More Power out of 425

[Blackguywithouta400]

So for once im at a total loss on direction here. I want a new cam and or a higher compression piston. The goal would be to have more top end pull then i currently do. I was thinking of the HRC copy cam, or a 13:1 compression piston i know i would have to run race gas with the piston i guess the ideal thing would to get them both but we cant just yet. What do you guys think?

Piston?
Cam?

Or should i just find a FCR?

[Dave400ex]

Well for the Piston I would get one from Sparks or TC if you do that. Then a TC or Sparks Cam. I`m sure a TC or Sparks Cam would be about the Best you can get. Sparks Sell JE Pistons too so he could hook you up. Sparks also has FCR Carbs. I think if anything I would keep the Piston and maybe do the Cam and Carb.

[Blackguywithouta400]

WarriorMan thats a chunk of change there, Im sure i can get the same piston Sparks or TC has if i just call JE and cut out the middle man markup. Now how about there higher end cams? Im sure they will tell me i need better rockers with the HRC im good with the stock ones. It really comes down to what mod will give me the top end power more. i wish i knew.

[Dave400ex]

I would keep the Piston you have. If you do get one just get it from JE. Sparks Sells JE so they should be the same unless you does something to them. Sparks has Two Drop-In Cams. One is like $160 and the other One is like $360. They are Expensive, but I`m sure they are Good. TC has Cams from $175 to $205 or so. I`m not sure what will give you more Top End. I thought more Compression gave you Low End so I don`t think the Piston would help you. Call some Engine Builders and ask.

Compression = Torque = POWER.

Check out the search feature and look into cams there have been a few good ones before.

Damn warriorman you know your parts and prices:D

[VegasEx'r]

I thought that higher compression translated into more power everywhere, but that it was mainly in the bottom end. If I am wrong, somebody tell me. I think if I were in your shoes, I would want the cam, carb & piston, & I would probably get them in that order. The HRC copy because it is a cheap, easy upgrade, then the FCR carb, because I think it would add more power than the piston, then the piston, because it's gonna add power. Just my .02.

BTW, if you do get the HRC copy, let us know how it compares to the xr cam. I'm thinking I might do the same thing later this year.

[Leo]

More compresion = more power.. :D

The proper camshaft and the proper compression ratio are however very much dependent on each other..

The wilder the cam, the higher the compression ratio you can get away with (as a rule)..

Camshaft overlap has the effect of not only allowing more fuel / air mix to enter at high rpms, but it also allows the mixture to be slightly dilluted with exhaust gas.. this effectively reduces combustion chamber temp, which helps prevent pinging (or predetonation)..

I guess what it boils down to is if your going to run a 13:1 piston, get the wildes camshaft you can find.. It should give you great top-end, and the very high compression should help offset the low end power loss from the wild camshaft.. While your ripping and tearing, you might as well go for the gusto..

I would think that once you went that wild with the motor that the factory carb would start to become a serious bottleneck as far as gains go..

Leo

[Wheelie]

IMO---Buy the HRC cam, or a cam with similar specs that will give you good mid to top power without the requirement of hardened rockers, etc. Keep the piston you have, it's not that old, and you should be able to make that 425 flat out scream with 11:1 comp. If the cam doesn't provide enough juice, buy the FCR. Or the FCR then the cam.....whatever you decide.

Also higher comp=more heat, and more stress on the bottom end.

Good Luck on your decision!

[K_Fulk]

If your just looking for more topend you can get bigger valves and get a full race port job done. If you dont already.

[knighttime]

Since you already did a lot of engine work not too long ago, I would get the FCR carb and c what that does.

Then you can open the engine up later if u need to.



:cool:

Get the carb Kendrick,,,you might be overly impressed with it and then ya won't have ta go tearin into your motor,,,FCR all the way,,,hands down.:) I've also been thinking of a different cam but I think my next mod after the port work will be a new carb without a doubt. Kinda like Leo said that stock carb might be a bottleneck now,,it's only gonna get worse if you replace the piston and cam. I know Gabes tried numerous pistons and cam's his input would be nice on this subject...I'm bettin he's gonna suggest the carb too..:D

I have a the curtis sparks full race cam with a stock bore 10.5:1 je piston. It added alot of mid to topend power with alittle loss of lowend power. I am going to order a 87mm 12.5:1 piston and the fcr carb today. If you want a 13:1 je piston its cheaper to buy from a engine builder becouse they need to be special made for you. And I was told they will not make just one.

[nakomis0]

I'm also gonna say go with a carb. You already have a 11:1 piston? and a aftermarket cam? Definately carb.

If you want a 13:1 je piston its cheaper to buy from a engine builder becouse they need to be special made for you. And I was told they will not make just one.

I was told by J&E that they have standard production on the 13:1 piston.

The people at Cometic gasket did claim to have a "special" gasket for this higher compression. It uses an extra ring around the bore to compensate for the extra stress on the head bolts etc. It is also thicker than some other gaskets and requires you to deck the cylinder in order to achieve a true 13:1.