Crazy High Compression - 260 PSI... Even possible?

Roo

Roo

it's all good
Site Supporter
Location
Lake Orion, Michigan
I have about 18 gallons of gas through this motor so far, equaling about 4 to 5 hours of straight ride time.

Did my first compression check today - 260 PSI'ish. WOOO :ugh: Is this even possible...? Runs like a champ thus far... ticking time bomb? What is the highest PSI some people are getting away with?

No wonder this thing is so snappy and barks like a mofo!

Quick run down:

-803cc Lamey PV Motor
-Total Loss Ignition set at:

Static 28
Begin Retard 5000 RPM
Rev limit 9250
Desired Timing 3 / At Specific RPM 9250

-Running 94 Octane Fuel
-Plugs look good
-Running 1 quart of oil to 6 gallons of gas, VERY heavy mixture, I know
-NEVER any WOT runs, always blippin' the throttle

I have not used this guage in 2 years. Obviously, I should check with another guage or two and compare (have not got that far yet, need to come up with another guage).

Looking for feedback from others.

IMG_2301.jpg
 
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E

egbrig

Yes 260 psi. is posible but try a Snap On guage. Whats your bore and stroke? Whats your trapped volume? If you don't know these then back to Snap On guage with the correct adaptor.
 
Idok

Idok

F1pro
Location
Nations oldest muthaF+++kin city
of course its possible...

you could have some extra oil in the cyl..that'll make it read high...

water in the mtor will do the same thing as well...



we compressin tested a stock stroke Lamey this weekend and it blew 300 on 1 cyl and 56 on the other :(







if it really is 260 you are WAAAAAAAAAAAAAAAAAAAY low on octane...not to mention something isnt right
 
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Roo

Roo

it's all good
Site Supporter
Location
Lake Orion, Michigan
I tried testing it like 5 different ways...

plugs out, open throttle, closed throttle, plugs in, etc...

I pulled the motor apart for addressing.
 
Rickster

Rickster

Matakana Menace
Location
Bay of Plenty, NZ
Roo said:
Culprit found: base gasket.
Click to expand...

How does missing/torn base gasket affect the compression of the engine to that extent? A missing base gasket (sealed with 1211) will increase your compression and decrease your squish a little, but to that extent I seriously doubt it.

I ran for a year without a base gasket, and only lost a few thousands in squish, and gained a few pounds in compression. Not worth it IMO.

Mile9c1 said:
What, was it missing??
Click to expand...

Even missing the base gasket, which from memory is ten thousands of an inch, will only increase your compression 5-10 pounds.

I think there is something else happening in this engine.

Rick
 
Roo

Roo

it's all good
Site Supporter
Location
Lake Orion, Michigan
No, it is all in the base gasket in this situation for sure, hands down.

Last year when I ran the motor, compression was around 185ish running this thicker base gasket.

This year when I reassembled the motor, I replaced the gasket with good intention, but in all honesty did not think twice about the thickness of the old compared to the new (high-on moment).

If you saw the two side by side, you would understand and is definitely the problem. The only thing changed from last year is a 1MM bore up and a rebuilt crank.

-Andrew
 
D

Don 79 TA

Still Fat....
Location
Madision/Huntsville AL
are you sure your gague is good?
260psi on low octane definately equals disaster waiting to happen
personally i have found the law of diminishing returns taking place with compression, past 220 to me it felt like the motor was to tight and not as free and powerful
i seem to like 210-220 range, and a good guage makes all the difference, i learned that lesson the hard way.
 
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