engine build
06-20-2013, 11:44 PM
#1
Advanced
Thread Starter
Member Since: Apr 2012
Posts: 52
Likes: 0
Received 0 Likes
on
0 Posts
engine build
hi there im doing an engine build on a c4. we've ripped the crossfire out after having so many problems with what we though to be the fuel injection. after ripping the heads off and realizing that none of the valves would seat we decided to redo the heads. ceramic coat the valve covers, do a carb swap port and polish the intake manifold and ceramic coat it aswell as port and polish the heads. i know the heads are the 76cc cast iron heads that came stock with the original motor. we've sent them out to be planed/decked 0.005 to get the quench down a bit aswell as going ahead to get a 0.015 head gasket. from what ive been reading the motor has about 0.025 clearance without a headgasket. taking 5 off that leaves us with 0.020 and 0.015 head gaskets that should leave as at the perfect quench with not too high of a compression ratio. the motor has been bored 0.030 over and i beleive that it has a dish piston in there. i was using a calculation of 4cc's for the dish pistons but im not quite sure. so im looking for a bit of insight on that. the other thing im unsure of is deck clearance. how much does the stock motor have? http://www.summitracing.com/expertad...ion-calculator
bore 4.030
stroke 3.48
78cc cylinder head volume (-1cc for decking and +3 cc for headgasket)
4cc effective dome volume
zero deck clearance
0.015 compressed headgasket thickness
8 cyl.
coming out to around 9.6:1 so i had the questions of stock deck clearance average dome piston cc's if the calculations im using are correct. and if there are any other ideas for the top end build that would be great
bore 4.030
stroke 3.48
78cc cylinder head volume (-1cc for decking and +3 cc for headgasket)
4cc effective dome volume
zero deck clearance
0.015 compressed headgasket thickness
8 cyl.
coming out to around 9.6:1 so i had the questions of stock deck clearance average dome piston cc's if the calculations im using are correct. and if there are any other ideas for the top end build that would be great
06-21-2013, 01:35 AM
#2
Melting Slicks
want to know the volume of your combustion chamber? want to know the volume of the piston dish (or hump) and cylinder above the piston to the deck at TDC ? Want to know the volume of anything regardless of how off the wall it's shape ?
it is easy, cheap, and surprisingly accurate to do (without burrette tubes and all the associated hassle) and can be done in any position (even upside down)
(1) take modelling clay, completely fill the chamber that you want to find the volume of. smooth off the surface so there is no excess clay, but the chamber is completely full.
(2) remove the clay and roll it into as near as a perfect sphere as possible. Use some outside calipers, preferrably calibrated in millimeters, and measure the diameter of the sphere and divide by two to get the radius of the sphere.
(3) cube the radius (radius x radius x radius)
(4) multiple the radius cubed by pi (3.1416); multiply this by 4/3
(5) viola ! you now have the volume of the chamber regardless of how uneven or irregular the chamber may be.
I know, how can something so low tech and easy be accurate? trust me, it is. I measured some chevy heads "known to have 58 cc chambers" and found them to be 57.6 cc. If you use the type of modelling clay that hardens, you can even label and keep the sphere's for future reference.
it is easy, cheap, and surprisingly accurate to do (without burrette tubes and all the associated hassle) and can be done in any position (even upside down)
(1) take modelling clay, completely fill the chamber that you want to find the volume of. smooth off the surface so there is no excess clay, but the chamber is completely full.
(2) remove the clay and roll it into as near as a perfect sphere as possible. Use some outside calipers, preferrably calibrated in millimeters, and measure the diameter of the sphere and divide by two to get the radius of the sphere.
(3) cube the radius (radius x radius x radius)
(4) multiple the radius cubed by pi (3.1416); multiply this by 4/3
(5) viola ! you now have the volume of the chamber regardless of how uneven or irregular the chamber may be.
I know, how can something so low tech and easy be accurate? trust me, it is. I measured some chevy heads "known to have 58 cc chambers" and found them to be 57.6 cc. If you use the type of modelling clay that hardens, you can even label and keep the sphere's for future reference.
06-21-2013, 04:18 AM
#3
http://www.chevelles.com/forums/showthread.php?t=78709
http://forums.corvetteforum.com/c3-t...evy-heads.html
L2417F is apparently it's replacement
http://forums.corvetteforum.com/1567719318-post8.html
http://forums.corvetteforum.com/1567718305-post7.html
06-21-2013, 09:29 AM
#4
Safety Car
Alot of misconception on your part about what your doing to this engine and what effect it has.
I want to try and clear it up for you.
Quench is the distance from the piston (top or crown) to the the cyl head (the quench pad of the head).
Cutting down the deck surface on the cyl head does not effect quench in any way.
Head gasket, cutting the deck surface of the block, and piston compression height are what effect quench.
With a .015 gasket and .025 in the hole you are at .040 quench....
To get the piston .020 in the hole your going to have to have the BLOCK decked .005, at ehich point you will end up with .035 quench.
Also
The standard formula machinist use for decking SBC 23* cyl heads is .007 per 1 cc.... so you have to mill the cyl head deck surface .007 to remove 1cc from the chamber. Taking .005 off the heads is going to drop the chamber about 3/4 of a cc (which does nothing to change the quench). 3/4 of a 1cc is not going to do anything for the compression ratio either.
Will
I want to try and clear it up for you.
Quench is the distance from the piston (top or crown) to the the cyl head (the quench pad of the head).
Cutting down the deck surface on the cyl head does not effect quench in any way.
Head gasket, cutting the deck surface of the block, and piston compression height are what effect quench.
With a .015 gasket and .025 in the hole you are at .040 quench....
To get the piston .020 in the hole your going to have to have the BLOCK decked .005, at ehich point you will end up with .035 quench.
Also
The standard formula machinist use for decking SBC 23* cyl heads is .007 per 1 cc.... so you have to mill the cyl head deck surface .007 to remove 1cc from the chamber. Taking .005 off the heads is going to drop the chamber about 3/4 of a cc (which does nothing to change the quench). 3/4 of a 1cc is not going to do anything for the compression ratio either.
Will
06-21-2013, 09:38 AM
#5
Melting Slicks
Alot of misconception on your part about what your doing to this engine and what effect it has.
I want to try and clear it up for you.
Quench is the distance from the piston (top or crown) to the the cyl head (the quench pad of the head).
Cutting down the deck surface on the cyl head does not effect quench in any way.
Head gasket, cutting the deck surface of the block, and piston compression height are what effect quench.
With a .015 gasket and .025 in the hole you are at .040 quench....
To get the piston .020 in the hole your going to have to have the BLOCK decked .005, at ehich point you will end up with .035 quench.
Also
The standard formula machinist use for decking SBC 23* cyl heads is .007 per 1 cc.... so you have to mill the cyl head deck surface .007 to remove 1cc from the chamber. Taking .005 off the heads is going to drop the chamber about 3/4 of a cc (which does nothing to change the quench). 3/4 of a 1cc is not going to do anything for the compression ratio either.
Will
I want to try and clear it up for you.
Quench is the distance from the piston (top or crown) to the the cyl head (the quench pad of the head).
Cutting down the deck surface on the cyl head does not effect quench in any way.
Head gasket, cutting the deck surface of the block, and piston compression height are what effect quench.
With a .015 gasket and .025 in the hole you are at .040 quench....
To get the piston .020 in the hole your going to have to have the BLOCK decked .005, at ehich point you will end up with .035 quench.
Also
The standard formula machinist use for decking SBC 23* cyl heads is .007 per 1 cc.... so you have to mill the cyl head deck surface .007 to remove 1cc from the chamber. Taking .005 off the heads is going to drop the chamber about 3/4 of a cc (which does nothing to change the quench). 3/4 of a 1cc is not going to do anything for the compression ratio either.
Will
If I recall, the piston should be a +5cc or +4cc in your equation. In either case, your compression ratio will not increase that much, it will remain low nines. Depending on how much its costing you to do those 624 heads, it might be cost effective to pick up a set of used 128's or 113's which breathe better. You will also be able to bump up your CR to 11.0:1 if you want.
06-21-2013, 11:17 AM
#6
Advanced
Thread Starter
Member Since: Apr 2012
Posts: 52
Likes: 0
Received 0 Likes
on
0 Posts
Thanks very one for all of your help the reason I'm just doing the 624 heads is its al I could get my hands on I've heard that they're prone to cracking and also don't flow very well. Another reason is that the person who is building the top end of the motor is doing it all for the old crossfire injection setup. So I'm not wasting too much money on this at the moment. Trying to keep the top end build under $500.
Thanks so much for the info on the clay i guess I'll have to give it a try now. I'm also going to call the person who build the bottom end of the engine.
This is the first Chevy 350 build I've done... Well any motor for that matter. This is the first that I've ripped apart. So I'm trying to learn about quench and all of the other associated things. As long as my calculations are in the right area that's okay. They can get better over time when I fully understand things a bit better. So quench would be the space in between the flat part of the piston and the flat part of the head? I've also heard a couple different calculations for distance off per cc 0.005 was the most common I saw per cc so that's the one I was using. I beleive the 624 heads I have are the smaller valves aswell. I'm not looking for a ton of holy **** factor. Just a nice Sunday or occasional track drive.
Thanks so much for the info on the clay i guess I'll have to give it a try now. I'm also going to call the person who build the bottom end of the engine.
This is the first Chevy 350 build I've done... Well any motor for that matter. This is the first that I've ripped apart. So I'm trying to learn about quench and all of the other associated things. As long as my calculations are in the right area that's okay. They can get better over time when I fully understand things a bit better. So quench would be the space in between the flat part of the piston and the flat part of the head? I've also heard a couple different calculations for distance off per cc 0.005 was the most common I saw per cc so that's the one I was using. I beleive the 624 heads I have are the smaller valves aswell. I'm not looking for a ton of holy **** factor. Just a nice Sunday or occasional track drive.
06-21-2013, 12:54 PM
#7
Advanced
Thread Starter
Member Since: Apr 2012
Posts: 52
Likes: 0
Received 0 Likes
on
0 Posts
well ive found out that the block hasnt been decked at all so im using the 0.025 standard as a reference.
bore 4.030
stroke 3.48
78cc cylinder head volume (-1cc for decking and +3 cc for headgasket)
4cc effective dome volume
0.025 deck clearance
0.015 compressed headgasket thickness
8 cyl.
id be at somewhere around 9.06:1 with a quench of 0.040 if im not mistaken.
bore 4.030
stroke 3.48
78cc cylinder head volume (-1cc for decking and +3 cc for headgasket)
4cc effective dome volume
0.025 deck clearance
0.015 compressed headgasket thickness
8 cyl.
id be at somewhere around 9.06:1 with a quench of 0.040 if im not mistaken.
06-21-2013, 03:50 PM
#10
Advanced
Thread Starter
Member Since: Apr 2012
Posts: 52
Likes: 0
Received 0 Likes
on
0 Posts
https://www.facebook.com/photo.php?f...1&l=d6ef65d540
https://www.facebook.com/photo.php?f...1&l=d5802e45af
there they are "a326 10 a10 203" is the part number on the piston i beleive they look similar to the stockers but closer to flat tops which still, give a -5cc. and with that
bore 4.030
stroke 3.48
78cc cylinder head volume (-1cc for decking and +3 cc for headgasket)
-5cc effective dome volume
0.025 deck clearance
0.015 compressed headgasket thickness
8 cyl.
ill be at a 9.95:1 compression ratio! thats right around where i was looking to get and definitely helps insight the motor for the next head.
https://www.facebook.com/photo.php?f...1&l=d5802e45af
there they are "a326 10 a10 203" is the part number on the piston i beleive they look similar to the stockers but closer to flat tops which still, give a -5cc. and with that
bore 4.030
stroke 3.48
78cc cylinder head volume (-1cc for decking and +3 cc for headgasket)
-5cc effective dome volume
0.025 deck clearance
0.015 compressed headgasket thickness
8 cyl.
ill be at a 9.95:1 compression ratio! thats right around where i was looking to get and definitely helps insight the motor for the next head.