Yenko 427 Engine Information
 

I have a 427 L72 Yenko complete engine in my car. Does anyone have any information or links that can provide more info. It has the Yenko located in the block casting front drivers' side on an angle. The heads are cast 3946074. The intake has the winter foundry marks. I understand this block casting was from earlier blocks, possibly 69?

That Holley has an odd choke linkage on it. Is there a part number stamped on it?

It’s a 950 3 barrel list 3916. That’s the choke setup they used. A 1030(some say 1050) 4604 3 barrel is identical but uses dump tubes on the rear secondary flap instead of boosters.

Hi... I've never seen one of these, thanks for the info.

Yenko sold ZL-1 block castings in the '70s, no complete engine assemblies. Disassembly would be the only way to determine build configuration.

From what I read, the castings with the Yenko on front right were early builds like in 69? Possibly from a wrecked Camaro? Also, the head casting numbers were on 69 ZL1's, I could not find if that was a standard head for years afterwards.

No ZL-1 Camaro had a Yenko block.

Chevrolet produced the last production ZL-1 block castings [3946052] early August 1969. Lockport [LC] did some 053 castings in the late '80s.

The 2025 Chevrolet Performance catalog still lists an 053 block casting, much improved over the original.

The 3946074 head was produced into the '70s.

William, I was looking for the 053 block,couldn’t find it. Do you have the part number for that block? Thanks. Jeff

The part number for the 053 block in the 2025 catalog is #12370850.

Online GM parts dealers show it as discontinued...

Could be one in stock somewhere.

That's possible, but if there is one in the system, those sites will usually do a search for it and that option didn't come up. If someone REALLY wants one, they would need to call a dealer and have them search the system.

I believe most of the Yenko blocks were used in Can-Am racing ..

Since this is a complete motor, with a early Yenko block, would I assume it came out of a car Don had replaced the motor with. Did he sell complete motors in the 70's. My gut tells me this could be a late 68 or 69 motor but will search for some identification on it. It just has all the parts from a full motor that Chevy would have put in the ZL1 except it has the Yenko block. So little information out there. I have also been told so many different things. Thanks

What’s the casting date of the block and the heads?

It is not a 69 block.
Don had those Yenko blocks cast in the mid-70's.
GM did not let Yenko used the molds in 69 - the blocks were still in production.

You seem to have included a picture of your Trans Am's original Pontiac 400 cid engine casting number 481988 XX, which confuses matters.