big bore questions

[below100hz]

im gonna have to rebuild my 400 and im considering doing a 416 or a 426 kit but im just concerned about the 11:1 compression, i really dont want to run race gas, is it really needed or is 93 octane pump gas fine? ive also heard that some cams will cause the compression to get lowered is that true? and what stage cam would be better for that? anyone know about how much it would be to get the cylinder bored out?
thanks

[underpowered]

93 on 11:1 is fine, if it make you feel better you can jet a little fat for some extra insurence.

A cam has nothing to do with the compression. the comp ratio is how many time the piston compresses the air. for ease of math, i will try to expalin it. say you have an 11:1 piston and the motor has an 11" stoke. there are 12" inthe combustion chamber. the piston takes what is in those 12" and compresses it into a 1" space, taking out 11" of it, thus compressing it 11 times to make it al fit. the cam has nothing to do with the compression of the combustable gasses.

for a bore, it varies by shop. The usually run anywhere from $30-$60.

[zeppelin]

your close with the compretion ratio thing , let me see if i can make it clearer. okay if you have a 10:1 ratio. (this is an uncommon ratio, but i'll just use it for an easier explanation.) imagin a cylinder divided into 10 sections, at the top of the pitons stroke the air will be compessed into only one section, one tenth of the origional size of the cylider.

[underpowered]

Originally posted by zeppelin
your close with the compretion ratio thing , let me see if i can make it clearer. okay if you have a 10:1 ratio. (this is an uncommon ratio, but i'll just use it for an easier explanation.) imagin a cylinder divided into 10 sections, at the top of the pitons stroke the air will be compessed into only one section, one tenth of the origional size of the cylider.

thats what i was goin for :D , just made it more complicated than it needed to be.

[F-16Guy]

Originally posted by underpowered
93 on 11:1 is fine, if it make you feel better you can jet a little fat for some extra insurence.

A cam has nothing to do with the compression. the comp ratio is how many time the piston compresses the air. for ease of math, i will try to expalin it. say you have an 11:1 piston and the motor has an 11" stoke. there are 12" inthe combustion chamber. the piston takes what is in those 12" and compresses it into a 1" space, taking out 11" of it, thus compressing it 11 times to make it al fit. the cam has nothing to do with the compression of the combustable gasses.

for a bore, it varies by shop. The usually run anywhere from $30-$60.
A cam may have nothing to do with the compression RATIO, but it does affect cylinder pressure. A longer duration cam will keep the valves open longer, giving the piston less time to build cylinder pressure. That is why they're usually coupled with a higher compression ratio piston, which will produce more cylinder pressure to offset the loss created by the cam.

[GPracer2500]

Originally posted by F-16Guy
A cam may have nothing to do with the compression RATIO, but it does affect cylinder pressure. A longer duration cam will keep the valves open longer, giving the piston less time to build cylinder pressure. That is why they're usually coupled with a higher compression ratio piston, which will produce more cylinder pressure to offset the loss created by the cam.

Bingo!

Cams absolutely affect dynamic compression, i.e. the observed compression of a running engine. To reiterate what F-16 siad, aggressive cams with lots of lift and duration leave the valves open so long (and so much) that some compression is lost through them that would not be lost with a less aggressive cam.

Some aggressive cams may produce less power everywhere in the RPM range if a high compression piston is not used. I've experienced this phenomenon myself with a street motorcycle by experimenting (using a dyno) with different cams. Unless you're running an appropriately high compression, a mild cam may perform best.

[below100hz]

i ordered all my parts but im wondering if i can have my cylinder bored out before the piston comes or am i better off waiting? alsois it worth pulling the whole motor out? i can get at everything pretty well where it is.
is there any online repair manuals that anyone knows about for a 400ex? like a clymer one

[GPracer2500]

No need to pull the motor.

I stongly prefer the Honda service manual. CD-ROM versions can be had from E-bay sellers for something like 5 bucks.

Deffinitely take your new piston to your machinist so he can set the clearence properly.

[ww228king]

just tell them that you want an 88mm bore ..no need to take all that stuff to them...they look at you stupid....like what the heck do you want me to do with your piston....88mm for a 426 or 87mm for a 416...............i love my 426...with the front sproket at 14 teeth, wow it is strong down low...comes up in forth,,,,but need rev box badly...

[honda460ex]

Take them your piston, they will need it... Most good machinest will not even attempt to bore a cylinder without the piston that is going to be used. Different pistons, different brands, different boring requirements. Trust me. Me and Underpowered experienced this first hand. His 426 piston was the same size (circumfrence) as my old 440 wiseco piston. Different pistons, different manufacturers like I said.

[ww228king]

lol....88mm is 88mm .....if your old 440 piston was 88mm then it was a 426.....but anyway....c&j from rocky mount, nc does all my boring and never screwed up.....i mean how can you...set the bore machine on 88mm and turn your oiler on and turn the power on and leave it be for about 25 mins....when you buy a piston it tells you what size to bore your cylinder....i hope you dont go by the piston when you tell them what size to bore a cyclinder....you will be a lil small....85 is stock 86 is 406 , 87 is 416, 88 is 426, 89 is 440....i have always gone with wiseco pistons and never had any problems ....come on guys ...you know this stuff

[honda460ex]

Lol, whatever man.............. No offense, but I hate wiseco pistons. They are not true to specs or compression from everything I've seen. When i built my 406 I used a wiseco 11 to 1, when I built my 440 I used a wiseco 12.5 to 1, when I tore it down and stroked it I had to hone out my cylinder to fit my JE 13 to 1 89mm piston.... In other words, my wiseco 440 piston, also supposed to be an 89mm piston, was not true to specs. It was small, and it has the part number stamped on it. It's a true 89mm wiseco piston, just as my JE is a true 89mm piston from JE. In other words, they are different.... I'm not a dumby here, I'm speeking from experience. I always build my own motors.

[GPracer2500]

AFAIK, you can't set the cylinder-to-piston clearence without mic'ing the piston to see exactly (i.e. to the thousandth of an inch) what the diameter of the piston is. Knowing it's a 88mm piston doesn't quite cut it.

Maybe there's a machinest here that can put in the final word??

[ww228king]

sounds kinda messed up to me....if you told the people that you were going with a 89mm ....then you should have an 89 mm bore.....why did you have to bore it again to a 89mm.....i know one thing for sure ...i would loveeeeee to see some body cram a 89mm 440 piston in a 88 mm 426 hole.....it will not fit... i think the shop ripped you a new one ...you should change your people that do you boreing.....i think they got you on that...plus i dont mind cleaning out the cyclinder by honeing before you install new stuff.....but boring and going with the same size piston...lol no way....hone and bore...hmmmm not the same bud

[ww228king]

you dont measure the piston...are you guys useing rings.....you have to allow for the rings....

[GPracer2500]

I'm reading a spec sheet that came with a new JE piston. It clearly indicates a suggested piston-to-cylinder clearence and specifies where on the piston to measure it's diameter: "...measure piston diameter .500 [inches] up from bottom of skirt..."

Boring and honeing are different steps but the machinest will be doing both and he SHOULD REQUIRE the piston to get the clearences correct.

To the original poster--take your piston in with your cyclinder AND take the spec sheet that should come with the piston. If they are experienced in working with the piston brand and application your dealing with they may not need the spec sheet--they'll allready know those details. But if your machinest mostly builds car engines with cast pistons or something than you'll want to equip him with the info he needs to do the job right.

[ww228king]

dang rookies......anyway.....if you got to measure every dang piston you order in order to get the correct bore then you need to quit buying sorry pistons ...if you buy a 88mm piston a 45mm piston or a dang 97mm piston ...i dont care if you get a 200mm piston.....you are gonna bore you cylinder to what you have ordered.....then tens of thousandths crap that you were mentioning is what ring seat is all about......you mean to tell me that you guys order a 89mm piston then measure the piston again when it comes in an it WILL BE 89MM PISTON then bore your cylinder....then what is the use of ordering a dang 89mm piston if you have to measure thing when it comes in.........if you guys dont trust what you buy then ....just give up...lol

[aviator4]

Wow, ww228king, you're all messed up. I know a number of machinists that build all types of engines from model airplane engines all the way to big-rig engines, and everything in between. can tell you that NONE of them will bore a cylinder without having the piston first.

as far as the machinist "looking at you weird" - I would expect that if you showed up with a cylinder and said "just bore it... okay?" - I'd get a strange look and then an "I'm sorry sir, I'm not going to kill your engine for you" or something.

The thousanths of an inch you're referring to, you're partially right, the rings to have specific gapping that has to be measured and then the rings may need to be filed, BUT, if your cylinder clearances are too big you get piston slap and galling. If they are too smal, you will cease that sucker right up!

below100hz, take everyone ELSES advise her and TAKE THE PISTON WITH YOU!

[ww228king]

i guess people dont trust themselfs.......nor trust there work.....yeah in the old way of boring , true !!! you will need something to go by.....but now.....the mechine is set up to bore on its own..........push in the size and it is on......if somebody needs a piston to bore a cylinder then they must be doing it the out of date way...(by hand).....catch up with today guys

[honda460ex]

Ha ha, ww228king, please stop man..... Obviously no one is agreeing with you. I know a wiseco dealer who is also a machinest, has been for some 30 years. He will not touch a cylinder still to this day until he has the piston in hand and measures it out himself. He has 2 automatic bore machines as well. As far as honing and boring... lol, when you are honing something, you are still shaving the cylinder walls out in there. Just not to the extent as if you were boring it. You hone a cylinder to fine tune it just perfect. It's a slower process of boring. Every machinest bores and then hones a cylinder to get it just perfect within specs. Yes, honing cleans up the cylinder as well after boring or just to remove light scars, but that's not the only reaon you hone... Oh yeah, and i didn't have to rebore from my 89mm to my 89mm, I had to hone it out. It was not so far out that I would have to bore it. That's what I'm telling you smart guy, the difference was not huge, but they were different from 2 different piston manufacturers... Ha, I'm done! Anyone else??? lol

Originally posted by ww228king
i guess people dont trust themselfs.......nor trust there work.....yeah in the old way of boring , true !!! you will need something to go by.....but now.....the mechine is set up to bore on its own..........push in the size and it is on......if somebody needs a piston to bore a cylinder then they must be doing it the out of date way...(by hand).....catch up with today guys


i get what hes saying....:huh

[ww228king]

thank you.....426 still running strong

[GPracer2500]

I think that was sarcasim, hence the "huh" face.

the :huh face means i TOTALLY get what hes saying

[below100hz]

so i brought the cylinder and piston to the machine shop today... i was thinking it was gonna cost me under 100 to get it done but the guy said between 150 and $200 to bore it, pressure check my valves to make sure theyre good, change the seals, and put my cam gear flange on my new cam. i dunno maybe it will be a little less than that im not sure, what do you think about that price?

[honda460ex]

What get's you at a machine shop like that is the time, and yeah, to have all that done, I can see it being around $150 or so. If it was just boring, you can usually have that done for $40-60. So, me personally, I think that's reasonable. Anything over $180 though I think is pushing it.

[aviator4]

Yeah, to get all that done, the price range isn't too out of whack. The boring of the cylinder is actually only a small part of that list.

[below100hz]

the gaskets kit that came with my big bore kit is STD bore, is that right or is the head gasket supposed to be bigger i thought?

[below100hz]

bump ^^
just got a call from the machine shop, i need new intake valves, good thing i brought the head with me. what can cause them to get warn down so fast? its only 4 years old

[aviator4]

Depends on where the wear is. It could be cause by improper timing, the wrong fuel, compression problems or it could simply be a defect in workmanship from the get go.

Did he say you needed vavles or valve seats? Also, Valves can usually be re-lapped or ground at least once. Unless the stems are bent, you might as him about that.

[tex440]

..Take your new piston to the shop,they will need to match the piston to the bore.
.. also,if i remeber right,Wiseco has 2 of what they call 440cc pistons..some ppl have gotten a 88.5mm,makeing it a 435 witch lets you get another bore on your motor,an 89mm piston witch is a ture 440cc.Leveing no more meat for an overbore.Unless you use another new sleeve,witch you have to anything over 426cc,if i remeber right..

[GPracer2500]

Originally posted by tex440
..Take your new piston to the shop,they will need to match the piston to the bore.
.. also,if i remeber right,Wiseco has 2 of what they call 440cc pistons..some ppl have gotten a 88.5mm,makeing it a 435 witch lets you get another bore on your motor,an 89mm piston witch is a ture 440cc.Leveing no more meat for an overbore.Unless you use another new sleeve,witch you have to anything over 426cc,if i remeber right..

89mm is actually 435cc. JE has a new 89.5 piston which is a true 440cc. Didn't know Wiseco has a 89.5 also.

[GPracer2500]

Originally posted by below100hz
bump ^^
just got a call from the machine shop, i need new intake valves, good thing i brought the head with me. what can cause them to get warn down so fast? its only 4 years old

Among other things, poor filtration that allows fine particulates to enter the intake stream can also cause the intake valve faces to wear. If you've been running a K&N in dusty conditions, consider switching to foam-type filter.

Also, whatever reason caused you to need a rebuild in the first place might be the same reason your intake valves are shot.

[homemade wrx]

Originally posted by ww228king
i guess people dont trust themselfs.......nor trust there work.....yeah in the old way of boring , true !!! you will need something to go by.....but now.....the mechine is set up to bore on its own..........push in the size and it is on......if somebody needs a piston to bore a cylinder then they must be doing it the out of date way...(by hand).....catch up with today guys
like everyonehas said, I too know numerous engine builders, yes with CNC boring machines, that won't touch the engine without spec'ing the dimensions of the pistons themselves, because if it doesn't fit to the listed tolerances, they are the first one's blamed...