2270(or so) Build Options

[yeahmag]

It's all about reducing the amount of case and cam clearancing needed.

[Mark Henry]

Hmmmm... I didn't have much clearancing required for the Chevy rods and 80mm crank, but it's the only stroker I've built. I took my time and checked it a lot. Time will tell if I did an adequate job ;-)

Chevy/Buick journals are smaller than type 1, so should require less clearance work?... maybe you're comparing the clearancing required for type1 rod with 78mm versus Chevy rod and 80mm crank?

It's the rods with that T4 combo and a big lift cam, say the web 163/86b. One cam lobe comes close to a rod and you have to clearance the rod big end, so you have to match both sides and then all the rods must match.

Also I was confusing the Type one 2007cc, 78 X 90.5mm build I'm doing right now, lots of case clearing...dry fit over and over again.... (IMG:style_emoticons/default/wacko.gif)

[groot]

Curiously... As a noob when it comes to T4 builds... Why not run the 2.0 rod journal and not reduce the cam base? Isnt the crank strong enough and the reduced cam circle weakening the cam?

If my idea is wrong, can someone please educate me as to why?

You can, but your rod options are limited with the 2.0 journal. And the stock rods are pretty heavy and short for strokers.

[yeahmag]

Kevin,

What cam did you decide on for your 2316 build?

[groot]

It's the rods with that T4 combo and a big lift cam, say the web 163/86b. One cam lobe comes close to a rod and you have to clearance the rod big end, so you have to match both sides and then all the rods must match.

Also I was confusing the Type one 2007cc, 78 X 90.5mm build I'm doing right now, lots of case clearing...dry fit over and over again.... (IMG:style_emoticons/default/wacko.gif)

Yeah, Mark, that's the combo I went with: 163/86b, reduced base circle, 80mm with Chevy journals, 5/16 rod bolts. I did have big end clearancing to do, not too much... very little on the case.... could have been lucky, though.

[groot]

Aaron. 163/86b... not trying to turn 7000+... I have another engine for that. Purpose is reliable power without too much RPM.

I wouldn't be concerned about the amount of clearancing that I had to do... its was minor. The crank flex would be a bigger concern.. but, for my build, I'm okay with it.

[Dave_Darling]

Curiously... As a noob when it comes to T4 builds... Why not run the 2.0 rod journal and not reduce the cam base? Isnt the crank strong enough and the reduced cam circle weakening the cam?

I'm not sure what level you are asking that question from, and the other replies require a bit more knowledge than a total noob would likely have, so I will try to fill that in.

When we talk about making the stroke of an engine longer, that is generally done by swapping in a crankshaft where the rod journals are farther away from the main bearing journals. Specifically, the center of the rod journals are farther than the center of the main journals. Because the piston is directly connected to the rod journal, that means the piston travels further up and down (or side to side in a 914 engine!) which is a longer stroke.

When you do that, you are going to take up more space inside the engine. Due to the layout of the internal bits, there is one place in the cam and crank rotation where a connecting rod on a long-throw crank will try to occupy the same space as a cam lobe. Whether or not this happens is influenced by a bunch of factors, very much including how long that stroke is, how big the big end of the rod is, how tall the cam lobe is, and so on.

It's not really feasible to move the cam down, or the crank up, so you try to make room by carefully taking material off the outside of the rod (which then needs to be balanced again along with the rest of the rods) and possibly by making the cam's base circle (the part that doesn't open the valves) smaller. This latter means that you can get the same lift from the cam but the edge of the lobe will be closer to the center of the camshaft, so it takes up less room in the case.

This is a simplification of what's going on, but I hope it helps.

--DD

[Blown59]

Curiously... As a noob when it comes to T4 builds... Why not run the 2.0 rod journal and not reduce the cam base? Isnt the crank strong enough and the reduced cam circle weakening the cam?

I'm not sure what level you are asking that question from, and the other replies require a bit more knowledge than a total noob would likely have, so I will try to fill that in.

When we talk about making the stroke of an engine longer, that is generally done by swapping in a crankshaft where the rod journals are farther away from the main bearing journals. Specifically, the center of the rod journals are farther than the center of the main journals. Because the piston is directly connected to the rod journal, that means the piston travels further up and down (or side to side in a 914 engine!) which is a longer stroke.

When you do that, you are going to take up more space inside the engine. Due to the layout of the internal bits, there is one place in the cam and crank rotation where a connecting rod on a long-throw crank will try to occupy the same space as a cam lobe. Whether or not this happens is influenced by a bunch of factors, very much including how long that stroke is, how big the big end of the rod is, how tall the cam lobe is, and so on.

It's not really feasible to move the cam down, or the crank up, so you try to make room by carefully taking material off the outside of the rod (which then needs to be balanced again along with the rest of the rods) and possibly by making the cam's base circle (the part that doesn't open the valves) smaller. This latter means that you can get the same lift from the cam but the edge of the lobe will be closer to the center of the camshaft, so it takes up less room in the case.

This is a simplification of what's going on, but I hope it helps.

--DD

I sort of understand what youre saying... I get that fundamentally there is a shift where at one point the outer edge will be further away in the rotation. What Im not understanding is what the differences of each are.

For example, I was going to use a 78mm welded crank with a 2.0 rod journal, 2.0 H beam rods (5.325) 22mm pin, and KB 96mm pistons with 80mm stroke. My understanding is this allows to run in the case of my build a 163/86b without a reduced cam base. I was under the impression a reduced base with this cam would weaken the cam. So, to keep things as robust as possible on the top and bottom end, this was the route we were going.

What I dont understand is how that is any worse than the type 1 or Buick?? FYI the rods will be lightened and balanced by my builder.

Just looking to understand something maybe I just cannot see or that isnt computing for me...

[Jake Raby]

Curiously... As a noob when it comes to T4 builds... Why not run the 2.0 rod journal and not reduce the cam base? Isnt the crank strong enough and the reduced cam circle weakening the cam?

I'm not sure what level you are asking that question from, and the other replies require a bit more knowledge than a total noob would likely have, so I will try to fill that in.

When we talk about making the stroke of an engine longer, that is generally done by swapping in a crankshaft where the rod journals are farther away from the main bearing journals. Specifically, the center of the rod journals are farther than the center of the main journals. Because the piston is directly connected to the rod journal, that means the piston travels further up and down (or side to side in a 914 engine!) which is a longer stroke.

When you do that, you are going to take up more space inside the engine. Due to the layout of the internal bits, there is one place in the cam and crank rotation where a connecting rod on a long-throw crank will try to occupy the same space as a cam lobe. Whether or not this happens is influenced by a bunch of factors, very much including how long that stroke is, how big the big end of the rod is, how tall the cam lobe is, and so on.

It's not really feasible to move the cam down, or the crank up, so you try to make room by carefully taking material off the outside of the rod (which then needs to be balanced again along with the rest of the rods) and possibly by making the cam's base circle (the part that doesn't open the valves) smaller. This latter means that you can get the same lift from the cam but the edge of the lobe will be closer to the center of the camshaft, so it takes up less room in the case.

This is a simplification of what's going on, but I hope it helps.

--DD

I sort of understand what youre saying... I get that fundamentally there is a shift where at one point the outer edge will be further away in the rotation. What Im not understanding is what the differences of each are.

For example, I was going to use a 78mm welded crank with a 2.0 rod journal, 2.0 H beam rods (5.325) 22mm pin, and KB 96mm pistons with 80mm stroke. My understanding is this allows to run in the case of my build a 163/86b without a reduced cam base. I was under the impression a reduced base with this cam would weaken the cam. So, to keep things as robust as possible on the top and bottom end, this was the route we were going.

What I dont understand is how that is any worse than the type 1 or Buick?? FYI the rods will be lightened and balanced by my builder.

Just looking to understand something maybe I just cannot see or that isnt computing for me...

The standard base circle of a 163/86B is 1.150"
The combo you are trying to use will still need a reduced BC, of 1.065" or so, if you try to run it otherwise, the rods will need to be clearance to an unsafe level.

[Blown59]

I sort of understand what youre saying... I get that fundamentally there is a shift where at one point the outer edge will be further away in the rotation. What Im not understanding is what the differences of each are.

For example, I was going to use a 78mm welded crank with a 2.0 rod journal, 2.0 H beam rods (5.325) 22mm pin, and KB 96mm pistons with 80mm stroke. My understanding is this allows to run in the case of my build a 163/86b without a reduced cam base. I was under the impression a reduced base with this cam would weaken the cam. So, to keep things as robust as possible on the top and bottom end, this was the route we were going.

What I dont understand is how that is any worse than the type 1 or Buick?? FYI the rods will be lightened and balanced by my builder.

Just looking to understand something maybe I just cannot see or that isnt computing for me...

The standard base circle of a 163/86B is 1.150"
The combo you are trying to use will still need a reduced BC, of 1.065" or so, if you try to run it otherwise, the rods will need to be clearance to an unsafe level.

Jake, thank you for that clarification.

So, if I am understanding correctly... The BC of the 163/86b will need to be reduced slightly, but still giving the cam most of its rigidity. Along with the bottom end clearancing, should give a good balance of top and bottom end machining as to not have one more robust and leaving one weaker?? Or am I wrong?

[Jake Raby]

Run a 1.065"BC and then clearance the rods as necessary.
Don't worry about cam rigidity.

[Blown59]

Run a 1.065"BC and then clearance the rods as necessary.
Don't worry about cam rigidity.

Jake, thank you for the info.

[Mark Henry]

You're worrying about the wrong thing, the crank is where you need to limit flex. I run and have built many engines with HD dual springs and I've never worried about the RC cam.

[Jake Raby]

You're worrying about the wrong thing, the crank is where you need to limit flex. I run and have built many engines with HD dual springs and I've never worried about the RC cam.

Same here. The reduced BC only calls for a little longer pushrods to be used as a negative.I have ran cams with a BC of 1" and one of them is still on the road now after 21 years. Its in my 356C.

[Mark Henry]

You do realize high lift cams like the 163/86b require dual springs and all the valve train upgrades right?

A stroker crank is far from the easiest engine to build and while it's been done it's not one I'd recommend for your very first engine build.

[Blown59]

You do realize high lift cams like the 163/86b require dual springs and all the valve train upgrades right?

A stroker crank is far from the easiest engine to build and while it's been done it's not one I'd recommend for your very first engine build.

Thank you for correcting my cam flex concerns. And yes, dual springs, valve train and head work are all part of the build amongst other aspects.

Everyone needs to learn one way or another. How many engines have how many people screwed up in learning?? Its all part of the process. And if I spend money building one to learn on and spend more to build the next stroker... The cost is still more than one stroker engine. Either way, it cost more than one build. And who knows.... First stroker may last 70k???? In which case, money well spent.

Time will tell... In the meantime, I enjoy reading.

[VaccaRabite]

Everyone needs to learn one way or another. How many engines have how many people screwed up in learning?? Its all part of the process. And if I spend money building one to learn on and spend more to build the next stroker... The cost is still more than one stroker engine. Either way, it cost more than one build. And who knows.... First stroker may last 70k???? In which case, money well spent.

Time will tell... In the meantime, I enjoy reading.

My first motor ran about 10 miles before I had to tear it apart due to low oil pressure because I was learning. I missed something that anyone with experience would have taken for granted and I just didn't understand fully at the time.
Second motor ran hundreds of miles before I tore it apart to try something different. Nothing was "wrong" with the motor, but I had learned more and wanted to change things on the top end.
Third motor has run thousands of miles. I have to fight the urge every season not to tear it down to build something else. I really want to build a stroker to replace my 2056, but with the 2056 running so well...

Zach

[Jake Raby]

Everything I know about all the Porsche engines I work with came from direct experience, and mistakes. It is truly THE ONLY way to learn. It is also the hardest path.
I didn't have forums or etc to use as resource material. I did something, and if it blew up in my face, I knew not to do it again. The first time it isn't a mistake, but the second time the same thing is done, with the same result is is a mistake.

Today the amount of resource material for these engines is almost too great. There's as much misinformation, as proper information, which is actually worse than no information.

People are too timid these days. Build it the best way that you think, and if it blows up in your face, you'll understand what it's like to walk in the shoes of an engine builder.

[yeahmag]

Zach,

That's exactly how I ended up where I am. Built 2x 2056cc (with parts from Jake, Thanks Jake!) over time and now I'm starting to build up a 2270 that's much more aggressive. My class is all about power to weight, I want more power, and the I'm not that far off the pace of the guys who have a much lower ratio than I do. Should be interesting.

I've been spending some time trying to figure out what static CR I want with both the 86b/86c and the 163/86b. The easiest design puts me at 10.8:1 static, which is way outside my normal rule of thumb of low 8:1 dynamic CR (above 9:1 dynamic). I'd need to add quite a bit of volume to the chambers or a big dish in the pistons to get down to 9.5:1 (which puts me right about where I'm comfortable with in dynamic compression). The fixed numbers I'm working with are:

Bore: 96mm
Stroke: 78mm (maybe 80mm, still debating)
Head CC: 50cc
Target Deck Height: .040"
Rod Length: 5.325"
Intake ABDC (86b/86c): 54 degrees

Dynamic CR for the 86b/86c At 10:1 static I calculate 8.56:1 dynamic. At 9.5:1 static I calculate 8.14:1 dynamic.

So, I can move around the DH a bit and add a dish to the piston, but I'd prefer to keep the quench area that a tight deck affords me. I *think* an 80mm diameter, .2mm deep dish in the piston will get me to the needed 60cc combined (piston dish + heads), but I'm still modeling. I also need to mock up the motor and see if I need valve reliefs, which will add some cc to the volume.

[Jake Raby]

10.8 is too high for a 163/86B on 93 octane unless operating above 5,000' elevation.