Rempa

Greetings,

I need some advices to take a decision about the piston head on my 305.
There's one of them that is broken and it doesn't look like an original piston head:






Here a pict of the 7 others and (I suppose) original ones.




What should I do? does the broken part really matter? can I still use the broken one? or should i replace it by another standard 305 piston head like this down there? It's definitly another kind of shape and compression ratio...




Thank you for your help.

Viprklr

iTrader: (5)

Using a broken piston is un-wise.
If you just replace the 1 you'll need to get everything rebalanced. If you re-use the 1 you should still get everything rebalanced and you take the chance of destroying your engine.
Pistons are cheap. Replace 'em all.

Rempa

Thank you for answering,

Do you have any advices for a specific piston type? there are so many...flat head, forge, hyper...giving that I'll replace them all, what would be a good option to add some power to this stock engine?

midwest

Thats the skirt thats broke. Its what stabilizes the piston and keeps it from rocking.

Sonix

iTrader: (1)

That's a flat top piston there, coupled with stock dished ones.

you can just buy one new dished stock piston, and replace just the broken one.

If you've got the cash, i'd buy a whole set of 1.56" compression height pistons, flat top, cast. You don't have the HP to need forged or hypers. Check the compression height. **MOST** aftermarket pistons have 1.54" compression height, this puts the piston .020" further down in the hole, which lowers your compression ratio and kills the quench effect.
Check that factor before buying pistons.

I'd just buy "std" pistons, ie don't bother overboring the engine (this is a 305 right?). Then just buy a honing tool, get some mineral spirits and get your buddy to pour it over the hone while you "drill" down the bores. That'll give you a cross hatch to help seat the new rings.

Pistons - $150 or so
Rings - $80
Bearings - $40
hone - $50
Shipping to (was it columbia?) - $$$$$$!


PS - I'd also want to know what caused that piston to break. Keep a close eye in there and see if you can find a culprit.

Rempa

mmmh, I can't find an online shop that's selling those stock pistons ans if I find it, it's expensive to buy all the dished pistons set...I found Keith Black hyper pistons sold for US$200...they are pretty cheap.

Part Number: KB143
CHEVY 305, V-8
Bore: 3.736 Rod Length: 5.7 Pin Diameter: 0.9272 Stroke: 3.480 Comp. Ht: 1.561 Sizes: STD .020 .030 .040 .060
Minimum Clearance: Crank-to-Deck Clearance: 9.025 Weight
Piston / Pin: 470 / 145

What do you think? I'm asking cause you said I hadn't the HP to need them but given that it looks like a good offer...(money talking).
Or maybe someone know about a site where I could buy the missing piston

Ps Sonix: It's in Dominican Republic

Sonix

iTrader: (1)

Contact ohio crankshaft,
http://www.ohiocrank.com/home.html
Phone them and tell them you want ONE single stock replacement piston for a 1987 camaro 305, with the dished stock pistons. If they can't sell you one factory exact replacement, they might be able to point you to a company who can. That's a $15 part at most right there.

$200 for pistons is a lot. I only spent $200, but that's flat top hypers for a hot 350. I wouldn't spend that kind of money on a mild 305, if it were me.

Unfortunately most of the cheap pistons (speed pro, TRW, etc) have the 1.54" compression height. You can use that, but you'd have to deck the block .020" to get back to normal. Running it as is, is an option, but not ideal.

I'd still just try to replace the single piston. Hone all cylinders and slap it back together with new rings.

ljnowell

detonation probably.

Sonix

iTrader: (1)

You think it would only detonate on that one cylinder, and it would shatter off the skirts? It's a flat top, so a bit more compression (unless it's a 1.54" Comp height one). I would expect aluminum specs on that spark plug then, check that Rempa.

I would have guessed improper clearance to the crank, but that seems highly unlikely. I think detonation is probably the only viable answer. But just because it's a different piston, or due to....?

Rempa

I don't remember finding the broken part in the crank down there...As you can see on the pict, the broken one is different, so I think it may be:
1) The guy that had the car needed to replace the previous piston, and He only found this broken one on this island...
2) Someone dropped it before the install, it wasn't even after...
3) Detonation???

I'm negociating with Ohiocrank as you said, they said they had Federal Mogul #454NP standard in stock for US$20, I'm asking for comp ratio to be sure...any comments about this part?

Sonix

iTrader: (1)

hmm, broken during install and installed anyway sounds quite logical, since you can't find the pieces.

Those are $11/per on summit
http://store.summitracing.com/partde...P&autoview=sku
Those are quite different from what you have.

It would work, but wouldn't be ideal. Tell them you want the exact factory replacement for what you have. Send them a picture if they want. Ask how you get the *exact* factory replacement piston. 1.56" compression height and all. It's not that weird of a request, they should be able to set you up.
Worst case you buy 8 of those and replace them all. $90 or so from summit. But if you're buying all 8 definitely get flat tops. At least that would make up for the compression height difference.

five7kid

iTrader: (14)

The Z454NP is the full dish version. You don't want that.

Z536NP is the dish & relief version, like stock. That's what you want if you only get one.

If you get 8 pistons, and can live with higher compression, go for Z534NP.

Those are all 1.540" compression height, so I would recommend going for all 8.

Rempa

I think I'll go for the 8 for a good balance and little update, some others pistons have been hit too... What are the diferences between a 1.540" and the 1.560" compression height? same for flat piston and dish ones, what are the differences?

Thank you for answering

Sonix

iTrader: (1)

Five7 do you think he can purchase identical stock pistons with a 1.56" CH? I couldn't find any on my end here...

It puts the piston .020" down further. Go for the Z534 then, it'll up the compression to make up for the loss with associated with the compression height

Rempa

This forum is so impressive...It's like wikipedia but in very hard mode, so much infos....Thank you for the patience and advices

here's what I'm planning to do: Buy the eight of those Federal Mogul Z534NP, Flat with valve reliefs and deck the block 0.20" to go back to standard mode. What do you think?

ljnowell

Broken on install is possible. The only reason Ithrew detonation out there is because of a different piston being installed. Who knows what the comp ratio is in that hole. Could affect only one. Another thought would be rings. If the end gap is off it could make them butt and break the piston, usually that takes the rings with it. A stretch, but possible, would be that the one hole had a problem, they "fixed it" and in the process screwed up the rings or something else, tore it down and put new rings on and left the broken piston. its really impossible to tell ,as anything is possible. The important part is, you have a broken piston.

Just took a closer look, damn, how did they break it there?

InfernalVortex

iTrader: (4)

Since you're not in the US it changes things a little, but at this point you may as well do a rebuild. You've got it apart, you're doing machinework... your $20 piston just changed into $500-$1000 rebuild project.

jtrescot

In my opinion, $500-$1000 is an awful lot to spend on a 305.

Rempa

Yes, I spent a lot of money in this car...1000$ is the average...but when I opened it...water pump, oil pump, gas pump, filters, manifold, lifters, camshaft, I could have throw it away but what for? there are 350 here but they come from old truck, you don't know what happened to the engine, people here love to BS and sell you a piece of junk for US$1000, It's cheap to have a Camaro in the US, it's a disaster to have it in a country where it's not supposed to be imported...I'm trying to do a "factory" rebuild project, because of the money, because I think it will be the first and last Muscle car I'll buy in this country, because the car I'm dreaming about need to stay in the US (Corvette stingray 76) he he...
But now I can be sure that this engine will be like new and I will start the restoration of the body: brakes, exhaust, painting and finally interior.

Sounds like the classic story but it turns into an epic one when you move it to an island

five7kid

iTrader: (14)

Didn't find any, but I didn't look that hard.