Lynn E. Hanover

Thats what I use. They seal just fine, and do not wear on the rotor housings. So the apex seals are not the problem.



Lynn E. Hanover

Old Grey

Did you put the corner seals in upside down, black unmachined surface out

Does all the seals have the right protrusion ie weak springs or sticky seals



If you have all new rotors, seals, springs it should make good compression, unless you bent the side seals when you clearanced them, put them on a plate and look for gaps underneath. Or you rotor housings might look good to you but aren't, whats it like at the compression face near the trailing plug. Your clearances might be wrong ie using metric dimensions with a imperial feeler gauge



Take photos and post them, let some experts have a look as it might be something you are missing

PDF

I would almost bet money that the rotor housings are the problem. Put a good straight edge across each of the spark plug holes. If you can rock it from side to side or see daylight underneath then you've found the problem. Even if there are no cracks visible there can still be high spots. Its also worth checking the housing in several places right around to the exhaust port, I've seen them go hollow in the center before.



Both these problems are very easy to fix. Take a piece of round bar or thick wall tube that is known to be straight and free from surface imperfections, about 2in in diameter, and wrap a strip of 180 grit wet & dry sand paper half way around it. While keeping the bar square to the housing sand the chrome surface, gradually rolling the bar (and the sand paper) as you go. Make sure the sand paper is a little wider than the housing. You can finish off with finer grit but 180 seems to be fine enough for me. Keep checking with the straight edge until the surface is straight!



It does wonders for your compression readings!!



As far as I can tell this is mainly caused by running too hotter spark plugs.

Old Grey

I used to use a round oil stone(dressing stick), remember you have only 0.006" of chrome thickness so if the dips are too deep you can expose the mild steel insert. There seems to be about 0.004" of porous cracked chrome on 0.002" of normal chrome that looks slightly goldish. The goldish chrome is indication your getting close

REMSPORT

used new competition corner seals (no rubber inserts) with new competition springs (like belleville washers, not wire).



Good suggestions on the rotor housings. I'll check those. I've already put a different engine in the car (yeah it works) and am focusing on its final tuning. The "bad" engine is sitting on the garage floor. Eventually when I get the time, I'll tear it down (again) to perform an autopsy. I'll let you know what I find. Thanks for the suggestions. I definately want to solve this mystery!

PDF

Don't use the later style corner seal springs with lapped or older, non-nitrided irons, the surfaces will get grooves chewed in them in no time due to increased spring tension on the seal. Stick to the earlier wire type corner seal springs and you won't go wrong.

j9fd3s

seems like overheating does this too, rotor housing shrinks width wise, and the metal sags in the center