Stroker kit vs. stock crank with higher compression

[Carl Beck]

Given the broader choice between a) buying the stroker kit and building that engine, building an L28 with 10:1 compression, c) buying an L28 built completely by Rebello.

I'd spend the extra money on having Rebello do the complete engine build, including intake and tuning - then install that yourself.

There is a large difference in performance between engines built by shops like Rebello - and engines built by people that rebuild two or three L series engines a year. Not to mention matching the intake system to the engine and fine tuning everything.

FWIW,

Carl B.

[doradox]

Stock L-20B

HorsePower -@ 112 @ 5600 RPM

Ft. lbs. Torque 108 @ 3200

Keep in mind,these numbers are at the flywheel .

Below are my actual numbers at the wheel.

That's a nice power curve for grandma, or a tractor, but where did your HP go? Your intake, head, cam, exhaust couldn't handle the increased flow so you basically shifted your torque curve to a lower rpm and ended up with little or no HP gain. From my equation if you reduce rpm you have to increase torque to make the same HP. Also your displacement increase from 2.0 to 2.3 is a 15% increase where the increase from 2.8 to 3.0 is only 7%. Looks like my math still holds. You didn't gain more than about 15% HP. I am assuming drivetrain losses absorbed that in your dyno plot vs. the stock numbers you quoted.

Steve

[Z train]

That's a nice power curve for grandma, or a tractor, but where did your HP go? Your intake, head, cam, exhaust couldn't handle the increased flow so you basically shifted your torque curve to a lower rpm and ended up with little or no HP gain. From my equation if you reduce rpm you have to increase torque to make the same HP. Also your displacement increase from 2.0 to 2.3 is a 15% increase where the increase from 2.8 to 3.0 is only 7%. Looks like my math still holds. You didn't gain more than about 15% HP. I am assuming drivetrain losses absorbed that in your dyno plot vs. the stock numbers you quoted.

Steve

What vehicle is the motor in?

What is it going to be used for?

What am i doing with the gears?

Edited October 5, 2010 by Z train

[doradox]

What vehicle is the motor in?

What is it going to be used for?

What am i doing with the gears?

All good questions but my math still says the 3.0 stroker 10:1 short block vs. the 2.8 10:1 short block will produce about 7% more hp.

We can go on and on about a hundred different variables and in the end we will concluded that "their ain't no replacement for displacement". Forced induction aside.

BUT, if that displacement gain is small (7%) and the cost high there may be a better way. I was just trying to quantify the hp gain in terms that would help the OP decide if the additional cost is worth it to him.

Steve

[Z train]

1)All good questions but my math still says the 3.0 stroker 10:1 short block vs. the 2.8 10:1 short block will produce about 7% more hp.

2)We can go on and on about a hundred different variables and in the end we will concluded that "their ain't no replacement for displacement". Forced induction aside.

3)BUT, if that displacement gain is small (7%) and the cost high there may be a better way. I was just trying to quantify the hp gain in terms that would help the OP decide if the additional cost is worth it to him.

Steve

1)Good?How about extremely pertinant?The motor is in my wife's 620.It's is going to be used as a "run around/ranch/toy for her".I'm also dropping from the 4.37 gears to 3.88's which will put cruising rpm smack in the middle of that motor's torque "table".

It also has a Weber & a header + a cam from Rebello's.I am not looking for HP as it is a ranch truck,and Dave's cam selection worked better than i could have hoped for.

2)Absolutely.

3)Why is it that you ignore that the major attribute of a stroker is torque?This is what makes the stroker work so well on a street car.And torque wins street races.

[doradox]

1)Good?How about extremely pertinant?The motor is in my wife's 620.It's is going to be used as a "run around/ranch/toy for her".I'm also dropping from the 4.37 gears to 3.88's which will put cruising rpm smack in the middle of that motor's torque "table".

It also has a Weber & a header + a cam from Rebello's.I am not looking for HP as it is a ranch truck,and Dave's cam selection worked better than i could have hoped for.

2)Absolutely.

3)Why is it that you ignore that the major attribute of a stroker is torque?This is what makes the stroker work so well on a street car.And torque wins street races.

So that dyno chart was for an engine that was far from just a stoked stock motor? And you compared that to a stock motor and told us all how you got a 50% increase in torque from a stroker yet neglected to mention the other mods? So how much did the stroker part of it add and how much was from carb, cam and header. The OP was comparing short blocks, not a stock engine vs. a highly modified one. Again, I was trying to quantify the gain from going with increased stroke only NO OTHER MODIFICATIONS.

A stroker, by definition, is a bigger engine displacement wise. We agree that there ain't no replacement for displacement. That is what makes it work so well on the street. It's a bigger engine! There is nothing magical about a long stroke. A larger bore will also give more torque. As the surface area of the piston is larger the pressure on the piston produces more force that pushes on the rod that pushes on the crank. More force on the same lever gives more torque. Since most engines are limited to how much you can over bore them the only other way to substantially increase the displacement is to increase the stroke. I didn't say it was bad or a waste of time or anything else. just that a 7% larger engine can be expected to put out 7% more hp.

Torque never won any races unless it was accompanied by rpm, which by now we all know, equals HP.

Steve

[jmortensen]

If I may get on my high horse for a second, there is no way in hell that a stroker crank alone is going to net you a 50% increase in torque when you're comparing an L28 and an L31. Now if you have a really big cam in the L28 and you put a small cam in the L31 and play with cam timing, etc, I could buy that. But for engines built similarly, no way.

I think the math on the stroker is the best way to estimate what you're going to get. It's not always that simple though.

Running the exact same setup before and after, Tom got 0 hp and 10 lb/ft of torque. My guess is that there is more to be had there and he'll probably end up with about 12% more power and torque, you can stay tuned to the thread to find out.

http://forums.hybridz.org/index.php/topic/94521-hbzers-guess-my-31-rwhp/

Mark's original stroker put out a whopping 137 hp and 157 lb/ft of torque:

http://forums.hybridz.org/index.php/topic/38495-31-stroker-horsepower-rating/

And in its latest iteration it puts out 267 hp and 250 lb/ft to the wheels through 40mm carbs:

http://forums.hybridz.org/index.php/topic/24798-na-31lhead-camshaft-questions-no-shortcuts-max/page__st__140

As you can see, a stroker isn't a guarantee of anything, and I think a similarly built non stroker will put out very similar numbers when measured by hp/liter. IMO if you're looking for a fast car, build the non-stroker. There comes a point at which it is cheaper to go with the stroker than it is to keep going on the non stroker to increase hp, but I don't think most people get there. When you do get there, consider that I bought a 315 hp V8 motor with 320 something lb/ft of torque for $1100 with 30K miles on it. It looks brand new inside. When you get down to it there are far less expensive ways to get power than by building a NA L series.

In autocross, having the stroker puts you into XP if I'm not mistaken. That's a pretty tough class to compete in if you want to be really competitive.

[Z train]

1)So that dyno chart was for an engine that was far from just a stoked stock motor?2) And you compared that to a stock motor and told us all how you got a 50% increase in torque from a stroker yet neglected to mention the other mods? 3)So how much did the stroker part of it add and how much was from carb, cam and header. 4)The OP was comparing short blocks, not a stock engine vs. a highly modified one. 5)Again, I was trying to quantify the gain from going with increased stroke only NO OTHER MODIFICATIONS.

6)just that a 7% larger engine can be expected to put out 7% more hp.

7)Torque never won any races unless it was accompanied by rpm, which by now we all know, equals HP.

Steve

1)Yes and no.

2)As an illustration of what a stroker can do.A "non-stroker" can never hope to achieve stroker "numbers".

3)Most of it as the header is quite point-less with a low RPM motor( i used it because i had it laying around and i'm in the process of having an L-16 manifold prepped)

4)The OP DID NOT mention "just a short block"in his original post.If you are doing a rebuild,then you are replacing the cam-this is a moot point.

5)What if?

6)Wrong-Horse-power increase with displacement increase is NOT linear.

jmortensen- I looked thru those topics you linked.And i noticed one common thread.Tell me what it is.

[doradox]

I have a two part question for our resident engine builders. Use the bore/stroke of an L28 for comparison.

First, is the power/torque gain for a fun-to-drive street/autocross powerplant with a full 3.0L stroker kit using 10:1 pistons worth the added expense compared to just using new 10:1 pistons and sticking with the L28 rods and crank?

1)Yes and no.

2)As an illustration of what a stroker can do.A "non-stroker" can never hope to achieve stroker "numbers".

3)Most of it as the header is quite point-less with a low RPM motor( i used it because i had it laying around and i'm in the process of having an L-16 manifold prepped)

4)The OP DID NOT mention "just a short block"in his original post.If you are doing a rebuild,then you are replacing the cam-this is a moot point.

5)What if?

6)Wrong-Horse-power increase with displacement increase is NOT linear.

2). Really? what magic does a stroker possess? Would you prefer an SB 307 (long stroke small bore) over an SB 302 (short stroke big bore). The 302 is renowned for it's "numbers"

3). Pointless? Really? The best thing I ever did to my stock SB 400 (400 ft*lbs @ 1200 rpm 4200 rpm redline)) was to put headers on it. Made a huge difference. Your statement just is not true.

4). You are interpreting "a full 3.0 stroker kit" as including a cam? What does the cam have to do with making an engine a stroker? Nothing. By your reasoning you would cam the 2.8 also. So where does that leave us? Oh that's right, the difference in displacement and what it costs to achieve that.

5) For the third or fourth time. Comparing apples to apples. 2.8 liters vs. 3.0. Not cams, intakes, headers, porting or any other variables. What is the gain just from the displacement increase. 7%

6) And that is based on what physics? A motor is an air pump. Do you really think a 7% bigger pump will magically pump more than that? All other things being equal (do I need to keep saying that to you?) at 100% VE the 3.0 will put out 7% more HP that the 2.8 at 100% VE. It's ingesting 7% more fuel air mixture and so has only 7% more energy available to produce power. It's physic and thermodynamics. Not the magic of stroke.

What logic or physical laws can you use to make your point?

Steve

[jmortensen]

jmortensen- I looked thru those topics you linked.And i noticed one common thread.Tell me what it is.

You didn't understand them.

[Z train]

2). Really? what magic does a stroker possess? Would you prefer an SB 307 (long stroke small bore) over an SB 302 (short stroke big bore). The 302 is renowned for it's "numbers"

3). Pointless? Really? The best thing I ever did to my stock SB 400 (400 ft*lbs @ 1200 rpm 4200 rpm redline)) was to put headers on it. Made a huge difference. Your statement just is not true.

4). You are interpreting "a full 3.0 stroker kit" as including a cam? What does the cam have to do with making an engine a stroker? Nothing. By your reasoning you would cam the 2.8 also. So where does that leave us? Oh that's right, the difference in displacement and what it costs to achieve that.

5) For the third or fourth time. Comparing apples to apples. 2.8 liters vs. 3.0. Not cams, intakes, headers, porting or any other variables. What is the gain just from the displacement increase. 7%

6) And that is based on what physics? A motor is an air pump. Do you really think a 7% bigger pump will magically pump more than that? All other things being equal (do I need to keep saying that to you?) at 100% VE the 3.0 will put out 7% more HP that the 2.8 at 100% VE. It's ingesting 7% more fuel air mixture and so has only 7% more energy available to produce power. It's physic and thermodynamics. Not the magic of stroke.

What logic or physical laws can you use to make your point?

Steve

2)displacement.302 what?SBF?Or than minorly less a piece of crap 302 SBC?

3)400's were a pile of junk also.Comparing V-8s to L motors is a non-sequitur.

4)Brush up on your reading comprehension,

5)What part of can't be done don't you get?What works for a 2.8l will not(always) work for a 3.1.

6)DO i need to keep telling you that CI & HP increases are not LINEAR?

[Z train]

You didn't understand them.

Quite the contrary.And you didn't answer my question.