vortec headed 383

[billbayliner]

Re: vortec headed 383

I'm curious.
Why a D shaped quench surface piston with a Vortec cylinder head? Why a not a LCQ style profile piston that more closely mirrors the Vortec Q surface?

And what Q dimension are you shooting for?

 

[gbeltran]

Re: vortec headed 383

That's a nice cam for a jet boat. Dry exhaust? No way in hell would I self grind a cam. You got brass ones.

Didn't grind on the cam, just the rods.

I think the cam Lunati chose for him is about right on spec wise. I ran a cam with similar specs to the one Scott D is thinking of using, you definitely knew it was there idle wasnt the smoothest. Don't know how it would have worked with manifolds choking it off, or the fuel injection for that matter, mine was carbed and it idled around 800rpm. That was on a 350 though, those extra 30+ inches would have toned it down a touch.

 

[crussell85]

Re: vortec headed 383

I'm curious.
Why a D shaped quench surface piston with a Vortec cylinder head? Why a not a LCQ style profile piston that more closely mirrors the And what Q dimension are you shooting for?

What would you recommend for a piston then? I'd like compression to stay around 9.25-9.50, and my quench be around .041-.045.

 

[billbayliner]

Re: vortec headed 383

What would you recommend for a piston then? I'd like compression to stay around 9.25-9.50, and my quench be around .041-.045.

Look at the pictures in this thread. The picture in post 15 shows the LCQ piston mirroring the Vortec Q surface.*
You'll want all the quench you can!

V6 to V8 engine swap

The dish volume controls the static C/R.

 

[crussell85]

Re: vortec headed 383

could you post a link to a "LCQ piston"? I completely understand what you are saying about having the piston mirror the combustion chamber for maximum quench effect.

 

[Tail_Gunner]

Re: vortec headed 383

Here GrumpysPerformance.com • View topic - detonation, and how to reduce its likely hood

GrumpysPerformance.com • View topic - tumble and swirl, quench & squish

That should move things along

 

[Walt T]

Re: vortec headed 383

Keep in mind guys, I agree wholeheartedly that quench is a great way to get more out of the available air fuel mix. What is happening is the entire mixture is being pushed into a smaller area toward the spark plug the theory being it will burn faster therefore making more heat energy (BTU) available to drive the piston down and not get soaked into the piston, head, and cylinder wall. It works very effectively. It does NOT raise compression ratios. It does increase the heat in the smaller area where the burn takes place. The smaller area is the "D" which is why they're called that. Compression is changed by lowering or raising the head. It is a common misunderstanding when guys see those pistons that the compression ratio is way higher. A ratio is a ratio no matter how small the burn area becomes. Now compressing this burny stuff into a small area makes it all hotter which is what we want as described earlier. This obviously requires control over fuel quality. If you buy your gas at marinas you have less control and should carry 104 on board. If you build one of these for your family SUV (Hey may as well have some fun trying to make the baby go to sleep when you're driving around at 2 in the morning when it refuses to go back to sleep) you have control over fuel quality. Engine temperature is also a factor here. Raw water cooled boats do tend to run cooler than closed systems HOWEVER.... And this is a major problem... After awhile rust and corrosion will form in the passages and water becomes less effective in spots thereby possibly creating "Hot Spots" in the head or cylinder walls. Anyone who has found plugged head gaskets knows this. Do not do this in salt water cooled boats unless you know what you're doing. This is why some marine performance engines develop pinging later and it doesn't go away. This is a simple explanation for those who have asked and obviously there's stuff left out. You can control the temperature of the quenched burn.. if you know what you're doing. By cranking the engine and taking compression pressure readings you can raise and lower that to where you want it to be. The lower the pressure the cooler the burn, but less energy is available to the piston. This is why I stay away from D pistons for marine engines for customers who want a little more power for the family runabaout. I've been there and I've experienced them. Guys, this is big block power out of a small block Chevy. It's not for everyone. It is for those who know what they're getting. One thing I have also found is on some boats they are so loud you can't always hear the pinging. Or a captain doesn't know what that noise is. So.. if you want to do this, educate yourself as it's a science unto itself. Cam selection is critical as is intake and exhaust. If you want this, but are not an engine builder, find a machinist who understands this. Do NOT let a mechanic from your local marina who obviously has no dental plan build one of these. You will love it and it is worth the money in my opinion. Just do it right for how you will be running it.

 

[crussell85]

Re: vortec headed 383

Building an engine with proper quench is not about making more power it is about creating a space that will allow the air and fuel to create the the proper mixture therefore reducing/eliminating hot spots therefore reducing/eliminating pre ignition. It will create a smoother running engine that will be less prone to failure. Cam selection has nothing to do with the quench distance. Cams need to be ran with the proper compression ratio but the quench needs to remain the same distance. Compression ratio should be controlled by piston and combustion chamber selection. The only time this changes or is less important is when superchargers or turbos are used. It will also allow for a cooler running engine as long as the compression ratio is controlled while creating the proper quench.

 

[Walt T]

Re: vortec headed 383

It's not about me being right or wrong, it's about the average person who is interested in more power for his boat gaining knowledge about what they are buying or building. My entire point is educating yourself. One thing I have learned in this business is that there are many different theories from many different skilled techs who all know what they're doing about what is happening inside a cylinder. Everyone here is sharp and will figure things out for themselves. We all speak from experience and Crussell's statement is no less valid than mine since it's what he has learned. It's all information for those who want it.

 

[crussell85]

Re: vortec headed 383

I didn't want it to sound like a right or wrong reply. In my opinion building an engine with the proper quench distance is the most overlooked and ignored part of building an engine. Especially someone building a marine engine with marine head gaskets. From the marine head gaskets I've seen they average .051 compressed thickness. So if your crank, rod, and piston stack up to 9"and the stock deck height remains at 9.025 you end up with a quench distance of .076 which is completely unacceptable and often ignored/overlooked by novice engine builders. If the engine is built like this it will never run right and probably won't last more than a season if you even get that out of it without frying a piston or pistons.

 

[Bondo]

Re: vortec headed 383

Ayuh,... I know it was aways back in the conversation, but I just found this picture in my files that illustrates the differences in the length of risers that can be used to help with reversion,...

Stock on the left, goin' to really long pipes on the right,...
All of 'em mix the water close to the end,...

 

[Walt T]

Re: vortec headed 383

Crussel you are absolutely right that its overlooked. As far as lasting, well I've built many engines some of which are still going after 15 years. Of course it's just boating normally and goosing it for fun. Racing engine or serious high performance, well sure I agree if you're gonna build, build it right. The thing is we have the average mechanicky kinda fellow who comes here, asks about a cam and manifold. It's pretty obvious they don't want to pull an engine and build it correctly. So we gently put them straight as far as cams and manifolds, even 4 bbls. Sometimes I or someone will mention vortec heads is one way to go to get enough hp to make a difference. It will make a difference and it won't fry pistons. It's not ideal by any means since volumetric efficiency is nowhere near as good as it could be, but it will be better than camel humps. Keep in mind we're just trying to suggest something that may be within their ability and budget. Most folks are interested and happy for the information. I doubt many of them actually do this. Then someone pipes in about quench and squish which to these poor fellows is like a physics lecture. They can't see the woods for the trees. I do appreciate the links, and I highly recommend Grumpy, he explains it all so well I believe the average mechanicky guy can understand. I was vastly simplifying it in my essay and its so general that any expert could find mistakes. One thing I am good at ( at least I think so) is giving non mechanics information to decide whats best for them.

Bondo, excellent! The one on the far right where is that found? Is it custom?

 

[Bondo]

Re: vortec headed 383

Crussel you are absolutely right that its overlooked. As far as lasting, well I've built many engines some of which are still going after 15 years. Of course it's just boating normally and goosing it for fun. Racing engine or serious high performance, well sure I agree if you're gonna build, build it right. The thing is we have the average mechanicky kinda fellow who comes here, asks about a cam and manifold. It's pretty obvious they don't want to pull an engine and build it correctly. So we gently put them straight as far as cams and manifolds, even 4 bbls. Sometimes I or someone will mention vortec heads is one way to go to get enough hp to make a difference. It will make a difference and it won't fry pistons. It's not ideal by any means since volumetric efficiency is nowhere near as good as it could be, but it will be better than camel humps. Keep in mind we're just trying to suggest something that may be within their ability and budget. Most folks are interested and happy for the information. I doubt many of them actually do this. Then someone pipes in about quench and squish which to these poor fellows is like a physics lecture. They can't see the woods for the trees. I do appreciate the links, and I highly recommend Grumpy, he explains it all so well I believe the average mechanicky guy can understand. I was vastly simplifying it in my essay and its so general that any expert could find mistakes. One thing I am good at ( at least I think so) is giving non mechanics information to decide whats best for them.

Bondo, excellent! The one on the far right where is that found? Is it custom?

Ayuh,.... I believe it's a Hardin Marine riser,... possibly IMCO Marine,...

No numbers or stampin's on 'em,...

Lotsa neat choices,...