MDchanic

Nope - it's a 350 and they didn't have the stamped sheet metal baffle in the bottom of the lifter valley, like the 425s, 455s, and early 330s did.

The thing I'm looking at is a sign that the engine was abused by someone in the past, but it doesn't affect how it runs now.

- Eric

Allan R

How about lack of oil changes and gunk in the valley

barnfind

Might be a reflection but hole #2 (furthest right) looks cracked, scored

MDchanic

Nope. With 106,000 miles on it, it's bound to be a bit black, and the ZDDP cam break-in additive is black, too, so that makes it worse.
There's actually no real gunk in there at all.


Yeah, darned reflections. I just couldn't get rid of them.

- Eric

Magna86

Ok every piston looks like it has the same 2 marks near the top of the dish ring. Maybe contact from valve float/valve-piston contact due to high revving fun? This is actually fun and would be great we had these quizzes more often. :-)

Allan R

The rear intake seal let go and someone tried to fix it by stuffing it full of RTV?

MDchanic

Nope.

It was sealed with RTV, but nothing unusual.



Hey, you can't win twice.

Yes, OEM Oldsmobile pistons don't have valve reliefs.

At some point in this engine's life, every valve hit a piston, which means it was pretty well overrevved, but not for too long, as the top end is original and the bearings looked fine for their age.








I don't have a picture of #8 because it was too far in the corner.

Great work, everyone, and Magna, I don't know if you'll be allowed to raise your hand any more...

- Eric

Magna86

I still have remembered things from high school auto class! haha To think I gave up being an auto mechanic and now have a desk job. Can we for 3 in a row i never win anything.

MDchanic

I'll have to see what screwed up thing I can find next.

- Eric

Allan R

Eric & Magna - 2
Us Dufuses - 0

So is this what you mean by pistons with valve relief?

Charlie Jones

It kinda looks like the piston on the far left has some small "dings" in it . As though a piece of a broken spark plug hit it.

MDchanic

Yup. The factory never made ones like that, so any resemblance is purely the result of over-revving.



Yeah. I think you mean the #6 piston. I think it's some damage from detonation, but a very small piece of metal at some point is not out of the question.

- Eric

Smitty275

I think you all have missed the real issue with the engine pictured. It is not of enough cubic inches and should immediately be replaced with an engine of no less than 105 cubic inches more.

Macadoo

The pistons hit the valves? Darnitt, too late again!

Lars

more carbin buildup in #8 where the bad valve was and select fit pistons

z11375ss

lmao!!!!

Seff

I see valve marks on the pistons. On 2 and 4 the bigger intake is on the right (making the mark further north on the piston, on 6 and 8 they are on the left, so that fits.

The mark is visible just on the edge of the piston dish, at 10 and 0130 o'clock.


Tentative conclusion: Someone's timing chain slipped. (I should know, I did something similar to an engine once.... >.> )


EDIT: I didn't see page 2. Oops.

steverw

Looks kinda like some heli coils put in some of the head bolt holes? Ooops i missed page two to

MDchanic

Quite possibly. It had a loose, low-end replacement timing set on it when I got it.


Actually, no. The heads had never been off, so those are the factory original holes and threads.

- Eric

M-14

Olds engines have valve angles about 6 degrees to the piston, so it take a lot of valve float (hi rpms)on a stock engine to make them kiss the piston. Sbc have an angle at 23 degrees, they need valve reliefs in theirs hi-po pistons. Most engines with 4 valves per cylinder have valve angles of 35 degrees of higher. That's why you hear about bent valves when timing belts or chains break. Olds engines usually don't have bent valves when the chain breaks or jumps. That's the best engine cutaway I could find for the olds, you can see the chevy in the 2nd picture has more of an angles, & the buick nail head has a big valve angle. Look at the exhaust passage, it looks extremely restrictive.

MDchanic

Good information. Thanks!

I hadn't realized that the nailhead rockers worked "backwards."

I'd also just been wondering what the Olds valve angle is, as I need to make a valve stem height gauge, so thanks for answering the question I was thinking about asking!

- Eric

M-14

Yeah, the designers were really thinking out of the box on the nail head.
I've heard that the olds angle is around 6-7 degrees, so my info isn't a precise measurement (taken with a grain of salt).