My piston in hitting the crankshaft... What I need to know is, what do I do to create clearence? It is an internally ballanced crankshaft, so I dont want to grind on that. Right? And what would I use to grind on the pistons with? Flap disks? Scat Crank is made for 5.7 rods and these are 5.7 Scat rods. JE forged 31cc dish pistons. Experienced answers only please. I hate threads without pictures so here you go!
Longer rod, shorter piston... if the piston really is hitting the crankshaft.... I wish I could help more but I honestly have never heard of that. How much of the skirt would you have to remove from the piston to make your clearance?
Did you check the pin location on the pistons? That could be the deal. Or recheck the part #s on the crank and rods to make sure they are what you were sposed to have. N.N. P.S. Don't go grinding on any of the rotating parts!
In answer to the flap disk question. HELL NO. Find out what is causing the clearance problems and either fix that or have it fixed. First I would go back to the outfit that sold you the kit and ask questions. I'd also find out for sure if those are the correct rods. Stuff has been known to get put in the wrong box all too often. If the rods are the correct ones and they do appear to be with the pistons appearing to be at the correct deck height the crank counterweights may not have been machined correctly.
Was this a stroker kit? DO they have a tech line? If it is they sent the wrong parts, before you do anything check all the part numbers, once you grind they probably won't take it back
I have a 383. Id call them up and make sure they sent you the right pistons. Looks like your skirts are to long. Dont modify them. Make SCAT give you the right parts. If you modify the parts and they grenade for some reason scat wont honor any warranties.
I'd say that something is probably boxed wrong or an incorrect part. I agree, get ahold of whomever you puchased it from and see what they say.
I double checked everything. What I ordered is correct and compatible. All pieces are setup for 5.7 rods and 3.75 stroke... I will take actual numbers off of the parts tomorrow and call scat and JE monday morning and ask them. The wieght on the crank will have to be taken down about .020-.030 I think. I just imagined everything would have to be reballanced afterwards. I also got a .003 main bearing clearance on the mains so I will be talking to scat about that or just ordering .001 undersize bearings.
Crank, Rod and "Piston" have to be for the correct rod (5.7) and for a 383. Sounds like you may have 350 pistons, or pistons for the a 5.585 (400) rod. Either way, if your crank and rods are for 5.7 inch rods, I would think your pistons are wrong. As side note, just cause your crank is internally balanced, doesn't mean you don't need to balance your rotating assembly once you figure out the interference issue. It just has more or different counter weights on it than the stock 400 crank. My "balanced" 406 has a ton (actually 7 pieces) of Mallory metal in it because I didn't go your route with the internal balance crank. Lesson learned. I still think I saved $50 though.
I bought all the pieces seperatly. I couldnt find a "kit" with the pistons I needed. It took me a long time to get the money togeather so I checked and rechecked the compatability of the parts.
"The weight on the crank will have to be taken down about .020-.030 I think." No. Don't do it. Get the right parts.. "I just imagined everything would have to be rebalanced afterwords." Yes. They should pay for the re-balance.
List the part numbers for the crank, rods and pistons. Someone on here should be able to look them up and see if there is a issue. I see now that you bought separately. I did that too, so I wouldn't think that is that unusual.
Your deck height looks good enough, so I think the pin location is correct.... If the piston is at TDC in the picture..
If you bought the parts seperately then thats probaly the problem. You most likely have the wrong pistons. Im running TRW pistons but SCAT crank and rods. Got my forged pistons on clearance at summit. Think i payed 175 for the set. That was about 5 years ago.
The book I bought, How to build Big-Inch Chevy Small Bocks has a typo. It shows that the part number for my crank takes a 5.7 rod, scats website says 6.0... So I hope summit will take the crank back. Looks like they sell the 5.7 rod crank that is externally ballanced. They dont offer an internal. I guess that would mean the larger wieghts for the internal ballance will need 6.0 rods.
I also found the books publisher website and sent their customer service an email. Maybe I will get a free book or something.
The other option that may or may not be desirable would be to have the counterweights machined for clearance and the crank and rotating assembly rebalanced.
I am also building a 383. I went with the 6 " rods and pistons to match so that I could buy the internally balanced crankshaft. As I understand it, you either need to go in that direction (easy if you are buying new crank, pistons and rods) or pay the $ to extenally balance the new rotating assembly at a machine shop and go the 5.7 rod setup. as Yogi said: "when you come up on a fork in the road, take it"
Back in-the-day, we would trim the skirts on the pistons for clearance. Of course, that means taking the same amount of weight from each piston, equal to the most removed from one. Now a-days you can buy the right parts.
Are you sure it is the piston/crank that is hitting? We always had to watch cam/rod and rod/pan rail clearance when we built 5.7/406 motors.
I was looking at your pics and it can be fixed easily. Looks like your piston skirt is barely touching the crank , right? Up on the radius of the skirt,,on one side,,am I right? You could remove a slight amount of material and it won't effect balance,,,did you say 20 or 30 thou,,?,,,that is a slight amount,,might add up to a gram. Looks like it is hitting the radius of the counterweight,,should not take much to clear it. You said that the parts were bought separate,,,so no one will take the blame for some other guys parts not working together with theirs. Tolerance stack up,,that is what you probably have. These parts have a certain tolerance and the other guys parts take the tolerance from the other end. It is amazing how much the balance can be played with and it will still come out right. Ask some guys that know on here,,,,,it is a crazy formula to figure the bobweight on an engine. Many different ways to skin a cat. You blower looks really cool also,,,all of the parts look very good,it should really fly. Good luck. Tommy
In the second pic, it's in the position where the rod bolts usually hit the block, bellow the pan rail. It looks as though the block has not been clearanced at all. I've built several 383's, and always had to grind the block for rod clearance. If you rotated the crank the opposite way(rod on the other side of the block), you may find that it will turn until the rod hits again. If that is not the problem, take the crank/rod/piston out of the block, and re-install the rod/piston on the crank. You'll be able to get a closer look at where exactly the piston is contacting the counterweight.
Are you sure your pistons are hitting the crank? Looks like the rods are hitting the oil pan rail. I had my block "Stroker Clearanced" at the machine shop and still had to do some carefull grinding to get clearance. I also had to grind some clearance up inside the block at #7 & 8. Make sure your cam clears the rod bolts too. I used a tie-wrap as a way to measure for clearance, if it clears that it should be good, about .050" Here is some pics, the first one is a reference pic found on-line, the second one is what I had to deal with
Easy enough to find out if it's definately the pistons that are hitting. Take everything out of the block & bolt the rods to the crank. Check the rotating assembly outside of the block & you'll see what needs to be done. If it's a very small amount of contact I'd relieve the pistons but only once you make absolutely sure your pistons aren't designed to be used with 6.0" rods. If they are your deck height is gonna be off.
The only problem I know of on the 383 is a couple rods "may" hit the cam. That being said, I think you have the wrong crank, rod , or piston in there
Hey man, are'nt those piston upside down? Not sure, but I think the quench goes up. Edit; I see now the block is rolled, tried to delete but could'nt.
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