I don't believe a 360 with a 273 top end would make more low end power than a 360 with a 360 top end.
Engine is pulled - 273 rebuild or replacement 360 crate?
- Thread starter brodphish
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MOPAROFFICIAL
If it has tits, it's a liabilititty.
I don't believe in Santa Claus but nonetheless there are still gifts under the tree LOL
This 360, with 360 heads, with 2.02 valves, made 414 ft lbs. We don't have side by side graphs to compare but I'd bet the kitchen sink this engine makes more power off idle than the same engine with 273 heads.
Only thing 273 heads have going for them vs 360 open chambers is more compression.
Modifying And Testing A Dodge 360-Cube LA Small-Block On The Dyno
Only thing 273 heads have going for them vs 360 open chambers is more compression.
Modifying And Testing A Dodge 360-Cube LA Small-Block On The Dyno
MOPAROFFICIAL
If it has tits, it's a liabilititty.
I think you completely missed the context in my reply. At the time the op was exploring what parts he may use or could use from his older engine and a newer block and then it was being bounced around maybe to use a 360 but at that point , I believe the first page.. nothing was determined or settled and I was literally throwing an idea out there in the context that he was going to try and recycle some of the parts to save money. I have done it, it does work well in an idle to 4500rpm range, just like a 650 holley does compared to a 750. Everyone can play with toys however they like.
Good video BTW. The 360 has always been a sleeping giant imo. Heads n induction were always the gatekeeper to awakening them. I don't know if there is a video or not on worked small port head vs stock 1.88 360 heads on a 360 but its been done and I would only entertain the idea if its a near stock or very special circumstance type of build... or even out of just playing around. Its fun to make half *** designed junk into something surprising.
Thanks for clarifying. Agreed, if it's a situation where a guy is "using what he has laying around" then by all means, get it going any way you can.
I just start to take issue if people frame it as *these old 302 heads are awesome " because in reality, compared to just about anything else, they suck. I'm only against the spread of old misinformation.
Think... mission impossible 318 build. How many poor teenagers and 20 something's, just getting into the hobby, will absolutely try to copy that work, fully believing they're gonna set the world ablaze? Only to be disappointed when their car is a total dog ...
I agree, Richard Holdener done a bunch of head shootouts of various port volumes and hasn't found Low End Torque (Power) changes much, but possible that throttle response does, I feel people confuse driveability with a lack of torque which for various reasons don't make sense to me.
MopaR&D
Nerd Member
IMO the small-port-heads on bigger engines benefits torque only below about 2500 RPM which is the lower limit for most engine dynos which is why it never shows in dyno tests. In practical applications that's only really beneficial with low TC stall, tall gears, and/or heavy vehicles. Think trucks or C-bodies with stock drivetrains.
Yet, that 2-3000 rpm range is where most of our old cars spend driving around town and cruising down the highway. I like looking at dyno sheets and seeing how much power they make in the normal operating ranges. It's all good they produce maximum power at 5500+ rpm but how often are you there and stay there. (some of you guys do, I do not) That's why the mildly built big cube engines start making sense for street cruisers where the owners are looking for more usable power.
MopaR&D
Nerd Member
This is true but that's all light-throttle, by the time you're past about 1/2-throttle on anything that isn't big and heavy with tall gears and a sub-2000 RPM converter the engine is above 2500 RPM and the increased torque from larger-port heads gives better overall acceleration.
Under light throttle cruising head flow doesn't matter since the throttle itself is the main restriction especially if the intake manifold and camshaft are matched right for the application.
It isn't until you get into extremes like giant W-2-size intake ports where throttle response gets lazy and with old-school engines they're always combined with big single-plane intakes and a big cam. Ever hear of someone running those style heads with a mild dual plane and mild cam? I'm willing to bet if it was done that way the response and torque in the 2-3000 range would still be pretty good. But then it would be a waste of the head's potential...
MOPAROFFICIAL
If it has tits, it's a liabilititty.
302 Ford.
Great example.. short stroke and small high velocity ports.. if they were big 351 ports it would be gutless till 4000 rpm.. like the 302 boss.
Are we leaving them in the 60.. are we passing them half track or necking them out at the line. Where are we driving to begin with, city streets? Combos and application matters. Some are good for this...others are good for that. Port volume does what again? Think.
This isn't the thread for debating this and there are more ways to argue this than most could keep up with.
Great example.. short stroke and small high velocity ports.. if they were big 351 ports it would be gutless till 4000 rpm.. like the 302 boss.
Are we leaving them in the 60.. are we passing them half track or necking them out at the line. Where are we driving to begin with, city streets? Combos and application matters. Some are good for this...others are good for that. Port volume does what again? Think.
This isn't the thread for debating this and there are more ways to argue this than most could keep up with.
If you go with pipe max recommend average port velocities (fps list below) 260-300 average fps = Very good HP & TQ, if you put that into port sizes, eg.. would be around 250 cfm = 162 - 187cc, 300 cfm = 194 - 224cc that's a fairly big window and that's for very good, add in the windows for good and ok fps, the port cc windows are even larger for any given cfm.
So your very unlikely to have enough port size to put you into slow 225 fps or very slow 210 fps eg 250 cfm = 216 - 232cc thar's a lot of port for 250 cfm.
So your very unlikely to have enough port size to put you into slow 225 fps or very slow 210 fps eg 250 cfm = 216 - 232cc thar's a lot of port for 250 cfm.
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way you hear tell around these parts is that everybody and their mom is out there twisting 'em up to 6K all over, all the time.
*rolls eyes*
*makes wanking motion*
^^^ this. 1000% this.
MOPAROFFICIAL
If it has tits, it's a liabilititty.
What flows 250 cfm that 162cc w/o modifying the port? Nothing.
We aren't talking ootb.
If a head that flows 250 cfm and it's in the 162cc - 187cc range then it's average fps should be in the 260-300 fps range. Which according to the FPS list should make for a Very good HP & TQ combo.
Point was that's a fairly wide port volume window and most 250 cfm heads are gonna fall in there and you would need crazy big port to have a slow to very slow port for a 250 cfm head which would be around a 216cc - 232cc port volume for 210 - 225 fps.
Basically it takes a lot more port volume then a lot thinks it does to have low average velocity.
250 cfm was just an example, same thing applies for any heads usable peak cfm, point was the how much the port size could very and still have acceptable average fps.
TT5.9mag
Two atmospheres are better than one
Wow this thread is off the rails for a simple small block 400hp build. Hey OP get a junkyard magnum 360, stick a 230/.500 cam in it, an rpm air gap, a 750 carb and a set of headers.
Whatever you do, don’t do this……
Whatever you do, don’t do this……
That’s a disaster waiting to happen. Not only is all the work on the 360 crank to make it fit ridiculous, but a 318 at 4.060 will have paper thin cylinder walls that’ll move around more than Shakira and it’ll eat water faster than you can shut the key off.
Someone has been reading too many magazines.
MOPAROFFICIAL
If it has tits, it's a liabilititty.
Every factory Chrysler cylinder head with the exception of the max wedge stuff had way smaller ports than ideal, because they were passenger cars obviously ..but point made
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