Go big or go home... Big bore/Stroker talk

[KMPrenger]

Originally Posted by GretchenGotGrowl

Maybe just go to 12:1 as a first pass.

Here's my thinking on an ideal NA V6 strip car.

• Raise compression to about 12.5:1
• Go with lightweight rods and pistons
• Balance the rotating assembly to perfection
• Custom cam for peak HP in the 7500-7800 range
• Replace the valve springs/retainers
• Minimum 3600 stall
• Tune and move the rev limiter to 8000 RPM

Let that baby spin up and go.

I really like this. Would be a real beast on the high end, but I'm guessing wouldn't have as much "guts" down low as stock, or am I wrong there.

So here is a noobish question, but is raising the compression basically done by using different pistons with a different dome profile, or is there more needed to just simply raise compression?

[HP Turbine]

Originally Posted by KMPrenger

I really like this. Would be a real beast on the high end, but I'm guessing wouldn't have as much "guts" down low as stock, or am I wrong there.

So here is a noobish question, but is raising the compression basically done by using different pistons with a different dome profile, or is there more needed to just simply raise compression?

well the 3600 stall or higher will help keep the thing away from the low end.

[GretchenGotGrowl]

Originally Posted by KMPrenger

I really like this. Would be a real beast on the high end, but I'm guessing wouldn't have as much "guts" down low as stock, or am I wrong there.

So here is a noobish question, but is raising the compression basically done by using different pistons with a different dome profile, or is there more needed to just simply raise compression?

You should be able to raise the CR via changes to the piston dome, changing bore/stroke or shaving the heads. I would personally stay with stock displacement and just do the pistons.

The problem with low-end torque in a 60* V6 is that there really isn't much you can do. The 90* V6 they put in trucks are much better because of the air flow at low RPMs, but they are terribly hard to balance so they usually can't rev very high and don't produce high peak HP. You can gain some peak TQ in our engines via longer intake runners and stroking it, but you will never see the kind of torque you see in a 90* engine. The best way to get low-end torque in our engines is to force air into them. But we should be able to increase the peak HP a lot (IMHO). You can get around the lack of low-end TQ (and HP) by stalling it up. I think we haven't seen much gains from torque converters on our cars is that they aren't stalled high enough. The ones we've seen as supposedly 3600 stalls were actually closer to 3200 (at least mine was). That's not keeping us in the optimal power band like it should. A real 3600 stall will probably see some benefit (especially on a stroked engine like Jason is talking about), but if you stayed stock displacement I would go with a 4000.

[skibik]

I guess I am not a big motor head when it comes to building engines. I have have only stripped a couple of them down and reassembled them in my lifetime but that is about it. Now, when you are mentioning what goes into raising the compression and building custom pistons I would gather a person has to consider into the design of the piston the valve clearance to achieve the 12:1 or 12.5:1 ratio. The other thing that comes to mind with this engine is the VVT system and how will that react to the changes.

It is cool what you are thinking about doing and I look forward to your findings on what you can squeeze out of this engine.

Dean.

[GretchenGotGrowl]

Originally Posted by skibik

I guess I am not a big motor head when it comes to building engines. I have have only stripped a couple of them down and reassembled them in my lifetime but that is about it. Now, when you are mentioning what goes into raising the compression and building custom pistons I would gather a person has to consider into the design of the piston the valve clearance to achieve the 12:1 or 12.5:1 ratio. The other thing that comes to mind with this engine is the VVT system and how will that react to the changes.

It is cool what you are thinking about doing and I look forward to your findings on what you can squeeze out of this engine.

Dean.

You should be able to change the cr without touching the side with the valve reliefs. This is a picture of my 10:1 pistons (left) and the stock pistons (right). Notice the reliefs stayed the same, we just lowered the rest of the dome. To increase the cr you would just raise the dome.


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[DSX_Camaro]

Would you be able to keep the 11.5:1 (or even 11:1) CR if you went with the bored out route and then FI?

[GretchenGotGrowl]

Originally Posted by DSX_Camaro

Would you be able to keep the 11.5:1 (or even 11:1) CR if you went with the bored out route and then FI?

Jason should check my result, but it looks like going from 94mm to 97mm would raise the cr to about 12.2. If that's correct, you can easily get that .7 back on the piston. I dropped mine 1.5 and there is some more that can come off before you lose the affect of bouncing fuel off the top and onto the walls for good mixture with the air.

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[DSX_Camaro]

We could hit 300whp N/A so easily with this, it feels like cheating... So bore to 3.8L and then blow it and bring it down to 11.5-11... If this pans out the SS folks will have something to talk about.

[dmginc]

the thing here is cost. what would all this roughly cost? i couldnt see spending 10k to get to 300whp N/A...at that cost it would be wiser IMHO to trade up to an SS.

there is the cost of the sleeves, boring the block, buying the pistons, having the machined if you want to lower compression....could get expensive quick unless you can do most of the work yourself.

[DSX_Camaro]

I like my 31mpg highway, honestly. It kinda matters to me. And others that got the 6 for the same reason.

If you want the flipside, before I got my RS I considered a 2SS/RS 1LE... yeah...

[rtcat600man]

Originally Posted by GretchenGotGrowl

Maybe just go to 12:1 as a first pass.

Here's my thinking on an ideal NA V6 strip car.

• Raise compression to about 12.5:1
• Go with lightweight rods and pistons
• Balance the rotating assembly to perfection
• Custom cam for peak HP in the 7500-7800 range
• Replace the valve springs/retainers
• Minimum 3600 stall
• Tune and move the rev limiter to 8000 RPM

Let that baby spin up and go.

Sounds GREAT.............and $$$$.

For all that I might as well have an SS and a few mods.


Don't get me wrong, would love to see it come to the market, but it won't be for me either.

[dmginc]

i would be much more interested in cheaper/smaller mods to add some more HP to the car.

[GretchenGotGrowl]

Originally Posted by rtcat600man

Sounds GREAT.............and $$$$.

For all that I might as well have an SS and a few mods.


Don't get me wrong, would love to see it come to the market, but it won't be for me either.

I think you can do this sticking to 3.6L for about $4-5K once all the R&D is done. Of course, it all depends on interest and potential sales volume. Boring/Stroking will be more, but I would still like to see someone give it a try. A 3.9L setup like this would probably give most stock V8s a lot of trouble at the strip.

[Jason@JacFab]

Originally Posted by GretchenGotGrowl

Jason should check my result, but it looks like going from 94mm to 97mm would raise the cr to about 12.2. If that's correct, you can easily get that .7 back on the piston. I dropped mine 1.5 and there is some more that can come off before you lose the affect of bouncing fuel off the top and onto the walls for good mixture with the air.

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12.2 sounds good. I wouldn't touch a thing to try and drop it back down.

Originally Posted by GretchenGotGrowl

A 3.9L setup like this would probably give most stock V8s a lot of trouble at the strip.

I can see offset grinding the crank to 1.850" (Honda journal size) to gain about .175" of stroke... Of course custom rods will be needed... I think it would be find for an NA application, NASCAR, and circle track guys run that small journal all day long at 8k+ rpms... Going with this stroke, and a 98mm max bore would yield a 4.1. Going with 97mm bore would yield a 4.0.

I guess would really needs to be looked at, is will the head gasket take a piston that big, or would custom gaskets be needed also?

Just by offset grinding the crank to a Honda journal size, it would bump the engine up to a 3.8L (just barely, it would actually be about 3751.9 ccs , or 3.75L).