hey guys i gotta ? about piston compressions

[westcoastmxer]

hey guys im wantin to biuld my 300's motor up were itll be more powerfull..wuts the difference in .20,.40,and .60?will i have to use race gas or sumthin?also will a 330 kit give me alot more power than the .60 high compresion piston and how much more power will the .60 piston give me over stock?(is it worth it?)..also do u prefere a web cam or hot cam stage 2?and will hardined rockers make much more power?..thanx alot ben

[Cody_300ex]

Hot cams dosent make cams for a 300ex, sorry. Hardened rockers dosn't make any power difference, you just need them when you get a bigger cam because a bigger cam will wear your stock out prematurealy or break them. And the difference between .20 .40 .60 and .80 are the bore sizes NOT compression ratios. Compression decides what octane gas you have to run. So you order a .60 over piston you will need to take your jug/sleave to a local machcine shop and have them bore it .60 over. It should only cost about 40 to 60 dollars. And if its a 10:1 you should be safe running 93 octane and your stock rod, but if you get 11:1, 12:1, 13:1, 14:1 you will need to get a stronger rod and will have to run race gas.

[sparks400]

Originally posted by Lil_300Ex_Kid
Hot cams dosent make cams for a 300ex, sorry. Hardened rockers dosn't make any power difference, you just need them when you get a bigger cam because a bigger cam will wear your stock out prematurealy or break them. And the difference between .20 .40 .60 and .80 are the bore sizes NOT compression ratios. Compression decides what octane gas you have to run. So you order a .60 over piston you will need to take your jug/sleave to a local machcine shop and have them bore it .60 over. It should only cost about 40 to 60 dollars. And if its a 10:1 you should be safe running 93 octane and your stock rod, but if you get 11:1, 12:1, 13:1, 14:1 you will need to get a stronger rod and will have to run race gas.
nice post

[westcoastmxer]

thanx alot man im all confused wen it comes to motors..so do u think i need to get a cam or not?

[JOEX]

Originally posted by Lil_300Ex_Kid
Hot cams dosent make cams for a 300ex, sorry. Hardened rockers dosn't make any power difference, you just need them when you get a bigger cam because a bigger cam will wear your stock out prematurealy or break them. And the difference between .20 .40 .60 and .80 are the bore sizes NOT compression ratios. Compression decides what octane gas you have to run. So you order a .60 over piston you will need to take your jug/sleave to a local machcine shop and have them bore it .60 over. It should only cost about 40 to 60 dollars. And if its a 10:1 you should be safe running 93 octane and your stock rod, but if you get 11:1, 12:1, 13:1, 14:1 you will need to get a stronger rod and will have to run race gas.
Not so sure on the hardened rocker comment, I belive it has to do with the material the cam is made of, not the size.

[ghak99]

Originally posted by JOEX
Not so sure on the hardened rocker comment, I belive it has to do with the material the cam is made of, not the size.

I am with joex on the rocker thing.

I have run 12:1 for a while now without any problem with the stock rod.

[Cody_300ex]

Originally posted by JOEX
Not so sure on the hardened rocker comment, I belive it has to do with the material the cam is made of, not the size.

Thanks, I wasnt to sure on that but im sure how big the cam is does have a little to do with hardened rockers.


Originally posted by ghak99
I have run 12:1 for a while now without any problem with the stock rod.

I've heard a lot of horror stories about people breaking rods and destorying thier engine. i figure if i ever got a high comp pistion i would rather replace a rod now than a 700 dollar (if not more) engine later. I like to play by the rule "Better safe than than sorry." Ya know im saying.

[ghak99]

I know what you mean by better safe than sorry, but it seems to me that the 400ex has more rod problems than the 300ex when using 12:1. This could be due to the fact that there are more 12:1 400's than 12:1 300's being raced though.

[UglyMotha™]

Originally posted by Lil_300Ex_Kid
Thanks, I wasnt to sure on that but im sure how big the cam is does have a little to do with hardened rockers.



nope, it has nothing to do with the size of the cam only the material the cam is made of

[westcoastmxer]

i want as much power as i can get wut kinda cam do u guys prefere and how big?..so if i get a .60 piston will i have to change my gas or anything like have my cylinder bored?..thanx alot ben

[foleyit]

Originally posted by UglyMotha™
nope, it has nothing to do with the size of the cam only the material the cam is made of

Correct, the size of the cam doesn't affect your rockers. It's the material of the cam that affects the rockers.

[Cody_300ex]

Originally posted by westcoastmxer
i want as much power as i can get wut kinda cam do u guys prefere and how big?..so if i get a .60 piston will i have to change my gas or anything like have my cylinder bored?..thanx alot ben For the cam check out www.webcamshafts.com . Like I said in my other post if get a .60 piston YOU WILL HAVE TO HAVE YOUR SLEAVE BORED If you get a 10:1 piston You will NOT have to run race gas, But if you get a 11:1, 12:1, 13:1, or 14:1 piston You WILL have to run race gas. ok i think im done with my rant! :o :p

[westcoastmxer]

thanx guys:D ..another ? should i j/get the 330kit or get a high compresion piston and cam?also will i really need the hardined rockers?

[Cody_300ex]

Originally posted by westcoastmxer
also will i really need the hardined rockers?

if you get a new cam....Yes

[JOEX]

Originally posted by Lil_300Ex_Kid
if you get a new cam....Yes
Is this a 300ex thing? On other motors hardened rockers are only required on certain cams. It depends on what they are made off.

[UglyMotha™]

Originally posted by JOEX
Is this a 300ex thing? On other motors hardened rockers are only required on certain cams. It depends on what they are made off.


no it's not a 300ex thing, this kid just has no clue what he's talking about YOU ONLY USE HARDEND ROCKERS WITH A HARDEND CAM and if you don't go by this and get a cam that does not require hardend rockers then you will trash the cam

[04'400ex'er]

Originally posted by westcoastmxer
i want as much power as i can get wut kinda cam do u guys prefere and how big?..so if i get a .60 piston will i have to change my gas or anything like have my cylinder bored?..thanx alot ben

READ THE SECOND POST! A .60 piston is not what you are seeing. It's a .060 piston. That stands for 60 hundredths of an inch overbore. That means it is sixty hundredths of an inch larger than your stock piston. If you buy this size piston, or any overbore, you will have to have a machine shop bore your stock cylinder to the size of your piston. You can get this piston and run regular premium gas. The size of the piston has nothing to do with the type of gas you have to run. What determines the type of gas you run is the compression of the piston. Compression is the amount of pressure, in a sense, that the piston builds when it drives up the cylinder. If you buy a 12 to 1 compression piston, you will need to run race gas or half and half. 11to 1 is approx. the highest compression you could run on pump gas. Also, the higher compression, the more power. I would go with a 330 kit, or somethin like that, i dunno about 300's, with 11 to 1 and the hottest cam you can get. Also i would have the head ported and polished by Curtis Sparks. Also, I'd get a stronger rod, stiffer springs, and hardened rockers for reliability.

[JOEX]

Originally posted by UglyMotha™
no it's not a 300ex thing, this kid just has no clue what he's talking about YOU ONLY USE HARDEND ROCKERS WITH A HARDEND CAM and if you don't go by this and get a cam that does not require hardend rockers then you will trash the cam
That's what I thought;)

And he thinks he's the next wilkin250r:rolleyes:

[UglyMotha™]

there could never be another wilkin :cool: :D

[westcoastmxer]

thanx alot guys..and thanx uglymotha 4 clearin that up because i was about to buy hardened rockers:rolleyes: ..i think ima go w/a 330kit:macho

[Cody_300ex]

Originally posted by JOEX
And he thinks he's the next wilkin250r:rolleyes:

Hey man im only 13 I think im pretty smart about motors for that age. Ive rebuilt my 300ex engine and a 400ex engine. I've had a lot of compliments on my smartness about motors in general from people that build costom engines for a living. So could ya get off my back man...ok. :cool:

[wilkin250r]

My reputation proceeds me. :) :cool:

Camshafts do not come in different "sizes". You can't fit a "bigger" cam. You can get a cam with more lift, or more duration, but they are not physically bigger in size. To get more lift, the lobes are slightly taller, but that's typically only about 0.020".


As for hard-faced rocker arms, it depends on the type of camshaft you buy, and I haven't really researched all the available types for the 300EX, so I'll explain the difference.

To get a camshaft that gives you more power, the camshaft manufacturer has one of two choices. Either take a stock camshaft and modify it, or mold a whole new camshaft from scratch.

To modify a stock camshaft, the manufacturer grinds the camshaft down, and then welds new metal on top of it, and re-grinds it to new specs. The problem is the new metal that gets welded on top is slightly harder than the original metal of the stock camshaft. If you use your stock rocker-arms, the harder metal of the camshaft will chew them up. This is why you would need a hard-weld (hardfaced) rocker arms. They take your rockers, grind them down a little, weld new material to the face that contacts the camshaft, and grinds them to spec. Now they are the same hardness, so they won't chew each other up.

Method number two is to mold a whole new camshaft from scratch, and is usually done in the same metal the stock camshaft is made of. So since it is the same metal, you don't need hardfaced rockers. These are often called drop-in cams. In fact, if you DO use hardfaced rockers with the stock or a drop-in cam, the hardfaced rockers will chew up your camshaft.

[MIKE400EX]

READ THE SECOND POST! A .60 piston is not what you are seeing. It's a .060 piston. That stands for 60 hundredths of an inch overbore. That means it is sixty hundredths of an inch larger than your stock piston.


.060" is sixty thousandths of an inch.
.60" is sixty hundreths of an inch.
A piston that said to be "60 over" is .060" oversize (measured across the diameter).

[keepitpinned]

how many more cc will the .40 over give you on a 400ex

[cals400ex]

Originally posted by keepitpinned
how many more cc will the .40 over give you on a 400ex


do you mean .040 over? this is approximately a 406.

[Chef]

You need to go by the cam manufacturer's directions as to hard rockers or not. I think that all but 1 of Web's cams need hard-welded rockers, because they are a hardweld cam. If you find a billet cam, like mine, you do not need hard rockers. The hard rockers will eat at your cam, and ruin it.

[04'400ex'er]

Originally posted by MIKE400EX
READ THE SECOND POST! A .60 piston is not what you are seeing. It's a .060 piston. That stands for 60 hundredths of an inch overbore. That means it is sixty hundredths of an inch larger than your stock piston.


.060" is sixty thousandths of an inch.
.60" is sixty hundreths of an inch.
A piston that said to be "60 over" is .060" oversize (measured across the diameter).

Whatever you know what i mean

[cals400ex]

Originally posted by Chef
You need to go by the cam manufacturer's directions as to hard rockers or not. I think that all but 1 of Web's cams need hard-welded rockers, because they are a hardweld cam. If you find a billet cam, like mine, you do not need hard rockers. The hard rockers will eat at your cam, and ruin it.


where can i find a good cam for drag racing? i heard megacycle cams are not being sold anymore but i really don't know.