High compression...yikes

dirtyoz

dirtyoz

Location
Alaska
I rebuilt a 61x to go in my FX-1.

Here's the list:

Hotrods crank
coated pistons
FP B-pipe limited
Protec rec head ??
MSD enhancer

Compression after 3 tanks of fuel = almost 200psi
Been running 92 pump gas.

I am a little freaked out about the psi. I dont want to hassle with using avgas on this ski. But I have no signs of detonation.
I have tried 2 different guages and will try a 3rd tomarrow. To boot, the plug hole is long threaded, and I used short threaded guages.

My point is, I thought this was a rec head. Why is the psi so high? Its only supposed to get like 175-180.

I used no gasket, just the O-ring and 518 on the jacket.

Oz
 
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Crab

Crab

thanks darin...noswad!
Location
Seattle
dirtyoz said:
The domes are fixed (non-interchangable). I actually called Protec before I installed the head to make sure this was the rec model. His description matched my head. ?!?!?!
Click to expand...
Check the domes with a large 50cc syringe.
 
dirtyoz

dirtyoz

Location
Alaska
surferdude345 said:
someone might have decked the head
Click to expand...

Thats what I was thinking, but I remember matching it to another used one I purchased and from what I remember it was the same.... aside from boss locations. Maybe I should pull the head and compare again.

Since its an o-ringed head, would installing a gasket be the right thing to do? or would it make the o-ring less effective?

P.S. I Love the BRAP this puppy puts out.
 
dirtyoz

dirtyoz

Location
Alaska
crab said:
Yes, and I would check the squish before pulling it. Use something besides water, the surface tension makes it harder.
Click to expand...

So I am not familiar with the squish procedure, could you elaborate on that?

And Craiger, by "jacket" I dont mean "coat night" HAHAHA........yes, I havent forgot about that! HAHAHA
 
djkorn1

djkorn1

kidkornfilms
Site Supporter
Location
Cleveland Ohio
The drypipes will rattle them a lot and break the cyllinder if it blows.

I wouldn't run that kinda psi without race gas. (Actually, I wouldn't run it ever!)
 
blaster800

blaster800

Location
sunbury ,ohio
FYI My personal experience : bought a B-1 61-x out of Colorado , brought to Ohio , (porting,msd,mild bore,dual 44's riva red pipe ), engine runs 215 psi compression in ohio it was at approx 180 psi in Colorado 4000 ft ,This engine runs absolutly perfect and extremly strong with instant hit , has shown no signs of deto, I just run 93- 94 octane and dont scream across the lake wot for over 1 -1.5 minutes at a time max ''wot is no fun anyways'' , engine still runs perfect after 2 years ! I can get buy with a lot of compression with good gas and surf style riding ''at least with this engine''
 
dirtyoz

dirtyoz

Location
Alaska
I never thought of the altitude. I should because I ride snowmobiles in winter?!?
Our lake is only 600'
So your saying 4000' will make a 35 psi difference in your compression?

I cant ride WFO for more than 10-15 seconds anyway, and about a 3rd of the time its a high speed bail.
I wonder if my new coated pistons were domed higher than stock. I think I am going to pull the head and check for detonation. I really like this motor and dont want to zorch a top end just because I was lazy.
 
blaster800

blaster800

Location
sunbury ,ohio
If i remember ,Its been a while , I believe it made 30 psi difference !!!!! I think he was at 185 psi max in Denver and my compression now reads 210 -215 psi , as long as you stay away from the long runs you can BLIP and BURRRRRRRP all day in the surf and flat water just run the highest octane you can get and be aware of your engine , Mine runs great on 93-94 with no ill effects after 2 years / FWIW
 
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