Don Terrill’s Speed-Talk

pitts64 wrote: ↑Sun Jan 12, 2020 9:03 am I wouldn't mind going bigger so long as I keep the idle vacuum up for power brakes.. In my area brakes are just as important as engine performance..

bobmc wrote: ↑Sun Jan 12, 2020 8:02 am what is the last domestic engine with mechanical lifters?

Tuner wrote: ↑Sun Jan 12, 2020 2:14 pm

bobmc wrote: ↑Sun Jan 12, 2020 8:02 am what is the last domestic engine with mechanical lifters?

Mopar Slant Six until 1980.

Tuner wrote: ↑Sun Jan 12, 2020 3:03 pm In the mid '70s a 405 HP rated 454 marine engine used in the common family type jet boats was the basic low compression PU truck engine with a cam that I recall was about 220 @ .050 and .500 lift. I think the LC was wide, 114 or 116 maybe. The engines were rated at 405 Hp with the low-rise CI intake and a QJet. Some of them came installed in jet boats with an adapter and a vacuum secondary 780-800 Holley Ford Marine engine carb that is a clone of the SCJ carb.

They idled smooth at low RPM (as is necessary in a boat) but I don't recall a specific vacuum number or any complaints about insufficient vacuum for brakes. In the late '70s and early '80s I put several of them in PU trucks for people and they all ran well with the stock engine with just a valve spring and push rod change. The 454 engines that had positive valve rotators needed a shorter valve spring and I recall using a stock replacement spring for a 427 FE Ford to get the right seat pressure and spring rate for the .500 lift. The stock PU 454 pushrods were 5/16" so I installed 3/8" and guide plates.

Because this cam had such a wide useful RPM range, idle and low RPM smooth for rock crawling and still buzz 5500+ no sweat, they sort of caught on in a local clique of 4WD off-road rock crawling and mud bogger guys. I recall the disappointment when that cam wasn't available from GM any more. The part # and specs are in an edition of the Chevrolet Power Manual I don't have (or can't find, rats).

Roadknee wrote: ↑Sun Jan 12, 2020 7:36 pm

Tuner wrote: ↑Sun Jan 12, 2020 3:03 pm In the mid '70s a 405 HP rated 454 marine engine used in the common family type jet boats was the basic low compression PU truck engine with a cam that I recall was about 220 @ .050 and .500 lift. I think the LC was wide, 114 or 116 maybe. The engines were rated at 405 Hp with the low-rise CI intake and a QJet. Some of them came installed in jet boats with an adapter and a vacuum secondary 780-800 Holley Ford Marine engine carb that is a clone of the SCJ carb.

They idled smooth at low RPM (as is necessary in a boat) but I don't recall a specific vacuum number or any complaints about insufficient vacuum for brakes. In the late '70s and early '80s I put several of them in PU trucks for people and they all ran well with the stock engine with just a valve spring and push rod change. The 454 engines that had positive valve rotators needed a shorter valve spring and I recall using a stock replacement spring for a 427 FE Ford to get the right seat pressure and spring rate for the .500 lift. The stock PU 454 pushrods were 5/16" so I installed 3/8" and guide plates.

Because this cam had such a wide useful RPM range, idle and low RPM smooth for rock crawling and still buzz 5500+ no sweat, they sort of caught on in a local clique of 4WD off-road rock crawling and mud bogger guys. I recall the disappointment when that cam wasn't available from GM any more. The part # and specs are in an edition of the Chevrolet Power Manual I don't have (or can't find, rats).

My Chevy power manual lists 3863143 for high performance street and marine use. It’s mechanical lifter, 242 @ 0.050, 114 LSA, .500 lift, lash 0.024 int, 0.028 ext. It looks like a lot of duration, but with the lash and wide LSA I imagine it idled pretty well.

pitts64 wrote: ↑Tue Jan 14, 2020 6:07 pm I forgot about the 375 horse 396 cam.. My buddy has a mint 69 Chevelle with that motor in it, 18,000 original miles. It idles real nice. It has that rippled exhaust pipe with resonators at the back, it has a nice sound.. I doubt the extra cubes will make up for the loss in compression. I'm more then likely going to try Cam Doctors suggestion. He has a very good following on here...