Well my Cutlass is back in the yard minus the 3.8, Paul says the flex-plate appears not to be counter-weighted ... ? My Rock Auto 79 Buick Century 231 flywheel does with 7 drill holes on the backside ?? Oh-boy here we go
Wonder if I could spin motor fast enough with starter to notice whether a balance problem exists if it bolts up properly? Will probably need a different starter just to try.
Guess I've been thinking some of the Pontiac turbo on a 301, I believe that was kind of a flop and am not certain why, it was an early domestic V8 turbo that was clearly eclipsed by the Buick V6. I do believe the Buick effort advanced turbo technology into the real performance arena, one of the reasons I was considering trying to convert a stocker 3.8 thinking some of that might rub off on my brain enough to learn from a success and use with whatever engine I choose. My textbook starts with history saying forced induction came from Europe and was originally a method to make a smaller engine a "larger" engine without changing its bore and stroke, not necessarily for racing. I drive a turbcharged diesel (and own one) and have been doing so for 25 years. The text says diesel engines have lower exhaust temps which makes turbo'ing them easier parts wise and more effective as the charge is thus cooler. Got a hole in my Cummins N14 intercooler and did have a noticeable power loss tho the leak was small. 40psi my max boost and I notice very little boost when truck is not loaded or rolling on level ground. (something is regulating boost)
I did do some reading about rolled fillet cranks, believe Pontiac used them in cast cranks on the 301 Turbo engines as well as the 455 SD with stronger blocks (main webs and lifter valley reinforcements). Think they used forged conventional fillet for Ram Air 4,5 and TA 303,366. My understanding is the rolled fillet must be cast in, it cannot be machined in, so you will not find a forged crank with them. Their positive effect might be negatively impacted by grinding the crank if that is necessary and need to be supplemented with larger bearing clearances and oil supply enhancement or actually become a negative if using low oil clearance bearings. Cranks do not usually crack on a Poncho the first thing to happen is a spun rod bearing or a broken factory rod if rpm is too high. Mains rarely ever fail. It was my understanding the rolled fillet makes the joint between the rod or main pin and the adjacent counterweight less likely to crack from the forces which actually cause this area to flex by allowing more flex. I was having my cranks ground with larger fillets for a similiar reason and using a larger oil clearance and oil supply system to complement the effort. I wanted to modify factory cast cranks to their utmost instead of buying a forged replacement made overseas. Effort appears to have been thwarted by crank shop(s) on my first one .. so I will be buying a foreign forged as I have people and a done block waiting.
I believe the split pin Buick crank might be a weak point, dueling rod pin centerlines doesnt seem like a performance enhancer more of a band-aid that might work well enough to a point to me. The book referring to a viable stock cast crank low rpm turbo build might be referring to an odd fire crank with a single rod pin. Is this what the "rolled fillet" on both main and rod crank that is available in certain blocks was?
My goal of converting a stock 231 to a turbo that would exhibit more power than a stock Chev 350 was based on the same article I used for building the 302 conversion, goal being less than 400HP. 360HP I think it was. In stock form the 302 made more HP and torque than the 350 above 6000RPM so it didnt seem like as hard a goal to attain as this one. Trying to find those numbers and misplaced them. Just read some more in my text, actually has several pages about Buick ... says the non-intercooled turbo system improved the 105hp stock na 231 performance to peak 165hp@4000 / 265ft-lb@2800 .. the 86 intercooled Buick offering further improved those numbers to 235hp@4400 / 330 ft-lb@2800, guess these figures would be car off the assembly line ... modifications could bring those numbers up. Boost was limited to 13psi and sfi wastegate and full electronic control with knock sensor reducing timing when necessary was incorporated. In 1976 the Indy pace car featured a modified 231 with stock block, crank and rods that made 315hp with 22psi boost ... might not have lasted too long on the street with those numbers and book doesnt specify all mods. Book is by A. Bell and is well respected .. have his other book too, 4-stroke Performance Tuning. Guess Im just figuring the more boost the more potential HP avaiable so the trick must be building the short block so it will rev and take as much boost as possible if the 800 HP figures are being chased. Maybe there is an advantage with the 6 as it has less ra weight and moving parts to keep together than a v8 and if you are going to buy premium lightweight parts anyway ( I did with my 302 and Poncho) and turbo it to a larger "effective" displacement comparable or greater power levels may be attainable.
