416 Bore Question

[EX_Junkie]

I'm going to order a piston and a cam for my 400 so that i can go to a 416. What do i tell the machinist to bore it to? Is it .040 or .080 and is that 40 hundreths or thousanths?

[Chanman420q]

.080 and its hundreths

[Tommy 17]

.040 is 406
.080 is 416
.120 is 426


its . tenths hundreths thousandths

[sickmojave]

at what stage do you have to change the studs or is that just higher compression that makes you have to change them? say I went to a 416 but stayed with a 10.8:1. would I have to change the studs?

[Bad Habit]

Most shops that know what they are doing won't let you just tell them how much to bore it out. They will want the piston so they can exactly match the bore to the piston diameter. This is the best way to get it done correctly.

When talking about bore size, it is pretty much always referenced as thousandths of an inch. As in 80 thousands (.080), 40 thousands (.040) etc.

[cals400ex]

i agree, i would just give him your piston too.
say you have the # 0.045
the 0 is the tenths place
the 4 is the hundredths place
the 5 is the thousandths place

yellow416, i think you have your #'s a little messed up. it should be hundredths, not thousandths. ;)

with 10.8:1 you SHOULD be fine with the stock studs. i am running a 10.8:1 piston with thinner gaskets and i am still using the stock studs. when you get higher than 11:1, i would suggest getting new studs unless you just want to get them now for added insurance. good luck

[hawiianpwr]

No Cal, Yellow is right its thousands:)

This would be .40 hundreds
This would be .040 thousands

[JOEX]

Depending on how you read it, they are both right.

.4= four tenths
.40= forty hundreths
.04=four hundreths
.040=fourty thousandths

:) Joe

You need to take the paperwork that comes with the piston to the machine shop, don't just say bore this cylinder .080 over:cool:

[EX_Junkie]

Lol i understand it now. Thank u guys for your help. I'll be ordering everything today so i geuss i'll start tearing the quad down tonight.

Anyone know what places i can get my stock carb bored?

Originally posted by EX_Junkie
Lol i understand it now. Thank u guys for your help. I'll be ordering everything today so i geuss i'll start tearing the quad down tonight.

Anyone know what places i can get my stock carb bored?

Rocky Ridge racing does it for about $125, sparks is like $175 and I don't know of any other companies that do it..

[bmw500hp]

Originally posted by Yellow416ex
Most shops that know what they are doing won't let you just tell them how much to bore it out. They will want the piston so they can exactly match the bore to the piston diameter. This is the best way to get it done correctly.

When talking about bore size, it is pretty much always referenced as thousandths of an inch. As in 80 thousands (.080), 40 thousands (.040) etc.

Take the piston with you and leave it with the shop. If for no other reason it's an issue of responsibility.

[cals400ex]

Originally posted by hawiianpwr
No Cal, Yellow is right its thousands:)

This would be .40 hundreds
This would be .040 thousands


yep, sorry about that. i read the earlier post wrong.

[Flat Broke]

Originally posted by JOEX
Depending on how you read it, they are both right.

.4= four tenths
.40= forty hundreths
.04=four hundreths
.040=fourty thousandths

:) Joe

Joe,

Your breakdown is right, but the earlier answers are not interchangeable. 40 hundredths would be .40 as you indicated where it was initially shown as .040 which would be 4 hundredths or 40 thousandths. I know it's splitin hairs, but thats just what machining tolerances is... :)

As far as whether or not to leave the piston with the shop, that depends. The reason the shop needs the piston is to set the piston to wall clearance properly for the ring set that is provided. The clearance between the piston and wall will change as the piston heats up. If the clearance is too tight you could have ring bind or even sieze the piston to the cylinder wall. If the clearance is too great, the rings will not be able to control the oil properly or contain the compression desired. This would result in burnt oil and/or lost compression. With certain pistons (JE comes to mind), the piston comes with a spec sheet that the machine shop can use for reference. The maker of the ring set may actually call out the cylinder to wall clearance in some instances. If it were me, and I was worried about leaving the piston, I wouldn't use the shop, but if you needed it for something else (thermal barrier coating etc.) the shop should be able to mic the piston to get the reqiured dimensions in a couple of minutes and use the manufacturer's spec, or existing clearance guides to do the machine work.

Sorry for the long post, and this is more of a general 4cycle engine answer as opposed to a quad specific response, but proper blueprinting practices should be used no mater what type of motor you're building.

Chris

[Bad Habit]

Originally posted by Flat Broke
With certain pistons (JE comes to mind), the piston comes with a spec sheet that the machine shop can use for reference. .......... but proper blueprinting practices should be used no mater what type of motor you're building.

Chris

I used a JE piston and my shop wanted both, the actual piston and the spec sheet.;) The shop I used is only a few blocks from my house and is one of the nations premier cart builders. He knows how to build motors. All the cart motors are 2 smokes and he admits that he's not a 4 stroke guru, but he certainly knows how to do things to the letter. I feel fortunate that I have him and his knowledge of motors so close to me.

[RAPTORAZ]

Originally posted by sickmojave
at what stage do you have to change the studs or is that just higher compression that makes you have to change them? say I went to a 416 but stayed with a 10.8:1. would I have to change the studs?


I believe the stud issue has been linked to their removal. If left undisturbed (like when the jug is just overbored, 406,416,426) they are fine. However if they are removed (like when you do a sleeve replacement, for example, when doing a 440 kit) they no longer stay in place and turn. Which causes the subsequent head gasket failures. My 10.8:1 compression 416 has not blown a head gasket since I put it together(over a year ago). But I made sure the machine shop did NOT pull the studs while boring it.