1600 Stroker motor build....

petex19

petex19

True Classic
Fall project is pulling 1500 motor and building up a 1600 stroker motor using a Fiat Punto 67.4mm crankshaft and stock 1500 con-rods and pistons.

XWeb members have been very generous with their knowledge and personal experience but I still have questions....

Stock 1500 crankshaft is 63.9mm and I'll be using a 67.4mm crankshaft for the build so does that mean the distance the piston will protrude above the block deck will be 3.5mm or will it be half that amount 1.75mm ???

Secondly does anyone know how much a piston can successfully stick out above the block deck and be okay? Midwest sells Wiseco flat top pistons that have a chamfered top and stick out .075" or 1.9mm but will only work with a stock 1500 head with recessed area and stock camshaft giving 11:1 compression.

Has anyone done a 1600 stroker using a U.S 1500 head and if so what route did you take with your pistons?

I don't know if I should leave the recessed area and have 1.6mm or so milled off the piston tops and have them chamfered; or should I have the head recessed area milled flat and have 3mm or so milled off the piston tops flat.

I would like my compression at 10.5:1 which I've read is optimum for 93 octane fuel.

I'm so looking forward to dropping the motor and passing my winter building up a beautiful stroker bad ass engine but I want to make sure that I have a good game plan going forward.

I almost forgot, I am planning on installing a 40/80 camshaft with a lift in the 10.5mm range

'PeteX1/9
 
I'm probably going to be doing this as well but with Scat rods. You will need pistons with the proper compression height and I haven't seen anything available that will get the compression you are looking for. You could buy lower compression stroker pistons from one of the vendors (last I check Obert has them) and shave the head and block to get the proper compression. It is my understanding that you cannot use stock 1500 pistons with a 1600 crank. I was planing on having Wiseco make some for me that will give me 10.5:1 without shaving the head or block.
 
In my hunt on the web I found this amazing website that lists everything needed for a stroker build.

http://jupiterfiatpower.tripod.com/id6.html

But the interesting part is that in the listing for the 67.4mm crankshaft it mentions using shorter con-rods which I can only imagine they sell. Further down the performance catalogue they mention a complete stroker kit which comes with pistons that have the pin relocated.

So i'll need to contact them as to which is the preferred method of getting the desired stroke length. Moving the piston connection or shortening the con-rod.

'PeteX1/9
 
It will be half the stroke increase

petex19 said:
Stock 1500 crankshaft is 63.9mm and I'll be using a 67.4mm crankshaft for the build so does that mean the distance the piston will protrude above the block deck will be 3.5mm or will it be half that amount 1.75mm ???
Click to expand...

So it will be 1.75mm. However, you are assuming that your piston tops are flush with the block now, I would seriously doubt that is the case. Do you know if your motor has ever been apart?

If it has been through a rebuild, the pistons are even further down in the hole than stock. When they rebuild connecting rods, it shortens them slightly.

Too early to start fretting about this measurement now. Get the motor torn down so you know what you are dealing with. 1.75 mm may have them still down in the hole instead of proud. I think the last time I measured my old race motor, I found the pistons were down in the hole between .020 and .027. That would translate to around .5 to .7 mm. So your pistons might only be a mm or so proud of the block. But no way to know before the teardown.

Pete
 
I have a stock 1500 block sitting here and the pistons are about .25mm below the deck at TDC.
 
petex19 said:
Has anyone done a 1600 stroker using a U.S 1500 head and if so what route did you take with your pistons?
'PeteX1/9
Click to expand...

Since I started importing these crankshafts I have built a few of the motors. I always use the pistons MADE for this installation, and I stock them in two oversizes.
If you want higher compression, you will need to either have pistons made, or perform head modifications.

Chris Obert
 
I'll try poking around your website Chris to find these build specific pistons but just in case I can't find them could you post a link.

'PeteX1/9
 
Great job finding those, I wasn't as luck searching. Hopefully Chris.O will chime in as to what compression one could expect using these special pistons with the 67.4mm crankshaft with a 1500 U.S. spec head and stock con-rods. I'm assuming that these pistons won't go above block deck so would having the head milled to remove the recessed area still be possible for a compression increase.

I'm aware that I would need to install a 1300 tensioner bearing to take up the slack in the timing belt. I'm aiming for 10.5:1 compression or at least 10:1.

'PeteX1/9
 
petex19 said:
Great job finding those, I wasn't as luck searching. Hopefully Chris.O will chime in as to what compression one could expect using these special pistons with the 67.4mm crankshaft with a 1500 U.S. spec head and stock con-rods. I'm assuming that these pistons won't go above block deck so would having the head milled to remove the recessed area still be possible for a compression increase.

I'm aware that I would need to install a 1300 tensioner bearing to take up the slack in the timing belt. I'm aiming for 10.5:1 compression or at least 10:1.

'PeteX1/9
Click to expand...

Honestly? I have no idea.
The US spec 1500 head, if it's different from what came on the engine Fiat made with the crank, (possibly) changes everything. Plus the camshaft you use will also change compression ratio.
My late good friend Mark Plaia would simply cc the head's combustion chamber and mathmatically calculate, using the displacement (bore & stroke) and the combustion chamber volume, to determine the compression ratio...
Possibly someone has the formula, or it's on the internet?

Chris Obert
 
The timing of this whole conversation is perfect as this past weeks "Horsepower tv" episode which I happened to PVR was about calculating compression ratio using the online calculator found on Summit racing website. Determining all the various measurements required to enter into the formula will have to wait until I remove the BVhead and have it on my bench. I only asked Chris. O as I thought he might know.

Summit racing online calculator:
http://www.summitracing.com/expertadviceandnews/calcsandtools/compression-calculator

I assume that using the online compression calculator is based on the pistons not going up past the block deck height so I'm guessing to get the 10:1 compression I'm after I will probably need to have the piston tops milled and have a calculated amount of the cylinder head recessed area milled off to get the desired compression ratio I'm after.

In that particular "Horespower t.v" episode they calculated a compression ratio of 10.8:1 but were after 10.5:1 and achieved exactly that by installing a thicker head gasket.

It'll be interesting how much variance in the compression numbers is achievable for our SOHC engines just by factoring in different head gasket thicknesses?

'PeteX1/9
 
Last edited:
It should work either way...

petex19 said:
I assume that using the online compression calculator is based on the pistons not going up past the block deck height so I'm guessing to get the 10:1 compression I'm after I will probably need to have the piston tops milled and have a calculated amount of the cylinder head recessed area milled off to get the desired compression ratio I'm after.
Click to expand...

Depending on how they have the questions set up, you will either enter a pop-up cc value, or you can just enter the "down-in-the-hole" volume as a negative number.

Pete
 
I watched the episode too... They did a good job of explaining how to calculate the compression ratio...

But I did think, it must be nice to have a engine like a big block Chevy where you can just go to 'Jegs' and easily find a dozen head gaskets in stock from 0.018 up to 0.090!!!
 
Info. I found on the internet:

Specs not in the Manual:
[FONT=Arial,Helvetica][SIZE=-2]Clearances approx. (stock) Piston to Head = 0.040" plus (+) compressed head gasket 0.050" (total squish clearance 0.080/090", Inlet valve to Piston =3mm+; Exhaust =4mm+, combustion chamber volume 50cc, cam timing stock 12-52/52-12 * 0.050 lift (seat-seat 18-62/62-18 Fiat rate lift *0.020), cam timing add (advance) one tooth=17-45/45-17 * 0.050" lift; one tooth less (retard) = 7-62/62-7 *0.050" lift; less tappet lash =higher valve lift and earlier (longer) opening; ignition timing (static) 8-10deg (use less with porting and high comp. although some use higher), Static Comp ratio 9:1, Dynamic Comp ratio *6000 rpm 10:1 est., distributor advance 28-38deg, total advance 50deg approx, 1500 block 8mm taller than 1300. Block tunnels expand 0.0005" and pistons expand up to 0.001" at normal temp, preferred RON 95- 97 gas. Stock Pistons are semi racing type, Valve pocket clearance 0.120" side clearance can be reduced to approx 0.80" clearance. [/SIZE][/FONT]

Using the Summit racing calculator for my stroker build:

Bore: 86.4mm (diameter)
Stroke: 67.4 mm
Cylinder Head Volume: 34 cc
Effective Dome Volume: +.120 cc (Use (-) for Dome and (+) for Dish. cc)
Deck Clearance: .000 in.
Compressed Gasket Thickness: .050 in.
Number of Cylinders:4
Compression Ratio :10.49 : 1
Total Displacement (in.3) : 96.24
Total Displacement cc's :1577.7

I found the cylinder head volume on this website which gave a range of 30-34 cc. for a Big Valve head so I went for the largest of the range.
http://jupiterfiatpower.tripod.com/id6.html

The only part I'm not sure about is the dome volume for the stock pistons as no option is give for flat top pistons?

The 10.49:1 is based on a dish piston as the ratio changes to 10.57:1 for a dome piston so would our flat top pistons be somewhere in the middle?

So in my case to achieve these kind of results I would either need 1.75mm milled off of the stock pistons to bring them flush with the block deck which may not be possible or I would have to purchase the special pistons that Chris. O is selling for the stroker crank. I could also try to source shorter con-rods but that would probably alter the results?

Pretty neat calculating tool.

'PeteX1/9
 
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Has your head been milled?

petex19 said:
So in my case to achieve these kind of results I would either need 1.75mm milled off of the stock pistons to bring them flush with the block deck which may not be possible or I would have to purchase the special pistons that Chris. O is selling for the stroker crank. I could also try to source shorter con-rods but that would probably alter the results?
Click to expand...

It's not going to be 1.75mm that needs to be milled, it's going to be 1.75mm minus the deck clearance figure, which is unknown at this point.

Shorter con rods would be one solution, and it will alter the formula because your deck clearance will change (pistons will sit further down in the hole.

The reason I ask about your head is because if it is still stock, which is an "open chamber" design, I wonder if it will tolerate the 1.25-ish mm the pistons are actually going to pop up. That's not a huge number, somewhere around .050" pop-up. Of course, if your head is already milled to be closed-chambered, that option is gone.

Pete
 
No my BVhead has never been milled, only planed for flatness. I'll have to measure to determine exactly how much recessed area their is but it looked like 1mm or so if my memory doesn't fail me.

'PeteX1/9
 
Ahhhh... I see...

here I was not far off when I responded to your cam question...

WOW... are you in for a LEARNING CURVE! Hope it isn't too costly but you will be a SUBJECT MATTER EXPERT by the time you are through!

OR... you can send the entire thing to Matt or Chris O. and let them take the risks... or eliminate the risks! Steve C. In OZ is another good candidate.

If you choose to continue with this LESSON, just be prepared. You have MY support but little else when it comes to experience on this subject.

I can offer one word of solace but it MAY not be applicable here. Back in 1958 Chevrolet built a "truck engine" aqnd installed them into their muscle cars called a 348. It came in various trim levels with one four barrel and a tri-power set-up. Then in 1960 through '64 I believe, came the infamous 409 and with two 4-barrels produced 425 horsepower! Amazing for the day.

I say all that to simply say this... the pistons stuck up out of the block, and not just a dome, but about 1/2 inch or 3/4 of an inch of the piston sleeve, and used part of the head as its combustion chamber and not just for the "lid".

Hey, it worked well in the day and I believe the rings were quite a ways down on the piston, compared to the norm. Now GM makes 2 horsepower per cubic inch in many of their engines and I don't believe any one does this sort of thing any more...

Continue having fun!


petex19 said:
Fall project is pulling 1500 motor and building up a 1600 stroker motor using a Fiat Punto 67.4mm crankshaft and stock 1500 con-rods and pistons.

XWeb members have been very generous with their knowledge and personal experience but I still have questions....

Stock 1500 crankshaft is 63.9mm and I'll be using a 67.4mm crankshaft for the build so does that mean the distance the piston will protrude above the block deck will be 3.5mm or will it be half that amount 1.75mm ???

Secondly does anyone know how much a piston can successfully stick out above the block deck and be okay? Midwest sells Wiseco flat top pistons that have a chamfered top and stick out .075" or 1.9mm but will only work with a stock 1500 head with recessed area and stock camshaft giving 11:1 compression.

Has anyone done a 1600 stroker using a U.S 1500 head and if so what route did you take with your pistons?

I don't know if I should leave the recessed area and have 1.6mm or so milled off the piston tops and have them chamfered; or should I have the head recessed area milled flat and have 3mm or so milled off the piston tops flat.

I would like my compression at 10.5:1 which I've read is optimum for 93 octane fuel.

I'm so looking forward to dropping the motor and passing my winter building up a beautiful stroker bad ass engine but I want to make sure that I have a good game plan going forward.

I almost forgot, I am planning on installing a 40/80 camshaft with a lift in the 10.5mm range

'PeteX1/9
Click to expand...
 
All is not complicated . Installed crank with one rod with piston and measured how is piston up ( if you not like to buy 1,6 pistons) if need catted piston on top on lathe and polished -look on thickness og gasket and look to have piston head min 0,8mm ... possible need cc0,8 to 1mm from top of piston but ... installed and measured
 
yugoracing said:
All is not complicated . Installed crank with one rod with piston and measured how is piston up ( if you not like to buy 1,6 pistons) if need catted piston on top on lathe and polished -look on thickness og gasket and look to have piston head min 0,8mm ... possible need cc0,8 to 1mm from top of piston but ... installed and measured
Click to expand...

Agreed with this man.

Your complicating things too much. If your serious you need to get the parts messure up and go from there.
 
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