I have a set pof pistons, .060 427 BBC, L2239N. They are brand new and I believe are 12.5 to 1 with a 106 cc head. Do you think the dome could be milled off these to make a set of flat tops? I bought a bunch of parts, nice set of square port closed chamber heads, set of H beam 6,135 rods and a std block. I'm installing a 6-71 with 2 Holley 4150 DP carbs. I haven't researched the gasket thickness but with flat tops the comp would be around 8.8, correct me if I'm wrong. I don't think the domes were hollow on the older TRW piston but I could be wrong on that too. If not, I'll go .030 and buy a dished piston, thanks
No way, buy the correct dish pistons. You have to figure final static compression ratio using all of the variables including deck height, gaskets, chamber volume, piston volume, bore, stroke, etc. etc. There is even a small amount of volume in piston clearance and ring land above and behind the top ring. The blower will raise the effective ratio even further depending on drive ratio and cam.
MOST TRW pistons are "solid dome", and if yours don't have evidence on the inside of the piston they're not solid dome, then you can mill them flat. TRW's were always known as 'heavy" pistons, because of the solid domes. I am Butch/56sedandelivery.
I have TRW/GM 11-1 forgings in a '70 LT-1 block that I cut to lower compression for a blower. I measured the depth inside the crown in relation to the pin height and knew I would have about 5/32" thickness. At the Nationals one year I questioned a Chevy engineer about what I planned to run and he said no problem if I kept the boost and timing realistic.
yeah, check the dome thickness. I would guess that flat tops with a blower with under 10 psi will be ok. I'm running open chamber L88 heads on my blown 427, with small domes, I calculated it to be around 8.5:1, I race on pump gas. but be sure you crunch the numbers to get it where you want it.
Domes on these are like .485" tall. You might shave them down a little but I don't think there ever going to be flat tops.
I remember TRW's being heavy. I'm going wednesday to pick all this stuff up. I don't have a crank yet, so I can go 454 or 427 depending on the piston I buy. I think I'll go with a .030 over dish and try to get my comp around 8 to 1. Wonder how much more I'd gain going to a 454? I never cared about the externally balanced anything, and this is my first blower deal.
do a 427, just because it sounds better..... I go a lot faster in my 427 equipped Chevy II than I did in my 454 equipped 55. Mostly because I lost a thousand pounds by going to the lighter car. In other words, it doesn't really matter.
Yep 427! The longer 454 stroke gives a few more cubes and a little more torque but the blower set up should provide extra low end torque any way. I do remember TRW pistons are in general heavier especially in the earlier sbc 283, 302, 327 which had a lot of compression height. I've been collecting parts for a future build. A blown SJ 331 using a short (1.25") 35o JE blower piston and Crower 6.125" Rods. On paper it should work but time will tell.
Where is a good place to buy a 396, 427 crank? GM or whatever, I've been searching and found a bunch of 4 or 4 1/4 stroke cranks, found 2 steel 427's on ebay that had been turned .030 and .040 for like $500!
I had an old cross drilled 396 crank, I think it went 020, it had spun a main in it's previous life. But I used the modern version of the TRW pistons with it, and ended up spending some coin to get it balanced...needed heavy metal. I probably would have gone with a custom piston if I had though about it more. Although is is neat that I'm going as quick as I am with a pretty much stock 427. Factory heads, crank, rods, block, stock replacement pistons, etc. I think I still have another steel 396 crank, but I have some plans for it...
I'd go with a scat or eagle cast crank. I've seen a way more steel,factory, crack where the cast seems to have more cushion.
Sell the pistons and buy the right ones. I am sure somebody wants a cheap high compression 427. Unless you can do the machining yourself or get a sweet deal they will probably charge you almost as much the pistons cost after you sell the domed ones. I have used those same pistons and they work really well with Edelbrock heads.
Squirrel, that is right, it is pretty neat. It's more like we used to do, I went 10.30's in my old 68 Camaro with TRW's and super unleaded with 104 octane booster. It was drag only at the time, but it weighed 2900. Gas was way better then too. I think I found a crank, std 6223 gm that my guy at the machine shop put back years ago. He's digging now to find it. I'll sell the pistons or swap them for something. Thanks for all the help.
hi Not sure what you mean by cushion. I will tell you if this was my build I would use the strongest crank available. That is a forged steel Chevrolet crank. They are much stronger than cast anything, and stronger than billet. Believe it or not even forged cranks will flex under very high load. Chevrolet developed these engines specifically for hard racing back in the 60's.
I chose Callies. I think the other two you mentioned have plenty of negative reviews to back up my decision and I built my 427 small block before it was trendy to go on the internet and badmouth mfgs because the buyer made the wrong choice.
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