One thing leads to another... mean 318?

[rumblefish360]

This is true mostly due to there excellent cylinder head.
Chevy is also not so worried about valve shrouding it seems.

Which makes me think a 318 may actually do really well with a ported Edelbrock head.

 

[RustyRatRod]

figure an .125 over bore equals the same amount of horsepower as an increase of 1"of stroke.

I don't think that's a reasonable comparison. I believe a 1" stroke would far out power an 1/8" over bore. In a 440, for example, you're talking about going from a 3.75 to a 4.75 stroke. That's 557 cubic inches.

By contrast, a .125" over bore on that same 440 is only 465 cubic inches. See the difference?

 

[rumblefish360]

And hence my question to him!

 

[pishta]

Im aware of piston speeds and side loading and am not in the camp of high revving strokers. Also would like to see the notches in the 3.91 bore cylinders to clear the rod nuts. I had to nip my 4.00 bores to clear the stock rods on a 4.00 stroke crank...Iirc the cap bolts are smaller on an aftermarket forged rod. There is a point bore size wise where a 4" stroker crank is not going to fit, 318 is probably not one of them but a 273?

 

[273]

When It comes to power there really no reason not do the 318, it can take all the same parts as its to bigger siblings, the slightly smaller bores will have some effect, after an over boring it's really not that far off from a 4 bore.
With same cranks theres only like 20 cid difference give or take between them. Even at stock displacement, theres tons of strong 5.0l out there.

It all comes down to your requirements and level of compromises, If you build an engine to X power and stall and gear it etc.. to best performance and driveablity is a distance thought then it don't matter what size you build, but if you tied to a certain gear ratio eg. 2.76, 2.94, 3.23, 3.55 etc.. Higher gears are gonna be closer optimised to larger displacement, and larger displacements will allow you to get away with larger cams "more power' for any given gear ratio. Which is no problem for some cause they don't care about max performance for a given gear ratio and HP level, and more about building a decent so called under dog /6, 273, 318.

If your willing to gear it build it if not build a larger displacement.
Or take solace in your compromises.

 

[273]

its a comparison, Doc.
so for the way critical that tend to over think things, an .04 over bore equals the same amount of horsepower as an increase of .32 of stroke.

How does stroke increase HP ??

Bore only can increase hp cause it allows more air flow, nothing to do with increased displacement.

 

[AJ/FormS]

How does stroke increase HP ?

I'm not following you.....
I know there's a secret in your question; but I'm just not seeing it.

What would happen if you took all the 340 stuff and slapped it onto a 360, at same as 340 cylinder pressure?

Or how about a 383Magnum with a 440 crank?

or a 318 with a 4" arm

 

[273]

I'm not following you.....
I know there's a secret in your question; but I'm just not seeing it.

What would happen if you took all the 340 stuff and slapped it onto a 360, at same as 340 cylinder pressure?

Or how about a 383Magnum with a 440 crank?

or a 318 with a 4" arm

Would a identical built 340/360 have the same cylinder pressure ??

and if they did stock bore, 4.04" vs 4", the 340 piston would have more surface area so it would have more force driving the piston down, if both where stroked to give each the same displacement the 4.04" bore would have slightly less stroke multiplying the slightly higher force, which should theoretically equal out. But since they don't have same displacements 340 vs 360 and at similar VE% the 360 will have less force on the piston but have lot more multiplying "stroke" on that force, ie.. more displacement more torque. Not cause of stroke cause of overall displacement. But that is obviously just torque, so yes an increase of stroke on any given bore is gonna increase displacement ie.. torque but keeping everything else equal is gonna decrease powerband rpm, which should put you at similar hp output.

So how does stroke in it's self increase hp ?

 

[rumblefish360]

How does stroke increase HP ??

Bore only can increase hp cause it allows more air flow, nothing to do with increased displacement.

The larger the stroke over the OE stroke, the larger the displacement. The longer stroke takes in more air and fuel. Thus increasing the explosiveness within the cylinder. This creates more torque and HP.

Therefore, your statement of “Bore only increases HP” is false. Increasing ether will increase displacement and torque to equal HP.

Where you come up with these crazy *** things, IDK!

 

[273]

The larger the stroke over the OE stroke, the larger the displacement. The longer stroke takes in more air and fuel. Thus increasing the explosiveness within the cylinder. This creates more torque and HP.

Therefore, your statement of “Bore only increases HP” is false. Increasing ether will increase displacement and torque to equal HP.

Where you come up with these crazy *** things, IDK!

For your theory to be true the engine with the increased stroke you have make peak power at a similar rpm as the non stroked engine eg... 360 vs 408.

Say for my 360 create engine is suppose to dyno around 400 hp at 5400 rpm, if stroked it to a 402 keeping everything else the same.

It would have peak hp at a lower rpm?
How much lower 400-600 rpms lower ?
more/less ?

If say it's around 4835 rpm peak hp for the 408 both would have the same cid to rpm would be proportional for both engines and both would have similar power give or take the exact effect on those combos.

Not saying it would play out where power is always gonna be identical. True stroke is gonna add displacement there for each power stroke is gonna have more fuel and air there for more torque, But torque is just basically a snap shot of that power stroke, hp is all those power strokes added up. And we all know more displacement with the same top end is gonna mean less rpms, in general but not all cases depending on the combos and situation the rpm loss is gonna be somewhat proportional to displacement differences. Equalling out Hp, some are gonna have a bit of a gain some a loss and some a tie, but I bet that has more to do with cam timing and head ports effect on bore and stroke and rod ratios and frictional hp loss or gain.

 

[273]

Where you come up with these crazy *** things, IDK!

I always seem to see things from a different prospective then most on all subjects lol

 

[rumblefish360]

I await the day you out your theory into practice.

 

[pishta]

I'm not following you.....
I know there's a secret in your question; but I'm just not seeing it.

What would happen if you took all the 340 stuff and slapped it onto a 360, at same as 340 cylinder pressure?

Or how about a 383Magnum with a 440 crank?

or a 318 with a 4" arm

or....What would happen if you slap all the 273-4 stuff onto a 318? same crank, more bore. More torque, close to same HP even with decreased compression ratio becasue it uses the same head. Power at lower RPM too..
273ci thoughts?

 

[rumblefish360]

Raise the compression because it needs a rebuild.

 

[Wyrmrider]

lets say that the same head makes the same max torque no matter the size of the motor
it flows the same amount of air just at a different rpm
now bore makes a difference and so does friction
but that 1 inch stroker is going to max the head at a much lower rpm and for a lot wider powerband
the short stroke engine with a cam to ax the head may want a reailer to take it to the strip
we ran the amc with under 2 3/4 stroke to 3 3/4 305 to 427 inches
lots of chevies from 3" to 4 1/4 302 to 452 cu inches Crower ran a 200 ish Indy motor
sbm from 302 to 422
same heads
I know which one i'd want to drive on the street and which on the track

 

[RustyRatRod]

I always seem to see things from a different prospective then most on all subjects lol

This time, your perspective is incorrect.

 

[rumblefish360]

This time, your perspective is incorrect.

But he is convinced and his mind is closed to actually finding out anything new or in this case, correct.

Hey Bobby, my wife the RN just got a new coffee mug!
It says, “I can’t fix stupid but I can sedate it!”

 

[RustyRatRod]

But he is convinced and his mind is closed to actually finding out anything new or in this case, correct.

Hey Bobby, my wife the RN just got a new coffee mug!
It says, “I can’t fix stupid but I can sedate it!”

That's a goodun. lol

 

[273]

But he is convinced and his mind is closed to actually finding out anything new or in this case, correct.

Hey Bobby, my wife the RN just got a new coffee mug!
It says, “I can’t fix stupid but I can sedate it!”

For someone to change his mind on a subject, the other has to make a compelling or at least any argument, you yet to do either, not like you have to, but there's no reason to change my mind cause no one has said anything resembling a point.
And name calling what are you Five, I'm suppose to change my mind cause you don't agree, there is others on here do, talking with you is pointless, like you accuse me of, your mind seems made up.

 

[RustyRatRod]

For someone to change his mind on a subject, the other has to make a compelling or at least any argument, you yet to do either, not like you have to, but there's no reason to change my mind cause no one has said anything resembling a point.
And name calling what are you Five, I'm suppose to change my mind cause you don't agree, there is others on here do, talking with you is pointless, like you accuse me of, your mind seems made up.

Think about this. Find someone to arm wrestle with. Make sure it's someone in equal shape and of about the same strength as you. However, make sure that persons forearm is at least 1" longer than yours. You're not going to win. It's called leverage. That's the main reason above all others right there a longer stroke makes more power. Yes, it is a combination of things, but the longer stroke has more leverage for the pistons and rods to push against, so it's easier for the engine to produce more torque. If that doesn't convince you, you're in the wrong hobby.

 

[273]

Think about this. Find someone to arm wrestle with. Make sure it's someone in equal shape and of about the same strength as you. However, make sure that persons forearm is at least 1" longer than yours. You're not going to win. It's called leverage. That's the main reason above all others right there a longer stroke makes more power. Yes, it is a combination of things, but the longer stroke has more leverage for the pistons and rods to push against, so it's easier for the engine to produce more torque. If that doesn't convince you, you're in the wrong hobby.

I get that and have said exactly that multiple times so far and agree with what you have just said besides the condescending end part. Yes adding stroke or any means of displacement is gonna increase torque to a given combination.

But here's where i seem to differ from you guys, "RPM" to me rpm is on par with Torque, and yes adding displacement is gonna add torque but it's gonna come at the cost of RPM.

So more torque by adding displacement and lowering rpm powerband doesn't necessarily mean more power "hp". Is this last statement wrong ?
This has been my whole point.

 

[RustyRatRod]

I get that and have said exactly that multiple times so far and agree with what you have just said besides the condescending end part. Yes adding stroke or any means of displacement is gonna increase torque to a given combination.

But here's where i seem to differ from you guys, "RPM" to me rpm is on par with Torque, and yes adding displacement is gonna add torque but it's gonna come at the cost of RPM.

So more torque by adding displacement and lower rpm powerband doesn't necessarily mean more power "hp". Is this last statement wrong ?
This has been my whole point.

I didn't mean it in a condescending tone. I meant it to be funny. No, it doesn't come in at the COST of RPM. That's the wrong way to look at it. the torque comes in at a LOWER RPM which makes the longer stroke engine DIFFERENT. Better in some aspects and not in others. It all depends on what you're doing with said car. Some cars need high revving engines. Some do not. Just like everything else, it's all dependent on the usage.

Yes, I believe your last statement to be incorrect, all other things being equal, the 1" longer stroke will TRUMP (2020) the bigger bore every time as far as an engine to engine comparison.

Now, as far as a TOTAL PACKAGE comparison, the shorter stroke engine could certainly win out, simply because once again, it's all TOTAL PACKAGE DEPENDENT.

 

[273]

I didn't mean it in a condescending tone. I meant it to be funny. No, it doesn't come in at the COST of RPM. That's the wrong way to look at it. the torque comes in at a LOWER RPM which makes the longer stroke engine DIFFERENT. Better in some aspects and not in others. It all depends on what you're doing with said car. Some cars need high revving engines. Some do not. Just like everything else, it's all dependent on the usage.

Yes, I believe your last statement to be incorrect, all other things being equal, the 1" longer stroke will TRUMP (2020) the bigger bore every time as far as an engine to engine comparison.

Now, as far as a TOTAL PACKAGE comparison, the shorter stroke engine could certainly win out, simply because once again, it's all TOTAL PACKAGE DEPENDENT.

I appreciate It was in humour
But for the rest I'm guessing well have to agree that we disagree.
I think we're seeing the same point from different angles.

 

[yellow rose]

I was going to stay out of this but...273 is 100% correct. Horsepower IS airflow and piston area and RPM. Horsepower is work across time. The same cylinder pressure on a longer stroke crank doesn’t make more horsepower. But the same cylinder pressure on a bigger bore makes more horsepower. Every time.

That’s why in CID/weight cars and classes with a maximum displacement rule (Pro Stock for example or ASScar when Chrysler got back into it could run a larger bore and shorter stroke and wax GM’s *** all day long so ASScar made a max bore rule of 4.185 for the GM garbage to compete...remember this was with a 358 CID rule...which means Chrysler used a bigger bore, shorter stroke and more RPM which is all more horsepower) you see the bores as big as you can get them and them adjust the stroke and rod ratio for RPM, induction, port cross section etc.

When I get home I’ll take a picture of the Bettes book where he clearly states this. Any cursory visit through a rule book or most any time on the dyno proves this out clearly.

That’s why even a 3.79 stroke is even a bit much for W2 heads, especially considering how much you give up in rod ratio (yes, it matters). A Stroker with a 4 inch arm (or longer) is vastly under headed, which is why you see inverted torque and horsepower numbers. So to get the horsepower number over the torque number you either have to cam the hell out of or reduce the stroke.

So...I said all that to say that stroke doesn’t increase horsepower. It can’t. Not with the same induction. When it counts, RPM is King. RPM is a horrible task master, but it’s still King. Ask Roy Johnson. He will tell you it is. He will also tell you that the RPM limit killed the Hemi in Pro Stock. The GM guys were 500 RPM or more behind, and they cried like babies to get the rule changed, claiming cost savings. It’s Pro Stock, not cheap assed Stock.

 

[66fs]

I bought my duster last year with longer term plans to build a 408 for it. I was going to live with the 318 It came with (Not original to the car) but I didn’t know anything about the engine. So I dig in a bit check the timing chain, pretty sloppy. No worries, pull the heads to check them out, looks like some porting has been done to 360 open chamber heads with 1.95 intake valves. Cc’d the chambers 63 cc not too bad, they’ve been milled. Found out I have a Crower 224/224 cam, but one cam bearing looked a little suspect. Check pistons 0.106 in the hole means low compression about 7.8:1 pistons are 0.030 oversized. Well I’m in this far might as well go deeper.... pull engine, tear it down. Crank has had journals machined 0.010. Mains looked okay, rod bearings down to copper and a couple have some more significant scratches not sure if they will polish out or if it needs to be ground. Cylinders look alright but if I want more compression with kb167’s which travel higher up the cylinder we will need some machine work. So I took it to the machine shop today. We will see if 0.040 will work on the overbore of if I have to go more.
I’ll wait to see what they say about the cylinders and crank and pricing...I also have to consider the rods which have now been in and out a few times and reusing the rod bolts might not be a good idea if I plan on running the motor hard and this isn’t going to be A grocery getter. So with the time and or cost of pressing on and off the pistons, Buying and replacing rod bolts,, resizing I may be better off just buying Aftermarket rods such as eagle which cuts labour down, but adds to the amount of machining needed to bring crank back to balance as aftermarket rods are lighter then factory.
So what started off as a look see may have turned into a full rebuild... but I may be leaning towards building a mean 318... we will see.

Coming late to the party, and have not read many replies. 63cc ported 360 heads on a 318 sounds like a pretty good start, as soon as you get decent pistons. I'd also look into a custom cam or talk to a cam grinder with what you have, or will have, and your desires for the car. Intake and carb?

I think we need to start a thread on the relation of engine size and configuration to power. That way we can hash all this out, once and for all.