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Hopped up Briggs twin build

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ebinmaine

Are you planing the heads on this one?

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WHX??
On 3/21/2021 at 8:50 PM, c-series don said:

restored it a few years ago.

I've seen that one at the BS and yes as good as it looks! :handgestures-thumbupright:

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Greentored
On 3/23/2021 at 9:32 AM, ebinmaine said:

Are you planing the heads on this one?

The jury is out on that. Very little info out there on hopping these up, but the little bit I found says the opposed twins do NOT like compression, it kills the airflow and actually hurts them. This is also coming from guys who roundy round race them, which means high rpms, not bottom end grunt that Im going for.

Personally cant see how pretty much any internal combustion engine will gain power with a compression bump, yet these dont?

Right now, leaning toward milling them a small amount, and unshrouding the valve area like what was done on Hoss.

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ebinmaine
3 minutes ago, Greentored said:

leaning toward milling them a small amount, and unshrouding the valve area

I can't offer you any specifics on those Briggs twins either but my thought pattern is the same as yours.

 

I wonder if the circle track guys are running an RPM range that requires a level of airflow that a milled head can't quite accomplish? I'm only guessing...

 

 

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Bill D
Posted (edited)

I not sure you can unshroud the valve area on that engine due to pressed in valve seats,  if I understand correctly what you're talking about doing.  Those engines have been known to lose valve seats like the Onans.  I vote for milling the head slightly.  Bill

Edited by Bill D
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ebinmaine
15 minutes ago, Bill D said:

Those engines have been known to lose valve seats

Any thoughts on the cause? Do they run hot in one of the cylinders?

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Jeff-C175
24 minutes ago, Bill D said:

Those engines have been known to lose valve seats

 

I recently repaired a leaf blower for a friend that had the 8 HP Briggs single on it, and not too old either.  In fact that engine had very low hours on it and maybe only 8 years old.

 

It popped an exhaust valve seat!  Apparently not too uncommon with Briggs.  Loose fit?

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Greentored

No clue why these pop seats like the Onans, but I have heard of this as well.

@Bill D the unshrouding will be done on the head itself, like this:

k1.jpg

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Greentored
Posted (edited)

Im back on the Big Briggs build! 

New bronze exhaust guides are done

Oil holes added to rod caps, rods deburred, chamfered and cleaned up

Block honed and new rings installed, with 2nd ring gap filed .002 wider than top ring. This keeps gasses from getting trapped between the rings and possibly unseating the top ring- likely not an issue with the rpms I plan to turn this thing, but.....

Oil dipper mods: these splash lube engines had a single, bolt on rod dipper for 2400+ rpm, and a pair of them for under 2400rpm. I added the second dipper to splash more oil on off camber situations, but at the same time did not want it splashing a huge amount when I wind it up, so dipper #2 was modified to only touch about 1/2" of oil, and it will come into play more when things get into steeper side angles.

Block was also ported and relieved- look at how nasty and restricted the factory ports were, especially the exhaust! Rumor has it opening up the ports pays off big on these, and I can see why!

Stay tuned, much more to come!

 

 

 

 

 

 

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Edited by Greentored
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Lee1977
On 3/19/2021 at 9:11 AM, Jeff-C175 said:

I compared the 1984 GT IPL to the 1980 C-175 IPL.  The GT-1800 uses Briggs 422237 and of course the C-175 is the KT-17

 

Don't know why the Engine Bracket (25) , PTO Housing Rod (31) , or the Brake (23) are different yet.

 

I used the PTO engine bracket off my 12 HP Kohler on my Briggs Vanguard but had to space it out with washers as the upper mounting bolts holes were recessed about 1/4"

That engine may be the same.

 

 

 

 

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Thor27
Posted (edited)

the PTO bearing race is 1", same as a kohler 8.  for the pulley, I plan to use an adapter and a 1-1/8 pulley

here are some pics of the pto engine bracket with a kohler to compare.  As or the linkages, i don't have them yet to compare.

 

20210705_123628.jpg.4f75f2d8c91b290c01b377a903838a3f.jpg

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20210705_124151.jpg

20210705_123713.jpg

Edited by Thor27
Add pics from phone
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Greentored

Why is there not a place for others to "like" or put up a smiley face on my posts?

Kinda figured there was no interest so havent updated this thread.....

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ebinmaine
11 minutes ago, Greentored said:

Why is there not a place for others to "like" or put up a smiley face on my posts?

Kinda figured there was no interest so havent updated this thread.....

There's a place. 

I just hit thumbs up. 

Definitely interested... :handgestures-thumbupright:

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Greentored

Well heck, I better get updating then eh?

Heres a few pics showing head work in rough in stage- they were angle milled .045 to retain some chamber size for flow and get the squish where I wanted it above the piston, then unshrouded a bit. Compression ratio 8:1 instead of in the 6s.

Intake was split and ported, and made an adapter to run a Kohler command 25hp carb which is much larger, and has an accelerator pump. Some small mods to the pump circuit has it working awesome!

Made my first attempt at a 2:1 pipe and collector, and it came out great. ( I also built a shorty muffler for it, more on that later.)

Ignition timing was bumped up 2 degrees as well.

The engine is in the machine and has been flawless! The power and throttle response are incredible- much more of both than ever expected!

Stay tuned and I'll put up a video.

bs1.jpg

bs2.jpg

bs4.jpg

bs3.jpg

bs5.jpg

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Bill D

How did you change the timing?  The magneto mounts are fixed.  Pics please.

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Greentored
2 hours ago, Bill D said:

How did you change the timing?  The magneto mounts are fixed.  Pics please.

Marked the flywheel and just filed the trailing side of the key where it meets the wheel itself until I got another 2 degrees off my mark

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ebinmaine

@Greentored

Thank you for updating this.

 

Excellent work Scott. Very cool.

I'm particularly impressed that you went to the trouble to split the intake. That's a new one to me.

 

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Thor27
23 hours ago, Greentored said:

Why is there not a place for others to "like" or put up a smiley face on my posts?

Kinda figured there was no interest so havent updated this thread.....

Absolutely interested and following along!  

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Tuneup

Just assumed it was another project dropped, typical among many. Maybe all those out there in history were actually finished and we weren't updated? Yes, very interested. I don't know how you get the time so appreciate your energy.

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Greentored
17 hours ago, ebinmaine said:

@Greentored

Thank you for updating this.

 

Excellent work Scott. Very cool.

I'm particularly impressed that you went to the trouble to split the intake. That's a new one to me.

 

Yep, some of the early intakes were two piece, kinda like the Onans- made for easy port work.

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Greentored
4 minutes ago, Tuneup said:

Just assumed it was another project dropped, typical among many. Maybe all those out there in history were actually finished and we weren't updated? Yes, very interested. I don't know how you get the time so appreciate your energy.

I do have a couple dropped threads on here due to never finishing haha. It's tough to make the time, but if enough of that time goes by, I will get frustrated and just go full bore til its done.

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Bill D

Watching this makes me wonder what you would do with a 13 fin, K341?

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ebinmaine
4 minutes ago, Bill D said:

Watching this makes me wonder what you would do with a 13 fin, K341?

I've had that same thought

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Greentored
22 hours ago, Bill D said:

Watching this makes me wonder what you would do with a 13 fin, K341?

I built a pretty healthy 14hp K for Hoss- thread is in the engines forum- "Let's build a K321 torque monster."

The 14 was the biggest one I had at the time- a 13 fin 16hp, now that would be awesome!

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Tuneup

Not that I need to be more impressed by your creativity on these machines BUT we have a horizontally opposed engine here. Doesn't anybody see the great opportunity? Did anyone ever hop-up a VW? I'm not saying dual Webers or Delortos but a nice dual carb setup with stacks would be the bomb.

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