Well you sly dog you! What a great parts store house!
Do you have any clue as to the actual scale weight of the Travco?, not GVW
Do you know what rear gears are currently in it?
What does your hi-top scale at?, the one with the peppy 5.9. And what gears are in it?
I cannot speak to BigBlocks, never having had one.
Hit refresh as I'm adding as I go, cuz my computer has a tendency to freeze, and when it does, I loose the drafts.
OOPs. I see
So let's correct that to 33s and I get the 3.55s =3.29s, which represents a loss of performance of 7.3%, so the Travco, to remain on par with the same engine, would need 3.55s plus 7.3% = 3.81s
and the proof is;
with 3.55s and 30.6s , 70=2730 in direct locked up.
Whereas the 33 with 3.81s will do 70@2717 in Direct locked-up
By the math.
So lets start the want-list;
>must burn cheap gas
>Must get great fuel mileage
>Must have 3.81s or better rear gears. or somehow be at least as peppy as the hi-top.
> top cruising speed of say 75mph
>must be quiet in the cab
> no to the 2-speed rear axle
> yes to the A518 w loc-up
> 214/224 Comp roller, I need to know the rest of this story, advertised and LSA. I went to the Comp site but there is no navigating that new screw-up at least not for me.
> budget, budget, budget
operating elevation of about 1000 ft
So far it's kindof looking like a no-brainer to be the 408 bottom end. You already have all/most of the parts, and the A518 is a bolt-on. And you have a great selection of heads. The compression ratio of that combo is pretty easy to dial in. But that cam is pointing me in the wrong direction. Knowing a bit about Comps strategy, Ima guessing that is a 268/276/112+4 cam, which is a great power maker in a streeter.But if I'm right about the advertised specs, then the long exhaust duration steals power extraction and makes it a bit of a gas-hog, and there is nothing much you can do about it. In at 108, the power-extraction is only 106*. At that number, a lot of the energy in the expanding gasses is gonna go out the tailpipe. And because of that, the headers are gonna tug real hard on the intake during overlap, pulling mixture straight across the piston, and sending it out the pipes, not what you want. So lemmee know if I'm right or wrong about the Comp's advertised specs.
If it was my engine, for this combo, I would install a solid roller, because they have about the fastest flanks going, and I can get the advertised I need without sacrificing the power you want.
Then I can adjust the Scr to get the pressure I plan to run with at least something in your parts arsenal.
Here's my thinking; With a solid, suppose you could get an after-lash spec of 262/266/110+1 Your compression degrees would be 123 and the Ica would be ~57*. But here's the good news, your power extraction jumps to 116* with 44* of effective overlap.
But since it's a solid lifter cam, the .050 could be as high as 223/227 that's a great big winner right there. Don't care about the lift, this is not a race car.
Now, with 44* of Effective overlap, this engine will want a minimum cruising rpm of about 2200. That's a triple win! Now comes the hard part, getting the pressure down to stay out of detonation.
For iron heads
The Wallace likes 9.5 for 160psi@1000 ft and Ica of 57*. This is about perfect for IRON heads and midgrade gas at WOT with a tight-Q. The VP is predicted to be 162, which is spot on to get 6000pounds rolling with the crappy rear cruiser gear, that it's gonna take to cruise at 2200, with 33s; I get 3.08s for direct, 4.47s for overdrive. Hey that ain't so bad!
Ok but with alloy heads, you can jump the Scr up to 10.5 for pressure of 182, and I burn 87E10 right there, but the exciting part is that the VP has risen to an incredible 184. to This is gonna take a special induction system, and timing management, to soften the low-rpm hit so you can actually drive the thing. But running steady-state at 70 =2200 with 4.47 gears and 33" tires, with a VP of 184, the throttle will be barely open. Couple that with the 116* of power extraction, and modest 44* of overlap, I see a real fuel sipper.
And the best news of all; is that the cam is still a 223/227/110 @.050 so when you drop it into Second, at 55mph=3630/zero-slip, say 4200@15%slip, to pass some old granny, and the Rpm starts marching uphill, she will hit 5500 with ease doing 75mph @10% slip, still in Second gear,lol. Now, into overdrive and loc-up; 75 =2360, well past the minimum 2200.
I Like it.
So remember, that VP of 184 is gonna take some specialty work, in first gear, to not give your wife whiplash, every time your ankle bobbles. So now, lets soften the hit with stall;
Your starter gear is 2.45 x4.47 x 26.5/33=8.81 as compared to a 26.5" tire. That is an excellent number.
Lets say your stall is 2200, and this 408 has the potential to make 400 ftlbs there. At zero mph she has the WOT potential to plant
400 x8.81 x1.8TC multiplier =6340 footpounds, which I normalized to a 26.5" tire, so I can understand this. This might as well be a million ftlbs , because it is so huge. For normal take off, you might need 2500 to 3000, so your engine has like double of what you need , to burn rubber, if it was in a 3600pound Barracuda.
Now as soon as this rig begins to move, the multiplier in the TC will begin it's steady march towards it's minimum. Lets say in first gear from start to end, the multiplier averages 1.3. And lets say the 408 averages 440 ftlbs at WOT, over the useable rpm band, the new math is
440 x2.45 x4.47 x1.3=6264, and normalized to a 26.5 tire is 5030. This is really hard for me to fathom. Obviously, the 408 is only gonna need about 3000 of those at the best of times so, say 60% throttle (just guessing).
Ok let's get into second, with the Rs now at 3000rpm, and lets say the 408 is down to 415 ftlbs, then
415 x1.45 x4.47 x1.2 multiplier x26.5/33=2600ftlbs.. This is now coming into line with what the chassis needs , and as the rpm rises, power is still increasing, perfect.
Ok 5000 in second will be 63 mph, and into third the Rs will drop to 3450, so you have plenty of part Throttle torque there to climb the last 7 mph, easy peasy.
In fact, you have a preponderance of low-rpm torque in this scenario And I cannot help but wonder how you will be able to affect smooth power delivery with a single throttle body .
Ima thinking the 2000/2200 factory stall TC is out. Ima thinking you need a lil mushiness down there, say a 2600TC, so you can accelerate on the non-locked up part. If you get to 3200TC then VP don't count for nothing any more until everything gets locked up again at cruise rpm. Well hang on, is that bad? Not if you have a loc-up TC.
Another method is to retard the timing in first gear. And another is to run two or more staged throttle bodies. And another is to engineer an inverse proportional throttle activation mechanism, that opens the throttle very slowly in the first half of pedal travel, where you will be doing most of your accelerating, and then it speeds up to synchronicity at WOT. Yeah I like that last one . Now of course with a 2800TC you will need the lock up available at any time from second gear on, for fuel savings . With electric shift, that is no problem. There are several ways to engineer that.
For the coolest of cool, how about a gutted Thermoquad as a throttle-body, or any spread bore really, and a soft throttle stop for those testy take-offs. Hmmmm so many problems, lol, with too much VP. 184 is huge with a stroker.
My 367 has had a best of ~172, and I thought that was crazy.This 172VP netted tirespin at 50 plus mph, in 6.82 roadgear with 26.5 tires, from just a footstomp. And no help from a TC cuz mine is a manual trans.
184 is HUGE.
I would try it if I was you, cuz if it really is too much, you have enough parts to back up the bus.
However; recall that the iron numbers were pretty good as well with 162VP predicted at 9.5 scr@1000ft elevation. 162 and Iron is exceptionally good. If you ran that with a higher stall TC, to kill the effects of VP at take-off, and a loc-up to recover it at cruising, that would bring the iron heads into their own. Hmmmmm, decisions decisions.
I tell you what; how about backing off the Scr a bit with alloys say 10/1 Scr
Yeah, that will do it. Pressure predicted to be 171psi, down in the kerosene range for alloys, and VP predicted to run 173. Hey, that's a pretty good compromise! You can run any old stall-speed with that and tuning will be much easier. I like it. Well duh, I already ran 172,lol.
Ok this entire study is done on a solid-lifter cam with an Ica of 57degrees. With the new lower Scr numbers, you could easily put that on a hydraulic, and give up say 20 hp at 5000. Yur only gonna need those 20 once in a long long time .
Jus saying
Ok so to recap;
408 with alloy heads running 10.0 Scr and an Ica of 57 degrees to generate 173 psi at 1000 ft elevation.
My picks;
>You will need a timing computer.
>Headers yes, to make some power at higher rpms.
>You won't need the Keg; run it if you want to, but I'd leave on the shelf.
>If going EFI; run a single plain with a gutted big 4bbl.
>If carby'd; I'd stick a spreadbore hi-rise dual-plane on it with a spreadbore. >Fresh cold air absolutely yes.
>Run a minimum coolant temp of 180 to start but creeping up to 200 over time as you learn to trust your 7-blade mechanical fan on a thermostatic clutch.
>Run a stand alone trans cooler, to make it easy on your cooling system.
>Because of the length of your chassis, run the biggest pipes you can fit from headers to mufflers and at least 2.25s after that. Run long free-flowing 3 pass mufflers, 3 in/3 out and swedged down after the muffs. The big pipes have the advantage of running cooler, so the gasses condense and occupy less space, making it easier for the headers to do their magic. That's AJs Opinion. I hang mine down into the wind. But, then again, with the solid cam offering 116* of power extraction, a good dozen more than usual, your exhaust gasses may already be cool, relatively speaking. Yeah ok, run anything with the cam as described. But if you go to a wider LSA hydro, well you might want to come back to this ..
>I would run the loc-up on a relay triggered by a momentary-on sw, and grounded at a hobbs Vacuum sw to kick it out as the vacuum drops.
>The trans is gonna have to be beefed up a lil to put up with the abuse you are gonna dish out when you see how good this combo runs.
>You need to inspect your chassis. I suspect it is nothing more than a lightweight ladder-frame, and if/when you start pounding torque into it, it better not twist up and shred your fiberglass,lol. I'm no chassis guy so yur on your own there. Ima thinking outriggers,lol.
>Make sure your windows are secured, cuz when that 408 starts flexing, it might not be the only thing doing the flexing,lol.
Ok I'm just getting silly, I must be hungry,
Ok here is the last addition; I'm speaking from as you said; " What would AJ do". I invite anyone in who cares to shred me, cuz I wouldn't want to spend your money in the wrong places. Com'on boys , letRrip.
