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  #181 (permalink)  
Old 04-11-2011, 05:38 AM
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Bummer

Yes, I've machined the .083" deep 5.565" rod dish forged piston down to a flat top for use with 5.7" rods. Sounds like you just had bad luck, a block with a thin wall when taken more than .030" oversize. This is one reason I always short fill a block with block filler, it will help avoid that cracking problem.

A good shop could sleeve your cracked hole, then you could add a short fill to stabilize things a bit more and be back in business rather easily.

If you have another good block, I would not bore it to .040" over just to fit the 6 or 7 good pistons you have, best not to bore a 400 any more than you absolutely have too. If it is usable at .020" over I would leave it at that size and just buy new pistons, KB/ICON forged can be had for a decent price. You'll also have a lot more room for more lift with a real 5.7" rod piston rather than the cut down and re-eyebrowed short rod pistons.

I have only done the cut down piston deal with solid flat tappet cams, never with rollers because I know how little piston to valve clearance there is with the cut down piston.

I wouldn't even consider a hyper piston, even if you gave me a free set. Been there, seen how easy they break, cost me a 400 block when I was dumb enough to believe Keith Blacks hype and put a second set in after the first set broke(.030", then .040"). Not worth the cost savings. Nothing but forged for me.

There is a decent set of used TRW Forged L2477F.030 5.7" rod small (.140" tall 6.5cc)solid dome 400 pistons on Ebay right now for less then $200. You could keep the dome or mill it into a flat top. I've used these pistons several times. Listed as a 12.7-1 compression piston by TRW, will make 13.3-1 with a zero decked block and 64cc head. http://cgi.ebay.com/ebaymotors/Seale...item20b86a977e You'll have a lot more piston to valve clearance with these.

If you do decide the budget means using the pistons you have and just getting two more, and boring the 817 block to .040" over, I would definately consider it mandatory to short fill the block. Wouldn't even consider not filling it at any bore size, really. Short fill to the bottom 1/3 of the side freeze plugs is perfectly streetable, no worry about heat if you have a good radiator and pump.

Epoxy to fix port break-throughs when porting is common, not a problem. I've got a set of Dart Sportsmans that are epoxied on 3 or 4 pushrod pinch areas that were epoxied in 1992 and are still being used by a friend of mine without problem.

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  #182 (permalink)  
Old 04-12-2011, 12:07 AM
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well i got the 396 in it just gotta button up exhaust plug wires and change carbs tomorrow I always ran a stock converter with this motor this time i left the hughes converter in it im curious how it is gonna launch and what it will run should find out friday if the damn weather stays nice enough and my girlfriend has to go to salem before the 21st of the month so ill be getting the dart heads before then and it will save me the 100 dollars in fuel so i can put that back towards getting the small block going again if thats what i decide to do

i have an option here i have a complete 427 that i broke a piston on years ago and i still have that motor so i could sell all the small block parts and start putting that together for the truck I would really like about 12.5-1 compression and a comparable solid roller cam to what was in the 409 something big and make this just a trailer queen and RARELY drive it on the street but gotta figure out whats gonna be easiest right now since im out of work
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Old 04-12-2011, 01:41 AM
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i think this time when i put the 400 together i will buy these pistons are they decent
http://www.summitracing.com/parts/UEM-IC752-040/

they will give me 11.5-1 compression with the dart heads and i believe adequate valve clearance

what should be the clearance between the valves and piston

I heard it was different for intake and exhaust?
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  #184 (permalink)  
Old 04-12-2011, 01:50 AM
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Cam companies will tell you .100" intake/.100" exhaust to be safe, but I've run .060" IN/.075" EX without problem, and have read of quite a few running there or even tighter on the intake(.040"). Intake valve as it opens is chasing the piston down the bore, piston is moving away, so it rarely can get hit, but the exhaust is being chased by the piston as the valve is closing, much easier for it to get hit if the valvespring can't keep it in control, so that is why the exhaust needs more clearance.
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Old 04-12-2011, 09:50 PM
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I got the big block in it and running I love this motor it runs so good and is my ole faithful I always have her to fall back on
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Old 04-13-2011, 03:15 PM
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I found this set of pistons on my local craigslist

http://medford.craigslist.org/pts/2323191909.html

what rods would i have to use or do you HAVE to use a 3.5 stroke to run these pistons I tried to search but they must be an old style piston cause i cant find much on them and summit doesnt have the their site just says out of stock here is another piston that is very similar
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  #187 (permalink)  
Old 04-13-2011, 06:38 PM
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L2311F is an 1.560" compression height piston. Possible combinations are:

400 block, 3.48" stroke 350 crank/aftermarket 3.50" stroke crank and a 5.7" rod to make a 377/379 cube engine at .030" overbore.

400 block, 3.75" stock 400 stroke and the short 5.565" 400 rods to make a 406 at .030" overbore.

Also possible is 400 block, 3.25" stroke 327 crank and 5.85" aftermarket rods to make a 351 cube engine at .030" overbore...but it is very tight at a total parts stack-up of 9.035" in the stock 9.025" block, it will require extra thickness on the head gasket to prevent the piston from hitting the head.

It is a very heavy piston, very old school.
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  #188 (permalink)  
Old 04-14-2011, 10:27 PM
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I think im just gonna save and buy a complete rotating assy a 421" most likely I think ill be close to 615 hp with the new dart heads what do you think?

i just read a whole bunch on sleeving blocks. it sounds like they are not suggested for over 500 horsepower but neither is a gm 400 block so im gonna have it done anyway . and use it I have the other block but this one is a cheap fix i figure ill wait till i actually need the 817 casting

I borrowed a sonic tester and tested a dart block and both my blocks kinda interesting the thinnest spot i found was in my 509 cylinder 6 was .172 (the one that has the crack) next was the 817 block also cylinder 6 was .179 the dart block is a BRAND NEW 4.125 bore 400 main and its thinnes spot i found was .292 and they guarantee them to be .200 at .060

wich tells me my blocks are not that thin and makes me wonder why my block is cracked in the cylinder. maybe it detonated and broke the ring lan and that cracked the cylinder. I dont know what the hell happend

I honestly never ever heard it detonate though
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  #189 (permalink)  
Old 04-22-2011, 10:43 AM
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got my new to me dart heads yesterday I drove 230 miles to the guys house to trade and i gave him 400 dollars. I think my heads were just about wore out i set the head surface flat upside down and used a syringe to check how many cc the combustion chambers were and after having them surfaced and having to take .010" they came out to just about 57cc's

im really curious if you think my desktop dyno is somewhere close when it says 615 hp with these heads ?
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  #190 (permalink)  
Old 04-22-2011, 11:45 PM
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well my first pass was the best it went 14.5@ 90mph with a 2.0 60' and it mostly went down hill from there still went about 89-90 mph
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  #191 (permalink)  
Old 04-23-2011, 07:47 PM
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http://www.wallaceracing.com/hpcalculatorquarter.php
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Old 05-07-2011, 10:42 PM
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I tried to race the truck again with the big block on friday but we got rained out AGAIN!!

well the block should be done at the machine shop on monday i already got my new piston I decided im gonna machine it myself to match the others and i will balance the new piston and rod to match the others im confident in myself to do this work so all i got left is

head gaskets

rod and main bearings

rings

and i wanna try and find a good used 1050 dominator to go on top of it

I hope to have it done and in the truck by the first of june
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  #193 (permalink)  
Old 05-13-2011, 03:44 AM
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well i got the motor back together today Im gonna put it in the truck tomorrow and race it tomorrow night will update when all done with races
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  #194 (permalink)  
Old 05-15-2011, 09:17 PM
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well i didnt make it friday it had a horrible intake gasket leak and the valve covers were leaking really bad cause the bolts bottomed out in the head then my mini starter took a ****

but i finished it up today and its running really lean then and now i think the trigger wire to the starter shorted out and it melted the damn neutral safety wires off the shifter so i got a little work before I race friday I think were gonna put my buddys 1050 dominator on it and see how it runs
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  #195 (permalink)  
Old 05-16-2011, 11:18 AM
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about what size jet do you think i should have in this combo
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