[goatman65]

Checking the piston/deck clearance,machinist told me pistons are .003 below deck. I keep measuring .011. If I push the piston at 6 o'clock to eliminate rocking and check with a straight edge at 12 o'clock I get .004.

If I check at 9 and 3 o'clock I get .011. Where is the best place to check 9-3 o'clock? If so then i'm pissed because I wanted zero but he said he he likes .005 but ended up at .003.

If checking it at 12-6 o'clock is okay then I will be somewhat happy with the .004 I keep getting.

[Skip Fix]

Best place is right above pin(3&9) so you don't get the rock.

[dataway]

Anyone have a good picture of a setup for measuring the deck height ... assume a person doesn't have a depth gauge large enough to span the whole cylinder?

I was using the plunger end of a digital caliper in various ways, wasn't happy with the consistency of my readings.

[Cliff R]

Deck height is measured directly above the wrist pins. The pistons will "rock" some in the bores so you will get slightly lower readings if measured anywhere else and it's not a big deal. We like to see no more than .040" quench with these engines, but I wouldn't split hairs with it, .003" in the holes and a .039" gasket will be fine......Cliff

[cdrookie]

Originally Posted by dataway

Anyone have a good picture of a setup for measuring the deck height ... assume a person doesn't have a depth gauge large enough to span the whole cylinder?

I was using the plunger end of a digital caliper in various ways, wasn't happy with the consistency of my readings.

You can lay a piece of flat or square stock over the bore and measure off of it with your caliper. It won't be 100% accurate but should get you within a couple thousandths.

[goatman65]

Originally Posted by Cliff R

Deck height is measured directly above the wrist pins. The pistons will "rock" some in the bores so you will get slightly lower readings if measured anywhere else and it's not a big deal. We like to see no more than .040" quench with these engines, but I wouldn't split hairs with it, .003" in the holes and a .039" gasket will be fine......Cliff

That's what I was hoping for but everytime I check it I get .011, not .003 like he told me.

[Cliff R]

When it comes to this topic and the engines we build here I would leave it at .011" and use a .025" Cometic head gasket providing it is decked/squared correctly.

From a machining standpoint it can be difficult to make small cuts on the block and additional cost is usually beyond the price of the thinner Cometic head gaskets......Cliff

[goatman65]

Thanks Cliff, I feel better now,lol.

[HWYSTR455]

What are your bearing clearances? Maybe try gently tapping on the big end of the rod while it's at TDC and check again?

Zero and check your gauge?

If you're getting .011 and .04 at the 12 & 6 positions, and you cut that in half, you get .0035.

.

[goatman65]

Measured above the pin like Cliff said I get .011. If I push down on the piston at 6 o'clock and measure at 12 o'clock I get .004. If I set the piston square to the deck at 6 and 12 o'clock I get .011 no matter where I check it. Maybe i'm not doing it right.

It's the .004 that I get when I rock the piston that bothers me. If I buy the Cometic gaskets based on my .011 reading will the piston rock enough while running that the .004 clearance will be a problem.

[HWYSTR455]

So if you push at the 6 o'clock position, what is the reading at 6 o'clock? That's kind of what I was getting at with my other post, cut it in half, if it's not .011, then somehow you're measuring wrong. Or that's how I'm seeing it. Half the range of full travel of rock should be the measurement you're getting at the pin area.

Are the bearings lubed?

.

[STEELCITYFIREBIRD]

~0.004" is your tightest point to the head,

To clarify,for me and maybe others, the maximum # for quench recommended, 0.040", is based on @ the pin (3 and 9 oclock) or with piston tipped in bore (12 and 6 oclock)?


If you go Cometic, make sure the gasket bore is large enough for your bore and any chamfer there is at the top of the cylinder. (I didn't allow for that on my 400 and have to send mine back for a larger bore, gasket protruded into cylinder slightly)

http://www.shopengineparts.com/parts...%2c+%26+455+V8

[goatman65]

I'm going to put it back together and check again, I think I might be confusing all of us.

If I push the piston down at 6 o'clock I get .011 at 6 o'clock and across the pin area. At the 12 o'clock position it is .004. I always get .011 across the pin,9-3 o'clock.

.004 is the tightest point to the head,but only when I rock the piston. When I set the piston at the middle of it's rock travel using a dial indicator, I get .011 across the pin and at the 12-6 o'clock points.
I don't know how the machinist checked it, i'm guessing he checked it from the crank center. He also line-bored and square-decked it. Big ends of the rods were also done.

[goatman65]

I'm aiming for .040 quench. With a .030 gasket and IF my .011 is correct, i'll have .041. But, when the piston does rock when the engine is running, the .004 at 12-6 o'clock will give .034 quench. Is that too tight?

[STEELCITYFIREBIRD]

I'd call that perfect. Your max and min are both in range.

[goatman65]

Thanks for the help guys. I'll still check it again before ordering gaskets.

Right now i'm leaving for spring Carlisle.

[lust4speed]

Any combination .050" or under is still going to preserve the quench. Less is better, but questionable whether it makes a difference as long as you are in the zone. Some top builders say that the quench either works, or you reach a point where it doesn't, and .050" is usually given as a safe cutoff.

Ever taken a reading at 9 and 3 o'clock and ended up with .001" and .014"? First is disbelief which is then followed by cussing. Very reputable rod shop in Los Angeles really screwed up a set of used but very nice Crower Sportsman rods. Their job was to convert the rods to bushed which shouldn't be that difficult for a shop that only does rods. Not one, but all were out to varying degrees. Then they screwed them up almost as bad the second attempt. At least the second time the mistake was caught when they were returned to the machine shop. Rods were then shipped off to Crower and they came back not only perfect, but looking like new.

[HWYSTR455]

When you put it back together, make sure you have a film of oil on the rod and main bearings when you measure. Give it a few rotations as well before you measure, and first check it without rocking it, across the pin area.

If you rock the piston and take a max and min measurement at either the 6 or 12 o'clock, add it together and divide by 2, and that will give you a 'median' measurement. Compare that to the at-rest measurement, and that should give you an idea if your measurements are accurate.

Most (good) machinists measure all the components while apart, deck height, rod, crank, etc, then do the math for assembled piston/deck measurements. Doing a mock up takes more time, most don't bother, and rely on the original math. That's how calculations are done to determine how much to take off the block too.

I'm not going to get into the can-o-worms debate of quench, but will say I think it's overrated. Many prefer to have the piston slightly in the hole for a number of reasons, stability, not exposing the top ring to heat, etc. But many successful machinists recommend no less than .027-.028 when assembled, and shoot for .004-.008 in the hole.

Max depends on a number of factors, like if you use aluminum rods, add .010 or so, for example, or boost. But I've seen experienced builders shoot for .065 even. With no special circumstances, the .040-.055 range is acceptable.

Those are the general rule of thumb recommendations I'm familiar with, from doing deep dives in the topic.

Many successful engines are way above those numbers, and if you want to twist your brain on the subject, think about hemi chambers.

.

[pmd400]

I just checked the deck height on my 455. When measured with a straight edge parallel to the piston pin the right bank is about 0.003 in the hole while the left bank is 0.009 in the hole. Heads I'm using are 95cc 6x casting. I'm using crower 60919 and rhoads lifters. I don't really want to disassemble the short block and send it back to be machined. Should I use 0.39 felpro head gaskets or cosmetic mls gasket of differing thickness to obtain even quench across all cylinders?

[HWYSTR455]

That's so close I wouldn't worry about it.

.