Predator 212 Hemi, head gasket swap questions

[thefarmboy21]

For Father's Day, I got a new predator 212 with the Hemi head. Tomorrow we have safety training at work, then we just have to sit around, so I'm taking it with me to work on after we are done. I ordered a basic update kit from NR Racing....header, jet, air filter, low drag fan and a few other misc things. I also ordered a gasket kit for when I'm ready to crack it open and it came with a .010 head gasket.

I'd like to go ahead and change that before I ever even start the motor, that way HOPEFULLY there's less gasket junk to scrape off. My only concerns are 1. By going to an .010 gasket is that going to require different push rods? And 2. If I change the gasket and maybe port the head while it's off, will a jet change alone get me enough fuel to compensate for all the "bolt on" mods plus the increased compression? Because I'm a little worried it may cause it to lean out.

I've read mixed things on both issues. Let me know. Thanks.

---------- Post added at 11:33 PM ---------- Previous post was at 11:32 PM ----------

Also have 8 degree flywheels key and 18lb springs n

 

[bob58o]

Did you get a billet connecting rod? 18lb valve springs should allow your engine to rev to
rpms where your stock connecting rod is no longer safely usable. It may break apart at higher than 5X00 RPMS. Get a billet rod if changing springs, or keep the stock springs. Stock springs should allow you to turn 5200 RPM or something like that IIRC and the rod should remain whole.

1.) No, you should be ok with the stock pushrods. But google how to determine correct pushrod length and check for yourself. It is not difficult.

2.) Yes, you'll be able jet the stock carb to get a correct fuel air mix. Bigger carbs are required when turning high RPMs, not because they give more gas - because they give more air.
The faster you run, the more you need to breath. A new air filter, exhaust, and port work will get you more air, but should be able to compensate by using larger jets in the same carb.

---------- Post added at 11:29 PM ---------- Previous post was at 11:26 PM ----------

70mm bore
55mm stroke
70mm gasket bore
0.010" gasket thickness
0.025" (guessing) deck height
22cc Combustion Chamber
Flat top Piston

http://www.csgnetwork.com/compcalc.html
9.3:1 static compression ratio vs 8.3ish:1 with the stock gasket

 

[thefarmboy21]

I don't have a rod yet.....I am not planning on removing the governor YET though. I'm going to do a rod, cam and gov removal all at once. At that time I'll change the flywheel too. So it shouldn't turn more than 5000'ish RPM.

I got the valve springs because they were cheap to add to the kit and from what I've read and experienced.....it helps prevent valve float when turning the engine around the 5000rpm range.

I do know how to measure pushrods, however I didn't want to tear them motor apart unless I knew there was a chance I could get by with stock ones for now. I'll get chromoly ones when I upgrade the rest, but I'd like to go ahead and change the head gasket now.....but I don't have time to to wait on pushrods to come in.....plus the Kart fund is running thin right now lol.

 

[mckutzy]

You'll want the valve float to cause retardation in speed as to save the rod... The rod will let go shortly thereafter 5k rpm range with the heavier springs...
New springs new rod-old springs old rod...

Head gaskets are typically thin metal.

You can redrill the jet to what ever size needed when you put a new header/filter on...most of us do.

Here is a few other hop ups we typically do...

http://www.affordablegokarts.com/performance_basics.php

 

[thefarmboy21]

You'll want the valve float to cause retardation in speed as to save the rod... The rod will let go shortly thereafter 5k rpm range with the heavier springs...
New springs new rod-old springs old rod...

Head gaskets are typically thin metal.

You can redrill the jet to what ever size needed when you put a new header/filter on...most of us do.

Here is a few other hop ups we typically do...

http://www.affordablegokarts.com/performance_basics.php

So the factory valve springs are good to 5000 rpm? I just don't see why it's necessary to keep the factory ones IF I still have the governor limiting me to 5000 RPM anyway. When we changed the springs in the other Hemi we have, it seemed "crisper" in the top end and was still governed to 4900-5000 or so. We have a tach.

Also head gaskets on both our Hemi's appear to be .045 composite gaskets. I have a .010 metal/viton gasket to go on.....but if I pull the head, I'll probably port it too.

My kit came with a new jet (I also have jet drill bits) but I didn't get the GX140 Emulsion tube...is it necessary?

 

[mckutzy]

Gov in, is limiting you to about 3600rpm... Typically speaking, unless you mod the spring positions.
None the less... The stock springs are the best bet to inadvertent rod dissection.

140 tube helps with the jet to get a better mix...
I got a few of the jets and tubes from a rental shop that had a junk bin I could pick through...
Sold me a few for $5...

 

[thefarmboy21]

Gov in, is limiting you to about 3600rpm... Typically speaking, unless you mod the spring positions.
None the less... The stock springs are the best bet to inadvertent rod dissection.

140 tube helps with the jet to get a better mix...
I got a few of the jets and tubes from a rental shop that had a junk bin I could pick through...
Sold me a few for $5...

Actually you can do a simple governor "mod" by moving the spring and adjusting the throttle stop and it'll ride right around 5000 with everything still hooked up. Look it up on YouTube. Takes 5 minutes. We've done it....and put a tach on it. It's legit!

 

[bob58o]

I guess it makes sense. I'd rather not float the valves and use the gov to limit RPMs to the upper limits of the factory rod. If the rod is good at 5k, it is probably better to use a governor to stay at 5k or below, not valve float. Hmmmm

 

[mckutzy]

Fare enough...

I'll look into my own engines about this..

 

[Whitetrashrocker]

Heavier springs will rob a little hp but will snap closed and not float off the cam. Hence the reason you felt the snappiness.
Old rob with new springs I would assume ok if the gov is still operational.