How much compression do you have with standard head and RockSolidEngines Billet Head

[AussieSteve]

I'll take your word for it, but boy that's high. (I've read a lot of bull-you-know-what in some people's posts.) What fuel are you running? Any pinging?

among other things and the smaller the combustion chamber the more psi you get when shaving the head

I am aware of this. That's why I bought the hi-comp head and why we're discussing pressures.
As a bike mechanic, do you happen to know what compression ratio that works out to?
... Steve

 

[mountain80]

No I never bothered to calculate it, I was more interested in compression vs crank/rod life. Not to change the thread subject at all but at this time i have 4000 km on the engine with 2500 of that with the high compression head. I am eventually going to take it higher but i am maching my own billet head with 50% more fin surface than whats out there to handle the incrased heat output. If i blow a crank so be it.

 

[AussieSteve]

Not to worry. I wasn't asking just to test you or anything - after I posted I felt that it looked a bit that way.
The reason I asked was that I read somewhere the other day that the Rock Solid Engines compression rating of 16:1 is done or calculated differently to the usual test which produces a 6.5:1 ratio on the standard 66cc flat head. The same post said that in reality, if measured the same way, RSE's head is actually abou 9.5:1.

My measured 135psi also indicates this. Any takers?

4000km is great going. I figure a new engine every year for me. We'll see what happens.

... Steve

 

[Fabian]

Hi Aussie Steve

What was the compression reading on the standard cylinder head.

By the numbers, you have 50% more compression than my engine with the same RSE billet cylinder head - a signifcant difference, not to mention the lack of horsepower, considering i've also got the billet intake tube.
In it's current state, my motor makes no more power than a standard Chinese engine.

 

[AussieSteve]

Been a bit slack. Yesterday, I went for a nice long ride to test my mods. No worries there. Today, it's too hot to move away from my fan and beers for too long. I only got as far as swapping to a leaner #73 main jet.
The head swap is next on my list, probably later tonight, when it cools, after a test ride for the new jet.

By the numbers, you have 50% more compression than my engine - that's a big difference in compression, not to mention a lack of horsepower.
In it's current state, my motor makes no more power than a standard Chinese engine.

Yeah, there's definitely something pretty wrong. I've seen a dramatic improvement all round, with +1000RPM at the top. Unless the rings are really odd-shaped or nicked/chipped etc, it only leaves the barrel, (ovoid or distorting badly). Still, there should be no heat distortion when it's cold. I guess it's too late to ask, but on examination, did it look from the wear like the rings were barely rubbing on two opposing sides of the barrel?
... Steve

 

[jlebh1]

my billet head was the best thing iv ever done makes heaps more power over stock.

 

[Fabian]

Hi Steve, where abouts is your location - if we live in the same city, i would be very interested to check out both of our engines compression using the same compression gauge and going over my engine together; making a video for Tony.

Fabian

 

[AussieSteve]

I'm in Nowra, NSW. Nowhere near you, I'm afraid. (I was born and raised in Melbourne, Chelsea and Oakleigh, respectively.)
Pity, though - it would have been interesting.
Feel like a real long ride? I'll meet you half-way.
... Steve

 

[AussieSteve]

Well, it'll be a couple more days before I can test the compression of the stock head. I started to loosen the head studs to remove the billet head for the swap and the front right-hand nut was already loose - stripped. The billet head requires studs at least 2 mm longer, 3-4 would be better. It looks like I might have been losing a little compression, too, but don't know for how long. My first compression test may have been low. We'll see. I'll repeat both.
I noticed there wasn't a whole lot of thread when I bolted it down and knew I should replace the studs, so what can I say?
Had a problem with the thread too.
See:-
http://www.motoredbikes.com/showthread.php?t=24468
... Steve

 

[AussieSteve]

So, my little head stud saga continues, but I did get the stock head back on and did a comp test:- 2 x tests, first 112psi, second 115psi. The highest counts.
Now I've got to suspect that the head nut was already stripped when I did the billet head comp test. Otherwise, it's hard to imagine that the billet head is only 20psi higher at 135psi when I look at the relative sizes of the combustion chambers. As soon as I get my stud problem sorted, I'll re-test the billet head. I think that it might go a bit higher than 135.
The studs are M8 x 1.0mm (both ends) and I can't get that size threaded rod or fully threaded bolts locally. Got plenty of nuts.
... Steve