L70 TRI-POWER Z/28? LET'S TALK TECH

[@WillieHartz]

Congratulations on the 1 million views! Thank you for the videos Your a wealth of knowledge.

[@richardholdener1727]

Appreciate it!

[@robbisson1]

In the late 90's i met a former engineer from GM. He worked at GM in the 60's and early 70's. He said it was fun at work because they had the entire parts bin of GM. He worked on several projects, including the development of mid engine corvettes. His nane was Larry Nies.

[@andrewbecker3700]

The Yunick Dual Quad CrossRam '69 DZ302 is no question the king. But a 6 pack high compression 350 in 1967 is nothing to sneeze at. Surely under rated.

[@jamesgeorge4874]

What dealership technicians could do, and what a customer could check off an RPO list, and have done, back in the late 60's- thru the 80's, versus now, Is a night and day difference. I am on the other side of Michigan, but Berger Chevy is still a stones throw away, and all kinds of stuff came out of there, that was never featured in magazines, 30 years ago. Nowadays, you would be hard pressed to get a dealer to install a ZZ632, but 40-50 years ago, the top dog tech would have.....

[@mikes.1882]

Cool comment, thanks for sharing

[@corvettejohn4507]

Richard, there are GM pictures of this engine online, I downloaded them several years ago. I can email them to you if you are interested. From some research I did on this engine a few years back I believe the engine was basically an L79 327 configuration with a 350 crank and tri-power, so basically what would eventually become an L46 350/350 with tri-power. I don't think it was being considered for the Z/28, I think it was being considered as an engine option for the SS. The reason I say this is because SCCA did not allow manufacturers to de-stroke engines to meet the 5.0L displacement limit for Trans Am racing until 1970. So Chevy would not be able to homologate a 350 cid Z28 for the 1967 model year. This is why both Chevy and Ford offered 302's until 1970 when the SCCA changed their rules which they largely did for Pontiac.

[@richardholdener1727]

Thnx John

[@corvettejohn4507]

Richard, I sent you an email with L70 pics. You can see from the pics that the engine has double hump heads and standard depth pulleys. This points to a hydraulic cam, since Chevy put deep groove pulleys on all of their solid lifter motors. And their hottest off the shelf hydraulic cam at that time would have been the L79 cam.

[@richardholdener1727]

Thnx I brought that up in the video-though it would be either solid or that l79

[@corvettejohn4507]

Killing the '67 Camaro L70 tripower 360hp/350 engine option I believe could have been a result of two primary causes: 1) GM enacted a corporate wide ban in 1967 that banned multiple carburetion on all vehicles except the Corvette. 2) With the advent in the mid-1960's of large 4 bbl carbs like the Q-jet and the Holley 780 cfm and 850 cfm carbs, there was no longer any power advantage to going to tri-power on a small block 350 cid engine and tri-power added a lot of extra unnecessary cost and complexity. Where as multiple carburetion made good sense in the late 50's and early 60's when the largest 4 bbl carbs were only about 650 cfm, it no longer made any practical sense after the mid-1960's. Around '67, Holley introduced the 3 bbl 4150s in 950 and 1050 cfm that really killed any need for tri-power IMO. And finally, Zora and the Corvette group would have been jealous that this was a Camaro only option and would have complained to Chevy management siting the GM ban on multiple carbs on anything except a Corvette. In '66 and '67 the hottest Corvette small block offered was the 350hp L79 327 and a Camaro only 360hp L70 350 would have upstaged it.

[@TomSmith-cv8hk]

Glad they didn't go with the tri-power, it was a dated layout by then.

[@corvettejohn4507]

As far as cool one off Chevy prototype cars go, how about their 1972 Vega with an all aluminum 302 V8 and a TH350? Talk about parts recycling, the all aluminum heads and block dated back to 1960 CERV prototypes. Zora didn't throw anything away LoL.

[@richardholdener1727]

did any of those alum 283 heads actually make it on to production cars?

[@corvettejohn4507]

@@richardholdener1727 Well, they were offered as an option on the 1960 Corvette 315hp FI 283, but I don't know if any were installed on production cars because the high % silicone alloy used had porosity issues and warping issues. IIRC, when the production heads were pressure tested, only about 1 in 10 passed inspection. If any made it out the door on production cars, they were most likely recalled and replaced with iron heads. Also, some of the Corvettes on the Le Mans racing team in 1960 used them. These heads were the latest iteration of what started out as the 1957 Corvette SS racing car heads. They had larger intake and exhaust ports and 1.94" intake valves instead of the 283's typical 1.72" valves. All of these features were copied over into Corvette FI iron heads for 1961 as the 461X head casting. Ed Cole wanted to use a high Silicone Hypereutectic aluminum alloy so they could use as cast valve guides (and even seats originally) to save from having to machine for and add cast iron valve guides. Although it's unknown if any production Vettes left the factory with them, some early magazine test cars may have had them and sometime in the mid-1960's Chevy sold off the remaining reject heads (hundreds) as scrap so it's not uncommon for a collector to have some.

[@deanstevenson6527]

I'm sad...I missed the show...The development of that package was most likely limited based on the need to go for the big journaled crank for durability. An L70 Tri Power 350 with 360 hp gross engine probably wouldn't have survived like a big journal 350 eventually did.

[@dondotterer24]

87 truck was the first year with TBI.

[@Dan-d7n]

You ever hear of 62 Vette with factory aluminum heads

[@royblankenship5185]

Yes. They had casting problems. How cool would those have been??

[@corvettejohn4507]

Chevy offered the aluminum heads on the 315hp FI 283 in 1960. They were quickly withdrawn as they had warping and cracking issues.

[@richardholdener1727]

I've never seen any in person

[@cedricwilson2055]

If you want to start a fight, tell some one a377 makes more power than a 406

[@dondotterer24]

I'm thinking that the tri power would make more average more torque and maybe horsepower.

[@cedricwilson2055]

Nope runners too short. He’s dyno’d that on carbd ls

[@randypozdnikoff4099]

Pontiac had the tri power 421

[@richardholdener1727]

and 389s and 347 etc...

[@dondotterer24]

Have you seen the Martin Small block Chevy blow through intake manifold?

[@richardholdener1727]

I have