Slave Plate when Boring Street Engine?

[cwestra]

How important is it to use a slave plate, or torque plate when boring out an engine for street use?

[Ck[FIN]]

Its a good thing but not a must in a street engine. In my opinion.

[bb71challenger]

I have always heard its a good idea to use one on any rebuild but especially so on a small block because of the smaller number of head  fasteners.

[moper]

It's not used for the boring, but the honing. If you goal is stock performance or close, you don't neeed it. If you are building a hi performance engine, it's a must have. I bought my own when my shop didn't have any mopar one.

[cwestra]

My machine shop says they have the ability to do it but it will cost extra.  He did not say how much though.  What would a typical upcharge be to do this?

[72cudamaan]

Typically about 75-100 bucks to use torque plates. The only street engine it is neccessary to use it on is a late seventies to eighties 318 motor. It has been shown that just the torquing of the right side motor mount is enough to distort the cylinders enuf to cause a low compression issue.

[matt63]

Round bores seal better and make more power.  There is a whole art/science to using torque plates and trying to replicate the same stresses as when the heads are installed.

[Changin Gears]

I wouldn't bother on a street engine, having the "best of everything" can nickel and dime you to death.

[Chryco Psycho]

my machinist Swears the Mopar blocks are far more ridgid & do not distort significantly but he will bolt the plate on if you want to pay extra

[moper]

Next time anyone cares to, have the cylinder honed without the plate. Then bolt the plate to it and touch the stones to the walls again... You can see the shadows where the stones do not hit. I did that about 15 years ago. Now picture that as rings not hitting the walls evenly. You dont have to do it. The factory didnt. But there's a reason why a modern performance engine makes more power than it's twin from years ago. That plate is part of it. If fact now the high tech circle and road track engine shops are running running-temp water thru the block to get it the same temp and bolting on mounting plates, timing covers, and the torque plates to get the bore perfectly round in it's real world dynamic load. If they have the plate, it's cheap power, fuel economy, and longevity. Not mandatory.

[Chryco Psycho]

I tend to agree ,there should be some distortion no matter how slight it is

[cwestra]

Next time anyone cares to, have the cylinder honed without the plate. Then bolt the plate to it and touch the stones to the walls again... You can see the shadows where the stones do not hit. I did that about 15 years ago. Now picture that as rings not hitting the walls evenly. You dont have to do it. The factory didnt. But there's a reason why a modern performance engine makes more power than it's twin from years ago. That plate is part of it. If fact now the high tech circle and road track engine shops are running running-temp water thru the block to get it the same temp and bolting on mounting plates, timing covers, and the torque plates to get the bore perfectly round in it's real world dynamic load. If they have the plate, it's cheap power, fuel economy, and longevity. Not mandatory.

Do you recall what engine you did that on?

[72cudamaan]

I would definitely agree with moper on this. Technology is changing in the engine building industry as well as everywhere else. How much are u spending on this build? And what size motor is it?

[bb71challenger]

How much do we spend on free flowing air cleaners, carbs, cams, head work, performance exhaust, headers? I dont care if its just your basic 318, for less than a hundred bucks you are bound to gain at least 10 horsepower by having the bores honed with a deck plate. If the horsepower gain is not there then you will definitely make up the hundred bucks with a longer lasting, better running engine. Money well spent if you ask me.

[cwestra]

I would definitely agree with moper on this. Technology is changing in the engine building industry as well as everywhere else. How much are u spending on this build? And what size motor is it?

The build cost is certainly increasing with all of these unexpected issues.  I don't have the running total but essentially, new KB pistons, .030 over bore, new cam kit, dual roller chain, conn rod reconditioning, hardened seats, all new guides, valve job.  I'll be in it for over 2 grand, easy when done. 

The engine is a numbers-matching 340 6-Pak.  The car will be street driven with rare 1/4 mile passes & maybe a dyno pull or 2. 

I know, "what's an extra $100 to hone with a plate", right?  It's this nickel & dime stuff, however, that is adding up to some serious cash and I want to make sure I am doing what's appropriate for how the car will be driven.