Just stick a set of open headers on it and some slicks and you're race ready!
'Thing' was that the early LT1 was introduced in the face of increasing opposition to high powered cars from the tree shaggin' brigade, insurance companies, the manufacturers own warranty departments.......and finally the big killer, emissions and the final nail back then for high compression engines.......unleaded gas.
The 'saturday night special' 1971 429 SCJ powered Mustang I had back in the early 80's had a 4.11 detroit locker rear end, 11.2 compression ratio, solid lifters and a 780 cfm Holley......all 100% stock. It was rated at a very conservative and insurance 'friendly' 375 hp........and would have been a total pig to drive out on the street if not for the 4.11 axle. In fact it is was a pig to drive - with its need for 5 star gas or tetra ethyl lead additive it would only run at its 650 rpm idle speed in drive for about 10/15 seconds before gassing-up and stalling. It would light the tyres even on half throttle through 1st and second gears on its C6 auto box and 'chirp' its 295 BFG's going in to top.......lethal indeed and the very reason why you shouldn't should own one!

 

[teamzr1]

Refer to Page 78 of the 163 pages of the GM engineering PDF for the 1972 Corvette I attached below
Go through this closely as it specs all designs for that model year

As you see for the LT1 had mechanical valve lifters with 9.0:1 compression
No A/C with the M21 tranny as assumed when buying a manual tranny you want a racer and did not want the extra
weight of all the A/C parts and the added load onto the crank of the engine

 

[teamzr1]

A/C was an Option

 

[Mad4slalom]

Refer to Page 78 of the 163 pages of the GM engineering PDF for the 1972 Corvette I attached below
Go through this closely as it specs all designs for that model year

As you see for the LT1 had mechanical valve lifters with 9.0:1 compression
No A/C with the M21 tranny as assumed when buying a manual tranny you want a racer and did not want the extra
weight of all the A/C parts and the added load onto the crank of the engine

View attachment 20326

View attachment 20324

 

[Mad4slalom]

A wealth of info out there if you know where to look, thanks for that TeamZr1

 

[Mad4slalom]

The early LT1 as described was effectively powered by a factory 'saturday night special' engine - definition of a saturday night special is effectively a low end race car for the street. Just stick a set of open headers on it and some slicks and you're race ready!
'Thing' was that the early LT1 was introduced in the face of increasing opposition to high powered cars from the tree shaggin' brigade, insurance companies, the manufacturers own warranty departments.......and finally the big killer, emissions and the final nail back then for high compression engines.......unleaded gas.
The 'saturday night special' 1971 429 SCJ powered Mustang I had back in the early 80's had a 4.11 detroit locker rear end, 11.2 compression ratio, solid lifters and a 780 cfm Holley......all 100% stock. It was rated at a very conservative and insurance 'friendly' 375 hp........and would have been a total pig to drive out on the street if not for the 4.11 axle. In fact it is was a pig to drive - with its need for 5 star gas or tetra ethyl lead additive it would only run at its 650 rpm idle speed in drive for about 10/15 seconds before gassing-up and stalling. It would light the tyres even on half throttle through 1st and second gears on its C6 auto box and 'chirp' its 295 BFG's going in to top.......lethal indeed and the very reason why you shouldn't should own one!

That must have been a beast but a lot of fun

 

[Oneball]

it was the higher engine revs that would spin the a/c belts off apparently .

Most serious hi-po optional engine options on 60's and 70's yanks always seemed to exclude the use of other options like power steering, air conditioning and power brakes. The first two (as mentioned previously) was due to the fear of belts flying-off at 6000+ rpm and presumably warranty claims for belts puncturing radiators and engines blowing from overheating.........no power brakes.......low vacumn response for power brakes......another insurance issue (didn't stip thenm supplying drum brakes though!)

So more to do with engine tune and use than the lifters then. Makes more sense

 

[teamzr1]

A wealth of info out there if you know where to look, thanks for that TeamZr1

You're Welcome

Have to keep in mind as 1971 required only using non-leaded gas
CAT that was like a brick along with not very good exhaust system
Not much HP or Tq yet total weight
So the only way to make it more like a sports car GM made functions like power windows, A/C, radio, etc an
option to make car lighter a bit and helped less drag on engine
Being able to adjust the valves and roller rockers helped a bit in adjusting the amount of timing for some gains

Even then, the japs were flooding the USA with 4 banger ricers and most auto-cross events for SCCA and NASA on
purpose were designed to bias ricers doing better, so I recall back in mid 1980s we had to do everything
to get our C3s able to compete against them and that was stripping weight off, and bias oversteer to get around
those tight turns.