It was nice to see a generally positive article about our favorite engine, with excellent photos & even a comment about that "other" engine, that made me chuckle! On the other hand, I'd like to hear some feedback from the engine "gurus" here, because I thought that several things done and not done in the build up, raised questions. For instance, I suspect that since they didn't indicate milling of the heads, or the block, their compression calculations may have been optimistic? If so, shouldn't they have purchased domed forged pistons, not flat tops? And since they were stroking the engine & installing hardened exhaust seats, why not increase the exhaust valve size? Also a question on the Cam. Is this the same Cam advertised by J.Mummert, as having a power range up to 6000 RPM? In the tests it was hard pressed to peak out at 5200. I think many here, would be interested in feedback & further comments on the article. Thanks

Paul

Okay Paul.  I’ll take a nibble at this one.  As far as magazine articles go, this one had more information than is usually supplied but still lacked some critical assembly information such as bearing clearances, piston to wall clearance, ring end gaps, and exactly at what intake lobe centerline the camshaft was installed.  But also included were some blatant errors in the writeup thereby taking away some of the credibility.  Errors include: the number of links between dots for the cam timing is listed as eleven although the picture in the article shows twelve and the last year of production for the Y is listed as 1962 although its pretty common knowledge that the engine was used in the trucks through 1964.

 

But regarding the compression ratio, if the stroke is increased to 3.600” with a 3.800” bore, then the compression ratio with a 66cc head and the pistons at 0.023” below the deck will be at the articles mentioned 9½:1 with a composition head gasket.  The article didn't mention specifically that the heads were milled but calculations on my end with the article stating the the pistons were 0.023" in the hole indicate that the heads would be milled about 0.020" to get the CR to 9½:1.

The engine peaking out on power at 5200 could be the result of several things but the camshaft being advanced heavily would be at the top of my list if that's all I had to go on.  But then at looking at their graphs, the rpm scale stops at 5200 rpms with the power levels still climbing.  The dyno pulls were either stopped at 5200 rpms or the data simply wasn't included.

Lorena, Texas (South of Waco)

I didn't even notice they stopped at 5200rpm. I thought the engine should have broken 300hp. I'll bet it would have if they had let it rev higher. It was a good article overall.

I wonder when they'll let one of the pro's build one that hits the 450 - 500hp mark in one of those magazines. That would be nice.


Lawrenceville, GA