340 High Compression Pistons

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I just need you veteran Moparians to help me with the process I have never had to order custom pistons and live by Clint Eastwoods ( Sacred Words )
(A MANS GOT TO KNOW HIS LIMITATIONS)
With all the discussions about my 340 Rpm heads and how they are different because of how Edelbrock relieved some of the combustion chambers I want to make dam sure they are ordered correct the first time if u know what I mean .
This is my inventory
Oem 1969 340 block will need to boring to 4.080 ( 40 over )
Scat H beam stock lenth 6.123 rods
Stock steel crank
Block will need decking so stock deck height has changed
Running the Edelbrock RPM 340 heads which are 65 cc chambers ****
Hopefully this is enough info for u veterans to help me obtain a lite set of pistons with atleast 11.50.1 compression Im not sure With the alum heads if Race fuel will be manditory ???
If not and forum thinks I can move up to 12.1
I certainly will ok forum guide me in the right direction , the guys at Cambell performance have been really helpful so I might order thru them the pistons are almost $1000 shipped thanks again - Chris.

20180415_101638.jpg
 
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1Badcolt said:
Odering custom set net week from Cambell performance they have responded to every email I sent unlike some other piston manufacturers.
Click to expand...
Im looking at the same build with a .030 block. I need to rebuild my 340 that's got a cracked x head and damaged trw L2322 .030 pistons no longer avail. If I go the eddy heads, I lose my 12.6:1 compression because I can't find replacement trw's and cant find anything but lower compression flat tops to match the eddys. What are Campbell able to offer?
Thanks
 
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moparodbuster said:
What exactly are they making for you, are they copying an old piston design that's no longer available? How did you describe what you wanted... by spec's of old pieces or did you need to send them something to copy? I need to rebuild my 340 that's got cracked x head and damaged trw L2322 .030 pistons no longer avail.

Thanks
Click to expand...

Im going to have custom pistons made that approach 12.1 compression
I have the money to avoid the heavy slugs we were once forced to run .
I was going to use the older style domes but the weight is a concern to me I even asked if some were for sale but Im definitely going with lite weight
JE
Ross
Diamond
Brand pistons.
 
1Badcolt said:
Im going to have custom pistons made that approach 12.1 compression
I have the money to avoid the heavy slugs we were once forced to run .
I was going to use the older style domes but the weight is a concern to me I even asked if some were for sale but Im definitely going with lite weight
JE
Ross
Diamond
Brand pistons.
Click to expand...
Yup, I need to do exactly the same thing. I didn't know any of those piston mfg's made a similarly high compression piston to work with the eddys. Why did you decide on the Campbell customs and not either of the others you mentioned? What were they offering?
 
moparodbuster said:
Yup, I need to do exactly the same thing. I didn't know any of those piston mfg's made a similarly high compression piston to work with the eddys. Why did you decide on the Campbell customs and not either of the others you mentioned? What were they offering?
Click to expand...

I called many piston manufacturers and
Cambells and Ross were the only ones who would give me the time of day
U should plan on about $1000 shipped for a good set.
 
1Badcolt said:
I called many piston manufacturers and
Cambells and Ross were the only ones who would give me the time of day
U should plan on about $1000 shipped for a good set.
Click to expand...


Go online and check this jewel out I like the specs compression etc even @ 65 cc it still yields impressive ccompression unfortunately its for a 4.0 stroke LA unlike our 3.31.

Screenshot_2018-07-07-12-27-37.png
 
moparodbuster said:
Yup, I need to do exactly the same thing. I didn't know any of those piston mfg's made a similarly high compression piston to work with the eddys. Why did you decide on the Campbell customs and not either of the others you mentioned? What were they offering?
Click to expand...

Screenshot_2018-07-07-16-10-49.png
 
moparodbuster said:
Im looking at the same build with a .030 block. I need to rebuild my 340 that's got a cracked x head and damaged trw L2322 .030 pistons no longer avail. If I go the eddy heads, I lose my 12.6:1 compression because I can't find replacement trw's and cant find anything but lower compression flat tops to match the eddys. What are Campbell able to offer?
Thanks
Click to expand...
Hey Hoss
I just happen to have 2 heads that need a new home they have 2.02 set up
PM me thanks Chris .

20180527_154816.jpg
 
1badcolt, the question of how much compression you can run has a lot to do with the cam.... which has to do with the use. Can you give us more detail on what you will be doing with the engine/car? Is the cam selected?

IIRC, those recesses milled in the Edelbrock heads are listed as .060" deep. The volume in the very short cylinder shape of that milled recess is about 13 cc's so that leaves 52 cc's in the part of the 60179 Edelbrock chamber above the milled recess. (You could CC that part of the chamber to verify; I would.)

Let's see what can be done with a flat top.
  • Let's make it easy by starting with a thin Cometic head gasket at .027" thick, which is the minimum they list in their catalog for the MLS types. (Warning: I can't recall if the Edelbrocks have a surface finish proper for the Cometics MLS...needs answering.)
  • So we can compute this like a closed chamber head with a 52 cc volume, with a 'head gasket' of .087" thick. (.060" in the milled head recess + .027" actual gasket)
  • And let's further say that the Piston CH height is set as part of the custom setup and the decking and the rod and stroke to push the piston up about .035" from the bottom of the open chamber part of the head. That will give you quench effect.... that = good for high compression. The flat top of the piston would be .087 - .035 = .052" above deck.
  • Stroke is the stock 3.31" with a 4.08" bore.
  • Assume a head gasket bore diameter of 4.125" to keep the crevice down the side as tight as practical. (IIRC, that is a standard bore size number from Cometic. 4.100" would be even tighter.)
  • There is still a crevice between the piston top and sides of the milled recess. I don't know the exact diameter for that recess, but have assumed it is 4.140". A measurement of the diameter of that recess would be helpful.
  • Finally, let use the fairly typical 5 cc eyebrows. (Dunno what those you show actually are.)

Well, lookit that..... 11.92:1 SCR for those conditions.

Now whether the crevice down the side of the piston in the head and gasket is any issue, I don't know. Maybe others can comment. But it is gonna be a pretty small volume, around 1/3 to 1/2 of a cc unless that milled recess is a really huge diameter... and it is extremely short and < 1/2 of the approximately 1 cc volume of the tall crevice down to the top ring between the side of the piston and the cylinder wall. (Did I ask you measure that recess diameter yet?)

The CH of such a flat top piston will depend on the deck height. If you milled so that the deck is 9.585", then the CH needed to put the flat top of the piston .052" above deck is (9.585 + .052) - (3.31/2 + 6.123) = 1.859".

Note that this is working for a flat top BECAUSE of that milled recess. It makes things so you can pop the piston up above deck a considerable distance, and take advantage of that small 52 cc volume in the chamber above the milled recess. This may be of interest to moparodbuster as he sorts things out.
 
nm9stheham said:
1badcolt, the question of how much compression you can run has a lot to do with the cam.... which has to do with the use. Can you give us more detail on what you will be doing with the engine/car? Is the cam selected?

IIRC, those recesses milled in the Edelbrock heads are listed as .060" deep. The volume in the very short cylinder shape of that milled recess is about 13 cc's so that leaves 52 cc's in the part of the 60179 Edelbrock chamber above the milled recess. (You could CC that part of the chamber to verify; I would.)

Let's see what can be done with a flat top.
  • Let's make it easy by starting with a thin Cometic head gasket at .027" thick, which is the minimum they list in their catalog for the MLS types. (Warning: I can't recall if the Edelbrocks have a surface finish proper for the Cometics MLS...needs answering.)
  • So we can compute this like a closed chamber head with a 52 cc volume, with a 'head gasket' of .087" thick. (.060" in the milled head recess + .027" actual gasket)
  • And let's further say that the Piston CH height is set as part of the custom setup and the decking and the rod and stroke to push the piston up about .035" from the bottom of the open chamber part of the head. That will give you quench effect.... that = good for high compression. The flat top of the piston would be .087 - .035 = .052" above deck.
  • Stroke is the stock 3.31" with a 4.08" bore.
  • Assume a head gasket bore diameter of 4.125" to keep the crevice down the side as tight as practical. (IIRC, that is a standard bore size number from Cometic. 4.100" would be even tighter.)
  • There is still a crevice between the piston top and sides of the milled recess. I don't know the exact diameter for that recess, but have assumed it is 4.140". A measurement of the diameter of that recess would be helpful.
  • Finally, let use the fairly typical 5 cc eyebrows. (Dunno what those you show actually are.)

Well, lookit that..... 11.92:1 SCR for those conditions.

Now whether the crevice down the side of the piston in the head and gasket is any issue, I don't know. Maybe others can comment. But it is gonna be a pretty small volume, around 1/3 to 1/2 of a cc unless that milled recess is a really huge diameter... and it is extremely short and < 1/2 of the approximately 1 cc volume of the tall crevice down to the top ring between the side of the piston and the cylinder wall. (Did I ask you measure that recess diameter yet?)

The CH of such a flat top piston will depend on the deck height. If you milled so that the deck is 9.585", then the CH needed to put the flat top of the piston .052" above deck is (9.585 + .052) - (3.31/2 + 6.123) = 1.859".

Note that this is working for a flat top BECAUSE of that milled recess. It makes things so you can pop the piston up above deck a considerable distance, and take advantage of that small 52 cc volume in the chamber above the milled recess. This may be of interest to moparodbuster as he sorts things out.
Click to expand...
 
1951 Henry J [ Gasser ] building for Southeastern Gassers Association
This group has strict rules for appearance of car engine etc and weight breaks are given for certain intakes and Hilborn set-ups ,
Only certain cyl heads are allowed for each engine type .
 
I purchased the heads new in the box ready to run for less than half of retain price that's why im running them and will spend about $1500 having them ported and tunnel ram port matched and comp valve job performed . Im not running this on the street this will be used at the track only , cam is a Crower solid lifter flat tappet
544/558
304/310 or duration @ .050" I 250 E 254
 
nm9stheham said:
1badcolt, the question of how much compression you can run has a lot to do with the cam.... which has to do with the use. Can you give us more detail on what you will be doing with the engine/car? Is the cam selected?

IIRC, those recesses milled in the Edelbrock heads are listed as .060" deep. The volume in the very short cylinder shape of that milled recess is about 13 cc's so that leaves 52 cc's in the part of the 60179 Edelbrock chamber above the milled recess. (You could CC that part of the chamber to verify; I would.)

Let's see what can be done with a flat top.
  • Let's make it easy by starting with a thin Cometic head gasket at .027" thick, which is the minimum they list in their catalog for the MLS types. (Warning: I can't recall if the Edelbrocks have a surface finish proper for the Cometics MLS...needs answering.)
  • So we can compute this like a closed chamber head with a 52 cc volume, with a 'head gasket' of .087" thick. (.060" in the milled head recess + .027" actual gasket)
  • And let's further say that the Piston CH height is set as part of the custom setup and the decking and the rod and stroke to push the piston up about .035" from the bottom of the open chamber part of the head. That will give you quench effect.... that = good for high compression. The flat top of the piston would be .087 - .035 = .052" above deck.
  • Stroke is the stock 3.31" with a 4.08" bore.
  • Assume a head gasket bore diameter of 4.125" to keep the crevice down the side as tight as practical. (IIRC, that is a standard bore size number from Cometic. 4.100" would be even tighter.)
  • There is still a crevice between the piston top and sides of the milled recess. I don't know the exact diameter for that recess, but have assumed it is 4.140". A measurement of the diameter of that recess would be helpful.
  • Finally, let use the fairly typical 5 cc eyebrows. (Dunno what those you show actually are.)

Well, lookit that..... 11.92:1 SCR for those conditions.

Now whether the crevice down the side of the piston in the head and gasket is any issue, I don't know. Maybe others can comment. But it is gonna be a pretty small volume, around 1/3 to 1/2 of a cc unless that milled recess is a really huge diameter... and it is extremely short and < 1/2 of the approximately 1 cc volume of the tall crevice down to the top ring between the side of the piston and the cylinder wall. (Did I ask you measure that recess diameter yet?)

The CH of such a flat top piston will depend on the deck height. If you milled so that the deck is 9.585", then the CH needed to put the flat top of the piston .052" above deck is (9.585 + .052) - (3.31/2 + 6.123) = 1.859".

Note that this is working for a flat top BECAUSE of that milled recess. It makes things so you can pop the piston up above deck a considerable distance, and take advantage of that small 52 cc volume in the chamber above the milled recess. This may be of interest to moparodbuster as he sorts things out.
Click to expand...


Very detailed I printed it out and going to study it thank you very much for your time and efforts with this subject .
 
You're very welcome. I hope you have fun in the SEGA... it looks like a blast! The 3 classes makes it nice. And the high SCR makes sense now... a big cam and high revs for pure HP on the strip. These recessed heads may have actually worked out for you in this high SCR use.

Let me know if you have any Q's or find anything odd... I've been over this a coupla times now, looking for any mistakes. And, be aware that if you wanted to use a taller head gasket, like a Felpro 1008, then the .012" increase in head gasket thickness can be matched by a CH increase of .012" to keep at the same SCR. I just figured that limiting crevice volume is a good thing. But the 1008 may make things easier in terms of head and block surface finish, and the 1008's would be cheaper too.
 
BTW, have you considered using standard flat top pistons and just milling the deck to the get the pistons enough above deck to protrude through the head gasket and into the milled part of the chamber in the same fashion as described above? As an example, KB243's would require just another .020" of block milling (.035" total off of standard deck height) to get them .053" above the deck. And there are probably others that would work. The same could be done for any standard CH 340 piston.

And BTW, I see that the JE piston like you linked above has 6.8 cc eyebrow volume. So the SCR will drop around.2 if that eyebrow volume is used. And putting a chamfer on the edge of any piston top would be wise in this type of setup IMHO, to avoid a sharp edge that will get hotter than the rest of the piston crown.
 
1Badcolt dont forget to CC those heads,nomather what direction you take you have to measure everything more than once.
I think those chambers will be alitle bigger than they are supposed to be according to catalog,especialy after porting,they are most certainly going to be relieved alitle in the chambers as part of the porting.
Never ever go by the numbers in the catalog measure everything atleast twice to make sure :)
 
nm9stheham said:
BTW, have you considered using standard flat top pistons and just milling the deck to the get the pistons enough above deck to protrude through the head gasket and into the milled part of the chamber in the same fashion as described above? As an example, KB243's would require just another .020" of block milling (.035" total off of standard deck height) to get them .053" above the deck. And there are probably others that would work. The same could be done for any standard CH 340 piston.

And BTW, I see that the JE piston like you linked above has 6.8 cc eyebrow volume. So the SCR will drop around.2 if that eyebrow volume is used. And putting a chamfer on the edge of any piston top would be wise in this type of setup IMHO, to avoid a sharp edge that will get hotter than the rest of the piston crown.
Click to expand...


Flattops can work Im just trying to obtain some that are less weight than the traditional ( TRW / SEALED POWER UNITS ) not that they are bad but the less weight the better for my situation.
With you footnotes or comments u mentioned I could get compression high enough potentially with the lighter weight units ???

Screenshot_2018-07-03-17-48-44.png
 
1Badcolt said:
Flattops can work Im just trying to obtain some that are less weight than the traditional ( TRW / SEALED POWER UNITS ) not that they are bad but the less weight the better for my situation.
With you footnotes or comments u mentioned I could get compression high enough potentially with the lighter weight units ???

View attachment 1715196123
Click to expand...
These are 4.080 bore and 10.1 with a 65 cc chamber !!!
 
Yeah I looked at the SRP's and the CH is .036" lower than a standard 340 piston so that is not promising. Same goes for the Ross pistons. I'll keep looking. BTW, do you have to use stock rods and crank?

Some lighter flattops that would work are the KB 243's; usable off-the-shelf. The 1.840" CH is the same as the stock 340 pistons. Mill the block's deck to a deck height of 9.565"; IIRC that is quite safe but check that out. Then the KB243 pistons will stick up .053" above the deck and with the .027" head gasket, you will be at the 11.8-11.9 SCR range. The KB243 weight of 720 grams piston + pin weight is a lot lighter than the stock which is around 873 grams piston + pin. You'll take weight off the crank to balance these.
These KB's are hypereutectics, not forged, so keep that in mind.

And Hughes lists some Icon FHR's that would work and are forged, but they list a piston weight of 724 grams. I cannot say if they are listing piston only or piston + pin weight. These are not in the online catalog so that weight number that bears checking. (I think 70aarcuda knows but a quick call would do it.) The eyebrows are 7 cc's so the CR will be a few tenths lower.

BTW, I recall another piston MFR being mentioned that does custom variations for a lot less than $1000. Dang, wish I could remember the name.
 
The man heard his name called LOL... A ton cheaper, and I bet even with the block decked, still a bunch cheaper.
 
nm9stheham said:
Yeah I looked at the SRP's and the CH is .036" lower than a standard 340 piston so that is not promising. Same goes for the Ross pistons. I'll keep looking. BTW, do you have to use stock rods and crank?

Some lighter flattops that would work are the KB 243's; usable off-the-shelf. The 1.840" CH is the same as the stock 340 pistons. Mill the block's deck to a deck height of 9.565"; IIRC that is quite safe but check that out. Then the KB243 pistons will stick up .053" above the deck and with the .027" head gasket, you will be at the 11.8-11.9 SCR range. The KB243 weight of 720 grams piston + pin weight is a lot lighter than the stock which is around 873 grams piston + pin. You'll take weight off the crank to balance these.
These KB's are hypereutectics, not forged, so keep that in mind.

And Hughes lists some Icon FHR's that would work and are forged, but they list a piston weight of 724 grams. I cannot say if they are listing piston only or piston + pin weight. These are not in the online catalog so that weight number that bears checking. (I think 70aarcuda knows but a quick call would do it.) The eyebrows are 7 cc's so the CR will be a few tenths lower.

BTW, I recall another piston MFR being mentioned that does custom variations for a lot less than $1000. Dang, wish I could remember the name.
Click to expand...


Thank you - are KB243 pistons forged ??
 
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