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#1 Old 06-12-2007, 08:03 PM
 
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Shaving heads

Does anyone know the limit of how many thousandths you can shave w/out screwing up the timing belts and creating an interference valve setup? If I pickup a spare motor I was going to shave the head to bump the compression since it would only be for racing but I didnt want to shave it so much that the compression overwhealms the stock ECU tune or would make the valve come into contact with the pistons. More than likely .010-015" is the most I would go but if thats too much obvioulsy I dont want to go overboard. So if anyone has some ideas I'd appreciate the advice. Thanks!

~Dan

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#2 Old 06-13-2007, 05:09 AM
 
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i would highly recommend going to the factory service limit. im not sure what this length is because im trying to figure out myself.

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#3 Old 06-13-2007, 07:54 AM
 
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The FSM says the max is .008 in. They're mostly talking about taking out warp, any more warp that has to be taken out than that would put the cam in a bind. The main problem with milling the head is it changes cam timing, you can correct that with a adjustable cam gear.
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#4 Old 06-13-2007, 11:50 AM
 
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Wow all of .008" lol. So basically what they are saying is find a new head if the one on your car goes bad. Almost all the GM and Ford heads that Ive seen go bad were out of shape by .010" or more. Having the block decked is just as bad probably.

This makes me think the best route to take is getting a ka24e motor and using the DE head on it. That would bump compression up to 11:1 or more most likely. But nobody seems to know anything about the head swap so apparently its not done very often. Im guessing even then you'd have issues with the timing setup.

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#5 Old 06-13-2007, 12:23 PM
 
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I've milled a KA24e .012 in., some to get warp out, some because I wanted to, didn't run into valve interferance problems, but I did run into cam timing issues. I'm not allowed a adjustable timing gear in the class I race in, I used an offset woodruff key on the timming gear. Where the FSM says .008 is the limit, I think they're taking about warp, if the head is warped over .008 and you have it milled flat, then the cam galleries are out of alignment that same amount, milling the head won't align them.
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#6 Old 06-13-2007, 01:19 PM
 
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technically our motors are considered intereference type motors, because if the chain failed the valve would almost surely make contact with the piston, however older domestic type motors are considered non-intereference type motors, because no matter how you change valve timing or if the timing chain failed, it is pretty much impossible for the valve to make contact with the piston.
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#7 Old 06-13-2007, 04:55 PM
 
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Most engines with chains instead of belts are interference. I have a 24-v V6 probe thats non interference. I dont know why more engines arent made like this. Timing chains will go bad so why make people have to replace the entire engine when this happens instead of making it non interference??

But anyway, it sounds like its safe to shave the head .010" and thats what I planned to do. BUT I need to do more reading on using the de head on a sohc instead. Thats a much easier/cheaper way to get the compression bumped up.

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#8 Old 06-13-2007, 06:41 PM
 
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Putting a DE head on a E block isn't easy, if you're not up to doing precision work, forget it.If you want high compression cheap, put E pistons in a DE block, or just mill a E head and get a adjustable timing gear to handle the timing change.You're not going to run into valve interferance problems by milling the head unless you radically change your valve timing, as in jumped chain, broke chain or a very long duration high lift cam in conjuction with too much head milling. Any high compression engine is going to be a interferance engine, you can only put valve notches so deep in the pistons and still have high compression.
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#9 Old 06-13-2007, 10:45 PM
 
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Tom, you seem to fair pretty well with your stock engine so Im wondering if I will really need the extra motor to keep up. My intention all along was to outhandlethem but on the longer straights it makes me wonder. The guys at the track this year got some 91-92 preludes and they are dominating now. Stock ludes comes packing 160hp+ stock so it makes me wonder if I'd have enough motor. I would put money on the honda guys cheating because they have so many options to upgrade and change while still looking stock. Anyway after more research it does look like a challenge to get the DE head on the E block. More risk than reward anway.

Do you guys know if a .010" head shave would still require the cam gear change? I definitely cant get away with that because its an obvious upgrade that would be illegal for my racing class.

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#10 Old 06-14-2007, 08:09 AM
 
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.010 won't give you cam timing problems, but it also ain't woth it for the small amount it will increase your compression. I was wrong on the .012 needing the offset woodruff key, it was another engine that I milled .022.The inspectors at most tracks I race at are very familiar with V8s, most don't and won't take the time to do the indepth study they need for all the different 4-cyl. engines they encounter in a open 4-cyl class, some tracks limit the cars to sohc's only, some to fwd only, some to no foreign dohc. I outhandle fwd, I never qualify very well. But soon as the race starts I start to move up. The fwd's are steering and applying power to the track with one tire, the right front, it soon begins to get too hot. The Hondas handle a little better than most fwds because their engines are on the left side of the engine bay, while most other fwds engines are on the right. Plus Hondas have so many engine combinations that can be mixed and matched that the inspectors have a hard time keeping up.
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#11 Old 06-14-2007, 11:37 AM
 
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I know once the right front gets boiling hot on the asphalt the ricers are finished! lol

On dirt the fwd doesnt suffer as bad because the clay/dirt never gets hot because its wet for most of the night. But at the same time the dirt gives much less traction and friction so its hard for anything to get traction if its not setup right. I dont know if the stock de will be enough power or not. If it turns out not to be strong enough I will most likely shave the head a hair and do some major head grinding to open up the ports. Thats all relatively cheap stuff to do.

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#12 Old 06-14-2007, 03:10 PM
 
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.010 won't give you cam timing problems, but it also ain't woth it for the small amount it will increase your compression.
can anyone body else confirm this? whatever increases some compression will help toward my power goals. have you done this yourself tyrodtom? im not that good with math, but how much of a compression ratio increase will you get by doing this? im hoping at the very least .1 increase...

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#13 Old 06-14-2007, 06:11 PM
 
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stinky I cant give you exact compression ratio changes but lets just say the smallest change in piston/head relation can drastically alter the c/r. For example I have a 2.5L KLZE probe. The shop designed me 8.7:1 pistons to lower the c/r down from 10.0:1. The only thing they had to do was remove a few thousandths of material in the valve reliefs in the piston face. So lowering the piston depth a few thou was enough to drop the compression 1.3:1. Every engine is different of course. But shaving .010" off the head or block would probably raise compression somewhere around 0.4:1 or more. And for a big bore engine like a KA that extra c/r means TORQUE! You should talk to an engine shop, they might be able to help you out a little.

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#14 Old 06-14-2007, 06:57 PM
 
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According ti David Vizard, a very respected engine builder, there is 2-3% gain in HP for a whole point in compression ratio, that's a 1. increase, not .1 . With a longer duration cam you can gain a little more. I haven't done the math myself, but when I had my own head milled .012 there was no noticeable gain, but what I gained in compression, I may have lost by retarding my cam. I milled a CA20E .022 or.025, but it run like crap until I discovered the cam timing problem, once I figured out the offset woodruff key I needed and got the proper cam timing back the engine was quite a bit quicker, but I did several other things to it at the same time. Overhauled it, .5mm overbore,port-matched,balanced the rods and pistons to .1 of a gram, that engine was sweet, but it was the complete package, not just the milled head.
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#15 Old 06-14-2007, 09:53 PM
 
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stinky I cant give you exact compression ratio changes but lets just say the smallest change in piston/head relation can drastically alter the c/r. For example I have a 2.5L KLZE probe. The shop designed me 8.7:1 pistons to lower the c/r down from 10.0:1. The only thing they had to do was remove a few thousandths of material in the valve reliefs in the piston face. So lowering the piston depth a few thou was enough to drop the compression 1.3:1. Every engine is different of course. But shaving .010" off the head or block would probably raise compression somewhere around 0.4:1 or more. And for a big bore engine like a KA that extra c/r means TORQUE! You should talk to an engine shop, they might be able to help you out a little.
this is very good news for me! my race class (ITA) only allows a compression ratio up to 9.5:1. i plan on using nissan motorsports 9.1:1 pistsons and milling the head to achieve a higher compression ratio. .010" seems reasonable but i think i will play it safe and go with .080". i will def. talk to a few race shops and see what they have to say! good info in this thread keep it up everyone!

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#16 Old 06-14-2007, 10:00 PM
 
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According ti David Vizard, a very respected engine builder, there is 2-3% gain in HP for a whole point in compression ratio, that's a 1. increase, not .1 . With a longer duration cam you can gain a little more. I haven't done the math myself, but when I had my own head milled .012 there was no noticeable gain, but what I gained in compression, I may have lost by retarding my cam. I milled a CA20E .022 or.025, but it run like crap until I discovered the cam timing problem, once I figured out the offset woodruff key I needed and got the proper cam timing back the engine was quite a bit quicker, but I did several other things to it at the same time. Overhauled it, .5mm overbore,port-matched,balanced the rods and pistons to .1 of a gram, that engine was sweet, but it was the complete package, not just the milled head.
the late model ka24e has a compression ratio of 8.6:1! so if i use the nissan motorsports pistons and milling the head .080" - .010" i can get pretty close to 9.5:1. so i would see about a 5hp or so difference. of course, paired with others mods to make the car breathe more will def. help with power. especially tuning, that will really wake up the motor with 9.5:1 c/r. there will be more mods oviously for my 'race' car, but that will be shown in my build thread, when i updated it ^^.

also, you mention woodruff keys. what exactly are they and where do they go?

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#17 Old 06-15-2007, 12:28 AM
 
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The FSM max recommended milling is .008 not .080. I've went .012, to correct warp after a blown headgasket. I ran the head several races, no problems, but it just didn't seem to run as good as before. Could have been from the cam being retarded from the milling, could have been from the warped head putting the cam gallery out of allignment. Just think, when a head is warped, and you have it milled, that only makes the gasket surface flat, the cam galletries are still out of alignment, and you combustion chamber volumn is going to be unbalanced from cyl. to cyl also. If you milled a head .080 you would run into cam retard problems. The woodruff key is the piece of metal that fits in the slot in the camshaft and cam gear and locks them into one position, a offset key lets you vary that position a few degees. It would never be able to take care of what you would end up with with a .080 milling, if it could be milled that much. you would have to use a adjustable timing gear.
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#18 Old 06-15-2007, 12:27 PM
 
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Originally Posted by tyrodtom Last Post
According ti David Vizard, a very respected engine builder, there is 2-3% gain in HP for a whole point in compression ratio, that's a 1. increase, not .1
Is this guy a nissan engine builder or just a general engine builder? I disagree with his point that going from 9.2:1 up to 10.2:1 would only increase HP 3%. If you do that to a ford/gm V8 you are looking at a gain of 30 ft-lbs of torque AT LEAST. And on the KL engines Ive built for probes (2.5L V6) going from 9.2:1 up to 10.0:1 its an increase of ~18whp and 20ft-lbs on average. Thats a gain of 12+ % over stock compression and its not even a full 1.0:1 increase. If this guy is stricly a nissan builder he may be right though. Since its just a 4-cyl the bore/stroke are already so large that it may reduce the positive affects of compression changes because there's so much displacement per cylinder. Ive never built a KA, but I'd expect a 2-3% gain for worst case senario with poor tuning and machining. If compression was such a minimal gain why do 11:1 1.8L hondas make 198hp stock while a 2.4L DE can only make 160? I guess the only way to truly find out is dyno before and after raising compression.

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#19 Old 06-15-2007, 03:51 PM
 
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Originally Posted by tyrodtom Last Post
The FSM max recommended milling is .008 not .080. I've went .012, to correct warp after a blown headgasket. I ran the head several races, no problems, but it just didn't seem to run as good as before. Could have been from the cam being retarded from the milling, could have been from the warped head putting the cam gallery out of allignment. Just think, when a head is warped, and you have it milled, that only makes the gasket surface flat, the cam galletries are still out of alignment, and you combustion chamber volumn is going to be unbalanced from cyl. to cyl also. If you milled a head .080 you would run into cam retard problems. The woodruff key is the piece of metal that fits in the slot in the camshaft and cam gear and locks them into one position, a offset key lets you vary that position a few degees. It would never be able to take care of what you would end up with with a .080 milling, if it could be milled that much. you would have to use a adjustable timing gear.
oh, i did mean .008 not .080. before i shave the head, im obviously going to make sure the head isn't warped. if it isn't warped, and i milled the head .010, the cam galleries shouldn't be out of alignment, correct? unless of course the person doing the milling is a retard and messes it all up. but is .010 still safe even if your head isn't warped?

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#20 Old 06-15-2007, 06:02 PM
 
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If you mean is .010 safe as far as valve interferance, yes it's safe, i've went farther, but if you're going radical on your cam i'd check clearances.David Vizard is best known for his V8s, mostly road race and NASCAR engines. Have you ever just milled a head and no other changes in your set up, and then tested it? I said more can be gained with camshaft tuning, longer duration, etc. There's a lot of urban rumors about how much power you gain with each mod you do to a engine, for instance, bored .030, people expect big HP gains.In our 240s you're only gaining about3 cu. in. with a .030 overbore , our engines make about 1 hp per cu. in., so you're only going to gain about 3 hp from the added displacement, the power increase you feel is from the improved ring seal. I've been with a circle track team 18 years now, mostly sbc's When we do the engines, it's 5 hp here, 10 hp there,etc. but soon it begins to add up to a big difference. It isn't any one mod that's going to win races, it's a complete intergrated package that does it.
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#21 Old 06-15-2007, 06:14 PM
 
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One piece of good advice I will give you on entering circle track racing. Start out with a dependable engine, don't worry about HP, first get the handling and driving with the crowd your going to racing with figured out, then worry about getting more hp. Even though you now helping a experienced racer, he can do a lot of stuff to his car you're not allowed to do by the rules, the princibles are the same, you've just got to apply them differently in these cars.
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#22 Old 06-15-2007, 06:49 PM
 
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^im not getting into circle track. i drive on mountain roads and plan on moving away from it since theres too many dumb ass young'sters trying to show off. i know how to drive my car, and drive it damn good and damn fast, while at the same time being safe. im not trying to aim for a high horsepower number, yet. i plan on racing the stock ka24e while i build the better ka24e for ITA.

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