For sure, every time is a little different. In this case I had a head that I did six months back while I was in Colorado and had no core block. So I just did a 'best guess' target of 58cc on the head, knowing that I had another chance to make it right when I was doing the block machine work (now).

To the OP just figure out what you want and head for that target.

Well I was originally aiming for a 9.5 to 10 CR... having a cast crank and wanting to keep the car streetable and on your standard 91 octane I was going to try to keep the compression ratio down to 9.5, with the parts I have picked out, I think that's doable, I may need to redo the math and pick up the dished pistons if the CR seems to be getting too high. Right now the only thing I have left to pick out is what valves to use with the 3.445 bores.

There is only one easy choice in valves - the enginebuilder ones from ebay that everyone uses. Get his springs too (basically 340 springs).

Don't guess on the CR - measure everything or you won't know.

As I've learned if you get too small of a cam and time it too retarded it will ping even with 9.5:1 CR. But with the right cam it will run fine on 91 with 10.0:1.

Most of the guys (including me) who are building motors right now are working with the same parts:
- enginebuilder 1.70/1.44 valves and 340 springs
- Wiseco 0 deck pistons
- K1 7.005 rods
- OCG cam (actually I'm going with a custom Delta because I have used them before)

Variables are the cam profile, head porting, induction, etc.

If you really do the DCR calc and correct selection and degree-in of the cam you can actually run on regular on a 10:1 engine, then if racing you can switch to higher octane...

Using a DCR calculator will help ascertain the cylinder pressure once the intake valve actually shuts...if you went with a 10:1 and say a Comp 252 or 264 the lower duration and short overlap event (the time when both valves are open)builds pressure really fast...on a computer sim like desktop dyno it looks great lots of power...the reality is when you run a DCR calc and see that the DCR is almost high-9's and 10...no matter how much timing you yard out of it, it will need race gas.... but if you pick a little larger cam (220-230 duration @ .050), it'll bleed a little cylinder pressure off on the longer overlap and you'll be back to using something economical at the pump.

My last street build ran 10.3:1 SCR, engine builder valves an springs, 4 barrel, hyperpak intake, Erson 280/270... DCR computed to 8:1...had excellent street manners, nice vacuum at idle, got 21-24 mpg depending on the tune (typically 22mpg running 87 octane total timing at 47...best of-24 mpg super and running 50 for total timing), ran 16's at the track in a heavy car.

So work up your numbers, then plug them into a dynamic compression ratio calculator and input your cam numbers, try and hold to 8 or just a little over and see what it might take for the SCR... I bet if you went with the OCG 791, request a 110 lobe separation to limit the lumpiness for street use especially if you have an automatic, you're going to look at 9.8-10.2...

-D.Idiot

I used data over on http://www.slantsix.org/forum/viewtopic ... dd93adb5e4 with what Dart270 posted on the 346 OCG to put into Dyno 2003, but I'm kinda new with the program so I'm not sure if I put everything in right, but here's what I have so far:


http://tinypic.com/r/33csldx/5

FYI,

Your carburator if a 4 barrel should be set at 1.5 Hg.

Also you need to lower the compression ratio for use with that cam, with an SCR of 10.61, and the lack of duration the dynamic CR comes out to be 8.92...which may run strictly on super(91), and/or may need some help with a gallon or two of high-test per tank.

That being said the duration Lou shows for the cams is duration at 50, and the second numbers are duration at 20 so you'll probably need to add 15 more degrees to make the duration closer to "advertised duration" to be correct.. If this is correct then the actual DCR is closer to 8.42 which will allow you to use 89 or 91 on a daily driving basis.


-D.Idiot

I called Oregon and the 346 cam has 307 (approximate) degrees at 0 lash on the intake. Because of the lash ramps the actual timing at lash will be in the 280 degree range. But that also depends on the lash you are running and the actual (not nominal) rocker ratio.

Try those numbers in your program, and also make sure that you put in the ground-in advance of 4 degrees. Many people run slant cams with the ICL at 100-102, so you could even add a couple of more degrees. That will bring the powerband down (and narrower).

They list the lash at .012/.012, most likely it will be run a little looser at .014/.016 for best effect...given that the 791 would be a 280/280, set your cam parameters at 284/278, set the ICL at 102, you will have to measure and fit if you go any more than that.

Looking at the DCR based on these numbers you are 8.54, which is still fine for daily driving and running 89...with less total timing you may be able to run 87 if needed.

Running your numbers using my dyno program with actual airflow values (I use the stock head values so the computation is conservative, the programs are set for V-8's and large valves which do not translate to /6 correctly on the program), it all still looks good and advancing the cam between 100-102 doesn't gain much on the low end (2 hp/2-3 ft/lbs), so 102 should be fine and it have a nice broad power band at 3000-5500 which should serve well passing and at the track.

-D.Idiot

Here's the cam manager I have to work with, and what numbers I have in there now. It's set to .050 timing and I entered all the numbers out of the link I provided. I can't get the overlap to the 19 @ 50 he has listed, the calculator forcibly sets that one on it's own. The only number I don't know is the ramp rate.

Sounds like I have a new toy coming... my grandad is no longer medically fit to drive... T-boned someone at about 20mph the other day in his 91 Ram and from the sounds of it, did little more than bash up the grill and some of the front body. I helped come up with the 318 that's in it, now... but I wouldn't mind cutting some wires and taking it back a few years to the 225 style from 87, hopefully it's not too hard to get a slant in a truck a couple years after it stopped being a stock option. That 318 is only 170 hp, 260 lb-ft of torque, I think I can do better than that with the slant.

1993 is the cut of for the k-member being the same as the 70's/80's trucks...

Changing the slant to a truck completely changes your build now... you will be working toward all torque to get the heavy body and brick in the wind to move...best bet is to build for about 9.5:1 SCR and use the cam motogrey used for the build.

Technically if you applied the same techniques of rebuilding and engine improvement to the 91 318 it wouldn't have a problem hauling down 250 hp and 300+ ft.lbs since you aren't dialing for emissions (the 91 should have quench heads on it giving it a leg up when you dial in compression over the open wedge heads).


-D.Idiot

I have a hard time convincing myself to take apart the 318, it's only about 50k miles young, and it's all nice an fuel injected. I have to imagine that making big changes to the cylinder size and valves would involve a lot of PITA fuel settings adjustments in the computer, unless I switched it back to a carb... too bad it's one year shy of having a Magnum, I could have just lived with the 230/280 it puts out.

I say leave the 318 alone. What an unnecessary headache if it is working great already.

_________________
Casually looking for a Clifford hyperpak intake for cheap.

Just changing from the KB239 with the 5cc valve reliefs over to the KB268 with the 18cc dish drops my SCR to 9.12 to 9.28 depending on where the pistons end up from .010 to .020 down bore. I can probably mill the head to pick up the difference.
Not sure which cam you're referring to. I saw his Dart build, which Doc suggested the Erson RV15 intake lobe with Mopar 244 exhause profile... plugged in the numbers from his link. http://www.dutra.org/pictures/engine/er ... am60bd.jpg

Ran it without the 4* advance, in fact, a 4* retard cause the power bands to peak at the same place and drop off much later into the RPM rage.

With the retard on the cam, it came out to 187hp @ 4500, 232 lb-ft @ 3500, but I don't have my air flows programmed in. If they're close, though, that really doesn't beat out the 318 yet.

You are aware that the program is hp and tq at the crank and not at the rear wheels, the trucks measurements are at the rear wheels so that's pretty close with drivetrain losses at 170/260 at the rear wheels but the smaller engine has to run at higher rpm to make up for the lack of displacement the v-8 has...

Those numbers are too high to be useable in a truck anyway, you are looking at the value down low since you aren't going to be peaking above a certain rpm on the highway... peak at no more than 3000 rpm. You won't be able to use a peaky high duration cam as it will make the truck lazy on the low side and work great in 2nd gear on the highway.... You'll probably have to run a 3.91 rear gear...There will be a push over point in price where the 318 and it's displacement will trump the $2500 slant six long rod build, you can get more power out of it running the 600 cfm carb but the mileage is going to go down fast as well (this is where a blown application would get the most of power you are needing to haul the 4-5000 lb brick around.

Another issue to cover is: Do you have an adapter plate to mate the /6 to the LA bellhousing?

-D.Idiot