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gvincent

Bore ? on 350 and 400 SBC Choices

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Let me see if I got this straight

a stock 350 SBC with a .020 bore is a 353 CID

a stock 350 SBC with a .030 bore is a 355 CID

a stock 350 SBC with a .040 bore is a 357 CID

a stock 350 SBC with a .060 bore is a 361 CID

now with a 400 SBC

a stock 400 SBC with a .020 bore is a 405 CID

a stock 400 SBC with a .030 bore is a 407 CID (The 406 mentioned in threads)

a stock 400 SBC with a .040 bore is a 409 CID

 

I know there are tons of combinations once you start swapping the internals but this is for stock rebuilt bottom end with a bore.

 

That being said I found these 2 engine descriptions:

 

400 SBC bored .030 over 2 bolt main, new valvetrain, Comp Cam xtreme 4x4 cam, magnum pushrods and lifters, Pete Jackson geardirve, chrome block hugger headers, Edelbrock Intake, HEI distributor, 7 quart pan, flywheel, clutch, pressure plate, NO carburator.

 

Rebuilt 350 bored .020 over, new pistons, forged rods, comp cams xtreme energy cam 1600-5600, Block is 86, heads are 74 casting number 333882 shaved, Three angle, new valves, screwed in studs with guide plates and roller bearing fulcrum and tip rocker arms, Edelbrock intake with Holley 600 double pump carb

 

I can hear the 350 run as it comes with a 81 Olds Cutlass attached for 1K$

 

The 406 has been sitting on an engine stand for 2 years with 17K on the rebuilt bottom end and zero miles on the top end for 1.1K$

 

Thoughts?

Opinions?

 

I can still get low (60-80K) mileage Caprice LT1 motors for about the same money.

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Some how I knew Doc would say that!

Happy Birthday Doc!

Do you think the 406 is ok from sitting in a garage on an engine stand for 2 years, I talked with the guy and he said that he goes out there and squirts oil in the cylinders and hand cranks it periodically.

It has been for sale for a while though....

Here is the most recent add:

http://boston.craigslist.org/nos/pts/268058149.html

He said he can take off one head for a look see inside?

He doesn't know much about the original rebuild but the guy is local to the town he lives in.

I can have him get numbers off the block and heads tomorrow.

 

I have been looking for a motor too damm long now!

 

Thanks,

Greg

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G.V.

 

Besides displacement, the larger bore of the 400 block will help to unshroud the valves which is always a good thing.

 

IF he has been doing as he says it should be fine.

 

If you purchase it, plastiguage a couple of bearings and maybe even check a ring gap or two before you run it.

 

Does it come with a balancer and flywheel/flexplate?

 

Was it balanced with these?

 

Sounds like a good deal as long as the cylinder walls are thick enough.

 

Mike.

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Thanks,

It's probably been 30 years since I have torn into an engine.

My minimal experience was mostly with VW air cooled engines and I built or actually slapped together a bunch of them back then for dune buggy and sand rail projects in the 70's, I have swapped plenty of engines but only once did a rebuild or actualy literally I just replaced the crank and crank bearings in a Buick GN turbo motor that I had spun a bearing on that I had put into a VW Bus.

If I buy this motor I will pick up the Plastigauges and a head and pan gasket set. AutoZone sell these gauges?

 

I also just found a stock GMC 400 small block with a 4 barrel that the owner just pulled, the add says he thinks it has a hung valve? $250

I may pick this one up as well just to keep as a rebuildable spare?

Thanks,

Greg

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If you're looking for the better power, the 400 would be the way to go.. but if you want to drop in and go (IE; you're not going to go through it) I'd go with the 350 that you can hear runing, and pull out yourself. (it's always nice to take it out your self, cause you'll know where evrything went) As far as engines you can't hear run, I've been burned a few times in the past: "Oh yeah, it's only been sitting less than a year since I pulled it out of the truck, it ran great. I just wanted a 350 cause the 305 isn't worth putting performance parts into, ect, ect". So... I cleaned it up, painted it, and jamed it in the car. Discovered soon after that the cam was shot, and it had a serious oil burning issue... :x At the time I didn't have the know how to take it apart and check it out, and just assumed it would be decent. Sounds like you'd be able to lok it over yourself though, so I'd say the 400 is the way to go.

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Thanks for all the advice guys,

Is there anything I should be looking for, I won't be able to drop the pan but he did say that 1 head has been taken off recently and placed back on so I can see the bore and pistons at least.

Aside from a socket set (Any guess on socket size to turn crank balancer pulley?)and a breaker bar to hand crank the engine what else would you guys reccomend I bring with me to check this thing out. Should I crank it with and without the spark plugs installed? anything I should feel for while hand cranking the engine?

I already have the various engine casting numbers but am not sure what heads are on the engine and after doing a web search it seems there were alot of different heads that came on the 400's

Any other questions do you think I need to ask?

Thanks,

Greg

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Balancer bolt should be 5/8. Yes I would pull the plugs, would make it easier to turn over. If I bought it while it was out I would go ahead and freshen it up, check the bearings crank and rods, probably would go ahead replace the rings. After all is done at least you know what you have.

 

You can always buy a anew head gasket, install the head back on. Drain the oil, replace oil filter after filling with new oil. Then bolt on a starter, and turn it over. I would attach a mechanical oil pressure gauge and check the oil pressure, then pull the plugs and do a compression check on all cyl. If some are low, then add some oil to the cyl. and try again.

 

The 1st method is the sure way.

 

IMO.....

 

John

 

PS: I like both the 350 and 400, but for raw power you can't beat the 400.

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5/8" socket, six point, 6 inch extension if the lower crank pulley is on, big breaker bar, 7/16" socket, long extension and ratchet, 9/16" box end wrench. That'll get the valve covers off, heads off and turn the crank.

 

Plastiguage is a thread of material, not an actual guage. You put a piece of it across the journals and torque the cap back, either rod or main, then take it back off, compare the smashed thickness to the chart on the wrapping. They make it for checking different clearances, .0005 to .003 is what your looking for.

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