1600 Stroker motor build....

petex19 said:
I still want to upgrade my ignition system to either an MSD 6AL box or an Allison's automotive distributorless ignition but can't decide.
Click to expand...

I would not use an MSD6AL box. The Allison's auto system works well, just don't expect it to be plug n play.

The MSD box will definitely boost your spark, but at the expense of vastly reduced cap, rotor & plug life. I used one on my Volvo, but got tired of replacing the cap & rotor twice a year - gets expensive.
 
Some comments

You are describing almost my exact engine.

1) I have had problems with the PBS header on both my hot 1300 (SX-1 cam and S2 cam) with this header inducing a bad flat spot between 2000 and 3000 rpm. Mark Plaia reported the same from his all-PBS 1600 back in the day.
It seems the PBS header lengths may be optimized for high rpm (it being a race header) and not the street rpm band. On both engines, switching to the stock 1974 exhaust manifold and muffler fixed the flat spot completely. I have an IAP header that I want to try next.

2) I think for a 1600 the SX-1 is too limiting. I think you need more cam. Also the SX-1 cam makes a bunch of valve noise due to its steep ramps. Your enging will always sound like the valves are out of adjustment, even with tighter gaps.

3) I am now running the S2 in my engine. I have considered going to a hotter profile with the PBS-type base circle, just as you are planning on doing. I have now decided that I want to get away from this "limitation" of reduced base circle. For one thing, many people claim that reground cams are a bad idea period. Second, I cannot just go out and buy the cam I want (like you with the Piper cam). So I will convert my PBS head to Fiat 39.5 mm intake valves and new stock exhaust valves. I can then run available billet cams.
 
Does anyone know what the normal clearance between main bearings and crankshaft journals is for the 67.4mm crankshaft as found in the Fiat Punto. I've read that for the X1/9 the tolerance is: Normal clearance between main bearings and crankshaft journals is .0019 to .0037" (.050 to .095 mm)

If clearance does not fall within the maximum allowable limit of .006" (.15mm) bearings must be replaced after regrinding crankshaft journals.(by KMead)

I was just wondering if it's the same for the 67.4mm crankshaft as I'm doing a plastigage check.

'PeteX1/9
 
Stroker build parts have arrived so I started weighing and recording the new parts vs. the old.

New pistons from Greece 86.8mm 34.45CH


New Scat H-beam rods from CNC


New pistons, rods and 67.4mm Fiat Punto Gt crankshaft



Old 63.9mm crankshaft (2 lbs. heavier then 67.4mm crank)


Fiat 1500 forged con-rod


Stock 1500 piston and rod assembly





67.4mm Fiat Punto Gt crankshaft (20.2 lbs.)


New 86.8mm pistons are actuall heavier then stock pistons


Pistons with lighter rods save a lot of weight combined.


New scat rod


Hard to see but scat rod is .23mm shorter then 1500 forged rod.
128.27mm vs. 128.50mm of original rods



Current state of engine block before going to machine shop next week.



Stock flywheel



PBS lightened flywheel



In summary: Stock 1500 rotating assembly (Crank+Pistons/rods+Flywheel = 22200.9grams)

New rotating assembly for 1600 stroker (Crank+Pistons/rods+Flywheel = 19300.4grams)
so the weight saving is 2900.5grams or 6.4 lbs which is a 13.1 % weight saving in the rotating assembly.

'PeteX1/9
 
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Nice!

Pete - it looks like you forgot to add the gudgeon pin when weighing the new rod & piston. Also the old bearings are in the old rod - those will alter your weight differential.
 
Yes the gudgeon pin is in the new pistons and rings (pics 3&4 going down from top to bottom when enlarged you can see it in the pics). You're right the old bearings are still in the old rods so that would make the difference a little less. I'm posting the correct piston/rod picture with the bearings removed and I'll have to go back and adjust my calculations as I didn't account for (4)piston/rod assemblies. Good eye Hussein:wink2:




'PeteX1/9
 
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Machine shop finally finished with the engine parts. I really couldn't be happier with the results although the machine shop did far more of the build then I had expected. If you look closely at the pistons you will see that they even chamfered the tops of the pistons to ensure clearance with the head gasket pop-up. They degreed the camshaft and set the valve clearances aswell as completely dis-assembled and freshened the head. They even milled the cambox to accommodate the smaller base circle camshaft. My flash is broken on my camera so the pictures probably don't do the workmanship justice.







'PeteX1/9
 
Very Nice!

Not sure where I missed this, but why are the valve stems substantially different lengths between I/E? The springs are compressed at different rates?

I'm installing all the paper gaskets dry. Why would you add rtv to them?
 
Generally head gaskets are installed dry. Considering the head and block are freshly machined you won't have any problems. Also, if the surfaces were machined smooth enough you could go with an MLS head gasket.
 
So how much did the pistons finally end up plus deck?

Have you measured your combustion chamber volumes?

Don't rely on your rough calculations for the final CR... measure everything now while you can and do the math based on true volumes.

SteveC
 
Unfortunately I can't answer that as I have no idea??? Years ago as PBS was out of the BVhead market; I wanted a new BVhead so I brought my old one to a very good local machine shop with a flow bench along with a stock head and they replicated the PBS head right down to the longer valve stems to accommodate PBS's smaller base circle camshafts. Had I known then what I know now, I would have sourced a Euro stock head and had it ported and polished but I can't change the past.

'PeteX1/9
 
I'm at work but will measure everything myself when I get home to verify. According to the machinist and his build notes, my compression is 10.6:1 with decked block and head and piston pop-up. He wasn't able to get the squish down to optimum at the expense of over 11.1:1 compression but he did the best he could.

'PeteX1/9
 
I'm not exactly sure what the best gasket sealer is which is why I'm asking for others personal experiences. I just got off the phone with my machinist and he used a very thin coat of "Ultra Grey" between the part and the gasket on everything that he bolted onto the block before I picked it up. I was really most curious about the threads on things like the oil pressure sender as I certainly don't want any leaks.

'PeteX1/9
 
For threaded senders that don't use a sealing washer, use teflon tape, but not too much. 3 wraps is sufficient.

Anything that uses a sealing washer doesn't need thread sealant as well.
 
So I've confirmed all the machinist measurements and valve clearances.
The end result is this:

Bore: (diameter) 86.8 mm
Stroke: 67.4 mm
Cylinder Head Volume: 34.5 cc
Effective Dome Volume: 2.5 cc Use (-) for Dome and (+) for Dish.
Deck Clearance: -.65 mm
Compressed Gasket Thickness: 1.5 mm
Number of Cylinders: 4
Compression Ratio : 10.6 : 1
Total Displacement (in.3) : 97.38
Total Displacement cc's :1596.39

I'm very happy with the results and on with the build.:)

'PeteX1/9
 
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