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Finn Hammer's Savage (Read 2062 times)
FinnHammer
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Re: Finn Hammer's Savage
Reply #240 - 04/15/24 at 08:39:11
 
This side view reveals that things are tight, but it is easy to get to things, and easy to assemble and take apart, something you can't hardly say about the stock arrangement..
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« Last Edit: 04/15/24 at 09:49:40 by FinnHammer »  

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FinnHammer
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Re: Finn Hammer's Savage
Reply #241 - 04/15/24 at 08:39:56
 
Top view tells the same story. I reversed the wires going to the starter relay, and that helped a lot.
By now, battery is connected, carburettor is mounted with a #200 main jet and #20 idle jet, needle in the middle groove as delivered by Lancer.
Catch can is in the works.
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« Last Edit: 04/15/24 at 11:34:01 by FinnHammer »  

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Re: Finn Hammer's Savage
Reply #242 - 04/16/24 at 10:52:06
 
That input shaft cleaned up nice, and you are only .001" oversize.  Seems impossible given the phonographic finish you started out with.  How did you manage to get so lucky?

I assume you have only installed the head temporarily.  Did you save your old head gasket so you can check piston-to-valve clearance when you get your new rocker arms?  What is your deck height?

I like the intake boot you made.  The divergent feature from the elbow to the carb might work better than my straight cylindrical boot.  How thick is the material?  Is there any concern over the boot collapsing at WOT?  By any chance did you do any sort of test on the Polypropylene, EDPM and the cyanoacrylate glue to see how they behave when exposed to fuel?  I had a problem with ABS plastic deteriorating.  Those components are exposed to a heavy dose of fuel vapor.

What is the purpose of the white nylon bolt & nut that you have installed in the elbow?

Looks like you will be on the road soon.  You will have all summer to play.   Cool

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Re: Finn Hammer's Savage
Reply #243 - 04/16/24 at 23:58:39
 
Regarding the hole in the shaft, I like to think it is not just luck, but also a fair bit of skill   Cool Wink, combined with competent selection of tool. A reamer is the most dilligent tool in the machine shop, when it comes to producing a hole that meets strict demands to both dimension and surface finish.

I torqued the head down, shame on me, I fear this will cost me a head gasket, and the not unconsiderable hassle of cleaning Loctite 592 off the RR stud. I guess I had better start to adhere strictly to the WIMGA* rule. Frankly I am under the impression that others have already done this piston and cam conversion, so that if I just don't also throw bigger valves into the mix, I'd be safe. Deck height was eyeballed to 1.5mm, but due to liberal amounts of Redline assembly lube, I am not sure.


Will I absolutely have to do a clay test on the valve/piston clearance?
Has anyone here done the conversion already without experiencing catastrophical engine failiure?

I tend to work from my flaky memory, which is perhaps not such a good idea, since when I check on the durability of EPDM rubber, it is stated that apart from its many favourable durability properties, resistance to fuels and oil is not one of them. The isocyanate glue is used in the industry to make custom o-rings, by gluing lengths of rubber string together end to end, so I have little doubt about that it will endure fuel too.

But as I write this, I realize that I have lived my life without an intimate relationship with gasoline, and its property as a solvent, so I guess it is time to drop the assembly into a can of gas to see if it swells, cracks or gets slippery. If I could get hands on an HDPE elbow, I would take it. I have all sorts of thin glass fibre sheet, and I am already preparing for a second version of the boot with embedded longitudinal stringers to secure WOT performance. Don't want to risk the boot getting sucked in Smiley.
The nylon bolt and nut is there, and where it is, to be out of the way of the seat, but to offer something to grab, when I want to pull the elbow out of the boot.

Edit, after 4 hours semisubmerged in the drink, the boot has swollen from 75mm to 90mm, what a bummer. I need nitrile rubber  https://en.wikipedia.org/wiki/Nitrile_rubber. The polypropylene shows no signs of failure, but then I am positively biassed towards polypropylene due to it's superiour properties as a high frequency capacitor dielectric.


*What Is Mike Going to Ask
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« Last Edit: 04/17/24 at 04:42:47 by FinnHammer »  

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Re: Finn Hammer's Savage
Reply #244 - 04/17/24 at 12:31:18
 
"Will I absolutely have to do a clay test on the valve/piston clearance?
Has anyone here done the conversion already without experiencing catastrophical engine failiure?"


That is a good question.  It all depends on your tolerance for risk.  The type of failure associated with clearance issues is generally not pretty.  Also, the main benefits from the flat-top piston are increased compression and tight quench clearance.  It seems logical to me that you would want to set it up with optimal quench clearance to take advantage of the piston design.  

The flat-top runs very close to the head, and the valves get really close during TDC overlap.  I personally would never put it together without checking all the clearances, and also the valve spring pressure.  Too much to lose if anything hits.
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Re: Finn Hammer's Savage
Reply #245 - 04/17/24 at 12:41:16
 
I have built a couple of flat-top piston engines, one with a 94mm, and one with a 97mm.

The 94mm engine had a Web 340b cam and heavy valve springs.  That cam has more lift and more overlap. The quench clearance was set up at .038". It had ample valve-to-piston clearance.

I used lead wire readings to verify the quench clearance.  Place appropriate feelers and strips of lead wire on the piston, install the head (without cam & rockers) with a used head gasket, tighten up the nuts, turn the engine through several turns, then disassemble and measure.  
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Re: Finn Hammer's Savage
Reply #246 - 04/17/24 at 12:42:57
 
Pull the head back off and measure the thickness of the lead wire and feeler.  If you don't have the desired .035" - .040" clearance adjust the base gasket thickness.
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Re: Finn Hammer's Savage
Reply #247 - 04/17/24 at 12:45:46
 
Once you have the desired quench clearance, check the valve-to-piston clearance.  You mentioned that your visual estimation of your deck height was about 1.5 mm (.060").  This is a picture of my deck height on the 94mm build.  It was about -.010".
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Re: Finn Hammer's Savage
Reply #248 - 04/17/24 at 12:56:24
 
What is the optimum quench clearance, and why not just measure it from the top of the cylinder to top of piston with a depth micrometer.
Then again, is there a need to replace valve springs, and in the case of a yes, which springs?
edit, just read it: 0.035" to 0.04"
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Re: Finn Hammer's Savage
Reply #249 - 04/17/24 at 12:56:59
 
The stock head gasket compressed thickness should be right around .028", so you want the deck height to be around -.007" to -.012".  

The main reason I asked Lancer to make the flat-top pistons was to achieve this tight quench condition.  That design improves combustion and suppresses detonation.  The result is improved power and fuel economy.  The tradeoff is that engine assembly requires a lot more attention to detail.

You can see from this picture that on my 94mm engine I had ample clearance (radial & vertical) on the exhaust valves.  I suspect that since your cam has a lot less lift and duration you should have adequate clearance too (key words and phrases, "should").  
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Re: Finn Hammer's Savage
Reply #250 - 04/17/24 at 12:59:32
 
On the 94mm engine, the intake valves also had plenty of clearance.  Again, since your cam has less lift & duration you "should" have ample clearance too.
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Re: Finn Hammer's Savage
Reply #251 - 04/17/24 at 13:03:44
 
But there are all sorts of dimensions involved, and as you know, every dimension has a tolerance, and then there is the potential for dimensional changes due to prior work accomplished on a component (i.e. resurafcing).

On my 97mm flat-top build, instead of having a negative deck height, the piston stuck up past the deck.  It had +.005" deck height.  So, the base gasket had to be adjusted.
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Re: Finn Hammer's Savage
Reply #252 - 04/17/24 at 13:09:32
 
And even after setting the 97mm engine deck height to within .035" to .040", I still had a problem with valve-to-piston clearance.  The intake valves hit the top of the piston.  This was with a DR cam.  Granted, the valves are 34mm, but that's only .020" (0.5mm) larger on the radius.  Even 33mm valves would not have corrected this condition.  The piston rocks.  As I recall, you want at least .080" clearance.
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Re: Finn Hammer's Savage
Reply #253 - 04/17/24 at 13:10:43
 
To correct the interference problem, I had to flycut the valve reliefs.
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Re: Finn Hammer's Savage
Reply #254 - 04/17/24 at 13:14:45
 
I can do the quench test now, and the clearance test with the old rockers, so i know how to pass the weekend.
Thanks for your continuing support.
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