Expert: Ben Deutschman - 4/18/2010

Question
QUESTION: Hi Ben, My name is Nathan, I have a 68 Dart with a 170 with compression problems.  At first, I thaught that my torque converter might be locked on because of the stalls at stops.  Soon after, I couldn't even put the car in drive without a stall.  Unfortunatly, I did a compression test after I purchased a new carb, plugs, wires, and distributer.  The test results were as follows, from front to back;  
cyl 1 = 70,
cyl 2 = 120
cyl 3 = 60
cyl 4 = 120
cyl 5 = 70
cyl 6 = 60
Last night I did the 'oil in the cylinders' trick and every bad cylinder's psi increased at least 20psi, one cylinder even doubled.  Does this mean rings??  Or is there still a chance that it could be valves or head gasket??  If it is my rings for sure, can I adjust my valve lash to give it better compression so I can run this old 170 a bit longer, or will the increased compression from setting a bigger lash just blow down through my rings???  Thanks for your time.

ANSWER: With Compression readings like those, and the Oil having caused some increase in Compression, I'd be leaning toward badly worn Rings, more so than Bad Valves. If the Valves weren't sealing, due excessive wear of the Valve Head, than the Oil would have done nothing to cause an increase in Compression. While worn Valve Guides can cause excessive Oil consumption, they would have no effect on Compression. Also, setting the lash too loose, while it will have little effect on Compression, it could help peen over the top of the Valve Stem, and/or flatten the bottom of the Tappet.

---------- FOLLOW-UP ----------

QUESTION: Thanks for the reply.  One more question if you don't mind.  I could purchase a 67 plymouth fury with a 225 to steal the engine, but I'm not sure if the 67 plymouth 225 will bolt up to my transmission in my 68 dart that presently has a 170.  Any help with this would be great, I can't seem to find anyone who knows.

Answer
The 170 and 225 share the same Block, the only differences I'm aware of the, is that the 170 has a shorter Stroke, and a lower "Deck Height", resulting in the smaller displacement. You can check Allpar.com (http://www.allpar.com/slant6.html)for more background information on the "Slant-Six.: