fresh motor starrt up
#15
Uuugh! I give up. I rebuilt the engine AGAIN. This time with a different set of rotors. Compression is up a little bit, but is still low at 60 psi for front and 75 psi for rear.
I've triple-checked everything. Replaced/redone all possible sources of compression leakage. And it's still not a good engine.
rotor housings good condition - measured and straight
end/center housings - lapped by Mazdatrix
fresh rotors with all seal grooves confirmed good
all new soft seals
all new hard seals with clearances from Mazda Comp. Tech Tips
Since I did my own street-porting, I even checked to make sure there was no port overlap.
While this is my first street-port engine, I have rebuilt stock motors before with no problems. Does anybody have any ideas/theories for what is going wrong?
Rich
I've triple-checked everything. Replaced/redone all possible sources of compression leakage. And it's still not a good engine.
rotor housings good condition - measured and straight
end/center housings - lapped by Mazdatrix
fresh rotors with all seal grooves confirmed good
all new soft seals
all new hard seals with clearances from Mazda Comp. Tech Tips
Since I did my own street-porting, I even checked to make sure there was no port overlap.
While this is my first street-port engine, I have rebuilt stock motors before with no problems. Does anybody have any ideas/theories for what is going wrong?
Rich
#16
Originally Posted by REMSPORT' post='899684' date='May 1 2008, 05:46 AM
Uuugh! I give up. I rebuilt the engine AGAIN. This time with a different set of rotors. Compression is up a little bit, but is still low at 60 psi for front and 75 psi for rear.
I've triple-checked everything. Replaced/redone all possible sources of compression leakage. And it's still not a good engine.
rotor housings good condition - measured and straight
end/center housings - lapped by Mazdatrix
fresh rotors with all seal grooves confirmed good
all new soft seals
all new hard seals with clearances from Mazda Comp. Tech Tips
Since I did my own street-porting, I even checked to make sure there was no port overlap.
While this is my first street-port engine, I have rebuilt stock motors before with no problems. Does anybody have any ideas/theories for what is going wrong?
Rich
I've triple-checked everything. Replaced/redone all possible sources of compression leakage. And it's still not a good engine.
rotor housings good condition - measured and straight
end/center housings - lapped by Mazdatrix
fresh rotors with all seal grooves confirmed good
all new soft seals
all new hard seals with clearances from Mazda Comp. Tech Tips
Since I did my own street-porting, I even checked to make sure there was no port overlap.
While this is my first street-port engine, I have rebuilt stock motors before with no problems. Does anybody have any ideas/theories for what is going wrong?
Rich
The apex seals may have been over size in length, and should be checked before installation. A slight overlength will result in a seal held off of the housing surface.
If the compression changes little between measured dry, and measured with motor oil squirted into the housing, then it would seem a mechanical fault as above.
A porting job with way late closing line will do it as well, but more like 100 PSI than 60 PSI.
Lynn E. Hanover
#18
Originally Posted by REMSPORT' post='899731' date='May 2 2008, 05:40 AM
Don't think its the seals. They were replaced once because the gaps were .008 total. New ones have been triple-checked to be .002-.004 total.
Are we talking side seals or apex seals? With the seals that have the joint about 1/2" from the end, a long seal holds the main part of the seal up and the end down, so a big leak that gets bigger with temperature. With the little corner piece,
the corner will be held down and the leak will be around the end of the long piece.
The side seals could be as little as zero clearance and work fine.
Lynn E. Hanover