The stock length rod will be ok. It's not ideal, but it will be ok. A +.020 rod with a different gasket would be better. Is this a 70mm bore? I can calculate compression for you if you want. Have you CC'd the chamber? Was this a 22CC head to begin with? At .050 milled you will be left with roughly a 16cc chamber. Better to actually CC the head though. I assume you are using a flat top and not dished piston, right?
Predator Non Hemi Question
- Thread starter MO Predator Racer
- Start date
70mm stock bore Flat top piston stock hemi, stock head milled 0.050". If it will make a big difference I will buy a 20+ rod and go with a 0.018" head gasket. That will put me at 0.027" below deck. Or a 0.027" head gasket will put me 0.036 below deck. With what I have now I will be at 0.039" below deck. Gonna wait for your answer. Thank you Very Much
I have a banzai 265 (clone) from EC and a mongoose 272 (gen 1) along with a 22mm round slide I'd let go for a good deal.
MO Predator Racer
Member
PM me please
Assuming your combustion chamber is now 16CC's, which should be close with .050" fly cut head. This is assuming you have started with a 22CC head. You should really check this yourself though. Your compression with the stock length arc rod should be "about" 11.65 to 1.
With the +.020" rod you will be about 12.32 to 1 compression assuming you have exactly .027 clearance with the head gasket. If you are running methanol, this is not a problem.
So, if money is not an issue, get the longer rod and maybe sell the other one. I would not let it keep me up at night though. More compression and a tighter squish will definitely increase power. How much power? Who knows? I guess it depends on how competitive you are and if your willing to spend the money.
Keep in mind that I am not a racer. I imagine if I was, I would look for any edge that I could get or afford. On the other hand, if your out there just for fun, just use what you got and make it work.
Ask away with any other questions regarding the engine and I will try to answer.
With the +.020" rod you will be about 12.32 to 1 compression assuming you have exactly .027 clearance with the head gasket. If you are running methanol, this is not a problem.
So, if money is not an issue, get the longer rod and maybe sell the other one. I would not let it keep me up at night though. More compression and a tighter squish will definitely increase power. How much power? Who knows? I guess it depends on how competitive you are and if your willing to spend the money.
Keep in mind that I am not a racer. I imagine if I was, I would look for any edge that I could get or afford. On the other hand, if your out there just for fun, just use what you got and make it work.
Ask away with any other questions regarding the engine and I will try to answer.
No Sir I have a Hemi head and block. Its not going in a go kart its for a bicycle, I want to hit 65mph. Thank you for all the help.
My compression calculations were for a non hemi head so they will not be correct. Sorry about that. I'm not sure how many CC's a hemi head would have after being milled .050". The hemi head will make less compression but the same still holds true. I would definitely get a long rod with that hemi head to make some decent compression.
The hemi has a huge combustion chamber compared to non hemi which is why most people like the non hemi head.
Watch your lift with a hemi head because they coil bind pretty quickly. I'm not sure exactly how much lift you can get away with. Make sure you have at least .060" between the spring coils at full lift. Also make sure the rockers don't bottom out. Should be ok with a .265 or even .275 cam I would think but I have never built a hemi.
The hemi has a huge combustion chamber compared to non hemi which is why most people like the non hemi head.
Watch your lift with a hemi head because they coil bind pretty quickly. I'm not sure exactly how much lift you can get away with. Make sure you have at least .060" between the spring coils at full lift. Also make sure the rockers don't bottom out. Should be ok with a .265 or even .275 cam I would think but I have never built a hemi.
Reign-Check
Member
I've had coil bind with a MOD2 on the hemi. It's an easy fix, but definitely an easy problem to have too.
Also, another thread/member previously posted a pic with the compression chart including the hemi...
https://4cycle.com/karting/threads/stock-hemi-predator-dyno-pull.117323/
I ordered the 20+ rod and a 0.018" gasket. Should I look around for a non hemi head? Will it even fit on my block? Same bolts , pushrods. I know the rockers are different, but with the regular head i can get ratio rockers pretty cheap compared to Hemi .rockers. Ive seen a head on EBAY the guy sells em milled to what you want for $85 Would that be a deal? or not worth all the extra $
Thank you again for all your help. Oh I did buy a 265 lift cam. Thanks
Your probably right Flattop. This **** is like a disease you just keep spending money.