Rusty Muffler
Active Member
I'm filled with doubt on whether I'm doing this right to get the percentages between the pressure in and the pressure after leakage. Engine has 1k miles, thanks!
. Please help!
Please do the MATH for me. Leak down test results my 301 V-8 1957 Plymouth
- Thread starter Rusty Muffler
- Start date
twostick
Senior Member
What kind of tester are you using?
Kevin
Kevin
Rusty Muffler
Active Member
MADDOX from Harbor Freight
They say that you want to see below 20% pressure difference. A fresh engine should be closer to 10% I'd think. Your numbers are generally bad I'd say. Did you measure each cylinder at TDC?
twostick
Senior Member
If you followed the instructions to the letter, with those results, you should hear air blasting out either the exhaust, intake or the crankcase, ie oil fill or dipstick tube.
Ideally, engine should be warm. It should be at verified TDC, using a positive stop. The indicator on the balancer could be off a few or several degrees and that can make your test results go off into la la land. You should have a helper with a socket on the damper bolt, hold the crank at TDC because the air pressure will push the piston down.
Anything over 10% leak down on a performance build usually indicates a freshen up is in the near future. Numbers like yours usually indicate FUBAR.
Kevin
Ideally, engine should be warm. It should be at verified TDC, using a positive stop. The indicator on the balancer could be off a few or several degrees and that can make your test results go off into la la land. You should have a helper with a socket on the damper bolt, hold the crank at TDC because the air pressure will push the piston down.
Anything over 10% leak down on a performance build usually indicates a freshen up is in the near future. Numbers like yours usually indicate FUBAR.
Kevin
Rusty Muffler
Active Member
Yes.
Rusty Muffler
Active Member
All cylinders indicate leakage at the rings into the crankcase. I was thinking it would use oil or smoke, it doesn't.
twostick
Senior Member
Any blow by?
If the machine shop did a poor job honing it or the cylinder finish isn't compatible with the ring choice, the rings might not seat. Depending on the ring material, if the engine didn't fire immediately the first time, it can compromise seating. That tends to fly in the face of no smoke or oil consumption tho.
What do your compression numbers look like?
Kevin
Rusty Muffler
Active Member
90-110 pounds across the board
twostick
Senior Member
Try moving the crank 10-15 degrees before or after TDC and see how much wind is passing into the crankcase.
Did this rebuild include oversize pistons?
Kevin
Rusty Muffler
Active Member
The pistons appear to be original to the rebuild meaning it wasn't bored.
65sporty
Old Man with a Hat
It sounds bad for the rings, compression numbers are low and leak down is high. I think it needs to come back apart
Rusty Muffler
Active Member
Well, I'll keep driving it and see what happens and sell it before I pull the motor again. In California it's hard to find a machinist around here, just rich elitists.
Jakter
Active Member
Worry less, drive more.
In a leak down or compression test, you are testing ONLY the compression ring, not the oil rings, too.
Depending upon which grade of rings were used, it could well take longer than you have been driving it for the rings to fully seat, which can also depend upon the bore finish. It if was not honed and/or bored, things should happen sooner, i suspect.
Many of the older "good" machinists have or will soon be retiring or passing on. Which means any newer shops will have a good bit of high-dollar computerized machinery in them. THIS is one thing which drives up costs. Not to forget about real estate and property tax coses, too.
Current and future engine "builds" seem to require a Rottler (or similar) machine to do line hones, decking (with deck plates), and power honing the bored cylinder bores. That stuff used to be in the realm of "race car shops", in prior times, but can be commonplace now. Then comes the capability of "plateau honing"!
Use of these machines ensures that any factory "hiccups" are corrected in the machining process, too. Whereas the prior operations kind fo took it for granted that what the factory did was accurate and correct in all respects. And even the old "on the deck" boring bar worked well, as that was what my late machine shop operative used for ages, dressing the cutting bit for every cylinder, for great results. Followed by a dingle-berry flex hone and his "calibrated arms" moving it up and down. Plus a dial bore gauge, with an inside-outside mircometer bore diameter gauge.
You'll NOT find a good machine shop by making phone calls, as many are 1-3 person operations and they are busy in the shop taking care of other customers. Not many have somebody just to answer phone inquiries, as that would only add to their operational overhead.
Drive the car, enjoy it, keep it serviced, legal, and re-check compression at the 5Kmile point, using the current info as a reference point.
The way rebuilds used to be judged included: no to little oil consumption, starts quickly, runs well, and does not smoke. If it starts easily, runs good, and uses no oil, you're pretty much there, by earlier standards.
Enjoy!
CBODY67
Depending upon which grade of rings were used, it could well take longer than you have been driving it for the rings to fully seat, which can also depend upon the bore finish. It if was not honed and/or bored, things should happen sooner, i suspect.
Many of the older "good" machinists have or will soon be retiring or passing on. Which means any newer shops will have a good bit of high-dollar computerized machinery in them. THIS is one thing which drives up costs. Not to forget about real estate and property tax coses, too.
Current and future engine "builds" seem to require a Rottler (or similar) machine to do line hones, decking (with deck plates), and power honing the bored cylinder bores. That stuff used to be in the realm of "race car shops", in prior times, but can be commonplace now. Then comes the capability of "plateau honing"!
Use of these machines ensures that any factory "hiccups" are corrected in the machining process, too. Whereas the prior operations kind fo took it for granted that what the factory did was accurate and correct in all respects. And even the old "on the deck" boring bar worked well, as that was what my late machine shop operative used for ages, dressing the cutting bit for every cylinder, for great results. Followed by a dingle-berry flex hone and his "calibrated arms" moving it up and down. Plus a dial bore gauge, with an inside-outside mircometer bore diameter gauge.
You'll NOT find a good machine shop by making phone calls, as many are 1-3 person operations and they are busy in the shop taking care of other customers. Not many have somebody just to answer phone inquiries, as that would only add to their operational overhead.
Drive the car, enjoy it, keep it serviced, legal, and re-check compression at the 5Kmile point, using the current info as a reference point.
The way rebuilds used to be judged included: no to little oil consumption, starts quickly, runs well, and does not smoke. If it starts easily, runs good, and uses no oil, you're pretty much there, by earlier standards.
Enjoy!
CBODY67
Jakter
Active Member
Coming up next on Fox and Fear, rich elitists are pushing machine shops out of business.
Ohhh, you wont want to miss it.
3175375
Senior Member
Growing up and working my whole career in Southern California, I can attest to the dramatic reduction of industrial activity. It was getting very difficult to do our engineering manufacturing work with Southern California shops. Thank goodness the company I worked for had facilities in Texas. We had almost all of our work done there.
Capabilities are vanishing in California.
I know that industrial emissions issues have long been an issue with doing business in CA, with the "chromed crankshaft" industries leaving in the 1980s, BUT might a side issue be the real estate values escalating, too?
In a recent news article about a McDonalds closing in CA, of course the new wage laws were prominently mentioned, BUT in a later sentence, it was mentioned that the landlord of the property (which was near a shopping mall) had raised their lease amount. Much MORE of a multi-faceted situation than just the wage rate increases!
CBODY67
Jakter
Active Member
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