Is building a stroked 318 better than a stroked 340/360?

[Dale Davies]

I get that. There is a big difference between saying you don’t have the money to buy parts and saying geometry doesn’t matter. If you can’t afford to do it that’s not an engine builder issue. That’s a consumer issue

Rod to stroke ratio is not that critical according to the magazine tests years ago between a stock SBC 350, a 383 using the 400 rods and a 383 with the 350 rods.
According to David Vizard, a 0.5" rod change in a high compression ProStock engine makes minimal difference in power. He states low compression engines are affected more, but not a lot. This agrees with the magazine article.
Now if you are building a max petformance engine and you have the bank to support the learning curve, go for it. For most street builfs worrying over this is immaterial.

 

[Mean416]

Rod to stroke ratio is not that critical according to the magazine tests years ago between a stock SBC 350, a 383 using the 400 rods and a 383 with the 350 rods.
According to David Vizard, a 0.5" rod change in a high compression ProStock engine makes minimal difference in power. He states low compression engines are affected more, but not a lot. This agrees with the magazine article.
Now if you are building a max petformance engine and you have the bank to support the learning curve, go for it. For most street builfs worrying over this is immaterial.

Agreed.

If you're building pro level race engines in a spec class. Say, NASCAR, pro stock, etc. Everybody is pushing the limits of everything. That last 10 hp means something over a 500 mile race. Joe blow racing with a stroker SB? Let's just focus on good quality parts, and a well matched heads/intake/valvetrain/exhaust/vehicle setup.

You have guys out there talking about freaking rod ratios and then not focusing on the importance of a quality/high stall torque converter with that big cam.

 

[273]

Bleeding edge racing engines (pro stock, F1, NASCAR, etc)

Don't think you got to go that far, bet any local circle track Chev that's doing well is cheating with 6" rods. But yes we live in a world with abundant of cheap inefficient power so for average dude it's fine don't mean his engine wouldn't be better if the engine was more finely tune, stroke, rod, bore, ports, cam etc..


But couldn't there be a reason people seem to gravitate more to stroking a 400/440 to a 451/470/500 over 528-543 even though kits are same price?

Even though I agree the average guy build doesn't need to worry about it, but we live in a dodge world so if you build any non stroker /6 (except the 225), A, LA, B, RB, 170-440 + 451/470 you got good bore/stroke/rod ratios you got to go out of your way to build a poor one.

 

[273]

Rod to stroke ratio is not that critical according to the magazine tests years ago between a stock SBC 350, a 383 using the 400 rods and a 383 with the 350 rods.
According to David Vizard, a 0.5" rod change in a high compression ProStock engine makes minimal difference in power. He states low compression engines are affected more, but not a lot. This agrees with the magazine article.
Now if you are building a max petformance engine and you have the bank to support the learning curve, go for it. For most street builfs worrying over this is immaterial.

Were the combo's highly tuned for each rod? Cam heads etc..

It's hard to do an apples to apples comparison, Eg.. Mainly what were talking about 318/340/360 vs there 4" stroke version, but what is an apples to apples comparison between a 365 vs 408?

Since both should be built with slightly different parts (cam, ports, Intake, exhaust to gears and stall) for whatever build level were talking about, and if one is better than the other (always make more power) you can't even build to the same power and compare. What are good comparable test between a 365 and 408?

But I get why people build 408s you can build 450-550 hp at street friendly ish rpms with little more than a credit card and a catalogue and don't have to run deep gears and high stall to get satisfactory results and it's light and small.

But If you flexible on the small part any 383/400/413/426 would fit the bill and could even add a 3.915 to any of these and keep good S/R/B ratios and run heads that don't strangle them.

 

[Mean416]

...It's hard to do an apples to apples comparison, Eg.. Mainly what were talking about 318/340/360 vs there 4" stroke version, but what is an apples to apples comparison between a 365 vs 408?...

Exactly. And that's why nobody outside of competitive racing teams are doing that. It's too much time and money and effort to do that, when that same time money and effort could be applied to big picture things.

 

[Dale Davies]

Were the combo's highly tuned for each rod? Cam heads etc..

It's hard to do an apples to apples comparison, Eg.. Mainly what were talking about 318/340/360 vs there 4" stroke version, but what is an apples to apples comparison between a 365 vs 408?

Since both should be built with slightly different parts (cam, ports, Intake, exhaust to gears and stall) for whatever build level were talking about, and if one is better than the other (always make more power) you can't even build to the same power and compare. What are good comparable test between a 365 and 408?

But I get why people build 408s you can build 450-550 hp at street friendly ish rpms with little more than a credit card and a catalogue and don't have to run deep gears and high stall to get satisfactory results and it's light and small.

But If you flexible on the small part any 383/400/413/426 would fit the bill and could even add a 3.915 to any of these and keep good S/R/B ratios and run heads that don't strangle them.

The magazine started by pondering the cheap way to a 383 SBC, which involved using the 400 rods and either the 400 crank with the mains ground down or a 3.75" stroker crank.
As a baseline they dynoed the 350. Then they changed the crank and rods. Pistons to keep the compression the same, but used the 350 cam.
After dynoing that combination, they got pistons to work with the 5.7 rods. Again the cam was the 350 cam. Dynoed again.
Then they tried one or two cams to compensate for the increased displacement but kind of followed the 350 tune.
This test was intended to show how the different parts function in a budget street build, not race oriented.
That was pretty much before stroker kits with crank, rods, pistons and rings were readily available in choices of strokes and rod length. Now if you turn a bearing, especially a rod bearing, it is just as inexpensive to get a stroker kit with all the reciprocating parts that match. With that you still have to consider heads, valves, the port flows and camshaft. That is determined by the bank account and how serious you are prepared to get.
Now regarding the converter stall; if a fairly stock camshaft is chosen, the requirement for high stall is reduced. Again, how serious do you want to get.
For a good street engine a stroker crank in the mid stroke range, a cam speced for the added displacement, port matching and pocket porting with probably a bit larger intake valves, should provide a snappy street driver. If you want a more race oriented engine and car, throw the bank account at it.

 

[273]

Exactly. And that's why nobody outside of competitive racing teams are doing that. It's too much time and money and effort to do that, when that same time money and effort could be applied to big picture things.

I generally get and agree with your main point, but your skating around the fact that 99% of the mopar engines are already built with great S/R/B ratios you got to go out of your way to build a poor one. Mainly being the 408 practically all of the stroker B/RB engines have better B/S/R ratios then a 408 and a lot can be built in ideal range. Even a 543 has slightly better B/S/R ratios than a 4" 6.123 small block. So it's mainly a paid choice to build it out of your mopar engine.

But in the end of the day most seem happy with that choice.

 

[Dale Davies]

I generally get and agree with your main point, but your skating around the fact that 99% of the mopar engines are already built with great S/R/B ratios you got to go out of your way to build a poor one. Mainly being the 408 practically all of the stroker B/RB engines have better B/S/R ratios then a 408 and a lot can be built in ideal range. Even a 543 has slightly better B/S/R ratios than a 4" 6.123 small block. So it's mainly a paid choice to build it out of your mopar engine.

But in the end of the day most seem happy with that choice.

The bottom line is that whatever floats their boat is good. After all it is their dime, so as long as they are happy with the result.
Considering the OP asked if building a stroked 318 was better than a 340 or 360, we should keep our focus in that direction. Big blocks are their own kettle of fish. Fit and weight are concerns there.
As to the stroked 318 vs 340 or 360, I figure build what you have if it is sound. Then we could get into the numbers match pot, where a stroker can sneak in, in disguise as it were.

 

[273]

The magazine started by pondering the cheap way to a 383 SBC, which involved using the 400 rods and either the 400 crank with the mains ground down or a 3.75" stroker crank.
As a baseline they dynoed the 350. Then they changed the crank and rods. Pistons to keep the compression the same, but used the 350 cam.
After dynoing that combination, they got pistons to work with the 5.7 rods. Again the cam was the 350 cam. Dynoed again.
Then they tried one or two cams to compensate for the increased displacement but kind of followed the 350 tune.
This test was intended to show how the different parts function in a budget street build, not race oriented.
That was pretty much before stroker kits with crank, rods, pistons and rings were readily available in choices of strokes and rod length. Now if you turn a bearing, especially a rod bearing, it is just as inexpensive to get a stroker kit with all the reciprocating parts that match. With that you still have to consider heads, valves, the port flows and camshaft. That is determined by the bank account and how serious you are prepared to get.
Now regarding the converter stall; if a fairly stock camshaft is chosen, the requirement for high stall is reduced. Again, how serious do you want to get.
For a good street engine a stroker crank in the mid stroke range, a cam speced for the added displacement, port matching and pocket porting with probably a bit larger intake valves, should provide a snappy street driver. If you want a more race oriented engine and car, throw the bank account at it.

I get it and got the magazine, and already have stated cheap inefficient power is in abundance, but were not Chev you have to pay money to build this out of your mopar instead of in.
But yes money spent on better top end is gonna give more in return than worrying about rod length. You literally just have to not build a 408 (4"/6.123") and some of the stroker big blocks to avoid this but a least with the stroker big blocks your generally getting displacements we don't already have can't say that with a 408. Not saying don't build a 408 but technically you'd probably be better off starting a 400.

 

[273]

The bottom line is that whatever floats their boat is good. After all it is their dime, so as long as they are happy with the result.
Considering the OP asked if building a stroked 318 was better than a 340 or 360, we should keep our focus in that direction. Big blocks are their own kettle of fish. Fit and weight are concerns there.
As to the stroked 318 vs 340 or 360, I figure build what you have if it is sound. Then we could get into the numbers match pot, where a stroker can sneak in, in disguise as it were.

As it concerns to this post, really is worth build a 390 over 365, is spending $$$ for 25 cid over worth it especially getting a worse bore size along with a even poorer b/s/r ratio. I don't think it is, to me it 318 vs 360 vs 408.
Does that mean the OP can't build a killer 390 no but to me it makes the least sense.

 

[Mean416]

To be totally honest I'm more and more just considering selling off the old power train stuff and building either a modern swap ie gen 3 hemi or just getting a newer ride that's already fast. I'm tired of just spinning wrenches and spending way too much money.

 

[toolmanmike]

As it concerns to this post, really is worth build a 390 over 365, is spending $$$ for 25 cid over worth it especially getting a worse bore size along with a even poorer b/s/r ratio. I don't think it is, to me it 318 vs 360 vs 408.
Does that mean the OP can't build a killer 390 no but to me it makes the least sense.

Yep, it's what you have and what you want to build. Why do people build slants or 273's. Because they can. I likevthe idea of a 390. It's an underdog. Everybody builds 408's. 415's not as much because of availability.

 

[Mean416]

I'm building a 340 based 418. But I damn well know it's going to be flow limited. It's all good though.

 

[273]

Yep, it's what you have and what you want to build. Why do people build slants or 273's. Because they can. I likevthe idea of a 390. It's an underdog. Everybody builds 408's. 415's not as much because of availability.

As long as it makes sense to the person building it, as long the goal realistically somewhat achievable and know the generally pros and cons I'm down with whatever people want to build, if OP decided on a blown 500 hp 2.2l kewl lets do it

 

[toolmanmike]

As long as it makes sense to the person building it, as long the goal realistically somewhat achievable and know the generally pros and cons I'm down with whatever people want to build, if OP decided on a blown 500 hp 2.2l kewl lets do it

I'm with ya. "Why did you build a 383. You should have built a 440!" It never ends. 512's aren't big enough but Hemi's are unobtainable. The Gen 3's are the new kid in town. Here's your 1000 horse but you better build the car to make it work. Way too many cars overpowered on the street.

 

[273]

To be totally honest I'm more and more just considering selling off the old power train stuff and building either a modern swap ie gen 3 hemi or just getting a newer ride that's already fast. I'm tired of just spinning wrenches and spending way too much money.

I almost bought a C5 Vette when shopping for my Valiant, for it general all around street performance/handling, it would take a lot for my Valiant to be on par especially after few mods to the Vette.

 

[70coupe]

I almost bought a C5 Vette when shopping for my Valiant, for it general all around street performance/handling, it would take a lot for my Valiant to be on par especially after few mods to the Vette.

Let's face it, anything over 350 - 400hp is disproportionate to the handling of the car anyway.

 

[Mean416]

I've thought about getting a GTO or a g8 and just modding one of those. GTOs are pretty cool as drag cars.

 

[Newbomb Turk]

I'm building a 340 based 418. But I damn well know it's going to be flow limited. It's all good though.

Then why use a 4 inch crank? You know you are air flow limited. And you gave up some rod/stroke ratio. Both are backwards.

You would make more power (the math is so easy to prove this I’m going to assume you know it) by a bunch, use less cam timing to do it if you used a 3.79 crank and a 6.250 rod.

You had to buy a crank right? You had to buy rods (or should have) right? So the only up charge is for pistons and I’m pretty sure a 4 inch stroke piston and a 6.250 rod will bolt right in. So really no need for a cushion piston is you don’t mind 1/16 inch piston rings.

So…6.123/4 is 1.5308. You better have a cylinder head with a HUGE cross section to feed it.

6.250/3.79 is 1.6491, which is a full point higher rod ratio. That’s pretty big. And it helps with small cross section intake ports.

Thats just one way geometry affects engine building. You can’t say it doesn’t matter. Unless it doesn’t matter to you for whatever reason. Still doesn’t mean it doesn’t matter.

 

[Mean416]

Because. Up until the flow limit of the heads it will make more torque everywhere than a smaller stroke engine. It will result in a faster car albeit with similar peak numbers to a smaller stroke engine. "The math" is so simple, I don't have to do it.

Wheras... that different rod ratio, probably indistinguishable by every relevant metric.

Dude, I know the theory. There was a time when I was thinking the same stuff. I was like, man with the right long rod engine, with fancy coatings, super high end machining, perfect ring seal, a vacuum pump, etc etc...i can make a TON more power!

But theres just no real evidence out there to support this. You saying it does, doesn't make it so.

You know what I would do nowadays, to make real power? Stick a turbo in it and be done. F*&$ the little BS.

 

[migsBIG]

love the info and ideas on this build. have some updated info:
A friend of mine needed a stock 318 for a driver. I'm going to give him one of my engines. The same friend has a contact with a 360 engine I can get for nearly noting and has speed parts on it. Decided to use the 360 block, pan and use all new parts in it. The remaining 360 parts are going on the other 318 and see how much power we can build with. Supposably the 360 has been sitting in a garage with big valves and a unknown cam swap. When I get it, I'll post it and pics here, along with the build info.

 

[DionR]

love the info and ideas on this build. have some updated info:
A friend of mine needed a stock 318 for a driver. I'm going to give him one of my engines. The same friend has a contact with a 360 engine I can get for nearly noting and has speed parts on it. Decided to use the 360 block, pan and use all new parts in it. The remaining 360 parts are going on the other 318 and see how much power we can build with. Supposably the 360 has been sitting in a garage with big valves and a unknown cam swap. When I get it, I'll post it and pics here, along with the build info.

In what way does this add drama and turmoil to the thread?? Isn't that what this is about now?

 

[Newbomb Turk]

Because. Up until the flow limit of the heads it will make more torque everywhere than a smaller stroke engine. It will result in a faster car albeit with similar peak numbers to a smaller stroke engine. "The math" is so simple, I don't have to do it.

Wheras... that different rod ratio, probably indistinguishable by every relevant metric.

Dude, I know the theory. There was a time when I was thinking the same stuff. I was like, man with the right long rod engine, with fancy coatings, super high end machining, perfect ring seal, a vacuum pump, etc etc...i can make a TON more power!

But theres just no real evidence out there to support this. You saying it does, doesn't make it so.

You know what I would do nowadays, to make real power? Stick a turbo in it and be done. F*&$ the little BS.

Thanks. You just made my point. You chose what you did because of what YOU wanted. And the geometry DID matter.


Now own it Like you said you would. You used a longer stroke (and lost R/S ratio at the same time) because of what would CHANGE if you used a shorter stroke (and consequently higher R/S ratio). So yes, geometry matters.

It just took all this bullshit for you to argue around to get to the point I knew you would.

Own it. Geometry matters.

 

[Mean416]

Thanks. You just made my point. You chose what you did because of what YOU wanted. And the geometry DID matter.


Now own it Like you said you would. You used a longer stroke (and lost R/S ratio at the same time) because of what would CHANGE if you used a shorter stroke (and consequently higher R/S ratio). So yes, geometry matters.

It just took all this bullshit for you to argue around to get to the point I knew you would.

Own it. Geometry matters.

Dude you're not making any sense.

I never said geometry doesn't matter. Don't put words in my mouth.

I simply don't think it matters nearly as much as you. There's plenty of dyno results out there showing effects of the big things. Head flow, displacement, cam changes, forced induction, etc etc.

There's nothing out there you can point to to support your arguments. Not one iota of data.

Not. A. Single. Test.

Honestly this is boring me now.

Peace, I'm out.

 

[dirty white boy]

Dude you're not making any sense.

I never said geometry doesn't matter. Don't put words in my mouth.

I simply don't think it matters nearly as much as you. There's plenty of dyno results out there showing effects of the big things. Head flow, displacement, cam changes, forced induction, etc etc.

There's nothing out there you can point to to support your arguments. Not one iota of data.

Not. A. Single. Test.

Honestly this is boring me now.

Peace, I'm out.

bet your *** every engine builder with a dyno can show you the difference in a long rod engine and a short rod engine!! and there IS a difference!! not as much as some think tho'....DWB