270psi compression need help

[muddymess]

I have been trying to get my r running again after I had a stroker crank put in. The motor has blown 2 head gaskets with only 5 min of riding. After fist time I sent the head back and had more milled off of it. 2nd time I tried to double base gasket it. I just did a compression check and I'm getting over 270psi. What am I missing here.

[derby]

Originally posted by muddymess
I have been trying to get my r running again after I had a stroker crank put in. The motor has blown 2 head gaskets with only 5 min of riding. After fist time I sent the head back and had more milled off of it. 2nd time I tried to double base gasket it. I just did a compression check and I'm getting over 270psi. What am I missing here.

What is the cc on the head currently?

[muddymess]

Not sure and won't be able to find out till probably Monday.

[muddymess]

http://i56.tinypic.com/103vghw.jpg
http://i52.tinypic.com/8ziaes.jpg

[Grande Huevos]

im not a motor builder or anything but im pretty sure when u mill ur head down u raise the compression, because thats making the piston come that much closer to the dome. and im pretty sure if ur motor was set up for a stroker crank then u switch back to non stroker it will not perform properly??? u might check into it.

[muddymess]

no i had a stroker crank put in it and since then iv had these problems im not trying to put it back to normal and when i said mill the head i meant milling the inside of the head to allow for the piston to come up into it and have more room.

i actually drimmeled out an oem style head gasket with the thick metal piece in the middle and it got the compression down to 210psi

[woodsracer144]

what cylinder are you running? how far did you stroke it? and what style piston are you running.

i've never heard of 270, highest i've ran is 210-220

I know a few guys make it so the top of the piston came above the cylinder and in to the head and they really milled the **** out of the head, my FTZ Cr cylinder was that way....

[muddymess]

Originally posted by woodsracer144
what cylinder are you running? how far did you stroke it? and what style piston are you running.

i've never heard of 270, highest i've ran is 210-220

I know a few guys make it so the top of the piston came above the cylinder and in to the head and they really milled the **** out of the head, my FTZ Cr cylinder was that way....

86 cylinder with spacer plate
Hotrods +4 crank
86 piston

i ran it at 270 for about 5 min then it blew the head gasket and poped the pressure fitting for the coolant line out of the head.

[woodsracer144]

How thick is your spacer plate?

[C41Xracer]

Is the +4mm compared to an 86-87 crank or 88-89

[jcs003]

that must be making alot of horsepower and torque.

[woodsracer144]

Well someone might chime in but I think a regular one 5 mm

[muddymess]

cant remember the thickness of the plate off the top of my head but it was just the usual plate used for the 86 cyl/ 87 crank combo.

its a +4 compared to the 87 style crank.

i rode it today after i got the compression down to 210 and it ran really well. only issue i had was that coolant was leaking out around the pressure fitted neck that blew out. I also had an issue with a fouled plug i need to find out what happened to. but the head gasket didn't blow so that's improvement.

ripping on her from a rolling start and having the front end come up was something new :D

[machwon]

Is this just a stock cylinder with a 4mm crank or is it ported for the stroke? 270 psi will really be a snorter motor but yes you will have the issues you listed. psi is not the right way to set up a cylinder head. The exhaust port height has a big effect on the static psi number and I'm not sure whats done to your cylinder. You need the cc value of the head and the squish to calculate the compression ratio for the octane fuel you will be using. This is also normally done after you have set the port timings you wish to run, at least thats how I do it.