Dyno 356 cam Extreme build!

delray

Well-Known Member
#21
james,glad to seen what i too thought could be a very potenional performance head and do something with it. with you now posting your head build. I also think now people can clearly see what kind of work it takes to really run a dyno cam with a 356 lift.
don't forget to slot the center bolt hole. i see it still looks round(stock).....:thumbsup:
by the way buddy , i am still holding out on one more potenional head..:wink:
 
#22
Oh ho! Another super secret squirrel experimental head!

I'm eager to see what you've come up with now!

On the head, yes it is slotted now. It bolts on fine.

As delray pointed out, the head fits the OHH, but the center rear bolt hole has to be slotted a little.

 
#23
The extra height of valves and rocker shaft assembly made it impossible to use a stock valve cover. I hope to make a billet aluminum one later on, but for now, I cut 2 stock ones, and welded them to together to make a tall one.

Being that this head was never designed to do what I'm doing, I had make a custom intake and an exhaust flange adapter. I made the adapter so I could use all the not all OHH headers I already have.

This thing mocked up looks pretty crazy!


 
#24
Anticipation of how all of this is going to work got the the best of me, and since I'm still waiting a on a few bits to put the engine together, I decided to put this top end on my Motorsports engine to test it out. It has also has a billet rod, coated piston, the heat treated crank, and a Dyno 255 cam. It is not as hot as the 356 cammed shortblock and doesn't have the lightweight crank and piston, but I thought it would be at lest give me a chance to test everything.

I put it on, and she fired up on the first pull (although she's tough to snatch over!) The whole tone of the engine sounds different than the OHH head. The head that was on the engine was ported and has bigger than stock valves, the OVRM flat out revs! I am just blipping the throttle in the video below, and it's trying to eat! It is so responsive. On the 3rd rev on the video, I kept the throttle cracked just a hair and still wanted to rev at around 3500 RPM. So far, it seems very promising! We can definitely say that an exhaust port can be made into a great intake port.

I'm going to run it a little more and pull it back off to check the wear pattern on the top of the valves, ect. I did run 22# Dyno springs with this cam instead of the 36# springs I'll run with the 356 cam.

After hearing it with 255 cam, I can't wait to hear what a cam with .101" more lift, and 20+ degrees more duration!




[video=youtube_share;btw0r-uiLl0]https://youtu.be/btw0r-uiLl0[/video]
 
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#28
Thanks guys!

That engine is going to be GREAT! This is what you'd call true engine "building."

I say keep that valve cover. It looks clean and it'll make people double-take.
The valve cover looks much cooler than I thought it would. I may end up leaving it on there just because it still looks like a Tecumseh.

This thing has been a lot of fun so far, and being that I made and modified so much of it, I'm not invested so much in it that if it blows up I'll be out all that much money. Don't get me wrong, I don't want that to happen, but if it does - I still had a blast.

After I get the other bottom end built, next big challenge will be modifying a billet flywheel for it.
 
#29
Awesome thread. Glad I didn't see any threads like this when I was looking to modify an OHH50 I had. I wasn't sure which parts might fit, so I got as far as the plastic cam and then gave the engine away. A thread like this probably would have had me spending a bunch of money. LOL
 
#30
Thanks Bob.
It's been a lot of fun!

I ran it for quite a while yesterday and pulled the head back off today. Everything looked good except the wear pattern on the top of valves. The contact area on the rocker shafts are small, so I thought I would need to run hardened lash caps with 36# springs and this pretty much confirmed that. It didn't hurt the valves, but I think it would wear the stems and create excessive lash pretty quick with the 36# springs. I've never built an engine with springs with that much seat pressure, but I figure that type of engine is high maintenance anyway - like most all high RPM engines are.

 
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delray

Well-Known Member
#31
james I can't really tell in the picture you posted. does it look like the top of the valve would of mushroom out little if you keep running it?
what kind of material is the valves made out of? where they easy to machine or hard? also what kind of material are the rocker arms made out of?
 
#32
It looks as though they would eventually dish out the top of the valves. The tip of the adjusters are small since they were designed for 5mm valves. I may end up making some different adjusters.

The valves are stainless, and they seem like normal stainless valves.
 
#33
Hi Tecumseh_Power,
I understand that in stock configuration, the OH195SA is about 6 HP. Do you dare make a prediction what
HP this engine will put out, when you are finished building? Maybe 12 to 15 HP on premium pump gasoline?
 
#35
I'm not sure, but based on other similar sized engines around the 200cc size at that kind of RPM I think it should be north of 15 HP. The head should have no problem moving a lot of air, it just depends on how efficiently it makes power. I'm actually more afraid of the durability of it more than its ability to make power.

I hope to get it to a Dyno and see what it will do. There was a guy locally that used to be a certified rebuilder and Dyno'd box stock class engines, but he's not around anymore.
 
#36
Came across a bunch of old Dyno Cam, Profiles. And found this one for the 356 Briggs 6.5 Intek OHV Cam.
Was wondering if it is the same one, (interchangeable), for the Tecumseh OHV?
If so, here's some great specs. Good luck on the motor.....
 

delray

Well-Known Member
#38
I see the max rpm is 8500 for the briggs intek…..interesting. the clone stuff is 8500-9000 and I seen the Tecumseh at 9000-9500
 
#39
The 356 is listed as 9500 for the Intek on Dyno's website now, it listed at a whopping 42-44# seat pressure on the springs. The clones are listed at 8500-9000 with 36# springs. Both cams have identical opening and closing events, duration, and lobe centers.



The big bore and short stroke of the Tecumseh, it would be more rev friendly that either of the other 2. On the flip side of that, I bet low end torque will be pretty crappy. I believe a loose clutch with a lot of sprocket wiuld be the key to making this cam fly in the Tecumseh.
 
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delray

Well-Known Member
#40
Tecumseh power
The big bore and short stroke of the Tecumseh, it would be more rev friendly that either of the other 2. On the flip side of that, I bet low end torque will be pretty crappy. I believe a loose clutch with a lot of sprocket wiuld be the key to making this cam fly in the Tecumseh
You should make up the lowend with the compression your going to have....:thumbsup:
 
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