318 head options ... again!!

[nm9stheham]

All the comments favoring flow refer to quarter mile times and speeds.......all emphasize mid to top end power for best drag strip times. Makes sense.

Ummmm..... when you take a 318 2bbl, and add small 4bbl, 340 cam, better flowing heads, the 60 foot times drop as well as the 1/4 mile times...

No doubt it helps.... but to make a complete analysis, one would need to how much better would the 60 second times be with higher compression too. So your using an incomplete way to analyze what are the positive/negative effects of one factor vs another. And, like I said, this is all referenced to drag strip times; there is much more to overall engine performance than that.

I am just saying common street use experience (lower RPM's, short burst of acceleration, etc.) favors compression..... and it makes sense, and you can get better torque and not kill gas mileage if you pick the cam right. This shows up in other racing venues (like road race or rally) as faster overall speeds. So it all goes back (for me) as what the OP really wants to do with this engine.

 

[scott2683]

Thanks everyone for helping me out here, after reading here, I'm not sure if I chose the right cam, or if I should use the 308 heads ... lol.

I don't want the car to go 120MPH, I'd like to have some low end grunt ... and that's where torque comes in as well.

 

[nm9stheham]

Magnum probably would be your best option better CR and flow.

Yep, they are made that way for a reason! Now if we could just find some $100 magnum heads! I credit the 1500-5700 flat torque feel of my '09 Challenger R/T 5.7L partly due to modern head design.

I am looking at a low buck 318 build and considering using the early 318 heads with the smaller valve for street use; hopefully that data of a nominal 60 cc chamber size for the 273/318 heads is right; that will keep up static compression. I might put in 1.88 intakes to help the flow but no more than that. A decent valve job and some port clean up will be done. It'll emphasize compression and quench ( I WOULD spend some $$ on the pistons to achieve this), using a torque cam (less duration than the OP plans), 600 cfm vacuum secondary carb, headers, not sure on the intake yet, and not expecting the RPM's to go much past 5000-5500. With spirited driving in the local mountains, winding it out past that is not useful to speed so I don't care about high extended RPM's; short bursts of the best possible torque in the 1500-5000 rpm range are what will work best for that application. (This is based on 30 years of rally racing, where the same performance profile is emphasized, and a super breathing, high RPM drag type engine with narrower RPM percentage hurts your speed.) Gas mileage and in-town driveability will also tend to be better than with a high RPM super breather with big cam, ports, etc.

And, I HAVE built a bigger valved/ported, but small cammed/carbed engine before, WITH good compression and quench, and it did run to higher RPM's. It ran strong 1500-6500, a VERY wide RPM range, but did not sacrifice the low end at all; I credit that aspect to the smaller carb and torque cam and the 10.3 SCR. But I only got into the 5500-6500 rpm range rarely in street racing or just to make myself feel good; it was not used in daily driving or hard mountain driving. So, again, we're back to the intended use and what will work best for that.

 

[318willrun]

if you want very mild, stock converter, and tall (highway) gears, and still want low end grunt, get a 360. Cheapest way. 360 magnums that run great can be had for 300-500 dollars, pending on miles. LA 360's can be had for about 300 bucks that run good. Love a 318, just sayin......

 

[Infecteddog]

Yep, they are made that way for a reason! Now if we could just find some $100 magnum heads! I credit the 1500-5700 flat torque feel of my '09 Challenger R/T 5.7L partly due to modern head design.

I am looking at a low buck 318 build and considering using the early 318 heads with the smaller valve for street use; hopefully that data of a nominal 60 cc chamber size for the 273/318 heads is right; that will keep up static compression. I might put in 1.88 intakes to help the flow but no more than that. A decent valve job and some port clean up will be done. It'll emphasize compression and quench ( I WOULD spend some $$ on the pistons to achieve this), using a torque cam (less duration than the OP plans), 600 cfm vacuum secondary carb, headers, not sure on the intake yet, and not expecting the RPM's to go much past 5000-5500. With spirited driving in the local mountains, winding it out past that is not useful to speed so I don't care about high extended RPM's; short bursts of the best possible torque in the 1500-5000 rpm range are what will work best for that application. (This is based on 30 years of rally racing, where the same performance profile is emphasized, and a super breathing, high RPM drag type engine with narrower RPM percentage hurts your speed.) Gas mileage and in-town driveability will also tend to be better than with a high RPM super breather with big cam, ports, etc.

And, I HAVE built a bigger valved/ported, but small cammed/carbed engine before, WITH good compression and quench, and it did run to higher RPM's. It ran strong 1500-6500, a VERY wide RPM range, but did not sacrifice the low end at all; I credit that aspect to the smaller carb and torque cam and the 10.3 SCR. But I only got into the 5500-6500 rpm range rarely in street racing or just to make myself feel good; it was not used in daily driving or hard mountain driving. So, again, we're back to the intended use and what will work best for that.

That's going against the way they're designing the newer motors. More intake flow, more port (it's not only larger but different), more exhaust flow, intermediate valve size falling between small and large 360 intakes and larger than 360 exhausts, larger cams, more intake air flow, and larger injectors. (basically more compression, more air, more fuel, more cam)

It's all balanced out well in better applications through the use of overdrive transmissions and relatively steep rear gears. You don't pick between sub-13s or over 140, you get both.

To me, it seems like shooting for over 10:1 with iron heads and a small cam simply isn't a good idea. Not only that, very few cams short of a 340 cam really provide much to write home about- and a 340 cam's not radical.

if you want very mild, stock converter, and tall (highway) gears, and still want low end grunt, get a 360. Cheapest way. 360 magnums that run great can be had for 300-500 dollars, pending on miles. LA 360's can be had for about 300 bucks that run good. Love a 318, just sayin......

Basically that. A 318 Magnum's also a weighty improvement over a near-stock LA 318. Unless it's gonna be a racecar...