Technical Myths … or old wife’s tales about engines

Jackie Treehorn treats objects like women, man!

 

The bottom side of the pistons on a V-8 will wear out before the top side will.

 

had a couple stroker cranks ground at len's in st. louis, and the ones they were shipping (nationwide) were on end. but i don't think it matters...

 

The first myth I thought of was the one that insisted that Y-blocks in the 50s were slower than a SBC.

 

Have you ever seen how they straighten a forged crank?

 

The close pins on the fuel line can and have acted like a "heat sink"

An older mechanic friend of mine, told me once that he cut a grapefruit in half and shoved it up against the bottom of the mechanical fuel pump on a GM 235 6 banger in a 51 Chevy pick up, and it drew the heat out of the vapor locked fuel pump.

Cool old trick.

 

That's in the REAL world..... On the HAMB, ask 100 people and get 110 opinions! We think outside the box more than 'real world' people!

 

Phil, if it's for the Pontiac, it probably IS warped, but those long whippy shafts go where they want anyway, so who could tell the difference?

 

Forging crankshaft in an extremely less than modern offshore foundry/machine shop.
Reserve an hour, pretty entertaining.

 

"We don't need no steeenking CNC...... or cutting oil."
Talk about a history lesson, that's 1860's manufacturing methods right there!

 

Yeah !
My...FIRSTHAND knowledge.
I wasn't going to reply to this spring thing, but since "silent rick" did, with a good answer...
If the springs are of good quality, they CAN...sit for a LONG time compressed, even coil bound without loosing much if any pressure.
INTERNAL heat is what causes springs to die. When a coil spring compresses and extends in a rapid succession, heat builds in the material itself from the molecules being exercised, THEN...the spring starts to die. This information is actually in a good spring design book !

Some time back, I bought two sets Comp Cams springs (235psi on the seat). I measured the pressure (with a verified tester) were of higher pressure than what I wanted (and what was advertised). I called Comp Cams, we talked.
They told me to coil bind the springs three times, back to back and check the load. WHAT ????
They are the experts...so I did. I took the coils apart, and did this task to both the inner and outer, separately. They were right ! They were still higher pressure, but much closer.

The springs sat for a day (ONE day) I went back out to set the higher measured springs separate with the lower measures springs.
THEY...every one (16) WERE RIGHT BACK TO THEIR ORIGINAL TESTED LOAD !!!!!

So I then took one spring, put the retainer on it and put it back in my vice, to ALMOST A coil bind (about .005" shy), and left it for 30 days.
I removed the spring and measured it, the spring, it lost 5-1/2psi. I went back out the next day...the spring was almost...back to its original pressure. It lost as close as I could tell on my analog tester...the spring was almost back, it lost only 3/4 of a pound pressure. I tested it again, a few days later, the same 3/4 psi loss.

Again, YES, I verified my tester with both an older setup spring and a new setup spring.

Another story about a coil spring that's even MORE head scratching. While it's a smaller wire, a lot less load. THIS spring sat almost fully compressed since about the middle of WWII (79 / 80 years). I don't know about pressure loss, but I know that it still pushed the 9mm rounds up into the chamber of a Browning High Power...just fine ! Even in rapid fire mode !

So yeah, reducing the spring load until your next race outing...not worth the time.

Mike

 

I'm a 1911 fan myself

 

One I've heard for years is “ break it in like you plan to use it”

 

I have found cranks that are not straight how the they got that way is anybody guess. When I assemble an engine I install all the upper main bearings lube and install the center main cap then turn the crank if the crank turns gets easier and harder as you turn the crank is not straight. If Ok then take a torque reading as you turn then add a main cap next to the center cap and check torque and remember that number as you add caps the torque should gain about the same amount with each cap if you get a bigger gain the block line bore should be checked.

 

Although I do agree that a spring compressed can change it's value over years of sitting, I don't believe it changes significantly enough to do any harm. I think miles or hours of running might have just as much fatigue factor on valve springs, and could result in failure more than sitting compressed.

 

That's the myth, a spring won't fatigue at rest, whether compressed or not, fatigue happens when it works beyond its rated limit.

 

I'm with @silent rick and calling BS on the valve spring myth. This has been a topic for gun enthusiasts for many years due to people wondering if storing semi-auto guns with the magazines loaded will weaken the spring; and the answer is no, springs do not lose tension from being stored under load for a long time. Springs lose tension from load cycles, or from being stressed beyond their working limit. Not from sitting still under pressure. Ask a metalurgist.

 

Just one example, but go to about 1:02:36 and wonder what your feet would look like working in sandals like that.

Lynn

 

I agree with the fatigue point-go past and its toast. Metallurgy has came a long way since the model T. You see it on U tube, car shows etc.--they find a junker 60's-90's, etc. that's sat there forever, they start it, tune it, drive it. Never seen 'em change valve springs, even after they get 'em running decent. New cam-yeah. I've let one sit for well over a year, ran same as before. Cranks? I'm old school so i go with the vertical storage idea, hard to change an old man's mind.

 

On our 287 SBC, we ran Truppi-Kling triple springs and a BRC shaft. 200 seat, 600 open, Ralph Truppi told us to back off valves when stored, plus with shut valves, less opportunity for moisture collection in cylinders, we ran 2 seasons, same springs, we were 22, we did what Ralph told us, Today I maintain a collection of cup cars, nope, leave rockers untouched between seasons.

 

Didn't he know that the real trick is to tape cow magnets to the fuel line to polarize the fuel molecules?

 

Wise decision!

 

I'm sure the vast majority of myth was based around a degree of fact. The fact someone had an experience and complained loudly enough about it might have been all it took?

 

I don't know diddly about valve springs or magazine springs either. But what I do know is that I was an MP in the early '70's. And at the start of every shift when we drew our 1911 from the arms room we also drew 3 magazines and the correct number of bullets. At the end of shift we returned the magazines empty. The Army's thoughts about spring fatigue may have changed since then.

 

Best springs IMHO for mid-range performance stuff is the old reliable Isky 8005-A, I have used them on FEs up to .660, and they fit many engines, BBChebbies and MorePowers and such. The set on my 406 car are at least 30 yrs old, and I put a set on my buddy's Boss 302 with 426 Hemi valves in 1979 and it's still chuggin'. IIRC there's a similar one, the 6005, that fit the small block stuff

 

If you drive your car at only half throttle every other day it will increase your engine life by 50% because at half throttle the piston doesn't go all the way to the top, therefore providing you with 50% more engine life in each cylinder.

 

I had always been told the same. One night my driver got in a small altercation with the sprint car. The only damage was a crushed header on the right side. I had spare headers, but not at the track. My driver said to just saw it off. I think we ended up with pipes ranging from 3 inches down to one broken off at the header flange. My driver went out and won the feature. I put a spare header on for the next race meet and ran the car the rest of the season without any burned valves.

 

always refill the gas tank when it gets to a quarter tank so it doesn't pick up trash. you wouldn't believe how times i have heard this.

 

Are you sure you're not thinking of the variable-length connecting rod?


https://patents.google.com/patent/US4370901A/en

 

In the heavy equipment bizz we do recommend customers to top off the fuel tanks at the end of the day to reduce the volume of air in the tanks, and so reduce the amount of condensation formed over night.