2G Can you bore 420a out

[2g_rebel]

I just picked up a motor for my car and has rust in cylinders. Can I have it bored out to run Evo pistons

 

[97egl]

Yes you can bore it for larger pistons, but you cannot run EVO pistons in a 420a. Completely different engine. You would need to get oversized pistons for your engine

 

[2g_rebel]

Yes you can bore it for larger pistons, but you cannot run EVO pistons in a 420a. Completely different engine. You would need to get oversized pistons for your engine

Okay now I'm new what makes it that I can't run Evo pistons. Is it the hight just asking so I know

 

[97egl]

Every dimension is going to be different.
-Compression Height will be different... if close you could use a thicker headgasket or deck the block to overcome that issue
-Wrist pin size will be different. You would have to bore or bushing them to make them fit,
Smaller Bore Size. The stock bore of the 420a is larger than the largest oversize pistons that are made for an evo. You would have to re-sleeve the engine to make the bores smaller to run the evo pistons and that would cost way way more than just getting forged pistons for the 420a if that's why you are wanting evo pistons.

 

[BLACK'98DSM]

You can safely bore the 420A up to 0.060" over. Often times you only need a 0.020" bore, for rust and mild scoring. Plenty of 420A pistons are available regardless.

The factory bore size is 3.445".
0.020" over = 3.465"
0.040" over = 3.485"
0.060" over = 3.505"

Here's a picture one of my blocks bored to 3.467", which is 0.020" over plus a little extra clearance for forged pistons to account for the extra thermal expansion. And decked to boost compression ratio.

These aren't sleeved blocks originally so the only limitations are cylinder wall thickness + concern of stress cracks under heavy load, and aftermarket parts availability.

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[2g_rebel]

You can safely bore the 420A up to 0.060" over. Often times you only need a 0.020" bore, for rust and mild scoring. Plenty of 420A pistons are available regardless.

The factory bore size is 3.445".
0.020" over = 3.465"
0.040" over = 3.485"
0.060" over = 3.505"

Here's a picture one of my blocks bored to 3.467", which is 0.020" over plus a little extra clearance for forged pistons to account for the extra thermal expansion. And decked to boost compression ratio.

These aren't sleeved blocks originally so the only limitations are cylinder wall thickness + concern of stress cracks under heavy load, and aftermarket parts availability.

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Thank you this has been so helpful

Every dimension is going to be different.
-Compression Height will be different... if close you could use a thicker headgasket or deck the block to overcome that issue
-Wrist pin size will be different. You would have to bore or bushing them to make them fit,
Smaller Bore Size. The stock bore of the 420a is larger than the largest oversize pistons that are made for an evo. You would have to re-sleeve the engine to make the bores smaller to run the evo pistons and that would cost way way more than just getting forged pistons for the 420a if that's why you are wanting evo pistons.

Thank you. This is why I asked.

 

[2g_rebel]

You can safely bore the 420A up to 0.060" over. Often times you only need a 0.020" bore, for rust and mild scoring. Plenty of 420A pistons are available regardless.

The factory bore size is 3.445".
0.020" over = 3.465"
0.040" over = 3.485"
0.060" over = 3.505"

Here's a picture one of my blocks bored to 3.467", which is 0.020" over plus a little extra clearance for forged pistons to account for the extra thermal expansion. And decked to boost compression ratio.

These aren't sleeved blocks originally so the only limitations are cylinder wall thickness + concern of stress cracks under heavy load, and aftermarket parts availability.

You must be logged in to view this image or video.

Would these rings work for honing the cylinder

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[pauleyman]

No. Those won't work.

 

[2g_rebel]

No. Those won't work.

I'm having trouble finding expansion rings for this motor

 

[pauleyman]

I'm having trouble finding expansion rings for this motor

Im sorry but I need to call this out. You keep talking about motors other than the one you have. Do you know how to rebuild a motor? You also mentioned " will these rings work for honing the cylinder: rings do not hone a cylinder. Its hard to interpret what youre doing and what skill level you have. Help us help you. Tell us what skill level you know.

 

[Canadian_CD9A]

Also share your budget, because the machine work (which is needed to overbore a block) can run up a hefty bill - and you can't do that yourself.

Pistons are extremely hard to find for these now. The only overbore pistons that Rock Auto has for the 420A are +0.50mm Silvolite 3228HC, which cost like double what I paid for them a couple years ago. Matching piston rings are +0.50mm ENGINETECH M87534 or +0.020" MAHLE / CLEVITE 41851CP (same size). You'll probably be adding bearings, a gasket kit, and a bunch else. This can cost $2,000 if you build the engine yourself, with up to $1,000 in machine work. If you have never done anything like this before, I suggest you don't buy everything to do the job yourself.