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Wes's Burb build/update/maintance

I not sure that formula is real world. my alt at pressure is (14.2*9.5)/1 =134.9. I have done plenty of compression tests that were 150psi or better.
Is a Shell station here has 105 octane AV gas on the pump. 5.99 a gallon last week. I wouldn't run straight av gas but I will mix it. Tank is almost full might be able to get 5 gals to mix with 35 gal regular. I am thinking 10 to 30 would be ideal
 
Wes Harden said:
Yes we had better gas when I built this. Plus the machine had strict orders not to mill the heads, but they did it anyway. I didn't have a lot of time, so it went together.

stolen from reference.com
For example, if the atmospheric pressure is 14.7 psi and the compression ratio is 11:1, the equation to solve for the psi is (14.7*11)/1. Therefore, the answer is 161.7 psi. People use this method of calculation to determine the pounds per square a piston produces

So over 165 psi might need to look for some heads
Click to expand...
My stock 1984 350 with only 80k miles had 180 psi static compression.
I don't know if that calculation is accurate
 
My stock 350 is ~150-160psi. My dads hopped up 302 with 10.5:1 is around 170-175 last I checked.
 
The issue with that math is the elevation. Small margin of error


Do you remember any details on the piston cc, gasket, or know the original had volume or casting numbers?
 
imiceman44 said:
My stock 1984 350 with only 80k miles had 180 psi static compression.
I don't know if that calculation is accurate
Click to expand...
Those engine we’re supposedly 7.8:1 in 1984. Lowest GM ever produced for the 350
 
Bent77 said:
Those engine we’re supposedly 7.8:1 in 1984. Lowest GM ever produced for the 350
Click to expand...
My point exactly.
So testing that way does not tell you anything about the compression ratio.
It only shows how tight the engine is.
If the rings are sealed good and valves are seated well you will get 180 which I was told is to be expected on a low mileage engine.
I don't see a way to figure out compression ratio without doing the math from physical measurements.
Cc the piston and the chamber, measure the thickness of the gasket and measure the stroke.
Short of that, experiment with octane and timing for best results like we did on timing and tuning by ear for decades.
 
Yeah you cannot go by compression tester numbers trying to figure out your static or dynamic compression ratio. Really all you are looking for on that test is consistency between the cylinders. One can get very different numbers on the same engine depending on a lot of variables. Current air density, warm or cold engine, wet or dry, battery charge, throttle blade wide open or closed, all plugs out or in.

You can have two engines built the exact same, and if one guys cam is advanced 2 degrees more than the other, they will have very different dynamic compression ratios.
 
So if memory serves, 416 heavy casting 305 heads. .047 felpro blue head gasket, .020 deck.
.030 over bore. The pistons are machine shop generic. Trw knock offs would be my guess.
Cam is summit grind #203. I have 1.6 ratio rockers.
Edit: Summit doesn't make cams anymore?
I found the cam card for that engine. No grind number listed.

IMG_20220123_135128.jpg
 
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Wes Harden said:
So if memory serves, 416 heavy casting 305 heads. .047 felpro blue head gasket, .020 deck.
.030 over bore. The pistons are machine shop generic. Trw knock offs would be my guess.
Cam is summit grind #203. I have 1.6 ratio rockers.
Click to expand...

I assume different setups can respond different ways, but if it's really .047 and .020 (.043 is probably the most common gasket thickness) and ideal quench is around .040, that could also factor in. 305 heads are already bumping compression up, all the differences may be combining to make the problem worse than it would be if only one thing was "off".
 
Wes Harden said:
So if memory serves, 416 heavy casting 305 heads. .047 felpro blue head gasket, .020 deck.
.030 over bore. The pistons are machine shop generic. Trw knock offs would be my guess.
Cam is summit grind #203. I have 1.6 ratio rockers.
Click to expand...
Any dome, or just valve relief?
 
Could very well be .043.
I don't remember having an issue when I built it. I could hear better then. When I do hear something, normally if driving next to a wall.
Is light throttle, acceleration.
 
Just relief eyebrows 4 ea, no dome flat.
Wish I knew if I made a build sheet and if I did where it was.
I recall checking valve to piston clearance with modeling clay, but not the measurement. Only that had plenty of clearance.
 
Another thing I am suspicious of is the timing chain.
It is a double roller with 3 position crank. It is set straight up.
But is tight, I might have needed a short chain to compensate for line bore.
 
Wonder how it's still together, I have not treated like a high compression engine. Mostly regular it's entire life, was a daily when first built. Say 97 till 2010/11 when I quit driving it all together. Then part time in 2018.
@ 10k on it since then.
 
Yes, they range anywhere from 52-60, depending on the retard running the beaker. Typically a cleanup pass doesn't take that much off of it
 
I know the heads have at least 2 clean up passes.
No clue how many before I got them.
 
Plugging in the basics into Summit's compression calculator using 58cc chamber on the 416 heads and 4.10cc for average two valve relief pistons comes up with a compression ratio of 10.56:1. If the heads had been milled it would decrease the chamber size and bump the ratio even higher.

10.5:1 is pretty steep with iron heads.
 
ZooMad75 said:
Plugging in the basics into Summit's compression calculator using 58cc chamber on the 416 heads and 4.10cc for average two valve relief pistons comes up with a compression ratio of 10.56:1. If the heads had been milled it would decrease the chamber size and bump the ratio even higher.

10.5:1 is pretty steep with iron heads.
Click to expand...
Yeah i Kept smashing the numbers through Heath's app trying to come up with a different number. 10.75:1 was what my brain math said
The 462 heads on my old engine came to 10.2:1
 
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