Just checking to make sure I am not making a mistake on my compression. I am wondering if some one else can verify my calculation of my compression is correct. I am using a compression calculator for the math here. I am going to be building a 196 clone motor for a mini bike. I calculated the bore of the motor at 2.677" --- the stroke at 2.126" --- The gasket at 2.9528" ( Is that correct? <) using a .040 thick gasket and a flat top piston at 0 deck height. The calculator is saying 9.719 compression or 9.72 just want to make sure I did this right before I order my piston this week. I am wanting to run 91 octane fuel. Is 9.7 too high for these motors with high octane pump gas? Would 9.5 be a safer bet. I will be running this motor with both a stock cam and later with a NR 280 high torque cam, part # 280-0211. Plan on running the UT2 piston with a .100+ rod.
Are my calculations on compression for my 196 clone correct?
- Thread starter DeadPixel
- Start date
- Tags 196 calculations clone compression correct
you can run 93 oct pump gas up to 10.1 compression with moderate timing. higher compression needs higher octaine. the best way to determine your compression is to have all parts in hand mock the motor with all clearances done and cc the head on the block with the piston sealed with grease or vasoline at tdc. the calculaters get close but don't take into consideration all the clearance things like valve pockets deck height etc.
I have always found this helpful from NR racing, for double checking. Nate knows his stuff though :thumbsup:
Compression sheet[\url]
Compression sheet[\url]
Not sure it was a number I found on another post. I was having a hard time finding diameter. It seams right to me though. The head gasket should be a little larger than the bore on a motor. I think the gasket on my SBC350 is the diameter of a SB400. Its so you don't have a hot spot on the ring in the gasket causing detonation. I could be way off on the diameter though. I will measure one when I get one for my build. As far as 93 goes I only can get 91 were I am at. I always hear of people talking about 93. Were are people getting this at. I would have build the motor in my truck with more compression if I could find this at a gas station. Is this an east coast thing? I live in Washington state.
How can you calculate it? Need Head CC's Then with the bore, stroke, piston Depth, and gasket bore and thickness you can use the online calculators to figure it.
https://www.rbracing-rsr.com/compstaticcalc.html
https://www.rbracing-rsr.com/compstaticcalc.html
You would think that you would be ok with 91 octane when running below 10/1 compression. I just got one of these Coleman's with a Hisun clone engine. The tag on the tank says to use 90 octane or higher. On an engine that is probably 8.5/1 ??? Strange. I will be using regular old 87 octane like I use in all my other clones.
Back in the 80's when I built my small block Ford I was going to run 10/1 compression but changed my mind because of the fuel issue and kept it at 9/1. I think my target octane for 10/1 was 91. I ended up always getting 91 for a few years anyway because Citgo was the last to sell leaded fuel in my area and it was 91 octane. Since then I just use 87 or 89.
You said you hear people talking about 93 octane. Most of them probably don't need it but just use it to play it safe.
Back in the 80's when I built my small block Ford I was going to run 10/1 compression but changed my mind because of the fuel issue and kept it at 9/1. I think my target octane for 10/1 was 91. I ended up always getting 91 for a few years anyway because Citgo was the last to sell leaded fuel in my area and it was 91 octane. Since then I just use 87 or 89.
You said you hear people talking about 93 octane. Most of them probably don't need it but just use it to play it safe.
Oops I forgot to add in my original post I did the calculation with a 18cc head as that is what is coming in the mail. I ordered a UT2 head the other day from the GX160 with the 26mm intake valve for my build. I used a calculator but will try this one to make sure it comes out the same. I need to find out the diameter of the gasket for sure because I might be wrong on it.