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I am in the middle of a drivetrain upgrade for my 1972 Olds Cutlass Supreme that has been in the family since bought new in 1972.
Stock is a 350sbo, TH350, 10 bolt with 2.73s open diff.
Last year I installed a 9-in rear end with 3.73s w/ tru-trac posi unit.
Totally upgraded the frame and suspension all around:
NOW, to the engine!
Mark is building me a ground-up build from a 72 SBO 350 block. It will be bored and stroked to 434ci. ProComp Alum. Heads. Hydraulic roller cam, carburetor, etc.
More details to come, but this is where I'll be updating the process of the build, results, install, etc!
I'm so excited!
** Build Specs on Post #7 **
Last edited by 72GoldOlds350; May 9, 2020 at 08:13 PM.
Very cool build, but I would like to ask why aren't you going with a 350DX diesel block instead of a 350 gas block?
I don't want to sound like a troll, but IMO, the block halo won't offer near the strength possible as the diesel block with 4 bolt caps in the long run, especially with the possibilities of the billet crank and good rods and pistons.
Do you have flow numbers on the heads? What intake valve size?
We have personally re-built and upgraded a 455 that will likely and eventually "outrun" the hp-strength capabilities of the block, and I will have my eyes open for an affordable 350DX block that can slowly be built over the next several years.
If I was to start over, I would do a 350DX block with 4 bolt main caps to start with.... With enough cylinder head flow and proper cam tuning, a 600-700hp NA street engine is quite attainable.
Valve sizes are 2.07/1.68, with simple clean up.
And his hp level doesn’t warrant having to use a DX Block. Gas blocks are good to 600 or so, especially with lighter, stiffer insides.
Last edited by cutlassefi; Feb 28, 2019 at 05:14 PM.
+1 on dyno numbers. Cam seems a little conservative. What's the target compression ratio?
Mark, do you machine the caps like Jim advises? My machinist said he had too much movement when cutting down the caps last time he did a halo girdle, so he used ARP washers to get 1-4 to line up with #5. Of course, he made a series of interesting choices (aka mistakes), so who knows on that one. But it hasn't grenaded. Yet.
+1 on dyno numbers. Cam seems a little conservative. What's the target compression ratio?
Mark, do you machine the caps like Jim advises? My machinist said he had too much movement when cutting down the caps last time he did a halo girdle, so he used ARP washers to get 1-4 to line up with #5. Of course, he made a series of interesting choices (aka mistakes), so who knows on that one. But it hasn't grenaded. Yet.
Compression ratio is 9.8:1.
We spot face the #5 main cap so the halo sits level. Otherwise you lose support by having the washers under the halo imo.
Chris will be posting numbers soon, did reeeeeal well😉 The Tq these little strokers are making is encouraging, we’ll just leave it at that.
Last edited by cutlassefi; Mar 21, 2019 at 06:36 PM.
Compression ratio is 9.8:1.
We spot face the #5 main cap so the halo sits level. Otherwise you lose support by having the washers under the halo imo.
Chris will be posting numbers soon, did reeeeeal well😉 The Tq these little strokers are making is encouraging, we’ll just leave it at that.
Thank you but I don't agree.
Let’s put it in perspective. In 1970 Oldsmobile made a W 31 350 correct? It was advertised at 330 hp, but I think everyone would agree that 350 was probably a better number. So, add headers, a much better intake, carb, camshaft, cylinder head, and piston, and I think 450 horse power would not be out of the question. Now add 85ci. To me it all makes sense.
Jmo.
Very nice indeed, good point about the W31, it was 350 to 360 hp according to our inside sources. This Lunati roller has similar duration numbers, big on a 350, about right with 427 ci and way more lift, nearly .100" and much better head flow.
Engine Build: 434ci SBO 350 & Much More!
