BBC Advice Needed
Thread Starter
Melting Slicks
Joined: Mar 2006
Posts: 3,456
Likes: 102
From: Piedmont Va
St. Jude Donor '11-'12-'13,'19-'20
Good solid plan...keep the 049s.
3/8s rods with good rod bolts are fine. You can easily hold 600hp+ on 3/8” rods.
Just make sure to get the pistons sized correctly so your piston to wall clearance is tight....(since your block has already been bored and honed.)
You should have a nice combo....
3/8s rods with good rod bolts are fine. You can easily hold 600hp+ on 3/8” rods.
Just make sure to get the pistons sized correctly so your piston to wall clearance is tight....(since your block has already been bored and honed.)
You should have a nice combo....
Also, when you say to balance the new pistons, you are talking to match them to lowest weight, but the rotating assy would still be externally balanced?
Thanks for your assistance.
-pappy
Dr. Detroit
Joined: Mar 2012
Posts: 10,095
Likes: 4,025
From: New Braunfels Texas
Yes....as stated...keep the 049's.....put pistons and cam in this. Rebalance as needed.
As far as pistons go.....measure the bore exactly and pick pistons from that......KB's go in tight.....4032 alloy forged go in tighter than 2618 do......I.E. 4.280 bore BBC will have .005 for 4032 for piston to wall....2618 will have around .007......this is the difference between an SRP and a JE race piece.
Jebby
As far as pistons go.....measure the bore exactly and pick pistons from that......KB's go in tight.....4032 alloy forged go in tighter than 2618 do......I.E. 4.280 bore BBC will have .005 for 4032 for piston to wall....2618 will have around .007......this is the difference between an SRP and a JE race piece.
Jebby
Le Mans Master
Joined: May 2006
Posts: 9,993
Likes: 1,136
From: League City Tx
Yes....as stated...keep the 049's.....put pistons and cam in this. Rebalance as needed.
As far as pistons go.....measure the bore exactly and pick pistons from that......KB's go in tight.....4032 alloy forged go in tighter than 2618 do......I.E. 4.280 bore BBC will have .005 for 4032 for piston to wall....2618 will have around .007......this is the difference between an SRP and a JE race piece.
Jebby
As far as pistons go.....measure the bore exactly and pick pistons from that......KB's go in tight.....4032 alloy forged go in tighter than 2618 do......I.E. 4.280 bore BBC will have .005 for 4032 for piston to wall....2618 will have around .007......this is the difference between an SRP and a JE race piece.
Jebby
Yeah.... what he ^^^ said....
The closer to .005" you can stay, the less oil consumption and ring flutter there will be.
Last edited by ajrothm; Apr 9, 2018 at 04:26 PM.
Drifting
Joined: Aug 2004
Posts: 1,883
Likes: 124
From: Lubbock TX
Clearance should be built into the piston. If you have a block honed at 4.030, the piston should fit the bore with perfect clearance. If you go with KB Hypers, you'll need to pay particular attention to ring gaps.
I've used SpeedPro for years without issue, all the KB's I've messed with were bricks, way heavy.
I've used SpeedPro for years without issue, all the KB's I've messed with were bricks, way heavy.
Thread Starter
Melting Slicks
Joined: Mar 2006
Posts: 3,456
Likes: 102
From: Piedmont Va
St. Jude Donor '11-'12-'13,'19-'20
Ok, so I'm going with 30cc dome SpeedPro and .050 gasket, .035 deck for a result of 10.10:1 static and 7.8:1 dynamic and .085 quench. Sound good?
Thanks again for the help.
Thanks again for the help.
Le Mans Master
Joined: May 2006
Posts: 9,993
Likes: 1,136
From: League City Tx
How do you know what the deck height is gonna be?
If you are putting new pistons in it, you will be final honing the cylinders to size. At that point, you may as well zero deck the block. That will true everything up and get your quench back to an acceptable range of .038-.045" depending on the head gasket you use.
However with 30 cc domes, my logic may create a bit too much compression.
Normally you order pistons while machining the block so you know exactly which pistons you need.
Thread Starter
Melting Slicks
Joined: Mar 2006
Posts: 3,456
Likes: 102
From: Piedmont Va
St. Jude Donor '11-'12-'13,'19-'20
How do you know what the deck height is gonna be
If you are putting new pistons in it, you will be final honing the cylinders to size. At that point, you may as well zero deck the block. That will true everything up and get your quench back to an acceptable range of .038-.045" depending on the head gasket you use.
However with 30 cc domes, my logic may create a bit too much compression.
Normally you order pistons while machining the block so you know exactly which pistons you need.
If you are putting new pistons in it, you will be final honing the cylinders to size. At that point, you may as well zero deck the block. That will true everything up and get your quench back to an acceptable range of .038-.045" depending on the head gasket you use.
However with 30 cc domes, my logic may create a bit too much compression.
Normally you order pistons while machining the block so you know exactly which pistons you need.
Thanks
The block has never been decked and the .035 was measured. The block has already been bored and I'm just planning to order a set of Speed Pros .030 from Summit and place on a best fit basis. I'm not planning on taking the crank out of it.
So I guess my question at this point is .085 too much quench? Will it cause any issues?
Last edited by CheezMoe; Apr 10, 2018 at 10:51 PM.
Le Mans Master
Joined: Apr 2001
Posts: 5,941
Likes: 281
From: Was New Orleans but swam to Baton Rouge LA
Cruise-In IX Veteran
Edit: Ok I figured out that .085 quench is way too much. So if the deck is indeed .035 with the new pistons, can I get away with like a .010 head gasket? ...or should I plan to bite the bullet at that point?
Thanks
The block has never been decked and the .035 was measured. The block has already been bored and I'm just planning to order a set of Speed Pros .030 from Summit and place on a best fit basis. I'm not planning on taking the crank out of it.
So I guess my question at this point is .085 too much quench? Will it cause any issues?
Thanks
The block has never been decked and the .035 was measured. The block has already been bored and I'm just planning to order a set of Speed Pros .030 from Summit and place on a best fit basis. I'm not planning on taking the crank out of it.
So I guess my question at this point is .085 too much quench? Will it cause any issues?
i should also add 0.035 seems high for a deck height. Factory pistons are normally only 0.020 in the hole. The pistons you have now P5047 comes back to an Enginetech piston. They state their pistons have a lower compression height by 0.010-0.020 to help with blocks that have been decked. That is why what you have measured now is so deep in the hole. When you replace the pistons you will need a new measurement.
Last edited by Sigforty; Apr 10, 2018 at 11:45 PM.
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Also, some pistons RAISE the compression height to get closer to zero deck without taking much or any off reg deck surface. +.010 is common. And boy would that compression have been low with those pistons and chambers.