Yamato compression

[ZUL8TR]

What are great cranking compression pressure values (lbs/sq.in.)for completly stock Yamatos for the 14 mm head and 18 mm head:

Y80
102C
302F

Per the stock inspection manuel the Y80 has a greater compression ratio than the 102 or 302 so I suspect it would have a higher cranking compression pressure.

Thanks

[johnsonm50]

What are great cranking compression pressure values (lbs/sq.in.)for completly stock Yamatos for the 14 mm head and 18 mm head:

Y80
102C
302F

Per the stock inspection manuel the Y80 has a greater compression ratio than the 102 or 302 so I suspect it would have a higher cranking compression pressure.

Thanks

Thats a good question, just to read what others are testing at. Manuals dont always give you more than an unexceptable difference between cyl's. The average #s could be useful now that the local seasons ended, re-build? or re-tune

[Matt Dagostino]

Gauges vary......................

Thats a good question, just to read what others are testing at. Manuals dont always give you more than an unexceptable difference between cyl's. The average #s could be useful now that the local seasons ended, re-build? or re-tune

Compression gauges are all over the place but to generally answer your question a good Yamato 80 will read 150-160pounds after roping it over 4 good pulls!

I would defer to Troy G, to answer for the 102/302 since he seems to be the Yamato expert nowadays

Later

[Islandmon]

Great question, one that I've thought about as well....................standing by

[mike ross]

102 should be 120-135. If cc's are close the 135 reading is good. If cc's are not close 125 would be good. Mikey

[14J]

Compression gauges are all over the place but to generally answer your question a good Yamato 80 will read 150-160pounds after roping it over 4 good pulls!

I would defer to Troy G, to answer for the 102/302 since he seems to be the Yamato expert nowadays

Later

You had to go there, should I tell them your toilet story

[Team B&H]

There is absolutely no difference in actual measurements of 18mm heads compared to 14mm heads as far as the engine is concerned. I made a fixture to bolt to the head from the block side so I could CC the head volume with the spark plug in the hole. I was hoping to find some advantage with one or the other. I did this with both 80 and 102/302 heads. My conclusion is the Japanese engineers knew what they were doing! But I did get great measurements on all our heads which was really useful to find the preferred ones before complete blueprinting was allowed.