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View Full Version : Piston size when honing block!! help!!



jo_aftermarket
02-13-2010, 10:54 PM
hey everyone,

i have a question regarding the play when honing a block.

i know the engine bore for the 5m to use standard pistons is anywhere from 3.2673 - 3.2776.... giving a play of .0103 of an inch,but my block was already honed once before and i plan on honing it again before putting it together...

what i wanted to know is can i hone the block again (making it the 2nd time) and still come within spec and use standard pistons? or must i oversize?

any thoughts and opinions are appreciated thanks everyone!!

gteduck
02-13-2010, 11:33 PM
the bore's are honed in accordence with the piston diameter!
i think it's around 2thou larger than piston! otherwise the piston's slap around if there's to much clearance! I'll look in my book and get back to ya! 2thou is .002"
the .0103 you mention is a general tolerance for the OD of the pistons, the bore's get honed based on piston OD. SO NUMBER YOUR PISTONS , DON'T MIX THEM UP!!!!!

gteduck
02-13-2010, 11:55 PM
THE HAYNES MANUAL SAYS!
Piston bore 81 through to 88 is, standard......3.2673"
maximum.....3.2776"

Pistons OD , 81 through to 86 , 3.2650" to 3.2669"

Piston to bore clearance , 79 through to 85 , 0.0020" to 0.0028"
86 , 0.0024" to 0.0031"

GOOGLE FOR TOYOTA TSRM TO BE SURE!!!!!!!!!!!!!!
DON'T BE LAZY!!!!!!!!!!!:thumbsup:
THESE ARE FACTORY MANUFACTURING SIZES , THEY MATCH LARGER PISTONS WITH LARGER BORES ,SMALLER WITH SMALL TO GET THE 0.0020" TOLERANCE IN THE CLEARANCE. THEY DON'T JUST PUT ANY PISTON IN ANY BORE AND HOPE IT'S OK.
THAT's FORD!!!!!!!!lolol

gteduck
02-14-2010, 12:08 AM
:thumbsup:

gteduck
02-14-2010, 12:14 AM
THE HAYNES MANUAL SAYS!
Piston bore 81 through to 88 is, standard......3.2673"
maximum.....3.2776"

Pistons OD , 81 through to 86 , 3.2650" to 3.2669"

Piston to bore clearance , 79 through to 85 , 0.0020" to 0.0028"
86 , 0.0024" to 0.0031"

GOOGLE FOR TOYOTA TSRM TO BE SURE!!!!!!!!!!!!!!
DON'T BE LAZY!!!!!!!!!!!:thumbsup:

Dave A.
02-14-2010, 11:13 AM
Check the piston to bore clearance w/ a feeler gauge before you do the honing and that will tell you how much leeway you have. All you want to do is deglaze the cylinder walls w/ the hone and not remove much metal.

jo_aftermarket
02-14-2010, 12:17 PM
Alright thanks boys :thumbsup:.... i already checked my haynes book but still am uncertain what i should do.... this is my first engine rebuild so please pare with me...

i pretty much only want to degalze my block as mentioned from Dave.i want to Take off the least material possible .... although i wouldnt really mind oversizing the block and pistons...

has anyone ever honed a 5m block that was already once honed before but still fell within spec to use the standard size pistons? i know there has to be a play of .0020- .0028 from the piston to cylinder wall but i am no where near my engine right now and wont be able to measure clearance till next weekend..

and does anyone have an idea on how much compression will me raised if i O/S lets say .020 or maybe even .040?

Dave A.
02-14-2010, 07:50 PM
Does anyone have an idea on how much compression will me raised if i O/S lets say .020 or maybe even .040?



Oversizing won't raise the static CR, but engine displacement will increase slightly.

Please ignore my previous post. The best way by far to measure your piston-to-bore clearance is with a cylinder gauge that has a dial indicator. That way, you can check to see if the bores are tapered and/or out of round as well as check the I.D.. I think this procedure is shown in the TSRM. If you don't know how to use a cylinder gauge and/or don't have one, have a machine shop check the bores and they can tell you if you will need to have the block bored oversize for oversize pistons.

Crocket
02-15-2010, 05:44 PM
Oversizing won't raise the static CR, but engine displacement will increase slightly.
.

That's not entirely true. I've already gone through the numbers for my 6M-GE rebuild, and oversizing the bore by .020" raises the static compression by approx. 0.1. Not sure what it is on a 5M-GE, but it should be easy enough to calculate given the 5M's stroke is 6mm shorter.

jo_aftermarket
02-15-2010, 06:13 PM
alrighty thanks guys...its much appreciated and gud to know :thumbsup:

gteduck
02-15-2010, 06:57 PM
get your hands on a dial bore gauge first. it should be checked top middle and bottom at 12 and 3 o'clock and at 45 degrees before and after 12 o'clock to be sure. IMHO while it's out do it properly!
get a good machine shop to do it.they will order your pistons to whatever oversize and comp ratio you want. they could even recommend a comp ratio for you. even ask about getting it all balanced, pistons , rods , harmonic balancer , flywheel , clutch pressure plate and crank. that with good even higher compression than stock is a great way to go. then later if you dont have the money now ,cams are more benificial and quick easy improvement. also get the block deck leveled so the 1st and last piston are even from deck at TDC . ring a good engine machine shop and talk to them.while it's out do a good job and then it'll treat you well! even if it's still a 5 m.:rolleyes:

jo_aftermarket
02-15-2010, 07:13 PM
NOw this gteduck i appreciate for a reply...and not when ur callin me a crack head or dumbass, for posting my own personal opinion..

but anyways ...yeah I will be taking the block to a machine shop...have her 0/Sed and decked... i am for sure oversizing the block now but i am hesitating rather to go .020 or .040 but im leaning more toward .040...

my uncle has rebuilt more engines than i could think of...so i might just get the block decked and also o/sed from the machine shop and might just rebuild it myself with my uncle...seeing how he has over 20 years experience...

might get the block reassembled my the machine shop depending on how much they charge per hour for labour...

OH btw like u stated better to do it right the first time. i hate having to redo things for nuthing..

gteduck
02-15-2010, 07:53 PM
do you get what i mean about getting it leveled? helps keep the comp even as the deck is not always level to crank! not CRACK! lol
and between going .020 or .040 you will get minimal extra power at .040 ,but at .020 you have a thicker wall and if some thing goes pear shaped you can go .040 with no troubles. Are you going to line hone the mains? and resize rods, it might be worth getting some 7mgte rods polished and shotpeened to if there compatable too! DUMBASS lol, Are you going to balance it all ,index and resize the crank. IT will rev better with a good balance, especially when you jam some aggressive cams in it.

only said that cause you sounded like a little nut swearing at everyone.:thumbsup:

jo_aftermarket
02-15-2010, 09:01 PM
thanks for the suggestions man...Roger that on the leveling lol...:thumbsup:

yeah my friend was sayin the same thing about going .02 instead ..so im just to say a tad o/s , & the walls will be thicker as u mentioned...

hmm to be honest im not sure yet what ill be running for my block internals just yet...im at the point where im searchin/buyin what i want to use.. and yeah i was thinking of getting the crank balanced...

lol i was thinkin cams...2.72 durations would be kick ass!

hmm never thought of that.. 7m rods with 5m crank...but scrap that idea..would need to use 6m/early 7m crank

jo_aftermarket
02-15-2010, 10:08 PM
anyone know what material the 5m & 7mgte pistons are made of...and what boost levels they could take ..

gteduck
02-15-2010, 11:11 PM
well like i mentioned in the thread where you lost your mind , i got a stock jap import and turned it up to 15psi, this was a donk with at least 120,000km on it and still stock head gasket at the ready to blow factory head torque setting, with a cam gear adjustment via a vernier cam gear it made 274 hp at the wheels, with boost peaking at 3500 rpm and dropping to 9psi by 6500 rpm ,i've got 3inch dump into 2 1/2 from firewall back so it was restrictive. GO 3inch all the way. I wish i did! . THE CAM gears will give you good kick at a quarter the price of new cams, and you can use them agian for that fine tune when you get the cam's. But check 7Mpower.com there are dudes making 500 odd hp with factory rods ,I can't remember if they had stock pistons or not and i'm not sure if 7mgte's are forged or if 7mgte rods are compatable in a 5m block. But if you turbo it you want forged pistons for sure, wiseco seem to be a popular good choice. DEFINATELY GET IT ALL BALANCED. It will rev out so fast on boost it's a must

jo_aftermarket
02-15-2010, 11:36 PM
lol just got a short temper..thats all

anyway, sounds like u have a pretty nice 7m build..got to get rid of that restriction tho..

ill check those pistons out..thanks for the heads up

gteduck
02-16-2010, 01:20 AM
dude my 7mgte is an old stock import. Mods are microtech injection ,custom restrictive exhaust, pod filter , vernier cam gear back near stock , arp head studs, cometic HG and i pissed of the manual boost control by fitting an 11psi actuator, I CUT THE STOCK 5-7 PSI OFF and fitted a after market sucker on the factory bracket ! ALL IN ALL IT'S GOT NO OTHER MODS . stock old ct 26 with a whole lotta play in the shaft now, a well oiled stock mk3 intercooler, courtesy of the old turbo! :32: BUT A NICE TIGHT EXTREME CLUTCH, extreme is the brand o clutch. google it. IT HOLDS VERY WELL !!!!! I'd recomend it any day. had it like that for about 5 years now. did HG about 2 1/2 year ago along with return to near stockcam settings , and actuator about 2 year ago , last tune was when HG got done. IT's a toyota unbreakable, just get a jap import 7mgte man. you were arguing with blokes that have aaaalllllllllll had 5m's , now never again!!!!!! 7mgte's go for 750 to 1000 bucks , well worth the effort to put in. DO IT DUMB

gteduck
02-16-2010, 01:24 AM
ASS CRACKHEAD!!!!!!!!!:laugh::zzzzz::laugh::zzzzz::lau gh::zzzzz::laugh::zzzzz::laugh: IT'S WORTH IT!!!!!! and don' forget to do somthing to your BRAKES.:duh:

jo_aftermarket
02-16-2010, 09:22 AM
i was going to go 7m-gte awhile back after i got a few quotes fom the local jdm guys....but i dont want to have to run into problems after installin the jdm engine (got to be carful up here depedning where u go) and the harness needed for the swap isnt exactly easy to come by ...

not to mention i would want to probably rebuild the 7m...so right there budget out the window lol...again nothin personal id rather just stick to 5m..o/s block and use supporting mods...and id rather use the orignal engine and not swap..if i decide to go swap = 1j or 2j..

btw i have a hks manifold made for the 5m...bolt to any t3 style turbo.. so once i want a bigger turbo i got the manifold......i have the hks turbo from the original 5m kit...it needs to be rebuilt but if i have it done ill most likely have it upgraded to use garret internals or upgrade it to a t3/t4....but for now im stickin to the ct26..

and for brakes...i got some plans in store for the supra while it hibernates(after the summer)...probably going to go 300zx upgrade....

gteduck
02-16-2010, 11:27 AM
yeah i've been looking at the 300zx and the R32 setup, but both involve $2000 worth of wheel's to fit in, a local joint out here makes a of the shelf kit with i think wildwood calipers too. check out a site called (SonicSupra.com) it's a local site in Canada somewhere. One of the first things i read about a 7m conversion. It's bloody good!!!!