I've been noticing quite a few rod bearing issues lately with the 350, mine included Is it because some of us are starting to push the 350 (as we should)? I've heard a lot of people say the 350 doesn't have the oiling issues the 455 does, but its the same oiling system by design. Yes the 455 has 3.25 mains VS the 350's 3.00, so in theory its easier to oil 3.00 than 3.25 Buick was breaking 455 cranks at 3.00 because the block was squirming around, so they went to 3.25 The 455 was fine with its original intention, big car, low rpm engine. Then the 455 went racing, issues arose, they've been addressed. Is the 350 going to have similar issues?
Your kinda talking two different things here even though the bad outcome may be the same! GM never built any true street motor with the notion that it would need to live at over 5500 rpm and at 2 times or greater then a stock power level. For instance for Pontiac to give the go ahead to put a motor into production it had to run at 4500 rpm for 24 hours with nothing more then a 5 minute half way point stop for a oil and filter change! When you concider the fact that the loads ( G force) on motors bottom end would be twice as high again at 5500 then at 4500 rpm and so on you can see how things that are not set up or made ideal for that intended rpm and power level go south really fast, and add some Detonate into the mix and your driving over the Crankshaft!!! In direct regards to your question a basic block design that may be ok with the stroke and recipercating weight of a 350 cid at 7000 rpm may start to swim around with the stroke ( G force loads once again!) and loads of a 455 at 5500 rpm. If your starting off with new Rods , or newly resized ones and do a tare down and find that the lettering imprints from the rear of the rod bearing are smeared looking in the rod bore then two things may be happening. Either your taking those Rods out of round due to rpm level ,or your Detonating the motor ! The latter will show up when you read the plugs that right way.
Most of the engines shown here on the forum with bearing problems have also had strong if not definite indications of detonation. Remember....you can't hear it until too late. When you double or triple the power and stress level, they don't take it as well as a stocker. When the heads are ported and more severe cam profiles are used, there's more cylinder pressure to contend with. Some might be flirting with 'the line' of dynamic compression. If many are keeping a stock rod alive for years @ 7000 rpm and whatever stroke and gram weight, it suggests that failures well below that might not be due to the weakness of the design.
something to check. with intake off push rods out use oil primer and drill. when running primer make sure the oil coming out of lifters have zero air bubbles. Oil only. If there is air there is a leak somewhere in the system. race secret Dan
Detonation will pound the hell out of rod bearings. Scary because you may not hear it. It's one thing to nail your car for an instant on the street, it's another to hook it up solid and run WOT through all 3 gears at the track. That's why I always add some Race Gas at the track. Can too much octane slow you down a bit? Sure, but I would rather that then rod bearing problems.
I only once had an issue with a spun rod bearing but it was my fault... Was going 120 mph and had to stop for a red light and geared down to 2nd and spun the rod bearing on deceleration. That was almost 20 years ago. Ever since then I have not had any issues and I was pretty hard on them. I thought I had spun a bearing on my turbo 350 however it turned out to be the timing chain that broke and that was at 8000 RPM with 20 psi of boost. And that engine had been reliable at low boost and 6000 rpm for years. I think if you do the oiling mods and pay close attention to the bearing clearances then there should be no issues. Fine tune the oil pressure with the TA kit that gives you different thickness gaskets. Adjustable oil pressure regulator is good too. The 1021 Hp Buick 350 used a stock style oil pump and it was not having any bearing issues except some signs of the main caps shifting front to back which we have covered with the girdle that is available. Bob Mackley has had no bearing issues with the pro charged 350 and it used a stock oiling system. I thought it was a good idea for me to use the belt driven oil pump and suck directly from the side of the custom alum pan so that we didn't need to suck oil all the way up through pickup through the block to the pump. But my application is a little more serious than most. I will be able to adjust the oil pressure without taking the cover off. Have you looked into the "scavenger" kit that helps eliminate some of the issues with the stock setup? I'm sure the 455 scavenger kit could be modified to work on a 350. If you want some extra protection from damaging bearings due to rod or main journals deforming under high RPM or HP applications then increase the bearing clearances and use higher volume oiling.
This is kinda off my topic, but I was reading in an old Musclecar magazine about the late 60's early 70's Buick performance, Denny Manner mentioned that the 400/430 and eventually 455 architecture was loosely based on the 215/300/340 and eventually 350 design. Why didn't the Big Block get the deep skirt design like the 350? I know the Big Block was designed as a thin wall/light weight design, but isn't the deep skirt 350 still lighter than a 350 Chevy? If so, a deep skirted 455 would still have been lighter than a 454 Chevy Yet all the focus back in the day was on the 455, I know I know, cubes are king, but I would think Buick would have offered SOME kind of hotter factory 350 being its a stronger design to start with. Just some of my ramblings and thoughts while my engine is out
I have talked with Dennis on the phone about the 350 and the changes they made to it over the years etc. They just never really saw it as a performance engine it was just meant to be the low cube engine. Of course they made changes to improve it over the years however with the drops compression and the smog era coming in it really choked it out by the mid 70s. Talking with Dennis about what we were doing with he twin turbos etc. on the 350 he was not surprised it could handle it. Yeah the Buick 350 with alum heads will be about 400 pounds vs a stock chevy 350 at 550 pounds... Of course they can lighten them up with alum heads and intake etc.. Just think the stock intake is 55 pounds and my sheet metal intake is 12 pounds, huge savings right there. I just need to weigh my billet crank because i know I lost some weight there.
I've wondered the same thing. What could've been had they done something more with the 350? I think with the new heads, rods, crank, etc. and all the cool builds going on with strokers, turbos, etc. that we're going to finally find out what I've always thought was possibly the most underrated V8 is capable of.
I might get flamed for this but so be it. the 350 has a couple designs that make it inherently bad for performance. the worst is its under square bore and stroke. while good for torque, the small bore make for small valve sizes. secondly the chamber shape is just plain awful. the total lack of quench is a real hindrance. hopefully the new heads will help, but the valve sizes will still be a limiting factor. denny manner is a very intelligent guy. he had 3 years to build a mean 350 before the compression drop. why didn't he? probably because he knew the power wouldn't be there without a serious sacrifice in driveabilty.
"I might get flamed for this but so be it. the 350 has a couple designs that make it inherently bad for performance. the worst is its under square bore and stroke. while good for torque, the small bore make for small valve sizes. secondly the chamber shape is just plain awful. the total lack of quench is a real hindrance. hopefully the new heads will help, but the valve sizes will still be a limiting factor. " Not flamed, but I'd like to explore this... Way too many other engine types out there that are ridiculously powerful, even being under square. If you see this as a limitation, at what rpm is that? Bear in mind factory castings capable of well over 260 cfm and alums with much more potential than that. What do you believe an appx. 2" valve is limited to for cfm or hp? (or any other metric you are familiar with) Plenty of ways to gain back the quench or negate it's need. What would be a reasonable max N/A power level despite the supposed downfalls? (Ignoring the builds chronicled here, therefore...any pre-conceived limitations)
nope. I'm not biting. I'm not getting into another discussion with you and gary farmer where you guys type novels and spell out the most peculiar reasoning ever heard.
My personal opinion in my limited experience, is that people get too wrapped up in the numbers. I feel that port velocity is just as, if not more in some cases, as important as max cfm flow numbers. I think these little 350's can scream if you concentrate on their inherent design qualities, which is a low rpm/high torque engine. I've seen too many people "Hog" their ports out, and they actually hurt the performance, making it a "Hog". Having a quench pad should make a big difference. The valves are going to be somewhat shrouded due to bore size. Port shape entering the cylinder could create some swirl. It will be interesting to see what the aluminum heads will do. I called T/A the other day and added my name to the list for heads.
Buick's offerings were different than Olds or Pontiac in that the 442 & GTO weren't avail. w/ a 350 (correct me if I'm wrong) whereas a GS was. W-31's were only 325HP & I'm sure Buick could've easily made a 350 w/that or a little more without giving up driveability given that a '70 High-Compression 350 was already rated @ 315. Interestingly, the GS 350 had tremendous sales volume compared to the relatively low sales volume of W-31's, which at least in '68-69 ('70?) was only avail. w/manual trans. & could be what accounted for that difference. More so then not being able to build a 350 with a few more HP it may have come down to not wanting to, being that a GS455 was only rated @ 350HP they may not have wanted a 350 rated within 25HP of that. There is a constant battle in companies between marketing, engineering, and finance and in the end they were in business to sell cars. As far as the design flaws you mention that could be limiting, you may be correct & I don't profess to know enough to debate that although I do hope the alum. heads fix some of the issues. I thought I had read that they would be able to accept a larger intake valve than the iron heads (1.920). I'm sure someone here knows more than I do about that.
