318 combo's

LXguy said
I think that software is highly optimistic. If you take a look at some of the "real world" magazine builds they've been doing recently, it doesn't seem like they got those numbers with similar (or more radical setups).

http://www.popularhotrodding.com/enginemasters/articles/mopar/0667em_mopar_318_engine/index.html

http://www.popularhotrodding.com/tech/0901phr_mopar_318_magnum_engine/index.html

http://www.hotrod.com/howto/113_0304_318_small_block_build/index.html

http://www.moparmusclemagazine.com/techarticles/mopp_0409_318_engine_build/index.html

Last, here's a guy with some details about all of these builds and a little editorial statement at the end:

http://www.dippy.org/forum2/index.php/topic,271.0.html

"Despite all of the modifications to these engines, the torque figures for both builds were lower than that of a basically stock Dodge Magnum 5.9 (360) engine baseline dyno test done for a Mopar Muscle article (Magnum Muscle: Serious Bolt-On Power For Magnum Mills). The camshaft was the stock factory 5.9 cam used in Dodge trucks. The only modifications to the 5.9 were bolt-ons; a Mopar M1 single plane intake, a Barry Grant Mighty Demon 750 CFM carburetor and TTI headers. The 5.9 produced 345 HP at 4,600 RPM and 426 lb/ft of torque at 3,800 RPM - an average of 1,000 RPM lower than both 318 builds."

I think in a heavy car like that you're really going to want a bigger cubic inch combo. More low end torque, less RPM to get the horsepower, thus less gear to make it work.

Example: The DOHC engines out of the 99-ish Mustang Cobras make decent horsepower, but you have to wind the piss out of them to get it (and they weigh about 4000 pounds). OK at the track. Not fun at all on the street. They also have OD so low gears are no big deal to them.

I keep coming back to the idea of screwing around with the stock 318 out of my Dart, but it is only going to weigh about 3000 pounds, its not a daily driver and I come from 5.0 Land so I'm used to working with the smaller motors.

Steve

It's funny you should mention that mopar muscle build. That 318 went 410 h.p with a 280H cam,KB 176 pistons,stock rods and stock magnums.Hell,they didnt even use an air gap intake and went with an M1 single plane. Later article they tore the engine down and discovered a bad cylinder.So bad they sleeved it. Then they went to work on the magnums and ported them. They got another 41% of flow out of the exhaust side! not all needed as they only managed another 34 cfm from the intake. But this was with stock valves and simple mods like 3 angle valve job,cleaning up the bowls and guide,short side raduis etc. No major porting done. Something I could do in a long day or a lazy weekend. And 90% of the work is done to the intake side.

And here lies the secret to the magnums advantage. Very little porting required and excellent flow balance of 75 to 80%. Cant put up big flow #'s like a 340 head but you dont need to because the exhaust is working better than a 340 could ever dream about. Therefore the exhaust and intake complement each other. Not at all like an L.A head where that nasty dogleg jams everything up.

I think of ports like this; as rivers or creeks that have dams which divert or direct the flow of the water. So if you have a big initial flow/area in the first section but then it's forced into this tight twisted section guess what? It slows down and even becomes turbulent! So we change the design. Reduce the initial flow area but drastically increase the exit area by straightening it out. Also,increase the depth of the river making the shape tall and skinny. Result is the water now flows evenly and rapidly!. In fact the exit flows so well it helps pull flow from the intake and speeds things even more. As long as we dont overdo it on the exit end...

Personally I feel that while the camquest #s are optimistic,I did input realistic flow #s for the magnum port job and because of the exhaust flow,these heads favour a single pattern cam. Most dyno programs are optimistic! They are all about selling parts.

However....

Speaking from experience I also feel another 50-60 h.p is not unrealistic after porting. So if mopar muscle got a dyno proven 410 h.p with a 280H cam and a bum cylinder,is 460 h.p unrealistic? Probably not. There was lots left to do to that motor....I figure they left at least 20-30 h.p on the table with thier combo.Add in porting and a cam change,lighter rods,engine balancing and blueprinting...who knows?