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BBC 427 Pistons

General engine tech -- Drag Racing to Circle Track

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vht
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BBC 427 Pistons

Post by vht »

Building a 427, 4.280 bore, pump gas. I have alum heads with a 122 chamber and looking for pistons. I have a set of H beam 6.135 rods bushed for floating pins. I don't want to spend a fortune so I was looking at SRP pistons also checked out Icon but my guy that does the machine work said he doesn't like Icon. Looks like it's down to the 212133 piston and with the 30 cc dome it comes out to 9.77 to 1. Thats assuming a 0 deck height and a felpro .039 gasket. The block has been align honed and decked. Any ideas on getting it to around 10.5 to 1? Mill the new heads or is there a thinner head gasket? Not having checked deck clearance yet, I'd almost bet the piston will be .005 to .008 in the hole if not more so once I can check that I'll know more but with the cam I got and alum heads, I can get by on 93 octane and 10.5. May not be worth worrying about but I'd like for this build to run pretty decent.
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Re: BBC 427 Pistons

Post by BillK »

Have you looked at Diamond or Wiseco ? I hate milling heads to get more compression. I dont know what guys are getting in your area to mill more than a light cut but I would probably be charging you at least $250 for the pair and that doesnt include correcting the intake. $250 added to your piston budget instead would let you get a custom piston with whatever dome you want. And you dont have to take a chance on intake manifold fitting issues.

Thats my 2 cents worth :)
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Re: BBC 427 Pistons

Post by rustbucket79 »

IC988 Icon pistons look to fit the bill. 38 cc dome

“I don’t like them” is pretty vague, we’ve used dozens of sets of both the budget and premium forged icon pistons with great results.
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Re: BBC 427 Pistons

Post by mag2555 »

Is this a resto where you want to keep the overbore to a minimum?

If not then open the wallet up bigger and go for the custom Pistons in a bigger Bore size, then you can save the cost of milling the heads or block deck and yet unshroud the chambers for higher power at the same time.
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Re: BBC 427 Pistons

Post by F-BIRD'88 »

KB FHR #9917 forged 427 piston solid 41CC dome.
Tell your machinist to stick to machining.
He's not a piston design engineer.
These are fine and fit the bill.
cr with .008" deck clearance .038" gasket is 10.61:1.

You must clearance check the piston dome to head combustion chamber clearance on this. Slight clearance trimming of the dome may be required.
Its a solid dome have at it. This also reduces the dome volume a little bit to tame the compression ratio...
10.50 ish)
Its a solid dome , you can trim it for clearance and flat mill the top of the dome all you want to get the CR correct.

You don't want to build it "to get by" nor cam it in an attempt to "get by" on pump gas.. Adjust the compression ratio for the job and fuel . 10:1 is plenty...
The worlds best machinist approved super piston will not stand up to excessive compression ratio on pump gas.
Making the final CR right for reliable 93 pump gas operation is what you want to do.
Last edited by F-BIRD'88 on Fri Nov 13, 2020 8:16 am, edited 3 times in total.
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Re: BBC 427 Pistons

Post by GuysMonteSS »

Have you checked the RaceTec/AutoTec line of pistons ??
The AutoTec are the street/strip 4032 version.They will do a custom or semi custom upon request.
Mike Lewis got me a set for my 513 BBC,semi custom,pin height where he wanted it and a dome from another model.
The price was good and they make a nice piston.
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Re: BBC 427 Pistons

Post by F-BIRD'88 »

Milling the heads and block decking both REDUCE piston to Valve clearance.. You want avoid that on BB Chevys.
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Re: BBC 427 Pistons

Post by cpmotors »

F-BIRD'88 wrote: Fri Nov 13, 2020 7:58 am Milling the heads and block decking both REDUCE piston to Valve clearance.. You want avoid that on BB Chevys.
Where do you come up with this stuff? Neither is an issue here, especially in a mild pump gas build.
You couldn't pay me to use an Icon/KB piston.

OP, RaceTec can easily do a custom in AutoTec line, I've done it a couple of times and for a reasonable price.
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Re: BBC 427 Pistons

Post by vht »

I'll check out the RaceTec pistons, I hadn't looked at them. I've never used Icon but it seems some people love them and some people hate them. I've seen problems with KB pistons but don't know if it was the piston at fault or the builder.
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Re: BBC 427 Pistons

Post by vht »

The IC766 Icon looks good, 37cc dome, the IC988 has the 38cc dome. You could play with head gasket thickness and get it where you want on comp. I couldn't find anything in the RaceTec, AutoTec line that was off the shelf pistons.
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Re: BBC 427 Pistons

Post by rustbucket79 »

The KB hypereutectic pistons (in a perfect world are fine) are fragile and break like glass at the first sign of detonation.

The icon lines of forged pistons are perfectly fine. For a typical street engine, you’ll never know what pistons are in the engine once it’s built, and will likely forget what brand they are after the third year. Find something that accomplishes your goal, without the need to machine the pistons or heads. Mahle/Icon/wiseco/SRP/whatever.
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Re: BBC 427 Pistons

Post by vht »

I figured I'd just go with the Icon's. It was said they are solid dome but they're hollow. A 37 or 38 dome will work fine, I think my heads are 122. When the machine shop gets them in, I'm going to check them before I order pistons.
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Re: BBC 427 Pistons

Post by Mark O'Neal »

cpmotors wrote: Fri Nov 13, 2020 2:50 pm
F-BIRD'88 wrote: Fri Nov 13, 2020 7:58 am Milling the heads and block decking both REDUCE piston to Valve clearance.. You want avoid that on BB Chevys.
Where do you come up with this stuff? Neither is an issue here, especially in a mild pump gas build.
You couldn't pay me to use an Icon/KB piston.

OP, RaceTec can easily do a custom in AutoTec line, I've done it a couple of times and for a reasonable price.
He can do an Autotec with a 38.1cc dome with two changes (bore and C/H) for less.
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Re: BBC 427 Pistons

Post by F-BIRD'88 »

If when you are going to mill the heads, mock it all up FIRST and check VTP clearance and dome to chamber clearance too. Find the close spots.
Milling the heads will REDUCE both these critical build clearances on your 427.
Minor clearancing of the dome edges, chamber edges may be required.
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Re: BBC 427 Pistons

Post by 69427 »

1.28 5.96 @ 115 @ #3250 Better in 2019
427 BBC by S&S Speed Center, AFD, Enderle MFI by Spud Miller
Sepanek Racing T400, Dynamic converter, Autoweld, Santhuff, Smith Racecraft,
Dick Fords Body Shop, Trackside Products,
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