Fuel????

[sefrayser]

I have one Predator 212 hemi that I just did the plug change, governor spring adjustment and throttle set screw adjustment on. It runs pretty good on my kart with a 12/60 gear. I may even go to a 14 0r 16 spur gear. Im going to buy another Hemi to trick out. I would like to run racing fuel or some other fuel. My plans are to do the valve spring, cam, flywheel, rod,pipe and polish/port head. I also plan to get rid of governor and any of the other stuff the hinder rotating speed. Will this support alternate fuel? What compression do I need to achieve my goal? I really don't want to get into a new piston or shaving head. What is a good cam to run? To be honest I don't even know what Im going to do with it. I may put it in the go kart or may get a doodlebug or drift trike. Its more a project motor for me and my son. I figure for around 500 I can have a beast of a motor.....for what it is.

 

[anickode]

Gas stations that sell anything besides the standard 87-94 octane E10 are few and far between. I know of two within a 40 minute drive from me. One has 91 octane ethanol free, and the other has straight up race fuel. I can also buy race gas down by Milan Dragway, but it's pretty pricey there.

Find out where you can get it before you go and build an engine that needs it. If you have to drive 2 hours round trip to pick up a 5 gallon can of go kart gas, you might want to reconsider, especially if this isn't a competitive kart. Gas has a finite shelf life, so you'd be wasting even more money to try and stock up with multiple cans worth if you aren't going to burn it in a couple months time.

The next option is aviation fuel, which is 100 octane low lead. It is illegal to use in anything but an airplane, and some places will be very strict about who they are selling it to, what you're putting it in, and where you go with it. It's also like $6.50/gal (and smaller airfields tend to be more expensive), so burning it in a hot rodded go kart would be a bit pricey.

There are also ethanol treatments for fuel (sta-bil makes one) that are suppose to stabilize the ethanol and keep it from separating and absorbing moisture, and help cut down on the corrosion from using it. This is the route I typically go for my power equipment. Mower, snowblower, generator, go kart, etc, simply because it's the most convenient.

 

[sefrayser]

I can get just about any fuel around me. Alchohol, nitro on the other hand Im not sure.

 

[anickode]

I can get just about any fuel around me. Alchohol, nitro on the other hand Im not sure.

A methanol motor would be fun.

Don't try and run Nitro (even in tiny amounts) in a go kart. I had a buddy try this in his very expensive briggs methanol race engine. He filled it with glow fuel for model airplanes, which is mostly methanol with 15% nitromethane. I guess he was trying to get a little extra kick out of it, and his engine blew up. Not blew, blew up. As in the head was gone, the side of the jug was gone, the Piston was in pieces, connecting rod was shrapnel, the crankshaft was bent, etc. He wound up in the hospital, and his surgeon said he hadnt seen shrapnel wounds that bad since the war (not sure which war, but if the doc is comparing it to a grenade blast, it's bad).

So don't do that.

 

[sefrayser]

I was more looking to run racing gas, something like 113 octane.

 

[Whitetrashrocker]

To be brief.
Higher octane fuel burns slower. You need compression and advanced timing for it to be used properly.
Putting high octane in a non performance engine actually hinders performance. The mods you listed help flow but not enough to warrant race fuel.

 

[sefrayser]

I planned on the 8 degree timing key. As far as compression I guess the only way to get more is to shave the head, which I really don't want to do. Like I said this is a project and I want to build a little beast without getting tooo crazy. Its more for my son. He is 4 and believe it or not he can tell you every part on the motor and even take things apart(after I loosen). What is a good cam to get? I have read and there are so many to choose from. Im just using it for more or less straight runs.

 

[anickode]

He's 4?

I would recommend a stock motor. Build it as you go along and he learns how to drive.

There is a domed (not dished) Piston for the hemi predators that gives you some crazy high compression ratio with a stock head gasket and and no machining.

 

[bob58o]

I used 100 octane gas with 11:1 CR and 32 degrees before top dead center ignition timing. My engine seemed to like the AR3911 plug better than the AR3910x everybody gets.
To get to 11:1, I milled the hemi head like 0.035"-0.040" to make a 17.5 - 18cc combustion chamber (instead of the stock 22cc). (maybe $35-$40 with shipping)
I replaced the stock 0.045" Gasket with a 0.027" Gasket. ($15)
I replaced the stock connecting rod with a +0.020" billet connecting rod ($83)....


Also replaced the carb ($30 - $80), cam (up to $100), valve springs ($10),.......

Valve Job ($30), Port and Polish (DIY), SS Valves with Keeper/Retainers/Lashcaps (($60)...
You could also do CrMo pushrods ($25), Reinforced rocker arms ($50), Billet lifters ($25),....

$500 bucks goes pretty fast.
A cam, rod, and flywheel will cost almost $300 (depending on the cam). I used the stock flywheel for my 7k RPM engine. It didn't fly apart yet, but it is not recommended.

---------- Post added at 10:14 AM ---------- Previous post was at 10:05 AM ----------

A really good cam shaft for lower RPM (under 7000 RPM) is the Black Mamba Jr.
Everybody loves it. Made by the ISKY family. SmallEngineCams.com

It needs 26lb valve springs, has 230 duration, and .275" lift. It pulls hard from around 3000 RPM to 6500 or 7000 RPM.

 

[Bbqjoe]

Bob is full of good info, but dam, he get's a bit windy at times!

 

[bob58o]

Bob is full of good info, but dam, he get's a bit windy at times!

I just hate follow up questions. LOL
Just Kidding.

-From the city of wind.

---------- Post added at 11:43 AM ---------- Previous post was at 11:35 AM ----------

Don't try and run Nitro (even in tiny amounts) in a go kart.

So don't do that.

I think FHB was running like 50% LOL.

So don't tell him that.

 

[Whitetrashrocker]

I think FHB was running like 50% LOL.

So don't tell him that.

It blew up too

 

[Scout]

He's 4?

I would recommend a stock motor. Build it as you go along and he learns how to drive.

There is a domed (not dished) Piston for the hemi predators that gives you some crazy high compression ratio with a stock head gasket and and no machining.

The bullfrog piston? I just got mine fired up today. I haven't run it on the kart yet. It's advertised as 11:1.

 

[sefrayser]

Let me be clear I have a stock predator on the kart now and when he gets gig enough that's what he will ride. The one I want to build is just st for me to play with. I want him to help. It seems the Predator Hemi's are hard to find here in my area. I did find 2 that I'm my way to get. I have to drive 60 miles but hey at least I have a couple to play with.

 

[Hellion]

I would like to run racing fuel or some other fuel.

I like this whole pick-the-fuel-first-and-build-the-engine-around-it scenario.

I just think you wanna be able to say, "it runs on rocket fuel".

 

[bob58o]

I like this whole pick-the-fuel-first-and-build-the-engine-around-it scenario.

I just think you wanna be able to say, "it runs on rocket fuel".

That's the problem with Hemi heads. In order to have a hot cam and High compression, you need to weld up the combustion chamber (or maybe cut valve reliefs in the piston?).

If you get a CR high enough where it needs 110 Octane, There isn't much room left for valve lift.

Not sure how this would apply to that domed bullfrog piston with valve reliefs cut.

 

[sefrayser]

Not rocket fuel but maybe JP5 or 6

 

[Whitetrashrocker]

Not rocket fuel but maybe JP5 or 6

Jet fuel is closer to Kerosene and Diesel than gas.
That would be a pinging smoke machine if you put in a kart engine

 

[Noseoil]

Build the motor first, then see what you need for fuel. Octane ratings go with compression, timing, cams & heat. Do some research, it's all out there. That or just put the cart before the horse & see how it works....

 

[bob58o]

I agree with the others. You should pick a cam first. One with a powerband that matches with your gear ratio, tire size, driving style, and where you ride. The cam will tell what Compression Ratio you need. The CR will tell you what fuel you need.

For instance, there is no reason to get a 9,000 RPM cam with 4:1 gear ratio and 20" tires if you are riding around the backyard of a house on a 1/4 acre lot.