K1500 engine build update

[VIKING_MECHANIC]

After months of working 6 days/week and delay in parts, I finally got a weekend off and made a significant progress.

Only major issue so far, is the threads were stripped on the crank and on the bolt. I got a new bolt and re-threaded the crank.

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Rotating assembly and new timing set installed.

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About a day later and the heads are on. I mocked up the intake manifold to see how the color would blend with the heads and block. It's a bit darker than what I wanted, but I like the tri-tone color. The oil pan I painted black to match the manifold.

 

[Schurkey]

I've never played with a balance-shaft V-6. I presume the balance shaft has to be aligned just like the cam has to be degreed. How is that done? Is the balance shaft gear driven by a gear machined on the back side of the cam sprocket?

What is your piston-to-deck distance? How thick are the head gaskets?

 

[VIKING_MECHANIC]

I've never played with a balance-shaft V-6. I presume the balance shaft has to be aligned just like the cam has to be degreed. How is that done? Is the balance shaft gear driven by a gear machined on the back side of the cam sprocket?

Yes it does. The shaft is driven by a gear behind the cam sprocket that is bolted to cam.

What is your piston-to-deck distance? How thick are the head gaskets?

I'm not sure on that. I had the machine shop do all the technical stuff. I gave them the new pistons and they machined the block and heads accordingly.
The gasket is 0.0396in.

 

[Schurkey]

NOW is the time to find out your quench clearance. If the pistons are in the hole the typical amount--about .025--and you have a .039 head gasket, your quench distance is going to be WAY TOO HUGE at .064.

If your new pistons are typical "rebuilder" stuff, they'll be short on compression distance, which means that even if you deck the block .010 or .020, they'll STILL be below the deck surface, and your quench will still be huge. Perhaps .080+ on a virgin block deck.

If the quench distance is too large, the in-cylinder turbulence is weak. Low swirl, slow burn, needs excess timing advance, engine is lazy, runs hot, and tends to detonate. Tighten up the quench, you need less spark advance for best power, less chance of detonation, and the engine runs and cools better. Makes more power on less fuel.

MAYBE you can find a thinner head gasket.

MAYBE the machine shop zero-decked the block already. If so, you're golden. With the pistons even with the top of the deck, your head gasket thickness IS your quench distance, and .035--.040 is about perfect. Doesn't look like it in the photo, though.

 

[VIKING_MECHANIC]

Since I don't have anything to do precise measurements with, I had the machine shop do all the machine work. I'm just going with a standard rebuild, no turbo or anything else like that. So I would imagine the shop did zero-deck it. The 0.0396in gasket is the thinnest my local part store has. According to Fel-Pro, the gasket thickness is 0.0396 To 0.0484in.

If you're referring to the top picture, #1 is at TDC and that's as much up travel it does before it goes back down.

Zero-deck is the clearance between the open valve and a given piston at TDC, correct?

 

[Schurkey]

I'm just going with a standard rebuild, no turbo or anything else like that. So I would imagine the shop did zero-deck it.

Unless you specifically asked for it, they almost certainly did NOT zero-deck the block. They may not have cut the decks at all.

If you're referring to the top picture, #1 is at TDC and that's as much up travel it does before it goes back down.

Yeah. The angle isn't great, and so it's hard to tell what I'm really looking at. From that angle, and as far away as the camera is, it seems to me that the pistons are down in the hole at least .025 and likely more than that.

But if there's a bevel on the edge of the piston crown, what I think I'm seeing may not truly be the case. You need to confirm with your machine shop what was done, and whether the pistons have full compression height or whether they are "destroked" and sit lower than they should.

Zero-deck is the clearance between the open valve and a given piston at TDC, correct?

No. Not at all. "Zero deck" has nothing to do with valves. We're talking about the top of the piston (the flat part, not the dome if there is one) vs. the flat underside of the cylinder head. The SBC has a "closed" or "quench" combustion chamber. You want the piston to come as close as possible to the head, without actually touching. Given that things expand and contract with temperature, parts flex with RPM, etc; a common "goal" is somewhere around .040 clearance. Sometimes less, certainly not much more.

If the quench distance is greater than .100 to .120, the chamber is "open"; it may burn slow and need lots of spark advance, but it's not likely to detonate. The biggest problems are when the quench distance is greater than ~.050 but less than .120.

 

[brian c lindsey]

sorry to change the subject , but i have a question you could answer , im having gauge issues with oil pressure , and im looking for and oil plug i can install aftermarket gauge to , i think there is a port on drivers side close to oil filter mount, dont want to put it on top where sending unit is, could you look at let me know where the oil galley ports are

 

[Schurkey]

sorry to change the subject , but i have a question you could answer , im having gauge issues with oil pressure , and im looking for and oil plug i can install aftermarket gauge to , i think there is a port on drivers side close to oil filter mount, dont want to put it on top where sending unit is, could you look at let me know where the oil galley ports are

It'd be better to start a new thread, and to tell us WHAT ENGINE THIS IS.

 

[Supercharged111]

I thought excessive quench, in the instance of a too thick head gasket or pistons way down in the hole, made an engine more knock prone. I stumbled upon this when looking at using a thicker head gasket to reduce compression and reduce the tendency to knock. Turns out that's a terrible approach.

 

[Erik the Awful]

Opposite. Too much quench area will also mean more combustion chamber volume, lowering your compression ratio and making you less knock prone. I've been playing with compression ratio calculators the last couple days because I was afraid I'd screwed up. Turns out, one of the online calculators that shows up pretty high on google is complete garbage. It told me my low-buck engine was 13.5:1. I did discover that if I have 58cc TBI heads my compression ratio will be 10.2:1. 64cc heads come in at 9.6:1 - but I plan on porting them out to around 66cc, which will give me 9.4:1.

What I did discover, playing with the numbers.
1) There's a lot of garbage out there as to cylinder head combustion chamber volume. Measure them.
2) piston valve relief size (6.5cc vs 7cc) makes very little difference
3) gasket thickness and deck height make big differences.

Schurkey has a good point about optimizing quench area as well as compression ratio. Basically you want to zero-deck the block, use a .041" gasket, and have a nice-sized combustion chamber. If you're trying to stay with a cheap-gas compatible 9.0-9.5:1 compression ratio, the most common 64cc chambers are too small - 10.1:1. 76cc heads would get you cheap gas friendly, but lazy performing 8.9:1. 72cc heads would have you at 9.3:1.

Speedmaster has a pretty decent calculator. Summit Racing's gets the exact same numbers, but the layout is funky.
https://speedmaster79.com/tools/engine-compression-ratio

Also, https://blog.k1technologies.com/what-is-deck-height-how-to-calculate-and-what-it-means