Ok now yer talking!
Hang tuff, while we go thru this.
But I know you probably paid a lotta money to get that cam into your possession. Do yo wanna go down this new road?
>>I can tell you for sure that the 223@050 cam I had was dynomite, as to torque from idle to just about what that dyno curve looks like.
Notice the peak is about 415ftlbs@ 3700, but from 2500 to 5000 it is hovering right around over 90% of that.
Then,notice,as you can see the power is nothing to brag about at 350. But,check out how very wide the top of that curve is. From 4000 to over 6000,it is making over 90% of that 350hp.
1) POWERBAND;
That is exactly what the A998 torqueflite needs, as the splits are 56% and 65%.Meaning, that engine will want to wind out to around 6600, to drop in at 3710(56% of 6600). Notice on the graph, that you will have to extrapolate the hp-line out to 6600. There it might be making 300HP and that is what it drops into at 3710.So you can see why I questioned the 268* cam,right?;you woulda had to rev it to at least 300rpm more to achieve I nice transition, with maximum average hp for that gear.That would then be over 6800rpm.
2) STALL;
Now, pay attention to the torque line below 3000rpm.Notice how it falls 25 ftlbs from 3000 to 2500. That is not bad. But look what happens below 2500, it drops another 25ftlbs by 2250; just half as many revs. Now think about the stock TC which might have been rated as high as 2250 with the 2bbl, hi-torque cam.Suppose that very same TC only stalled at 2000 with your previous doughy-combo. Notice the torque would have fallen perhaps under 300 ft lbs. This is another 50 ft lbs! Now are you seeing why the previous combo was doughy?
Lets put it into numbers; previous torque at 2000stall about 300.New torque with 2500TC about 375! whooee! That maths out to an increase of 25%. Now a 3000TC would peg the torque at 400, which is a 33% increase over the previous sucked out combo! So by now you can see how this stuff works. So;you already own the 2500, and that will be good, cuz it works pretty good to have the stall lower than the cruise rpm, which for you will be around 2473@ 62 with 27s. Perfect!
Ok, so we know the combo can hit at least two bases, namely;off-the-line tire fryer, and comfortable cruising at under 2500.
3) JUMP;
Lets talk about hammer down at 32 mph. This will be about 3330 rpm. Check out the dyno curve at 3330;What do we see, but over 400 ftlbs! And climbing! This means,Properly tuned,your A-body will be as mean as can be! Whooee, we just hit another target!
4) FUEL ECONOMY;
Power extraction is 360+(270/2-114), less 270, =121*
That is a whole bunch, and means the engine has the
potential to get great fuel economy. We just need to put the squeeze on, during the compression cycle, to maximize the pressure during the exhaust cycle.Then we can apply that maximized pressure to the crank, and out the back door. A fourth base and now a home run!
5) What's next?Ok we saw that the engine needs to rev to maybe as high as 6600 for a run to the traps. Of course you don't have to rev it that high; that's just what the tranny wants. So, 6600 will be about 57.5 mph.Close enough? 28s will get you 2 more mph.
6) The overlap on this cam is (262+270)/2- (2x110)=46* That tells us that headers are now an option, as opposed to mandatory.
>>So to recap your combo; We have seen the potentials for it to be a tire-fryer, great at hammer-down at 32 mph, great fuel mileage, that the powerband will work with the 2.74 low gear, that the 2500TC will be good and that headers are optional.
So that brings us back to the engine.
....The IVC is 360+(262/2 -106)-262,-180,signchange =57* Wow! we can work with that.
We have seen that the engine will want to hit 6600.That it needs a very wide powerband to use that 2.74 low tranny; from 3700 to 6600. These two combine to tell us that the heads are gonna have to be the powerhouses, cuz the cam is duration limited.So yes, the big valves are a good idea, and so is a high lift, and so is proper porting for midrange, NOT just max rpm. And that just put the headers back on the table.
Now here is the saving grace. remember that 57* ICA? Well that little tiny number tells us another target. If we target 87 gas,and we can, cuz we are making plenty enough torque, we can reduce our Scr to save some machining costs.With the right pistons (KB 190/191), we can achieve some pretty amazing things. We can reshape the combustion chambers in those LA heads, to achieve a tight squish. And we can adjust the compression ratio to just about any decent number we want.
Remember how eager you were to machine the heads down. Well that would have required a matching cut to adjust the intake drop in.And a new set of pushrods, and possibly the installation of adjustable rocker gear, right?That's adding up to a lot of money.
Now 6600rpm requires some oiling mods to live there. That means the engine has to come apart, completely. So knowing that, you might as well, freshen the block, and put the proper pistons in there.Sure more money right? That AJ, he's always spending other peoples money!. Well these costs are off set by the previous savings in multiple machinings, AND the use of 87 gas! What, how does that work?
Well with the KB 190/191s you get to build in tight-squish, which will allow you to run more cylinder pressure without detonating. Your current pistons are so far down that the chamber is huge. And there is no squish in it. That leads to problems with 87 and high cylinder pressures. So, by installing the right pistons and tightening up the squish, you can run that skunk-pee and add about a half a point of compression, which will maintain the power at a slightly higher level with that tiny 262 cam, But build more torque everywhere, and save you thousands of dollars at the pump, year after year, over the life of the engine.
So Having decided on a 262* cam, And knowing that 87 will support a Dcr of about 8.2 with iron heads, It's just a matter of punching the numbers into the Wallace calculator and it spits out a Compression ratio to target. And I get 9.75 For 165psi. Now that gives us a bit of wiggle room, if your particular combo requires a bit more octane.
Next what do we need to do to achieve that 9.75? OK, assuming a bore of 4.02 and a stroke of 3.58, that makes a swept volume of 45.44 cubic inches or 744.6 cc . And to make 9.75 with that requires a total chamber volume of 85.1cc
Now we're getting somewhere! Assuming a stock LA head of about 72 cc and an .039 FellPro at 8.9cc,that means we need to adjust the KBs to hit 85.1less (72+8.9)=4.2cc badaboom!This is very doable.
Since LA heads are open chambered, you will need to fit the KBs into them to achieve the 4.2cc, and to simultaneously hit .045 to .035 quench clearance. This will take some math on the part of your machinist. Some guys on here are very concerned about the clearance volume around the top of the piston just before the upper ring, and rightly so. But in the case of open chamber heads, not much can be done about it,and I have no experience messing with it. But the point I am trying to make is that this is totally doable. And at a reasonable cost. And the pay-back is more everything; more compression, more torque, more power, cleaner running, and more mpgs; leaving, in the long-run, more money in your pocket. And when you hear it bark to life, it will be more smiles for you, more rubber on the road, and more happy motoring for you.
Almost finally, is the heads; I'm no head guy, so this is where I have to trust somebody who is. I believe the 2.02s will be a nice improvement. And once the numbers are in, THAT IS THE TIME to select a lift number for the cam, and not before! The cam lift is the final piece of the puzzle. So there is no point in porting the heads for .550 lift cuz you probably can't grind a lobe onto a 262 cam to satisfy that. So your porter will need to know what's going on.It might also be a good thing to think about a mechanical cam. It is easily possible to get a flat-tappet solid lifter design to run like it was one size bigger than a hydraulic flat tappet. So now you sacrifice nothing on the bottom, but by opening and closing the valves faster, the dwell time at wide open is increased, and those long-tube headers can start to do their job.And maybe you can tighten up the LSA, a bit more, to increase that 350hp number, without the torque penalty at 2500stall.
So if you understand my mumbo-jumbo, Your combo's effectiveness will hinge on the effectiveness of the head flow, and the cam spec. These are in symbiotic relationship. There is no point in porting much above the cam, and there is no point in selecting more cam than the head can support. So until the heads come back from the porter, you can't select a cam, and until the cam is written in stone, it would be difficult to set the compression ratio. If the headporter knows his stuff, he might be able to work his magic to suit your cam and compression ratio.
At this level of performance, I would be hunting for the fastest lobes that somebody is willing to grind for you, and I would be running 1.6 arms to make it easier on the grinder, and easier on the lobes, cuz 6600 is getting up there, and will require some pretty good springs.
So now, I have spent a lot of your money, and you are probably near tears. What you thought would have a simple solution,according to AJ, doesn't.
Well I'm not gonna tell you what to do; you have everything right here in this one monster post, to make your own mind up. You can slam a lessor engine together, and get to a pretty sweet spot. But you won't cover all the bases, hit all the targets, have the most fun, pass the most gas stations,etc, until the engine is optimized, as above.
Parting shots;
My pet peeve is those factory chambers. They are not exactly a problem for dragracers. Nor for Joe average's DD. But for us streeters they cost a lot of money to work around. What with specialty pistons, specialized machining, careful parts selection,etc; it all adds up.
By far the best is a closed chamber with a zero deck piston. This minimizes the chamber surface area, minimizes the clearance volume, sets up the tight squish,and is adjustable to a degree as to compression ratios; so if properly set-up,you can go up or down one camsize and not get into detonation issues.
I'll tell you a secret, don't tell,ok? The factory teener cam is 240/248/112IIRC. It sets the ICA to 50* (compared to your 57*) and at 8.2Scr, the Dcr comes in at 7.2/140psi. It wouldn't take much stall to make that a TireFryer, say a 2500? There would be Zero machining required, Zero pistons,zero valve gear, and zero porting. Just slide it in and go melt tires. Since it is about 3 sizes smaller than the 262, I'm guessing it would torque peak right around the stall speed of 2500,and it would be done very early.But of course the torque at 2500 would be huge.Well not huge exactly but very near to what we saw in that earlier dyno graph, say 375 ftlbs.The power peak would probably move down 600 to 800 rpm, so say 5000,and the outshift would be about 6000 for that A998. The torque would be down and so then would follow the power, and since the outshift is early, you can skip the oiling mods and the deep pan. And of course you can leave the headers on the shelf. So for a guy who just wanted a tire-fryer, reasonable fuel mileage, and a cheap engine, this would be hard to beat, lol.
>If he didn't mind 4.10s, he could be right back in the game. 62mph would be 5100ish,in second,3160 in Drive. Torque multiplication with 4.10s would be 28% more than the 3.21s. Which would be more than worth the 3 cam-size deficit, or at least close to it. The 32 mph stomp gets you 4000rpm in first, and because you are running 4.10s this will blast to redline (about 42 mph) in a heartbeat. Now the headers are back on the table!
>>So the buy-in here is a teener cam and 4.10s,Badaboom.And no more hiway motoring. That's about $700 Canadian. You get the tire-fryer, the 32 mph stomp, a two gear charge to 62 mph that can continue to 75 mph, and an incredible flat powerband,That's hard to beat.
I bet you're thinking that you could stuff that 268* back in there, with its 60* ICA. I don't think so Bruce. Now you are moving the power peak up to the top again; don't even think about it!
>>And the punchline is? I ran a stock teener with TTIs . a TQ, 4.30s,a 2800TC, and enough spring to hit 6000 no problems. That was DYNOMITE!..... T-N-T. So Ima thinking a 360 would be dynomite times..... 360/318=times 1.132plus the big-port heads,lol
Wait, I think I already preached this in a previous post;
I think done,lol
