Better intake springs 3hp B&S flathead?

[Budget DIY]

Hi all. Just for fun and giggles, I came up with a plan to make the most rawdy 127cc, loud, fire spitting and obnoxious 3hp Briggs and Stratton flathead on the internet. I've got some secret sauce that I won't go into. But amongst other things, I plan on adding a RHB31 turbo from AliExpress. Stand alone E-oil supply and whatnot. AI told me that these tiny engines won't be able to produce enough CFM, but on paper, I fixed that issue. But now...

I can't seem to find parts, and I'm very much new to engine modding. Although I do know the theory well enough. And if I'm going to run close to 15 psi of pressure @ around 4200 rpm, I especially need better intake springs. Otherwise the turbo with the high RPM's, will just be causing valve float. So...

Does anyone know what part number I should be looking out for? What would be a better intake valve for this ancient flathead engine? I'd prefer to go the AliExpress route, but that site seems to be filled with Honda clone parts. I'm located in the EU (Netherlands), so ordering a (cheap) part from an USA website will probably cripple me with shipping costs.

 

[Budget DIY]

Oh, the engine is currently mounted to an unfinished/kinda abandoned motorised bicycle project. Lost motivation, got some different projects. And this turbo might make me interested again.

Frame has been notched to fit the engine, and reinforced again. Replaced both the front and rear hubs/kept the stock rims. Also notched the fuel tank, but it needs to g0 if I'll slap on a turbo. It's intended to be a friction drive, with a 1-to-1 ratio towards the roller. Roller can be pulled away from the wheel to go into "neutral". Theoretical top speed has been calculated to be about 45 km/h @ 3600 rpm, which will make me fear for my life. Adding all the boost and over revving the engine to about 4200 rpm will be a stationary party trick. While driving, the RPM limiter will be set to 3600 rpm. (spark cut electronics) Rear wheel brake lever will also cut the engine. Managed to keep the pedals, but had to widen that crankshaft by something like 15 cm? Also had to replace the rods to the pedals to some from a kids bicycle so that they are shorter and won't hit the pavement while cornering. On and the crankshaft pedal sprocket had been moved back in big time, by adding a thicc tube as a spacer.

And as with all friction drive setups: yes, I'll pedal up to some speed, before I engage the drivetrain.

PS: here is a vid of the white engine (and spare orange) running.

 

[landuse]

I look forward to seeing how this projects progresses. Have you tried Arc Racing for parts? They might have springs that will fit and that are stiffer that stock.

Ugh....I just saw that you are in the Netherlands. I am not too sure where you might get any parts there. Shipping is always going to kill you. It is the same here in South Africa. Buying anything from the US or UK is just prohibitive with shipping

 

[Budget DIY]

Exactly @ shipping costs @landuse . It needs to remain a for-fun project, without breaking the bank. And when shipping costs are 2x the price of the actual part, that's not ok. (this turbo project is going to cost me way too much moneys as-is already...)

Do you know what part number I should be looking out for?

 

[Hellion]

Oh, the engine is currently mounted to an unfinished/kinda abandoned motorised bicycle project. Lost motivation, got some different projects. And this turbo might make me interested again.
......................

View attachment 163199PS: here is a vid of the white engine (and spare orange) running.

No videos were posted. We cannot host videos the same way we can with photos. Provide a URL if you like.

I’m sure it’ll be the fastest bike ever in REVERSE. As currently configured in the photo, the engine is facing the wrong way for forward propel.

 

[Budget DIY]

No videos were posted. We cannot host videos the same way we can with photos. Provide a URL if you like.

I’m sure it’ll be the fastest bike ever in REVERSE. As currently configured in the photo, the engine is facing the wrong way for forward propel.

I'm sure I had added a YT link, but I'm guessing it got auto-removed because I'm new to these boards.

I'm sure it'll be going FORWARD. The engine is facing the CORRECT way, so I might get some kind of ram scoop going on.

You might want to look again at the pictures. It's a friction drive. The roller pushes onto the wheel, making the wheel spin in the correct direction.

 

[Hellion]

You might want to look again at the pictures. It's a friction drive

Blammo! Ya got me, mate . Outstanding friction drive thingamabob. Yes, you are crazy! I’d be worried about slippage... EDIT---> so I naturally thought it was chain or belt drive, you know, something SENSIBLE

As for your spring conundrum, can you adapt other springs to fit and possibly double them (a smaller spring inside the other)? I’m not seeing much available that isn’t stock OEM Briggs parts. Will the 5 HP Briggs Raptor springs fit? The valve spring gallery and compressing them to fit inside it is the only real concern.

 

[Budget DIY]

Video attempt.

 

[Denny]

A 3hp Briggs was never a hot rodded engine. I doubt you will find many, if any parts to upgrade that engine.

 

[Hellion]

I'm thinking he needs to join the 21st Century, Denny, and seek out an OHV or OHC engine of similar size. They should have plenty of such China engines there in the Netherworld

 

[Budget DIY]

Blammo! Ya got me, mate . Outstanding friction drive thingamabob. Yes, you are crazy! I’d be worried about slippage.

As for your spring conundrum, can you adapt other springs to fit and possibly double them (a smaller spring inside the other)? I’m not seeing much available that isn’t stock OEM Briggs parts. Will the 5 HP Briggs Raptor springs fit? The valve spring gallery and compressing them to fit inside it is the only real concern.

It's an abandoned unfinished project at this point. I had planned on using rods to push/lock and pull on a rod to lock the friction drive roller onto the rear wheel. Should add loads of force you don't see on more normal setups. Maybe weld a bit around the roller, so it gets loads of spatter from my flux-core welder to increase surface roughness.

As for rubbing trough the tire itself: this will never ever get to become street legal in my country, and I don't know any legal places to ride it. Which is part of the reason why I abandoned it. Slapping a tiny turbo onto it, makes it a party-mode thing. Backfires, electronic rev limiter, turbo spool noises... Yea, I can see that being fun.

Never did I REALLY open up one of these engines, so I don't even know what kind of springs are in it. Hence just asking before potentially creating a huge mess.

 

[Budget DIY]

I'm thinking he needs to join the 21st Century, Denny, and seek out an OHV or OHC engine of similar size. They should have plenty of such China engines there in the Netherworld

My "party trick turbo setup" requires a flathead. Other engines would self-destruct.

 

[Denny]

My "party trick turbo setup" requires a flathead. Other engines would self-destruct.

No they won’t ohv turbo engines and supercharged engines have been done before. With a one lunger I can’t see how a turbo will be able to build 15lbs of boost. If I were you I’d bolt the turbo on and deal with any problems that arise later. Just my opinion.

 

[Budget DIY]

I naturally thought it was chain or belt drive, you know, something SENSIBLE

I had to mount the engine this way for multiple reasons. It already didn't fit. But pre-turbo plans, this was my only option to make the tank/carb fit the frame. And to keep costs down, it made sense to ME, to go with a friction drive. That "drive train" in it's current setup was made from scrap metal I had laying around. Didn't have to buy a clutch, which would likely burn out. And because it has a kinda wide tire, it does make some sense. ^^

 

[Budget DIY]

No they won’t ohv turbo engines and supercharged engines have been done before. With a one lunger I can’t see how a turbo will be able to build 15lbs of boost. If I were you I’d bolt the turbo on and deal with any problems that arise later. Just my opinion.

I've done much research on this particular issue, and I found a way to bypass that issue you've mentioned. And I didn't encounter anyone else who had the same plans.

If I end up not building this turbo project for whatever reason, I'll give the "secret" away.

 

[Sparkwizard]

You will never reach 15 PSI without a big load on the crankshaft. NEVER. It will throw a rod before it reaches any measurable pressure in neutral.
Cool project, though. Build a custom chassis dyno for it so you can hold it back and build some boost.

 

[Budget DIY]

You will never reach 15 PSI without a big load on the crankshaft. NEVER. It will throw a rod before it reaches any measurable pressure in neutral.
Cool project, though. Build a custom chassis dyno for it so you can hold it back and build some boost.

I had planned on adding an alternator as a dummy load. But those are all minor details. I created this thread to find a component which I'm struggling with.

I'll be placing the carb infront of the turbo. I'll be going to overrev the engine by a small margin. (4200 rpm) Over reving and feeding the engine boost will likely cause horrible valve float, at least for the intake. The most critical and dangerous issue IMO is having the ignition phase back-feed towards the turbo. Throwing a rod is concerning, but not THAT dangerous. Igniting the fuel mixture in the turbo, is more dangerous IMO. Hence looking for intake valve spring upgrades.

 

[Whitetrashrocker]

Perhaps take measurements of the spring and look at spring mfg pages. You can buy them per size. Like how you can get different nuts amd bolts at the hardware store. Then just up size the coil count or wire diameter.

 

[Sparkwizard]

Please continue your reseacrch on boosted engines without load. A turbocharged engine makes ZERO boost with zero load. I am not new at this.

 

[Sparkwizard]

@Thepartsguy Help, please chime in!
A 10 cibic inch flathead at 15 PSI boost will make FAR too much power to be contained by an automotive alternator or most single V belts.
Certainly not a party trick. Definitely dangerous to be screamilg like that around a crowd of people.