Author Topic: 1200 engine compression  (Read 9643 times)

Offline Legend79

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1200 engine compression
« on: June 02, 2012, 09:15:18 am »
Any know what the compression should be on 1200 motor? I have one in my car that I have run for about 3 seasons now, I ain't touched it apart from a new clutch and oil changes, on a compression test it reads 155 on each cylinder, is this a good reading or should it be higher? The tracks we run on are probably what you in the US would call bullrings I think, pretty flat turns, is a 1250 engine any better?



Offline VMS Motorsports

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Re: 1200 engine compression
« Reply #1 on: June 02, 2012, 09:51:05 am »
Have you adjusted the valves? Does it have slotted cam gears?
Compression isn't everything, but there are many ways to boost it back up
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Offline TG01

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Re: 1200 engine compression
« Reply #2 on: June 02, 2012, 09:56:15 am »
In the US there is a legends rule on compression (open motors) of 165 at wide open throttle 10 revolutions. We try to set them with cam timing at 160 for a safety window of different gauges because if we are high it would be a Dq. These readings are done while the engine is hot.
I think that a good judge of engine (ring) condition is how even these readings are accross all 4 cyclinders as long as the readings are not crazy low. In stock form I THINK these will crank like 180psi.


Offline Legend79

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Re: 1200 engine compression
« Reply #3 on: June 04, 2012, 03:55:39 am »
My engine was tested at our nationals but the engine was cold n it was 155 across all 4 cylinders, I couldn't tell you anything about the internals sorry as I know diddly squat about bike engines, most guys here run the 1250 but my car had the 1200 in when I brought it, would the money be better spent rebuilding a 1200 or buying a 1250?

Offline VMS Motorsports

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Re: 1200 engine compression
« Reply #4 on: June 04, 2012, 07:55:27 am »
155 cold is fine. The rule is 165 maximum hot.
Unless you are having other issues, I wouldn't worry about it
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Offline Legend79

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Re: 1200 engine compression
« Reply #5 on: June 04, 2012, 01:44:54 pm »
Cool, thanks for the info, no issues really engine I get passed coming out of the turns quite easily by most other drivers but I figure I'm not on the throttle as much from the middle of the turn, I'm still learning how to drive it!!!

Offline VMS Motorsports

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Re: 1200 engine compression
« Reply #6 on: June 04, 2012, 02:05:47 pm »
Maybe a rear gear change is in order...?
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Offline Legend79

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Re: 1200 engine compression
« Reply #7 on: June 05, 2012, 03:16:47 pm »
I have a 3.30 which apprantly is what everyone runs, the ca had this when I brought it, I have been told that a 3.33 is better but I wouldn't have thought a ratio that close would have made that much difference, maybe I'm wrong?

Offline justfreaky

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Re: 1200 engine compression
« Reply #8 on: June 05, 2012, 04:17:43 pm »

                               2             3            4             5
Rear Gear
     3.30            6.60       5.18       4.26      3.68
     3.33            6.66        5.23      4.30      3.71

Better to be hated for who you are, Than to be loved for who you are not.

Offline VMS Motorsports

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Re: 1200 engine compression
« Reply #9 on: June 05, 2012, 04:57:30 pm »
Brakes are important in a bullring. Drag from calipers/bearings?
Driver style? Carb jetting? Timing?
Alot of things that can add up to tenths here and there
JIM BUCHER
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Offline TG01

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Re: 1200 engine compression
« Reply #10 on: June 05, 2012, 07:30:08 pm »
What gear do you run on the engine?
I only ask because if everyone else is in third while you are in fifth or something like that with the 3.33 or 3.30 you would lug the engine down and feel what seems like no power.

Offline VMS Motorsports

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Re: 1200 engine compression
« Reply #11 on: June 05, 2012, 09:05:55 pm »
Just had to bring that up, didn't ya Dan?
JIM BUCHER
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Offline Legend79

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Re: 1200 engine compression
« Reply #12 on: June 06, 2012, 12:47:32 pm »
I run it in 3rd gear, at the moment I'm about a whole second of the pace of the quickest guys, not too far behind middle of the pack

Offline VMS Motorsports

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Re: 1200 engine compression
« Reply #13 on: June 06, 2012, 02:03:34 pm »
Brakes are important in a bullring. Drag from calipers/bearings?
Driver style? Carb jetting? Timing?
Alot of things that can add up to tenths here and there
.
JIM BUCHER
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Offline TG01

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Re: 1200 engine compression
« Reply #14 on: June 06, 2012, 06:52:30 pm »
Sorry!
I just had to ask because in a stock car with an auto trans that stuff is a given. These cars have 5 gears to chose from along with a rearend gear.....just sayin.

What kind of RPM do you get? Maybe a gear change would be a good thing if you are not getting the RPM that you need?
Sometimes with different lines and styles the gear selection can be very different.

A good running engine as Jim said is key as well.

 

anything