Gentlemen:
I am currently rebuilding my 2F engine and I would like to raise the compression some. Not enough to require premium fuel. I was planning to mill the head .030 in hopes that I would get a compression ratio of 9(+)to 1. The stock compression is 7.8 to 1. I was reading in the Toyota Trails Nov. issue and a fellow asked on the tech section about milling the head from .030 to .050. The fellow on the tech page said that he would mill the head more than the .050. My questions are: Will .030 give me about 9 to 1 compression ratio? Will a 9 to 1 ratio require premium fuel? I also thought that I might take 5 to ten thou off the block if the block was not straight. Doing this I would take off .20 of the head for a total of .030. What do you cruiser experts think? Appreciate your help. Thanks, HOOT

my head is milled .060, and trust me, that's nowhere near 9:1. If you want compression that high, you're gonna have to buy new pistons from Man-A-Fre. Mill the head, though, every little bit helps.

Elf_Cruiser

Thanks for your reply. When you milled your head .060, what do you think the compression ratio is? It looks like I am overly optimistic about getting somewhere around 9 to 1. I only settled on the 9to1 because someone told me that one could go that high without having to use premium fuel. It sounds like 9 to 1 will definately need premium fuel. I was looking at the Man-a-Fre pistons and they say you have to use premium fuel with them. Have you had to go to premium fuel with your head milled .060? I just went out to my shop and put .060 on my dial calipers. Boy, that looks like a lot of metal to be removed from the head. Have you had any problems what so ever with your head milled that much? Just curious, what would be the max one could take off. Again my thanks, HOOT

9:1 compression should not require the use of premium fuel, but it is recommended. Premium fuel burns slower, thus reducing the chances of detonation, but you can also adjust the ignition timing to compensate for the higher compression. 9:1 should not be a prblem in a LC motor. Lots of chevy and ford small block guys run 13:1 compression, for drag racing. milling .060 off the head probably only raises the compression about .5:1.
-Laters

I would have the head & block cc'd to make sure you get what you want. Mark Whatley (the toyota trails guy) says the head can be milled as much as .100 w/o problems. there are lots of factors as to what will raise your compression thats why I think CCing will help you decide. if you want to stay on regular fuel its probably a good idea to stay under 9:1 although you could still run regular fuel on that, especially @ higher altitudes. are you going w/ a bigger cam? they make a huge difference in power band. w/ a 270d cam in my 2f it really starts moving along at 3000rpms & will pull up to 4500 (as high as i like to rev it). remember that if your cylinders are bore you have to mill the head to compensate. also its rumored that the post 81 2f's (flat top pistons) have higher compression (8.3:1) than the older 2f's although I've never heard toyota or a machine shop confirm this.

HTH

Hey, Thanks guys, I really appreciate your answering my post. Sixty, I am installing a torque cam from Downey. I have had the engine at the machine shop for about three weeks now, but the fellow has not started on the engine as yet. I don't know at this point how much the cylinders will have to be bored etc. All I know is that the engine was running smooth, no noise. Again my thanks, HOOT

I read an interesting post on the inliners.org which you should check out on this topic.

There is a difference between milling the head and block with respect to combustion chamber swirl and fuel burn and igniting pattern. The article made reference to block milling as more effective of the two and that milling the head to change compression after a certain point required attention to porting and bowl changes. I would check out the inliners.org or clifford sites as theres tons of guys there who've worked the inline 6 to death.

If its any help on figuring out your compression-

milling the head .060 will add 1pt of compression to a 250 or 292 roughly so i would expect similar gains in compression for a 2F. Stock compression for a 292 is 7.7:1.

I would find out more about the heads and bowl issues and fuel burn patterns for those heads. More is not always better-especially in heads.

I think some of the later heads are very thin around the combustion chamber, like screwing in a canoe- very close to water!

Hoot,
I have the downey HP cam. make sure you set your valves to about .18mm to .20mm NOT the factory settings of .12mm & .14mm. My machine shop talked me out of cc'n my head/ block b/c he said it was not neccessary & would waste money. I wish I would have b/c then I would have had him mill my head more & could have convinced him that I was not anywhere near 9:1 commpression. I asked him to mill the head .080" & he only milled it .040" w/ the cylinders bored .030". my head had been done before so I really have no idea what commpression I'm running. If i remember correctly it cost about $85 to have the motor cc'd & then you could get much more precise w/ the milling. as for how deep you can mill, I've heard the 2f heads (new & old) can be milled way beyond what is neccessary for 9:1 commpression.

HTH

How does raising ther compression affect torque? Does it affect just the top end or all through the power band?

screwzer,
raising commpression increases the amount of power that can be extracted from the fuel/air mixture. so this generaly causes an increase in torque & hp throughout the rpm range. but in order to see better power increase than just bringing up the commpression a camshaft that allows the motor to breath better is ussually added. this is what normally causes a loss in low-end torque. added commpression is always better/ more efficient until it causes pre-ignition/ pining/ detonation.

Don't know if this applies since I tossed the 2f before i ever drove my 40 but, my sbc 350 is at 9.4:1 and 9.7:1 compression is generally regarded as the max for 87 octane fuel. I believe factory chevys DO however go up to 9.7 on regular. 10:1 and above I feel requires premium fuel.

I would imagine that the 2F has about as much room as the lot of GM inlines that toyota bought the blueprints from to copy the inline way back when.

Simple decking the block and mild head milling plus mild 265-270 degree camming alone can bump the hp by 35%.
Compression is why the old muscle cars ran so strong and produced massive torque because the old leaded gasoline allowed much higher 11 and 12:1 compression without risk of detonation. Today you have to run down to the airplane hangar to find 104 gas unfortunately.

Hey, I sure am glad you guys got around to sharing some of your knowledge. I posted my message before Christmas. I kept looking for replies,but nothing came up. I was really worried. I thought that I must have asked a real stupid question and the rest of you all were laughing so hard that you could not run your computers. Only one guy answered and he was a lot of help. I really appreciate your helping me out. I will check out Cliffords and see what I can come up with. It almost looks like one could simply cut of a 50-60 thousands slice of the head and dress it up with a file. I was thinking about getting too close to the water jackets when I read that one could go over 60 thousands. I gotta to tell ya, put 60 thousands on your dial caliper and it looks like one helleva lot of metal. Again, my sincere thanks for you all taking the time to share your knowledge with me. HOOT Murray