need a heads recommendation Compression related.
I gotta do some math on my stuff later. I’ll be back.
A highly recommended exercise for guys like you who have a long engine-building history to review IMHO. I'll be interested to see what you come up with
I had a solid grip on the SCR, and a fair grip on DCR, in my 351C in 1975 (supported by measurements) but it was good to come back 40 years later, use the soooo-nice-and-easy online calculators, and find both the SCR and DCR were pretty much what I hand calculated way back when. And, it was good to get modern numbers to verify that the low 8's DCR range with iron heads and quench was near the limit... very few people attempted to compute DCR back then so there was little reference to what was OK.
And I also went back to my 7.6 SCR, 300 degree duration cammed Opel 1.9L rally engine (which I did NOT compute up in the early 80's and just 'ran with it', despite being warned that the cam was too big for a good rally engine) and found that the DCR was in the high 5's... OK, THAT explains why it was 'torque-free' below 3700 RPM LOL
The physics have not changed.
FWIW.... THE changes at the N/A hobby level in the last 50 years are:
- The easy online SCR/DCR calculators nowadays that give little excuse to not look at DCR. It just takes care and thorough research to find the right numbers to plug in. (So you don't have the garbage-in/garbage out problem.)
- The reasonable cost AL heads have been a revolution from 40 years ago and boon to higher CR engines.
- The roller cams and XE and Voodoo type profiles where there is little good reason to use the old slooow cam profiles, except to remediate a problem or save some $$ for the budget limited enthusiasts.
- Hyper pistons
- EFI
All the rest is the same physics.. head flow, crank and block strength, rods and bolts, oil pressure, piston selection, quench, header size and length, intakes, ignition timing tuning, etc. There are some better parts, but they are improvements on the good stuff that was already there.
Good discussion!
