thanks for all the help on the heads, there at the machine shop getting tanked and magnafluxed before i start on them. i decided that you guys were right about the guides and that how i'm gonna do them.

now i need to think about the cam, the motor is going to be a 350, ported 416's, perf. rpm manifold, 600 or 750cfm carb(whichever is needed), shorty headers, 3.73 gears, and the correct stall for the cam.

sorry, it can't be a roller, but i'm ok with a solid flat tappet.
i was looking at these two comps:
XS268
and
XS274

i'm not really familiar how these will act compared to a hydraulic and would like some input on what kind of cams you guys would run,

i do know that the xe268 is very mild in the 327 and that i could stand to go a fair bit larger.

Thanks!

 

el drool drool!

Be sure you have the heads machined for guide plates. You'll want to use collared rocker studs, such that they have a nice flat top, since you'll want to use poly locks, rather than "stovers" for the rocker nuts - if you're going to use a solid cam. Long trail of "if you...then you should...which means you should..." but that's my thought on that, first off.

Also, a stud girdle apparently helps you keep your solid cam settings longer.
I'd also recommend you install a starter bump button, underhood, to make re-adjustments faster.

ok, enough of that rigamarole - IMHO the xs268 is probably your best bet. Ported 416's can flow alright, but don't get carried away thinking they're the end all, so I wouldn't kill off your low end.

One thing to note, the advertised duration of these, and the duration @.050" are similar to the hydraulics, and you can see how they extend the duration @.050", while keeping the advertised the same- sounds like the perk of the solid cam right?

but wait, the advertised is measured at .015" tappet lift, not the .006" that hydraulics are. This means the advertised duration on that solid is higher. Be careful, tricky to compare straight across.

 

i noticed the adv. duration was at a different lift, i wonder what the duration is at similar lifts, it would be nice if they would compare them at similar lifts . i saw that the ramps are a lot more aggressive on the solids.

the heads are getting the full treatment(after i'm done porting, just in case i find water)

thats the cam i was heavily considering, i was thinking something around a 2200 stall would match that cam well.

i know dd2000 is not to be trusted but it predicts something like 380hp, 440tq with that cam, with a very good curve.

i'm going to try to go to the track one more time this year just to see what i can get out of this motor before i yank it out.

 

I'd go higher on the stall speed. I'm no expert, but my gut says thats a tad low.

haha, yea, and i'm making 375HP on DD, I don't trust it one bit.

 

You can't really compare solids to hydraulics, because of the way the specs are produced, and what they actually represent.

Cam duration specs are given onthe basis of lobe lifts; which in the case of a hydraulic, ends up mostly being translated to the valve. A typical hydraulic system loses maybe .005" or so of lobe lift in seating the valve, and then all lobe lift from there out, is "effective". A solid, on the other hand, has however much lash, at the valve, that has to be taken up, such as .020" at the valve or whatever; with 1.5 rockers, that .020" at the valve, = about .013" at the lobe, meaning the lobe has to move .013" before the rocker even touches the valve stemp tip. So out of the first .050" of lobe ramp, about .045" of the hydraulic is doing something to the valve, but only about .035" of the solid is.

Meaning, if you take 2 cams with the same .050" duration "spec", one hydraulic and one solid, the solid will be a considerably "smaller" cam because the valve begins moving later and returns to the seat earlier.

Meaning in turn, that to get equivalent effective duration at the valve (the only place it really matters.... on account of the engine doesn't respond to lobe profiles, it responds to valve action), you have to run a "bigger" solid, in terms of just the "specs" on paper. There's no "formula" or "calculation" you can do to evaluate it, but the difference usually amounts to about one "step" in a typical cam mfr's product line.

But at the same time, solids almost always have MUCH more aggressive ramps than hydraulics; which further complicates the issue of "equivalence". Generally, you can get any given level of high-RPM performance out of a solid with less of the "big cam" penalties (low vacuum, soggy bottom end, etc.), because the valves open farther faster, and spend less time dithering around near the seat.

Bottom line therefore is, the XS274 will give you about the same idle vacuum and so on, as the XE268 hyd; but will run considerably harder in the midrange and on up to higher RPMs. It will also tend to require more valve spring, to control the more vigorous valve motion.

With an auto trans and that low-numbered stock gear, and the small low-torque motor, I wouldn't go past the XS274. Any more than that, and you'll enjoy one of those cars that takes off like a bat outta hell at 4000 RPM, but takes about 5 seconds to get going to that point. I.e., will have no "leave" whatsoever, unless you put in ALOT of converter. You'll want it to be a small diameter one, so that it's really really loose below its stall speed, but couples hard above it; as opposed to a large-dia one, which will end up never really coupling tightly at any RPM. Which will make the car street-hostile but will partly make up for the lack of CID, at the strip.

 

Incidentally, 440 ft-lbs is PURE FANTASY LAND for that combo; even if it's a tiny narrow peak. I'd be VERY SURPRISED if any 327 that can run on pump gas (low enough CR) would make more than 400 ft-lbs, no matter what the rest of the combo is. 380 HP is not unrealistic however.

DD2000 is not to be trusted for its raw, absolute numbers. That is, don't fall for the hallucination of "it says 440 ft-lbs, that's what I'm going to get". Rather, use it to evaluate CHANGES to your combo; i.e. "if I use this cam, I get 5% less peak torque but 4% more HP but at a 4% higher RPM... is that what I want?" and the like. Don't worry what the "number" it gives you is, only what it does as you vary the inputs.

 

Ya know, that's what I was thinking in the beginning, but after reading that the advertised specs were measured differently, I thought differently. More along the lines of "if the advertised is similar, but measured at .020" rather than .006, it'll have a MUCH LARGER duration!" However, yea, I guess if the valve isn't open, then it's not actually giving the valve lift.
Thanks!

grumble grumble, still kicking myself that I didn't get an XS274

 

thank you, i'll be using a 350 this time, no need to go slower for the same amount of money. i made that mistake before.

i don't have dd on this computer but the 274 showed about 20 more hp at almost the same rpm, but a much softer torque curve.

the xs268 showd 20 more hp and 20 more tq than the xe268.

i have to wait till later to get the real numbers.

 

back home now, the xs274 loses around 20tq at 2000rpm but peaks only 2-3 lower than the xs268. it makes 20 more hp at the same rpm, but the 268 will make the same hp retarded 4 deg..

i guess a better question to ask is which cam would you run? with what kind of converter?(not just limited to these 2)

 

Add up the torque values for every incremental RPM that it gives you, over a reasonable range of usefulness; say, 3000-6200 RPM. Pick a REALISTIC RPM range; not "idle - 7000 RPM". So if it gives you torque values every 200 RPM, add up the values at 3000, 3200, 3400, etc. up to 6200 RPM, for each cam. Estimate the trap RPM that the car will run. I'd expect 6200 is plenty, since that's somewhere around 110-115 mph in one of these cars; with that stockish gear, it'll never see any more than that, so there's no point in building it to turn more than that, if it'll never turn more than that in the first place.

Whichever cam gives you a higher sum, will win the race. Assuming of course, the right converter, traction, and so on.

As far as whether one will have "enough" vacuum, sound "good enough", have "enough" bottom end torque, get "good enough" gas mileage, etc. etc. etc., you're pretty much on your own. Although, if the one has only 75% as much torque at 1500 RPM as the other, you can be sure that it will qualify as a "slug", comparatively speaking. Only you can be the judge of how important that is.

 

i think i'm going to order the 268, it has a better torque curve for the street and if i decide it's too tame up top i can retard it 4 deg. and it should run pretty close to the 274(<.5 avg. tq difference, 3000-6500 interval)

thanks for your help!

what do you think this would run?(assuming traction and converter) 100+ traps and mid 13's would be nice...

 

make sure you get a timing set that allows easy change of advance (most do, I used the comp set for $32, over the summit one that was $31...)
Also, a 2 piece timing chain cover!!!!!!!!! (get enough exclamation points in there? it's pretty crucial).

I think you'll hit your goal.

 

i already have a cloyes double roller, it has +4 and -4 slots.