Don't pound your bottom end....

[Stevesr]

Anybody have any stories to share about this? I was telling a guy in my local parts store about my 3.1 buildup plans and he said be carful how hard you pound the bottom end of these motors. It is the weak point of the 3.1. I didn't want to believe him but the owner of the other parts store we have in town said the same thing. He didn't like the 3.1 at all,said it was the worst motor GM ever made. I defended my position by telling him I had owned two Gradprix's and never had any problems whatso ever.....any thoughts?

SteveSr

[bszopi]

RE: Don

Are they talking crank, mains, etc or pistons and rods? Either way, I think they are wrong...

Curtis is putting down some big numbers on a stock crank and mains, but with aftermarket rods and pistons. Tiago dyno'd like 370+ hp (or some insanely high number above 300) on a stock bottom end 3.4L turbo'd and nitrous'd.

I'd like to hear more reason why they think its so bad....

[Guest]

Re: RE: Don

Are they talking crank, mains, etc or pistons and rods? Either way, I think they are wrong...

Curtis is putting down some big numbers on a stock crank and mains, but with aftermarket rods and pistons. Tiago dyno'd like 370+ hp (or some insanely high number above 300) on a stock bottom end 3.4L turbo'd and nitrous'd.

I'd like to hear more reason why they think its so bad....

Werd YO!!

For some reason people think these engines are bad, sure there might be common problems that come up, and regularly, looking at from the parts store perspective, but they also fail to realize that is one of the most common, if not the most common engine installed in GM vehciles, so there are a lot out there. I still feel that of more current GM offerings (mid '80s+) the 3800 is in far worse shape than a 3.1.

I'd like these parts store guys to qualify what they are saying, give actual reasons.

Another example is my truck, stock bottom end 3.1, 218 HP and 270 FT/lbs at the rear wheels, about 250 and 310 at the crank, holding up just fine.

[robby1870]

RE: Re: RE: Don

I agree with all that. I think most peole fail to realized the rods are forged and can handle 7000rpms, and shot-peening makes them even better. Its very rare that you hear of bottom end problems that werent caused by over revving or general prolonged bad treatment.

I would also like these peolpe to defend themselves.

[Stevesr]

The one guy who was the owner of the store went on to say the oiling system is flawed, and no one makes an after market oil pump that works any better than the stock one. The other guy sited the main bearings as the weak point.
I don't care what they say I'm forging head!!!

SteveSr

[StudlyCamaro]

yeah tiago had almost 400 ftlbs of torque at the rear wheels on a compleetly stock bottom end, I'd say that that alone is pretty good evidince that the bottom end i pretty stout

[RednBlack]

He apparently has a boner for these engines. What the fuck would the bearings have to do with making an engine weak? I have never had a bearing fail by itself. There is always an underlying cause. Bad clearance, no oil, dirt, or misapplication. (or..in Aarons' case..Water! ) The guy is a maroon!

[Scott_68B]

You can tell he doesn't know what he's talking about...the worst engine hands down GM ever made was the all aluminum Vega 4 cyl. engine, they were lucky to last 50,000 miles if you took care of them.

-- Scott

[geoffinbc]

Bad bearings, snapped cranks and snapped cams are all tales probabally due to the notorious intake gasket leaks left too long. I have seen them all happen first hand. But that is not because they are weak. Just the intake gaskets were. But they are good now.

No one really know the history of this engine and how it used to dominate Miget racing. The oiling system it just as good as any other engine. Plus now with main feed oiling and oil squirters on the pistons it is a world class oiler. My 3.4L was rebuilt and I never changed the pump. I still have pressure that NEVER drops below the half way mark on the guage even idling at 800 RPM on a hot day waiting to get over the bridge. Also I run 5W30 even in the summer.

[firechiken]

Weren't crank/rod problems common in the early to mid 80's? I remember my mom had a Pontiac 6000 wagon, an 86 I think, that threw a rod, and she was told that it was a problem for those motors. It had a carbed 2.8, so the intake gasket wasn't an issue?

[1QUICKHATCH]

I have see alot of 3.1's that have spun rod bearings (uaslly from running low on oil), but thats the worst I have seen with the bottem ends.

[smilinguy99]

The well-known intake gasket problem kills bottom ends as it would in any engine with the same problem.

Just so happens these engines are suseptible to the gaskets giving up and putting anti-freeze in the oil.

Bad reputations are easy to come by with this kind of help.

Read of a possible class-action lawsuit concerning this problem over at modern olds performance.

[sharkey]

worst i have seen is a spun rod bearing. if you keep driving a car with a spun rod bearing, eventualy the heat will become so intense and it will weld the rod to the crank, and that will break the rod throwing it through the block. most likely cause of the spun rod bearing is not doing routine oil changes or antifreeze in the oil, or the pump was shot.

[614streets]

If the block has bad core shift or a defect from the factory. Other than that the bottom end is stout.

[Froggx]

I've heard many stories of spun rod bearings in the 2.8's in fiero's, but not really anything else. I holed a piston in my fiero's 2.8 thanks to a massive exhaust manifold leak, but that has nothing to do with the construction of the engine, just the (mis)construction of my mind when bolting things down