Perf. upgrades:Head,Cam...and Pistons?

[TVST*R]

I am talking to Mark about doing Street Cams and Head.
Does it make sense to do Pistons (Stock or Oversized?) and Rings then? She does smoke on start-up, but doesn't seem
to burn much oil.
What is the additional cost for Pistons and Rings?
Thanks!
Tom

[So Cal Mark]

rebuilding the short block will add $2k to the job. I'd suggest a leak down test on the cyls first to determine wear. Any time you do performance upgrades you want to make sure the basics are in good condition since you will be increasing the load on them

[TVST*R]

I was thinking more along the lines of piston ring replacement...not a rebuild.
Is a leak down test like a compression test?

[mdrburchette]

A compression test is when you can determine how much compression the engine makes on each cylinder. Factors like carbon build up can affect the readings. You are looking for readings that are close to the same on all four cylinders. Just so the readings are within 10% of each other, it doesn't matter much how high the compression readings are.
A leakdown test is when you introduce compressed air into each cylinder with the piston at tdc (valves closed). Up to 10% leakdown is not too bad, but the best part of this test is you can basically determine the area of concern. We did a leakdown on my Devil X and found #1 cylinder had 45% leakdown. When I removed the oil cap, I could hear a hissing sound, indicating a bottom end problem. Hissing from the intake or exhaust can indicate valves not closing properly or leakdown on two adjacent cylinders can mean a head gasket failure.
Of course, others may have different thoughts....I'm just learning all this stuff as I muddle through Fiat ownership!

[So Cal Mark]

great explanation Denise !

[mdrburchette]

Wow, thanks Mark! Even my hard head lets a little of this stuff seep in.

[BrianAz]

Hi There,
I recently did a compression check on my 1980 Spider that I purchased a few months ago. Although I already knew from the blue exhaust smoke signals that an engine rebuild was high on the "to do" list, I wanted to see the compression numbers before pulling out the engine. Like most people I do not have access to a leak tester and have to make to with a hand held compression tester. After warming the engine the compression values were between 142 and 158 psi. To see where the compression leak was coming from (valves or piston rings) I poured a small amount of oil into each cylinder, let it spread around the piston edge for a minute or two and then pumped out the excess oil by cranking the engine. Do this with a large rag over the spark plug holes if you do not want your assistant who is cranking the engine in the car (cab down) to be showered with oil !! How did I do? Ask my teenage daughter. I owe her a new dress !! Anyway, upon retesting I got numbers around 250 psi so clearly the problem is worn bores and piston rings.
On with the engine rebuild !

// Brian.

[ventura ace]

Brian,
Your compression readings of 142 - 158 psi are not all that bad for stock components. Your readings up to 250 psi are pretty scary, and sounds as if you have quite a bit of oil in the cylinders, reducing the compression volume, and thus raising the pressure. I would run the engine a bit to try to purge the excess oil, and try the compression test again. If your readings drop back to 142 - 158 psi, then you might try repeating the compression test with oil, but only use about 1 - 2 teaspoons. Regardless, I wouldn't tear down an engine that has 142 - 158 psi compression.

A little smoke at startup (and not conuming much oil) may be more indicative of leaking valve seals around the valve stems. This allows a path for the pooled oil in the head to drool down the valve stems into the compression chamber, which then burns off in a little cloud of smoke the next time you crank the engine.

Alvon

[BrianAz]

Thanks Alvon,
I did'nt know what kind of numbers to expect and suspected with the blue exhaust smoke, even with the engine warm, that it was time for a rebuilld. Anyway, the engine is now out and on an engine stand so I'll continue with the rebuild.

// Brian.

[So Cal Mark]

if the engine was smoking while running, it needs more than valve guides