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-   -   GX140 Hemi build (http://www.diygokarts.com/vb/showthread.php?t=40212)

65ShelbyClone 10-30-2018 04:26 PM

GX140 Hemi build
 
2 Attachment(s)
I'm starting this so I don't get tempted to clog-up another thread with my own stuff.

I've had this GX140 for about 25 years and it was always used for experimenting. It was disassembled 10+ years ago and I thought it got thrown out, but low and behold I found the parts! The original head was ported, cut, and modified beyond use, so what now?

Enter the hemi Predator head. Stock 140 valves are 24/22mm; the hemi's are 27/25 and the ports are larger to boot. By my estimation, with valve springs it could move the 140's power peak to over 7000rpm without porting. So I got one. It will be styled after the second-gen Chrysler Hemi in orange with a black valve cover.

Anyone else thinking about this should know that the compression ratio will only be about 6.8-7.0:1 and there will be no quench because the piston is so small. Currently I'm stalled waiting for some parts.

pearl111 10-30-2018 06:01 PM

I am interested in what you are doing with the GX 140. As a member here on DIY I have learned how to do my own builds ( still learning ). What do you mean by THERE WILL BE NO QUENCH BECAUSE THE PISTON IS SO SMALL. Thanks.

tgus3 10-30-2018 08:03 PM

Quote:

Originally Posted by 65ShelbyClone (Post 510725)
I'm starting this so I don't get tempted to clog-up another thread with my own stuff.

I've had this GX140 for about 25 years and it was always used for experimenting. It was disassembled 10+ years ago and I thought it got thrown out, but low and behold I found the parts! The original head was ported, cut, and modified beyond use, so what now?

Enter the hemi Predator head. Stock 140 valves are 24/22mm; the hemi's are 27/25 and the ports are larger to boot. By my estimation, with valve springs it could move the 140's power peak to over 7000rpm without porting. So I got one. It will be styled after the second-gen Chrysler Hemi in orange with a black valve cover.

Anyone else thinking about this should know that the compression ratio will only be about 6.8-7.0:1 and there will be no quench because the piston is so small. Currently I'm stalled waiting for some parts.

wow cool i love the color..ill be following this:wai:

65ShelbyClone 10-30-2018 08:20 PM

Quote:

Originally Posted by pearl111 (Post 510729)
I am interested in what you are doing with the GX 140. As a member here on DIY I have learned how to do my own builds ( still learning ). What do you mean by THERE WILL BE NO QUENCH BECAUSE THE PISTON IS SO SMALL. Thanks.

I'm going to answer that in my other thread about the hemi head here:

http://www.diygokarts.com/vb/showthr...in this thread.

Quote:

Originally Posted by tgus3 (Post 510739)
wow cool i love the color..ill be following this:wai:

Thanks. It's actually "Chrysler Hemi Orange" is a slight pearl. I don't know if all brands of this color are the same, but Dupli-Color DE1652 has the worst coverage ever. There are two cans of paint on that tiny engine. Not two coats, two cans.

Tpdingo 10-30-2018 08:28 PM

Put hydrazine in the motor and I'll follow it. :P

Just kidding, I'm looking forward to this thread regardless :lolgoku:

65ShelbyClone 10-30-2018 09:17 PM

If I do that there won't be any motor left. Maybe not any of me left either, just a crater in the garage floor.

Nitromethane might get involved at a later date, but only at a point when I'm done with testing and the engine becomes expendable.

bob58o 10-30-2018 10:35 PM

Do we get a sneak peak? What parts are we waiting for?

Are you estimating that the stock cam will give you peak power around 7k RPM? If you have the tools, is there any way you could find out and report back with the Intake Center Line of the stock cam?

landuse 10-30-2018 11:40 PM

Quote:

Originally Posted by bob58o (Post 510758)
Do we get a sneak peak? What parts are we waiting for?

Flux capacitor??

65ShelbyClone 10-30-2018 11:58 PM

Quote:

Originally Posted by bob58o (Post 510758)
Do we get a sneak peak? What parts are we waiting for?

Just a few basic items the engine can't run without. :P

Quote:

Originally Posted by bob58o (Post 510758)
Are you estimating that the stock cam will give you peak power around 7k RPM?

I think it's hypothetically possible, but not sure. More that the head *should* flow enough to not choke the engine below 7k. It might take rockers or more cam to get there.

Quote:

If you have the tools, is there any way you could find out and report back with the Intake Center Line of the stock cam?
I can, but first have to build a fixture for holding an indicator in line with the valve. It's straightforward with a Honda's inline valves, not so much with a hemi.

bob58o 10-31-2018 08:10 PM

1 Attachment(s)
Quote:

Originally Posted by 65ShelbyClone (Post 510767)
I think it's hypothetically possible, but not sure. More that the head *should* flow enough to not choke the engine below 7k. It might take rockers or more cam to get there.

I ran some numbers in my Engine Analyzer Program to see what I got.

I used 2.50" Bore, 1.77" Stroke, 3.303" Rod Length, and 6.8 :1 Compression Ratio (but I'm not sure how you got there unless you have a flat top piston or a milled hemi head - I got 6.8:1 with a 22cc chamber, a flat-top piston, 0.010" head gasket and the piston sitting at 0.020" in the hole).

I used 27/25mm valves and average port diameter of 0.85" with flow efficiency percentage of 34%. I used 38 cfm for the intake flow (carb).

For exhaust I used 0.85" diameter and 16" long with flow efficiency at 85%.

I used the specs for a CL1 cam (for gx200) with 1.05:1 rocker ratio.

Here's what the program spat out....
Pk TQ around 4300 RPM and Pk HP around 7300 RPM.

65ShelbyClone 10-31-2018 11:04 PM

That's cool, thanks.

All I did was divide the 212's displacement by the 140's displacement(144cc ) to get a multiplier(1.472), then multiply the (212's) peak power RPM(~4800) by it. It comes out to about 7100rpm that way. Should I see if the stock rod can do it? :roflol:

Quote:

Originally Posted by bob58o (Post 510802)
I used 2.50" Bore, 1.77" Stroke, 3.303" Rod Length, and 6.8 :1 Compression Ratio (but I'm not sure how you got there unless you have a flat top piston or a milled hemi head - I got 6.8:1 with a 22cc chamber, a flat-top piston, 0.010" head gasket and the piston sitting at 0.020" in the hole).

I went with what other people report on the hemi chamber volume (22-23cc) until I measure mine. Gasket will probably be 0.010" and the piston is a flat top, but I don't think it's any more than 0.010" below deck. There again, still need to measure. It could be anywhere from 6.2 to 7.1:1 depending on the combination.

KartFab 11-01-2018 10:39 AM

man you are getting into briggs flathead compression ratio range here

65ShelbyClone 11-01-2018 05:34 PM

It shouldn't be too picky about gas. :P I'm hoping to put an ultralight flywheel on it and keep the recoil start, so maybe it won't kick too bad. Stock cam with compression release for now ought to help too.

65ShelbyClone 11-03-2018 04:14 PM

Parts were due today, but the U.S. Postal Service dropped the ball so they won't be here (and I can't button-up the engine until) at least Tuesday now. :censored:

In the meantime, here's why a 212 head gasket would be less than ideal.
https://i.imgur.com/ZRgoEwg.jpg

And I don't know why I took this.
https://i.imgur.com/NtSs1Q9.jpg

65ShelbyClone 11-05-2018 03:53 PM

Quote:

Originally Posted by 65ShelbyClone (Post 510908)
Parts were due today, but the U.S. Postal Service dropped the ball so they won't be here (and I can't button-up the engine until) at least Tuesday now. :censored:

Update: the PO played football with my box, but it was only three days late and they nicely taped-up the gaping hole. Come to find out the seller sent the wrong stuff anyway.

Is it Monday? I think it's a Monday.

bob58o 11-05-2018 04:08 PM

Amr 300? Looks perfect on there. Let's see ... 300cc per revolution on the blower. 70cc per revolution on the 4 stroke 140... Should be good for like 50 psi of boost with a 1:1 ratio. LOL

https://media.giphy.com/media/RHiD0K65NxxLO/giphy.gif

65ShelbyClone 11-05-2018 04:26 PM

It's actually the larger 500. Believe me, I still think about it using it. It would be kind of like this:
https://i.imgur.com/n8bjeVK.jpg

65ShelbyClone 11-10-2018 10:10 PM

Alright, back in the saddle.

Hemi 212 valve covers look taller in the photos. The stocker simply won't do given the theme of this engine, but it will at least keep the oil in for now. I know, lets make it shorter!

https://i.imgur.com/bOe3mXs.jpg
https://i.imgur.com/z0vFIQv.jpg

Brass shim stock because the thing was uneven by 0.008" from end-to-end. Shims reduced that to 0.001" before cutting.

https://i.imgur.com/aMmCoDQ.jpg

The letters are still visible shadows, but that's just due to the grain of the metal when it was die cast.

None of my torque wrenches would fit in the 140 crankcase and I have no 10mm crow's foot, so I had to make this hokey tool for tightening the rod bolts:

https://i.imgur.com/zUr0hFI.jpg

It is exactly two inches from center-to-center, so 0.857 is the correction factor. 12 (12+2) = 0.857. The welding is ugly because I'm not practiced.

Going by calibrated eyeball, it looks like 140 lifters coupled with 212 pushrods will net some usable valvetrain geometry.

I also blueprinted the intake flange. The yellow paper is a proof and it matches the intake port exactly. :wai:
https://i.imgur.com/EWVWC8q.jpg

65ShelbyClone 11-12-2018 08:16 PM

Quote:

Originally Posted by 65ShelbyClone (Post 511283)
Going by calibrated eyeball, it looks like 140 lifters coupled with 212 pushrods will net some usable valvetrain geometry.

Update 1: usable, not great. 212 lifters and 140 pushrods made a better contact patch, but they are still a bit short. Mock-up was done with a thick fiber gasket, so some of that length will be
recovered with a 0.010 gasket. It's going to require custom pushrods to get it correct either way and now there are enough spares for cutting up to make some. Titanium with steel tips maybe?

Update 2: VHT wrinkle paint is awesome. This the first time I've had wrinkle paint come out correctly on the first try. :thumbsup: The picture doesn't do it justice.
https://i.imgur.com/3FW7pUh.jpg

Inspiration:
https://i.imgur.com/Al1xEs1.jpg

65ShelbyClone 12-06-2018 09:38 PM

It's only money and you can't take it with you, right?

26lb springs, two Tillotson 324 clones, and a cog belt. The underdrive ratio looks really low, but it's geared for about 15psi with that large blower. Rotor leakage will probably be a bit high at lower speeds.

https://i.imgur.com/Ln5yFHP.jpg

I doubt that this little flywheel has enough material for machining the GX140 taper into it. If it does, I'll try it with the matching mag.

https://i.imgur.com/yVLVKv9.jpg

If not, I have a few other ideas.


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