grr8_65
Well-Known Member
Everyone says to mill the heads in order to increase the compression, would there be any benefit to milling the block, if you could get it in the milling machine? :-k
increasing compression
- Thread starter grr8_65
- Start date
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Sure. Some folks split the milling between the two. I ain't doing either on mine. I'm using the 198 rods and KB239 2.2 Chrysler 4 cyl pistons. I may have to use race gas. lol
theothergarth
Well-Known Member
As I understand it, Milling the block can be done. You would mill the block to zero deck the pistons. Doing the heads would decrease the chamber size. I was planning on getting my block milled to help bring the pistons closer to zero, but as it turned out, the KB 167 pistons coupled with the "302" heads I had brought me up to the 9.5:1 I was looking for so no milling was needed. Either way, if you take off too much material from either, you will change the geometry of the valve train and have to compensate with shorter push rods at the very least.
grr8_65
Well-Known Member
To follow up then, Which is better a small combustion chamber, or a large chamber with a modest to no deck height ?
805moparkid
Slant and AFX Guy
slant not SB...
if you have the motor part and are using stock style pistons mill the block! this keeps the valves in the head away from the piston and also gets the piston closer to the top of the bore where it should be... i took .110 off my slant head and only ended up with a 9.5:1 comp lol...
what is your plan for the car? racing? just a good street/daily driver?
theothergarth
Well-Known Member
ok, I was curious on that question as well, but moparkid please explain. What does "slant not SB" mean? How does milling the block keep the valves away from the piston? If you take material off either surface, the top of the piston and the valve are going to be closer together. What am I missing?
RustyDusty
Rabid Cross-eyed Opossum!
"Slant" motors are inline 6 cylinder motors (single head) that are inclined at a 30 degree angle from vertical. "SB" is referring to small block "V" motors with 2 heads. If you take from the block, and not the head, the valves stay tucked in the combustion chamber rather than protruding out from the head's deck into the cylinder bore when at lift. This is exaggerated even more by high lift radical cams. That way in case of a timing failure (Broken timing chain, etc.) your motor is safe from bending valves from valve to piston contact. This is called a non interference motor. If you milled the head down to the point that the valves protrude from the deck of the head into the cylinder bore and the timing chain breaks... some valves will be stuck at lift, and as the piston rises it will smack the valve. No good! That's aptly called an interference motor.
Cheers!
Drake
805moparkid
Slant and AFX Guy
exactly... also after my build i think trying to get quench would be of great value...
grr8_65
Well-Known Member
I plan on it being a "peppy" driver that I can drive from KY to Vegas. Have original motor in it now that's been rebuilt and runs well. Hope to get another /6 to "modify" and use on a daily basis. (My dad bought the car in Seattle in 1965. Mom used it for work, about 3 mile a day.)
moparlover
Well-Known Member
ideally you would put in 9.5:1 kb pistons, and the block and heads would be milled appropriately so that you get the right quench, and that everything is square & true
(blueprint specs)
depends on the budget however. generally you wouldnt want to just mill heads and block to try and get the compression way up to a good power making range (matched to the type of gas you are using.)
however, if it's an old engine and you are having compression problems, you could mill them slightly and install a new head gasket, and possibly new rings on the pistons and keep on driving without investing way too much.
it all depends on your budget. one option for you, since you are getting another /6 is to just run your current one "as is" and put your money into the new build. that way your car is on the street still, and you can get the new /6 set up just the way you like it (stroker scamp is a good buddy to have if you are lookin' for /6 advice)
(blueprint specs)
depends on the budget however. generally you wouldnt want to just mill heads and block to try and get the compression way up to a good power making range (matched to the type of gas you are using.)
however, if it's an old engine and you are having compression problems, you could mill them slightly and install a new head gasket, and possibly new rings on the pistons and keep on driving without investing way too much.
it all depends on your budget. one option for you, since you are getting another /6 is to just run your current one "as is" and put your money into the new build. that way your car is on the street still, and you can get the new /6 set up just the way you like it (stroker scamp is a good buddy to have if you are lookin' for /6 advice)
Also, keep in mind that once you mill off so much off of the heads and/or block, you may have to mill the intake manifold for it to fit right. This would then make all the parts specific for that engine and no longer interchangeable with others...
Straight six, this won’t mater. If using headers and you have power steering there may be a clearance issue with one of the runners contacting the adjustment screw on top of steering box. A shim under the left motor mount or a ballpeen hammer corrects that issue.
Stock pistons stay well below block deck height on a slant, making it a noninterference engine. Removing up to 0.100” from factory dimensions form head or block is about the limit before having to use custom length push rods.
My understanding is that removing material from the block is preferable to shaving head on these engines due to how far down stock pistons reside in their bore at top dead center.
Before you pull a cut depth out of thin air, you need to pull the head, measure what you have, and utilize a compression ratio calculator to design a configuration that keeps dynamic compression ratio in line with pump gas use.
805moparkid
Slant and AFX Guy
all KB has that ive found are the flat tops and then the dished piston for the later LOW comp slants...
exactly...
Some very good info being shared here :cheers: Thank you..
Frank took 40 thousands off my new head
as I requested and was advised by these /6 folks in this post :happy2:
If :-k and I say If, I remove my 170/6
I will have 50 thousands taken off my early low deck engine.
Thank you all for all the great info in the past and present.
Don't forget to take the potato out of the exhaust
and throw some real spark to it :toothy8:
Frank took 40 thousands off my new head
as I requested and was advised by these /6 folks in this post :happy2:
If :-k and I say If, I remove my 170/6
I will have 50 thousands taken off my early low deck engine.
Thank you all for all the great info in the past and present.
Don't forget to take the potato out of the exhaust
and throw some real spark to it :toothy8:
KB has nothing FOR the slant.
grr8_65
Well-Known Member
Thanks for ALL the wonderful information. I will run the original until I can get another built to fit the use. I was leaning towards milling both the block and head and am now convinced that's the way to go. I have a super six manifold and carb set that I will add to the new build along with an electronic ignition, which I also have. Need to get the body and interior finished before I tackle the other engine.
This is another example of why this group is almost family.
This is another example of why this group is almost family.
theothergarth
Well-Known Member
Ok, I knew what the difference between a slant and SB is, I just didn't follow what he was referring to in reference to my post....still don't.
I agree with the rest of the statement about keeping the valves tucked up in the combustion chamber, but what I was getting at was if you take too much material off either the head or the block you end up with the same problem....the valves going down into the bore, or the piston top crowning....either way, valve and piston meet in a bad way. Granted, it is more likely to mill the heads too far than milling the block too far.
Johnny Dart
Well-Known Member
RustyDusty
Rabid Cross-eyed Opossum!
You were referencing 302 heads and saying "heads" both of which would be small block terms. :blob:
ops:
theothergarth
Well-Known Member
I like oranges better I guess. :tongue10:
As I was scrolling down to the bottom of this thread I noticed something and had to scroll back up....yup....slant forum. Hadn't noticed that before. I had just clicked on the new link that came up on my main page. Scrolled down hoping no one had posted yet....bummer
I'm gonna shut up now
RustyDusty
Rabid Cross-eyed Opossum!
Hey now! It's apples or nothing in this forum! :butthead::toothy7:
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