piston ...[edit:]BIG PROBLEMS!!

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piston ...[edit:]BIG PROBLEMS!!

Postby DjTy » Sat Sep 16, 2006 9:53 am

edit:

OH joy, more surprises popped up:
Click here!!

I'm so sad and pissed off...

it appeared that they used plain normal 4" rings on it too, not the 4.060" ones...

I feel like strangling the guy who sold me this block.
/edit





Most likely if my block's cilinders turn out to be too wide for the pistons I will be buying a set of flat top pistons.

thing is I already need new rings which are pretty expensive locally as a set of 8 stock 350ci piston rings costing $125, and then the required bore and sleeve job which could be around $50 per cilinder... :(


So from summitracing I want to order these.

basically Hypereutectic aluminum 4.030 sized, including rings.
Image

Will this screw up my factory rebuilt balance of the crank or engine at a whole?

would I need new rod-to-piston connectors?


any other stuff I missed if I'm ordering just this set of pistons with rings?

I want to run a pretty high but good & clean compression and no oilburning smoke.
Last edited by DjTy on Mon Sep 18, 2006 1:03 pm, edited 1 time in total.
-Chevy Monza '76 2+2 V8 262ci (old) -> 355ci (oil problem) -> 355ci (piston broke) -> 350ci (current) ... LOL
-Opel Kadett E 1985 1.2Litre (Back up, had a broken condensor :P still need to find replacement accelerator pump membrane...)

My Monza in Cardomain!
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Postby Fastmax32168 » Sat Sep 16, 2006 3:57 pm

Well technically you are supposed to get the crank, rods, and pistons rebalanced. That said, Millions upon millions of chevy smallblocks have had the pistons replaced and put back together without rebalancing and run just fine. If you are building a street car you probably wont notice it.
I believe by piston to rod connectors you are talking about wristpins, and they will come with the pistons.
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Postby DjTy » Sat Sep 16, 2006 11:54 pm

yes, it's going to be a mild street car and second daily driver when the first is out of duty. I want to be done once and for all with the engine, but we do not have a balancing shop on the island.

this car is probably never gonna see strip/track duty, it's just gonna be a weekend cool ride with a bit of punch now and then when a ricer pulls up.

thing is that it is rebuilt and even the connector rod bearings have scratches. so the rebuilt is not that great of a job I guess, so I suspect the old but pretty new looking pistons in it not being balanced either. crank looks ok tho

well what ya think... I will need to order rings at any case, so outbore and hone to use those 4.030 pistons & rings instead ofthe old heavy dished ones?
-Chevy Monza '76 2+2 V8 262ci (old) -> 355ci (oil problem) -> 355ci (piston broke) -> 350ci (current) ... LOL
-Opel Kadett E 1985 1.2Litre (Back up, had a broken condensor :P still need to find replacement accelerator pump membrane...)

My Monza in Cardomain!
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Postby Fastmax32168 » Sun Sep 17, 2006 6:39 am

You need to have the pistons before you bore it so that the machine shop can get the dimensions right.
Roy
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94 Corvette Convertible LT-1 500+ HP
Trailblazer EXT LS6 powered
1991 K1500 6.0 LS swapped
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Postby DjTy » Sun Sep 17, 2006 10:04 am

Fastmax32168 wrote:You need to have the pistons before you bore it so that the machine shop can get the dimensions right.
Roy


I thought I could just tell em to prepare it for 4.030 diameter pistons... but it's not that easy?
-Chevy Monza '76 2+2 V8 262ci (old) -> 355ci (oil problem) -> 355ci (piston broke) -> 350ci (current) ... LOL
-Opel Kadett E 1985 1.2Litre (Back up, had a broken condensor :P still need to find replacement accelerator pump membrane...)

My Monza in Cardomain!
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Postby starfire383 » Sun Sep 17, 2006 7:32 pm

I don't know how many machine shops you have to choose from....... But my personal motto is if they'll bore without the pistons in-hand, then I'm at the wrong shop.

First, different piston types have different expansion rates. Such as a forged piston needs more clearance than a cast piston. This affects the finished dimension of the hole.

Second, not everyone's .030 over piston will actually be .030 over, there is a slight amount of variation in the manufacturing process.

A good machinist will target the finished bore dimension to the set of pistons you provide. Not only that, he (or she) should actually mark the individual pistons to which hole they go in. There will be a little bit of variation and you want the biggest piston in the biggest hole, and vice versa.

So get that block into your machinist, have it cleaned up and let them tell you if a re-ring will suffice. If they say to bore it, ask if it's gonna be .030 over, .040 over, etc. Come back with pistons and rings (different finish for different types) and then let them proceed.

They may even want to do a rough cut to see if it'll clean up at .030 over (or whatever) before you order pistons, then do the final cut after the pistons are there.

Good Luck!
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Postby DjTy » Sun Sep 17, 2006 9:16 pm

tnx, my dad also mentioned the same thing starfire just ment 3 hours ago while I was at his garage, "Tyrone, the shop would need the pistons you're planning to put in"

another problem...

we measured the block and pistons a bit (no micrometer till tomorrow 9am et) , and the results were 102mm piston and ~103.5mm block... without the rings there's lots of space...

so for the non-metrics: it looks like it was already bored to fit 4.060 pistons :S

looks like I may have to sleeve.... anyone know about the ideal block-bore for 4.060 pistons?
-Chevy Monza '76 2+2 V8 262ci (old) -> 355ci (oil problem) -> 355ci (piston broke) -> 350ci (current) ... LOL
-Opel Kadett E 1985 1.2Litre (Back up, had a broken condensor :P still need to find replacement accelerator pump membrane...)

My Monza in Cardomain!
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Postby gerbsinmd » Mon Sep 18, 2006 7:17 am

yikes!!! That piston to block gap seems a bit large. Do the pistons have any marks on them that designate the over-bore? A lot of the pistons that I have seen have the overbore stamped into them. Usually in the face if I remember right. Almost sounds like someone bored it and used the standard pistons. If you have to sleeve it, I would think it would be cheaper to find a different block than to have that one sleeved. Course they may be harder to find there than here in the US.

Good luck.

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Postby ColinOpseth » Wed Sep 20, 2006 12:37 am

Dude..

Do you want me to get you a rebuilt 350 here for your? Shouldn't cost more than $500-$700. They are advertised in the paper all the time.

Later,
Colin
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Postby greg72 » Wed Sep 20, 2006 8:43 am

Tyrone , i was thinking the same thing. Years ago i used to export parts to the islands. (They shipped out of Jacksonville FL which I always thought was strange because I am in the Tampa bay area) ..

Anyway we would ship it as "used parts" and the taxes , tariffs etc were much cheaper. I had customers request that i take the parts out of the new boxes and dirty them up a bit. Then repackage in different boxes.

I was thinking that someone could locate a rebuilt engine , maybe even just a short block as I think you already have a decent set of heads but I don't recall. Shipping by boat instead of air freight shouldn't be too bad , and it could be listed as a used part .
Greg
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Postby DjTy » Thu Sep 21, 2006 1:29 pm

thank you both very much, if I don't have any option left I'd appreciate it if one of you could. Luckily I have found a few other old 350's laying around at mechanics and I'm gonna see if one could sell me a block cheap. (with the correct bore of 4" of course ;)

could anyone tell me if there could be complications with just using a different non overbored 350 block with the current heads bearings & crank?
-Chevy Monza '76 2+2 V8 262ci (old) -> 355ci (oil problem) -> 355ci (piston broke) -> 350ci (current) ... LOL
-Opel Kadett E 1985 1.2Litre (Back up, had a broken condensor :P still need to find replacement accelerator pump membrane...)

My Monza in Cardomain!
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Postby MB77Monza » Thu Sep 21, 2006 8:43 pm

Tyrone, Its all depentand on the condition of the parts. As long as the crank is straight and the block doesn't need line bored then its a bolt in swap. If the decks are true then good heads should bolt right on. Personally I would let a qualified machinist check thinks out.
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