To hone or not to hone?

[2.8-350TBI]

Well, I am nearing the stage where I have enough money to keep working on my 3.4, and before sending it off to the machine shop, how do I know if it is a good idea to hone it or not?

From what I can tell, the engine was run pretty hard, and maintenance was not very consistent, which goes by what the driver told me; he ran the piss out of it.

The bearings have areas that look like they have had cavitation, and the cam bearings were worn down to the copper/brass, so it was abused, and it only had 140K

Which leads me to ask, how can you tell if it needs a hone?

The cylinders still have crossshatching visible half a quarter to a half-inch below the top of ring travel. The upper quarter inch of ring travel is polished smooth and the taper is big enough to feel with your finger. I have not measured taper but I have access to tools and can.

Suggestions? Ideas? What is an acceptable amount of taper?

[pocket-rocket]

Taper allowances are very very small if you are doing any sort of performance. You might need a ridge reamer to get the pistons/rings out, and any time I remove them I hone, unless for some reason it's been honed lately. When in doubt, take the block to a machine shop and they will get you set strait.

[2.8-350TBI]

Well, I will be running it as a 3.4/3500 hybrid with 3400 pistons just a cünt hair shy of 9:1 CR, and it will eventually be boosted.

The pistons are already out and the block is bare at the moment, only with the heads and intakes on it as a mock up.
They came out fairly easily too.

What is an acceptable amount of taper? I need to know so I can take it to school and measure it.

[geoffinbc]

If you can catch a finger nail on the edge at the top of the cylinder then it needs a hone. No measurement needed. Your better off going up a piston size and then you wont have sloppy pistons.

[2.8-350TBI]

Cant catch a fingernail! Its a pretty smooth transition.
Betterthanyou, thats exactly the reason I dont wanna hone if I dont have to; I dont want a loose piston clanking away in my cylinder walls.

[pocket-rocket]

Cant catch a fingernail! Its a pretty smooth transition.
Betterthanyou, thats exactly the reason I dont wanna hone if I dont have to; I dont want a loose piston clanking away in my cylinder walls.

Well you need to find out if your piston to wall clearance is in spec as well. If not, you are going to have blowby and possibly piston slap if it's too far out on the high side. If in doubt, a machinist will always set you on the right path.

[Joseph Upson]

Cant catch a fingernail! Its a pretty smooth transition.
Betterthanyou, thats exactly the reason I dont wanna hone if I dont have to; I dont want a loose piston clanking away in my cylinder walls.

I'd be more concerned as a result of the high mileage on the block. Although you can see the hatch marks, I would still run a hone through it. I have a three leg hone that I just used on the 25K block I'm about to do my forged build on eventhough the engine still looks new. The reason is to insure ring seating in a reasonable amount of time. The hatch marks are for proper oiling of the rings and ring seating.

[bob442]

theres only one option for pistons for a 3400 with 3400 heads right, IIRC the DOHC raised it to 12:1? reason i ask is because i'll be in the same boat tomorrow, and i need to know what to budget for so i can get this thing up and running for early spring. and i cant afford 600 for pistons ontop of a .020" over machine bill

[2.8-350TBI]

If its a 3.4 block with aluminum heads, you use 3400 pistons

Or the RWD 3.4 if you want to run insane compression and 93 octane +

TDC pistons are 2 cc's smaller than the 3.4RWD

[bob442]

well, i guess what i meant is if i changed pistons, i'd like to make an upgrade aka CR and material.

And back on topic, isnt honing for the profile, and cross hatching for proper abrasion for ring break in...

[2.8-350TBI]

Okay, well then you could use replacement pistons in standard sizes and choose compression from there, but if you do search for them as 3400 replacement pistons, because that will be a correct number.

While messing around on the CR calc I found this:

With a 3.4 block, 3400 heads, and .060 head gasket

3400 pistons net 9:41:1 (.050 quench)
3.4 RWD pistons net 12.38 (.070 quench) and 13.28 at .050 quench with a .040 head gasket
TDC 13.1/070Q with 060 HG
TDC 14.15/050Q with 040HG

[bob442]

So i would have to go with 3500 heads to even imagine having the car as a DD with Iron head pistons, 3400 block, 3500 heads, and get 11.56:1

http://wot-tech.com/shop/3400/pistons/cat_75.html

http://www.summitracing.com/parts/UEM-3483HC-STD/

I know ive gone threw this before, but its a new budget, and its finally going to be apart, and i have to make a decision before i waste time on cleaning up the heads

[2.8-350TBI]

I have a set of RWD 3.4 pistons if you wanna trade. I was dealing with another member but he hasnt chimed in so pm me if interested.

Turns out im going to be honing, i'd rather have the cylinder walls like new before putting it back together. Besides, like 3 thousandths will make a huge difference...