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 Post subject: Ford 170 pistons?
PostPosted: Sun Nov 14, 2021 10:05 am 
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Turbo EFI
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Has anyone tried using the Silvolite S1119 pistons for a 3.5" bored slant? The Ford 170 apparenbtly has a 3.5" bore (standard).
It has a 1.58" compression height and a 0.912" pin diameter. It's a flat top cast piston with no valve reliefs.

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 Post subject: Re: Ford 170 pistons?
PostPosted: Sun Nov 14, 2021 10:58 am 
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Turbo EFI
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Maybe an aftermarket piston for a performance ford would be useful.

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 Post subject: Re: Ford 170 pistons?
PostPosted: Sun Nov 14, 2021 12:07 pm 
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There are Speed Pro and Sealed Power forged V8 pistons that interchange into the bigger Ford 300 that are available, but the small Ford sixes like the 170 and 250 there is no interchange, and the aftermarket stopped making stock replacement forged pistons for them long ago. Custom forged are the only options for most all inlines engines like the Chevy, Ford and Chrysler, unfortunately!

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 Post subject: Re: Ford 170 pistons?
PostPosted: Thu Nov 18, 2021 12:34 pm 
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3 Deuce Webber
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Would a 87 or 88 mm piston be a good choice? That's 3.425" or 3.465".


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 Post subject: Re: Ford 170 pistons?
PostPosted: Thu Nov 18, 2021 5:39 pm 
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88 mm is perfect for most rebuilds.

Lou

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 Post subject: Re: Ford 170 pistons?
PostPosted: Thu Nov 18, 2021 8:42 pm 
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3 Deuce Webber
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Dart270 wrote:
88 mm is perfect for most rebuilds.

Lou

How would I search to see what is available? The list I found was by car and engine. Is there a particular engine to search for? I think I will be building a long rod, so will I need a dished piston for valve and proper compression? I don't mean to hijack the thread.


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 Post subject: Re: Ford 170 pistons?
PostPosted: Fri Nov 19, 2021 2:38 am 
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MazdaRX8/6 wrote:
Dart270 wrote:
88 mm is perfect for most rebuilds.

Lou

How would I search to see what is available? The list I found was by car and engine. Is there a particular engine to search for? I think I will be building a long rod, so will I need a dished piston for valve and proper compression? I don't mean to hijack the thread.


I have KB 239 hypereutectic 2.2 pistons in the slant in the 68B. They are 1.0 mm oversize so fit with appropriately an .084 over bore. The 1.5 mm OS would require approximately an 1.04 over bore. They have a 5 cc valve relief pocket and with a very light clean up cut on the block and a line bore are flush to the top of the block using the long rods. I have K1’s rods in mine. With a similar very light clean up cut on the head the static compression ratio came in at 10.62 static, 8.37 dynamic.
KB has or had recently a turbo version of the same piston with a 19cc dish. it is KB 268, those have an 18 cc dish.
The 2.2 L is a nice light weight modern piston, being hypereutetic and with the top rings high on the piston you need to watch the top ring gap. Follow the instructions.
Hypereutectic pistons increase the silicon content in cast aluminum pistons and result in a cast aluminum piston that approaches the strength of a forged piston. With a piston weight that is comparable to a cast piston.
To find other matches to a known compression height-bore size-piston pin diameter.
Get on line or on the phone with a tech person at Silvolite / KB. They should be able to sort their data base and come up with options. To throw out as big a net as possible give them the bore size range to include oversized pistons that you are willing to with, do the same for compression height that you can work with concerning rod length and what you will cut the block and head and the pin bore diameters that you would consider.
Keep in mind when changing piston pin bore diameters, they are not always a simple round shape. They can be round or have features like a drilled hole or a cut channel or a bell mouth to direct lube oil into the pin. Personally I would prefer to keep the pin with the piston being used and modify the rod piston pin diameter to fit the pin. That way the piston pin lengths to work with the piston pin retainers is not an issue.
When modifying pistons or rod ends always work with a very high quality machine shop.

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Last edited by DadTruck on Fri Nov 19, 2021 5:59 am, edited 1 time in total.

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 Post subject: Re: Ford 170 pistons?
PostPosted: Fri Nov 19, 2021 5:48 am 
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Turbo EFI
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I would like a bigger piston to use with stock (225) length rods. The larger bore should help when using oversized valves.

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 Post subject: Re: Ford 170 pistons?
PostPosted: Fri Nov 19, 2021 6:22 am 
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Supercharged

Joined: Wed Sep 17, 2008 6:48 pm
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Badvert65 wrote:
I would like a bigger piston to use with stock (225) length rods. The larger bore should help when using oversized valves.


so have the KB tech search the data base for
* pistons in the bore diameter that you can work with
** pistons with a compression height of a stock slant six piston as the shortest compression height to maybe a compression height that would bring the pistons close to what your piston recession needs to be to hit your targeted compression ratio. For stock rods that would end up being some tall pistons, but who knows what is really available until you look. I would then cut that down a bit to allow for a very light clean up cut on the block and head. Remember to include any valve relief areas. Unless those are huge that can be compensated for in the clean up cut.
*** pistons that have a pin diameter that matches the stock slant six pin first, that will save you more machining costs. To get a bigger sample then search for piston with pins that will work with an ID hone on the rod end, then to get a bigger sample search for pistons with pins that will work with a light machine ID cut on the rod end.

to make it easy on the Tech, I would have all the numbers tabled out in advance, then call and discuss on the phone so he understands what you are after. Then e mail the table to the tech so he can do some searching over a day or two when the call in lines are not backed up.

One more thing, I would include the table to have listed out: Cast, Hyper and Forged Pistons and cost. To get a good appraisal of what is out there. And be advised that you may need to modify the existing valve reliefs to fit with the valves that you choose.

Double check your numbers to get them right, be conservation as you can always easily mill another .010 to .015 to hit the target compression ratio and have fun designing your engines combustion chamber.

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 Post subject: Re: Ford 170 pistons?
PostPosted: Fri Nov 19, 2021 2:50 pm 
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Buick 215/Rover 3.5l . They are a 3.5" piston and need to rod ends "adjusted" to work.


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 Post subject: Re: Ford 170 pistons?
PostPosted: Sat Nov 20, 2021 10:20 am 
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When we worked up the Hooptie engine, we were going for a much shorter compression height. Ended up with an aftermarket Toyota hyper-eutectic for a four-banger. It was spec'd to 198 rods on a stroked crank. Came in 0.5mm over-bore increments. 1.2x CompHt. ??? Leaky brain.
For no stroke, we had another Toyota piston selected. Been too many beers ago, but I seem to remember a v6 pickup. I want to say around '90. The pin size was a bit smaller, but that's not a big deal. Readily available at the time, but such may not be the case now. I want to say it was somewhere around a 1.9x compression height. 1mm increments IIRC.

Always a challenge to find an over-the-counter option so if you break something, your not out hundred(s) of doll-hares for a single broken ring land in a custom set...

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 Post subject: Re: Ford 170 pistons?
PostPosted: Sat Nov 20, 2021 8:17 pm 
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3 Deuce Webber
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Car Model: Mazda RX8 slant six swap
Thanks guys. How can I search for rods?


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 Post subject: Re: Ford 170 pistons?
PostPosted: Sun Nov 21, 2021 4:39 am 
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I would just buy a set from Molnar. https://molnarrods.com/slant-six-rods

If you cannot get the narrow rods (for cast crank) from them, then you can mill the others narrower and the other dimensions are correct.

Honestly, you don't lose much by rebuilding the stock rods you have. Plenty of people have made way more power than you want with stock cast crank rods.

Best,
Lou

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 Post subject: Re: Ford 170 pistons?
PostPosted: Sun Nov 21, 2021 6:02 am 
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3 Deuce Webber
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Joined: Thu Oct 21, 2021 8:14 pm
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Location: Tennessee
Car Model: Mazda RX8 slant six swap
Dart270 wrote:
I would just buy a set from Molnar. https://molnarrods.com/slant-six-rods

If you cannot get the narrow rods (for cast crank) from them, then you can mill the others narrower and the other dimensions are correct.

Honestly, you don't lose much by rebuilding the stock rods you have. Plenty of people have made way more power than you want with stock cast crank rods.

Best,
Lou


Thanks, Lou. I'm wanting to move the piston to the top of the bore to try and generate some squish and use a more modern pistion with likely a shorter compression height, maybe with valve pockets. I think that is going to require longer rods. I'm wanting to make power with as mild a cam as possible to retain a smooth idle.

My build will be unusual.


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 Post subject: Re: Ford 170 pistons?
PostPosted: Sun Nov 21, 2021 6:35 am 
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MazdaRX8/6 wrote:
Thanks, Lou. I'm wanting to move the piston to the top of the bore to try and generate some squish
My build will be unusual.

In my opinion, you will not be able to get effective "squish", unless you either, use a custom piston, that has the dome into the combustion chamber, or partially weld up the chamber.

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