Hey, i'm looking to bore and stroke my 420A motor when i rebuild it this winter... but... i know that once the turbosystem is installed, this motor will only be able to hold so much... so i'm wondering if i'm running about 8 p.s.i, would anybody know how much i could bore my motor out to safely?? let me know, thanks!



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Dont bore it over, thats to clean the cyl walls, you can stroke it but te stroker kit would cost more then the turbo kit. If your going to turbo your car go to howellautomotive.com and get a bottom end performance rebuild kit: je 8:8:1 pistons, eagel h bear rods, clevett 77 upper and lower bearings. Then get a mls gasket kit, apr head studs, and total seal piston rings. If you get a Hahn kit, and a mbc you can run 14psi safely and at the track pull a high 12 if you can hook up. Hp I have no idea not many people post dyno sheets for the 420a...mostly becuase few do it.

 

First of all, boring a motor out isnt to clean the cylinder walls, its to expand them so you can run bigger pistons, and second of all... i like the website you gave me... could you put that list in a little better order and a little better wording? i wasn't able to find all of the stuff that you typed out on the website... thanks!

 

Their is a reason that they dont make after market pistons more the .40 over... and thats for a reason. The 420a is a selved block and if you go too thin the the block will lose its integrity and crack under extreme conditions. I made the same mistake once, I used to rebuild dirt bikes and what knot, and for them boring the cyl over to make a larger displacment was the way to go. I did some research and turns out the only way to make the 420a bigger is to get a stroker kit which will give you a 2.2 liter motor... which is hardly worth the cost. If you dont believe me call up howell and ask them, hell call up conceptillusion.com, exileracing.com, and roadracingengineering.com see what they have to say on the matter.

For the rebuild kit check out

howell

Or conceptillusions.com I would link it but their site wont let you.. their kit is more expensive (1600 compaired to 1200) but it includes:
JE Pistons 8:8.1 $499
Eagle Connecting Rods $309.00-.020
Melling Oil Pump $95.00
ARP Head Studs $99
ARP Main Studs $137.00
Cometic .020 Headgasket $82.99
Full Gasket Kit $159.99
STD Rod Bearings $39.99
96-99 STD Crank Bearings $49.99
ITM Water Pump $48.99
T Belt with Bearings $124.99

 

Alright yea, that makes perfect sense... thanks

.... what would you suggest for the top end?

 

to many people dont understand the point of boring a motor, its to prep it for new pistons, not to increase displacement

 

Stock the top end is fine. In the sights and sound section their is a 420a running on 26psi with a stock head besides ss valves. I would deff recomend getting a new t-belt and tensioner. If you want though you could port the head and get some ss valves. I wouldent recomend getting cams because to tune that you would need either a stand alone system like aem's for 1800 bucks, injectors, and a wideband. Or a $1400 portfuler system from hahn. Or a safc, sfmu, crane ingtion box, ingtion retard, wideband, and injectors. My friend did it and he did get some power but more psi makes more hp them cams can. For the valves, the only oversized valves avaible for the 420a are 1mm bigger... which arent really worth it.