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Mark has (as usual) done a better job of explaining it.
Higher Compression (1 Viewer)
- Thread starter FJ60FOOL
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About how much milling can a cruiser head tolerate before the piston starts getting into it with the valves? Ive heard 0.100 tossed out before on here.
Relix said:
Whoa there bullet! just making fun of myself. I get a bit punchy at 1am...
When you mill the head for higher compression - do you need to do anything to the valves and lifters?
thnx!
rob
Cams do decrease compression
It is a true statement technically. Some camshafts are designed to decrease compression. It's a combination of valve lift, Valve overlap & duration.
If you measure the volume & calculate Cr you have a set number.
Now if you are running a .660 Lift, 288 duration @ .050" cam you sure as hell aren't going to have the compression ratio that the engine is capable of. Now with that said.
The Oe Toyota camshafts & even the RV grinds are so conservative that you are never going to see the extreme duration & lift figures of a racing cam that will decrease running compression.
As for passing Emissions with Aftermarket Cams.
I have used up to 292 degrees of duration & up to .550" of lift in V-8's without failing the sniffer test here in California on freshly built engines.
I'd bet the I-6 engines can handle at least 260 degrees of duration & .450" of lift & still pass here in Cali with a properly tuned carb.
just my .02
Dave.
It is a true statement technically. Some camshafts are designed to decrease compression. It's a combination of valve lift, Valve overlap & duration.
If you measure the volume & calculate Cr you have a set number.
Now if you are running a .660 Lift, 288 duration @ .050" cam you sure as hell aren't going to have the compression ratio that the engine is capable of. Now with that said.
The Oe Toyota camshafts & even the RV grinds are so conservative that you are never going to see the extreme duration & lift figures of a racing cam that will decrease running compression.
As for passing Emissions with Aftermarket Cams.
I have used up to 292 degrees of duration & up to .550" of lift in V-8's without failing the sniffer test here in California on freshly built engines.
I'd bet the I-6 engines can handle at least 260 degrees of duration & .450" of lift & still pass here in Cali with a properly tuned carb.
just my .02
Dave.
Mark W
Yep, it's true. I just don't care that much.
.100 inch is the max factory spec for milling the head. No interference concerns with the valves at this point. I would bet that you would run the mill through the face of the head before you caused piston/valve interference.
Mark...
Mark...
Mark
I noticed that in your formula for a 2F you left the head alone. Is there any benifit to a pocket port or larger valves with these heads or is it a moot point in the usable rpm range?
Also, what is the Big Toyata manifold?
Thanks
Jonathan
I noticed that in your formula for a 2F you left the head alone. Is there any benifit to a pocket port or larger valves with these heads or is it a moot point in the usable rpm range?
Also, what is the Big Toyata manifold?
Thanks
Jonathan
One other thing, how much do you need to mill the head, with flat tops, to get to 9-9.5 CR?
Thanks
Jonathan
Thanks
Jonathan
What are you guys trying to get out of your 60's? Mill the heads, get higher compression, move to premium gas but where is that going to get you. You are not going to be running 11 sec quarter miles. You might see some hp improvement but it will be minimal. It's a lawn mower engine. Is it worth spending money on all these "mods" and moving up to premium gas? If you need more speed I think there are other options that need to be explored. If you are not in a hurry leave the 2f be what it is and stick with the "cheaper" gas. That's my .02 cents anyway.
jim here comes your medsFJ40Jim said:Mark has (as usual) done a better job of explaining it.
big torqure at low rpms, I think everyone here understands that the 2f will never be a racing engine....Some of us would prefer keeping the stock Toyota powerplant under our hoods, I mean if I wanted a SBC I would have bought a blazer instead... I don't see anything wrong with boosting the performance of the tractor motor we own... I'd imagine with a higher compression rate, & a nice fuel injection setup we could smooth out and broaden our torque curves giving us much more useable power...nikos8 said:
OK, I now know that a different camshaft will make 2/10ths of bugger all difference to a CR. Now time for my stupid question..Relix said:
What about a different CRANKshaft? Could the C.R. be upped that way? (Not that the mighty 3F is underpowered.. )
Mark W
Yep, it's true. I just don't care that much.
Of course. Longer or shorter strike with the same bore changes the displacemtn of the engine.
But there are not any options for changine out cranks in the F series engine, so it's a mote point.
Mark...
But there are not any options for changine out cranks in the F series engine, so it's a mote point.
Mark...
Cheers Mark. That goes into the "Little factoids" part of the brain. 
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