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  #31 (permalink)  
Old 01-24-2004, 12:03 PM
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Some pistons also have a larger and small valve relief, in this case you want the large one to match up with the intake valve (which is larger). We do not know what pistons we are dealing with, so this is why I tried to make it clear to him in my above post. Some things are hard to explain/visualize when typing, it would be much easier to just go out in the shop and show someone.

You are correct that with 4 valve reliefs, it really doesn't matter which way they are mounted on the rod, but it still matters which way they (the rods) are put on the crank.

Royce

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  #32 (permalink)  
Old 01-24-2004, 12:17 PM
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Yep, was not trying to pick. It really just depends on the pistons I suppose. The last couple engines I have assembled did not make a difference. Even with two valve relief SRP's I used the last one all mounted the same since the reliefs were the same size. With different size you would certainly have to be careful since chevy heads have two valve orientations on each side.

Chris
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  #33 (permalink)  
Old 01-24-2004, 01:04 PM
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Quote:
Originally posted by camaroman7d

You are correct that with 4 valve reliefs, it really doesn't matter which way they are mounted on the rod, but it still matters which way they (the rods) are put on the crank.

Royce [/B]
That makes no sense. Of course it matters how they are put on the rod. If they are not correctly put on the rod, the piston will be in backwards, putting the offset the wrong way. Can you say piston slap and cracked skirts? That's why they are marked FRONT.
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  #34 (permalink)  
Old 01-24-2004, 06:24 PM
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LOL, Good point Tom, I am not sure what I was thinking.

(I stand by my original post)

Royce
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  #35 (permalink)  
Old 01-24-2004, 08:23 PM
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I am not saying it is not so, but are you sure SBC pistons have an offset. I would have sworn the offset was only on the big end of the rod, but I cant say I have ever measured. Perhaps some do and some dont, but that would not make much sense either. Just out of curiousity what is the offset?

Chris
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  #36 (permalink)  
Old 01-24-2004, 08:34 PM
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Most stock or mild performance pistons incorporate a small pin offset to minimize piston slap. If these pistons are installed backwards, guess what happens!
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  #37 (permalink)  
Old 01-24-2004, 08:40 PM
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Interesting. I never noticed. Like I said earlier the last set I installed were SRP and did not have any orientation markings. Other than that the shop has always installed the pistons on the rods and marked them for me so I never paid much attention. Good to know.

Chris
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  #38 (permalink)  
Old 01-26-2004, 07:46 AM
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confused? who me?
slightly...
i marked the rods(still connected to the pistons) so i knew which cylinder they came out of. i intended to put them back in the same way. am i missing some steps? i am cleaning all the carbon buildup off the top of the pistons(stock-standard w/ 4 half-circle reliefs cut out of them) and cleaning out the ring grooves. i've had the crank turned .010 under and got matching bearings.
i broke one piston rabbit ear on # 1 cylinder when it flew out of the bore and hit the floor. my machinist/engine guy is replacing that for me and is micing the rod. the only wear on the crank was on the journal corresponding to # 1 cylinder, which is the piston i broke, so all my issues were related to the same place.

after that piston is replaced and the rest are cleaned, etc, i plan in putting them back in.

am i missing steps? ami confusing how to put them back in?
i believe the piston all have a notch on them, indicating which way they should face...which i think is the notch faces thefront of the engine.

but after reading all those posts, i'm slightly doubting my plan..simply because the discussion has confused me into not understanding, and that causes me to pause before i go and screw something up.
anyone care to set me straight?
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  #39 (permalink)  
Old 01-26-2004, 07:56 AM
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Have the old pistons checked with penetrating dye for cracks. Have the weight checked on the new piston and adjusted if necessary to match the others. In fact, I always invest in a balancing job on my engines. Not that expensive and a pretty important blue-printing spec for long life. Otherwise, it sounds like you are doing things ok. Just be sure your machinist is the best available - you are depending on him for the specialized measurements.
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  #40 (permalink)  
Old 01-26-2004, 09:06 AM
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Willy

If Zartan gets his 375 hp engine going, what kind of hp loss can he expect threw the drive system? Say a Nova or Chevy II system? Not sure what happened with S10 and Tom on this thread.

hr41pearl
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  #41 (permalink)  
Old 01-26-2004, 09:29 AM
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i am lucky in that my machinist has been doing it for 40 yrs!
he's good and he knows his stuff...and he likes explaining things to me.
he told me i didnt have to balance them because i was only going for 325 hp and i'm not gonna drive it crazy all the time.
i magnafluxed the engine.
he said he could tell by the wear patterns, or lack of , that the pistons and rods were fine.
i talked to him about using plastigauge and he said it's a good product
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  #42 (permalink)  
Old 01-26-2004, 09:51 AM
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Sounds like you are in good hands. Go with his advice.
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  #43 (permalink)  
Old 01-26-2004, 10:09 AM
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Hmmmmmmmm. I don't recommend balancing for any certain horsepower level. An engine built for 300 horses can be far more out of balance than an engine built for 450 horses. In other words, it's the components that dictate the need for balancing. I 've seen many stock or near stock engines that were way out to lunch, balance-wise. I recommend balancing any engine that the cutomer wants the best performance and longevity from. You may find a problem that you wouldn't find otherwise.
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  #44 (permalink)  
Old 01-26-2004, 10:29 AM
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Like I said, I always balance my engines and none are racers. Cheap insurance and just seems like the right thing to do. But there are millions of rebuilds out there that aren't balanced and have no problems.
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  #45 (permalink)  
Old 01-26-2004, 11:35 AM
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Re: Willy

Quote:
Originally posted by Thom Laybourne
If Zartan gets his 375 hp engine going, what kind of hp loss can he expect threw the drive system? Say a Nova or Chevy II system? Not sure what happened with S10 and Tom on this thread.

hr41pearl
Side bars....they happen. 15 percent loss is fairly typical. Sometimes more like 20.
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