Quench

[Driver4r]

Ive been planning out a 331 build in my head(.030 over 327).
This is going to be an RPM engine, its going to hit at least 10k(8k avg.)
My question is, is my quench to tight to the point where bad things will happen.
The plans:
Zero Deck the block even with the pistons(2 relief flat tops).
And Im going to cut 64cc heads down to 58cc(roughly .030).
(should be roughly 13:1)
I know im going to be cutting it close on valve clearance, but im also
wondering if my quench is to tight to the point of bad things happening.

(also on top it might get a 500 shot)
(fully forged build)

 

[Driver4r]

also:
Im going to be running a .015 shim head gasket.
The main goal is 13:1.

 

[Green79Scottsdale]

10k RPM?!?! Curiosity here... why the RPM goal? And why the high compression? What is this being used for?

For some reason my brain is telling me .030-.040 is a good quench number. Have you thought about using 305 head castings? They are already 58cc, and I have seem some impressive flow numbers from guys porting and polishing themselves at home. You might not be able to run big valves with chambers that small regardless what heads you run. That's why I ask about the compression. You might get good compression, but your flow #'s might not be up to task at your RPM goal. Smaller valves might be more controllable at those higher RPM's too. Factory forged parts? I assume you have the pistons and heads already, and are choosing to use that combo? Heads with bigger chambers for bigger valves and domed pistons would be preferable for your RPM target.

E85 readily available in your area? If it is, this could be a nice E85 motor depending on compression and whatever cylinder pressures you get with the cam you use.

Just some thoughts from me. Hope they were helpful.

 

[Driver4r]

Im gonna set the Rev limiter at 10k because I'm sure with 5.57 gears I'm gonna hit it pretty easily.

It's gonna be going in a little s10 with the engine set back 10" and a full fiberglass front clip(super light in the front)


Yes on e85. That's the plan. And the reason such high in the rpm is cause thats how a 327 made power, spin it up.
And the cam I'm looking at is 4-8500. I want it to sound old school gasser. The heads are going to be 906 vortecs because the are readily avaliable and flow good. They have 1.9/1.54 valves which are good enough for 331ci. They flow enough for a 355 to 6k.

Yea. The valves are gonna be damn close to kissing the pistons. So ill probly have to shim the springs to get just a hair more lbs on the seat.

The problem with domes is they don't burn worth a ****. They burn enough to shove the piston back down. But your also trying to shove a flame up hill.

Flat-tops are the most efficient piston as far as fla me travel goes. And I want every ounce of power and efficiency I can get (minus cam overlap).

And no. Currently all I have is a crank (small journal). And I have a lead on a 327 complete for the block.

 

[Driver4r]

And it's also gonna be driven in the street

It should be a bad ****.

Extra info:
I plan to run forged h beams for the strength.

 

[bucket]

I'd just run the proper dome pistons. It would just be one compromise instead of a few to make flat tops work. And I'm sure you are aware the block and heads need to be surfaced perfectly to run shim gaskets. And it seems like your RPM goal is a little pointless with vortec heads, may as well plan a lower RPM range. Remember, you either select every part you need for your goals, or you select your goals based on the parts you have to work with.

Have you thought about using 305 head castings? They are already 58cc, and I have seem some impressive flow numbers from guys porting and polishing themselves at home.

It's very refreshing to read this. Most people laugh when there is talk of porting 305 heads, but if you already have them and have some spare time, it's not a bad choice for a lot of street motors.

 

[bucket]

The heads are going to be 906 vortecs because the are readily avaliable and flow good. They have 1.9/1.54 valves which are good enough for 331ci. They flow enough for a 355 to 6k.

You basically said it yourself right here. A 355 is hardly any larger displacement and you are talking a hell of a lot higher rpm than 6K.

 

[Driver4r]

The rpm range is set in stone. It's the whole point for this build. I think what I'm gonna do now is set them in the hole .015. And that drops me half a compression point. I suppose I can deal with that.
As far as the vortecs go. A 906/062 is up to the job at hamd. And I could even polish them to make it easier.

And as for the shim gasket. I have them in my monte. All I did for prep was copper coated them. The heads were freshly surfaced. But the block was just cleaned off. And @11:1cr I had no issues of leaks.

 

[Driver4r]

The whole question at hand was. Was .015 quench going to make bad things happen .

 

[SkinnyG]

I think the general rule of thumb for 0.040" quench is to allow for rod stretch at high rpm and avoid piston-to-head contact.

BUT, I am no expert - I merely did a LOT of research online on quench when I ported a set of 305 heads for my 350 (using 0.015" shim head gaskets). More quench makes things more prone to detonation, but nobody said anything about going tighter.

Why not shoot for 0.035" or 0.030" and see if anything hits after 10,000rpm? If no contact, go another 0.005" less. In which case, I think a zero deck block would be best, because then you can play with head gasket thickness for quench. Easier than decking more.

I would avoid any dome and stick with the flat top to have better flame propagation across the cylinder.

You might need to ask this question on a automotive engineering forum to get a better answer.

 

[bucket]

The rpm range is set in stone... A 906/062 is up to the job at hamd...

...They flow enough for a 355 to 6k... And I want every ounce of power and efficiency I can get (minus cam overlap).

This just doesn't add up. Just because it CAN spin that fast, doesn't mean it will make any power that fast.


Why spend all that money on parts to build a motor for a specific goal, but use a set of heads that are in no way optimal for the rest of the combo? Not trying to harp at you, but it's better to spend money once rather than spending some now, and a lot later when "some" wasn't enough.

 

[Driver4r]

The vortecs won't be permanent on it. Just. Tide over for awile. I can get a pair of 906 vortecs for less than 100$. And have mabey 100$ in machining.

Now can you tell me a pair of heads that flow as good as the 906's in stock form that I can get for $200????. And you port on top of the 906 casting and it becomes a very competitive head.

The 10k mark is gonna be my rev limitor. I'm going to shift @8.5-9k. Just as I exceed the power band. And I say 10k because im sure by the time I hit the lights. I'll be pretty close to 10k with 5.57 gears. The cam I'm looking at makes power to 8500.

It's just that old school type build......
You don't have to understand it. Just go along with it.

 

[Driver4r]

@ skinney. Today I was playing around on a CR calculator and If I leave the pistons in the hole
015, and run a .015 steel shim. That makes .030 quench which is optimum. The problem I have with running a composite gasket(.030) is I don't want to blow it out cause its to much surface area. Now if it's steel core. Then that's a different story.

And I agree with you on the domes 100%. They have a burn issue. That's why I don't want to run them. If it was just a car show cruiser and didn't give a **** about efficency. Then mabey ide run domes just to say I'm running domes. But when it comes to the burn across the surface. They Suck. And it took research for me to learn this aswell

 

[Driver4r]

Bucket. If I had the funds to spare. I would buy some 300cfm heads for it. But I don't have 5k just to throw at heads.

I just used a calculator to find the cfm requirement of the engine at hand. And it came out to 957.755 @10k. Now I know not all 8 draw air at the same time. But just for the hell of it. Let's round 957 to 1000cfm. Now divide that by 8. We get 125cfm to each runner. And I know vortecs flow more then that.

Now I'm sure thats not the 100% correct way to find that #. But it should give you a pretty good reference point to base your search off of.

So I see no reason some vortecs couldnt possibly keep up with a wee little Ole 331.