CAM CHOICE.

bobzilla said:

In reply to Suprf1y :

I wish it was 2400. Sadly its 3500.

 

Did you edit the weight or am I losing it?

What is the compression ratio going to be?

with the manual and 4.10s, i think a XR274HR or XR280HR would be a ton of fun.  I calculate that you've got north of 10.5:1 compression, so the dynamic CR with a big cam won't be too bad.

**edit, it seems i chose the wrong motor when I ran thru their calculator the first time.  276 or the 282 both sound promising

i'd also do a good valve job on the heads, i've heard they need it as-cast, and make sure the springs are up to snuff.

Suprf1y said:

bobzilla said:

In reply to Suprf1y :

I wish it was 2400. Sadly its 3500.

 

Did you edit the weight or am I losing it?

Losing it. 

In reply to stylngle2003 :

Machine shop thinks I'll be closer to 9.5-9.75 to one with these pistons. 

In reply to bobzilla :

interesting.  i input 0 deck, .041" headgasket and 0 dish with a 64cc chamber, but the 0 deck is probably where I missed.  in that case, i'd stick to the smaller of the cams recommended, like the 276 you picked at the get-go :)

The cam in my '77 is a flat-tappet Howard's 231°@050, 0.470", 108LSA, 106ICL (#110961-08)

I like cams with tight lobe centers - the torque comes on strong, at the cost of some top end and some bottom end. It idles in gear at 8inHg, and is very very very driveable as a daily (in fact, it -is- my daily).

To make this cam work, I raised the compression to 10.9:1 (heavily ported 305 heads, polished chambers, 0.015" head gasket), added a 2500 stall converter, heavily doctored the Rochester (Cliff Ruggles' book), re-curved distributor, added a vacuum advance limiter, put in 3.73 gears, and added a modern high-torque gear-reduction starter (Thanks, FastEddie, for the tips on that other site!), and added colder plugs (R42T). All said, I got a best of 14.7mpg (Imperial, which is about 12mpg US).

I freaking love the idle, and it's just fine as a driver.  But I think I would go just milder on the cam. Having said that, a year or two after I got the truck on the road, I sent an email to Howard's saying I want to go roller with Vortec heads in the truck, but I wanted more mid-range torque (don't care about idle, fuel economy, or emissions), and they recommended #110265-10.  Youtube an idle of that cam, and it seems a bit snarly to me (https://www.youtube.com/watch?v=aoaz-UnqH-A).  I didn't end up buying it.

After having driven my truck for 4 years now, I -love- the idle, but I'm starting to get a bit tired of the shaking and bucking and farting of it (though it's probably because the Dynamax Super Turbo mufflers are too quiet). It -will- roast the tires if you load up the converter, or punch it from a standstill, but there isn't so much torque that you can't drive it in the snow (which I do.  Because Canada). Honestly I think I would pick something smaller, but you can get pretty aggressive ramps in a roller cam (large .050" numbers) and still keep the overall duration down which should improve power everywhere.

The V8 Firefly got a relatively mild cam (Lunati 256/262) because I didn't want the snowball effect of a large cam, but I needed a cam, and I wanted more power than the L03 305 I pulled. Haven't driven it yet.

Best advice: Contact the cam company of your choice.  Tell them exactly what you want to do with the vehicle, and what you are willing to give up. They have far more experience than we do (or so we hope - it might just be some young buck following the company's flow chart of goodness).

My two favourite companies are Howards Cams, and Lunati Cams.  They like to get to the grocery store first.

In reply to stylngle2003 :

so you're saying my WAG at the beginning might not be so bad. We'll also see what COMP says. 

Just remember cam selection rule number one:  the good cams are always at the bottom of the page.

bobzilla said:

Losing it. 

Not surprised.

That weight makes your choice seem even better. Though it's a very mild cam it does meet your power requirements and with short duration it will be easy to live with.  The small block is a very well known quantity, and your build very typical, so I'm curious to hear Comp's recommendation.

If it were me I'd probably run another 10 degrees on a small block with a 4.10 gear

Just make sure your cam is making power at your highway cruising speed, and you still have rev range to go.

AngryCorvair said:

Just remember cam selection rule number one:  the good cams are always at the bottom of the page.

I had a customer who we speced a 226 degree (at .050) cam.  For the engine displacement (not a large one), and the vehicle (not a light one), it would have been great.

A few phone calls later, we ended up putting a much, much larger cam in it, because he wanted it to sound evil at the cruise-ins.  Well, ok, whatever, it's your car.

After cars gets picked up, we get complaints.  Engine bogs horribly, carb needs tuned.  We get car back, tune it, get it running perfect.  It has 4.11 gears and a T10.  I can punch the throttle in 4th gear at 50-mph and break the tires loose with no bog.  He gets car back, car still runs awful.

Turns out, what he expected was to be able to cruise the car at 1000rpm at walking speed and nail the throttle.  No, you can't do that and you will never be able to do that, that is not going to happen with the cam you wanted us to put in it.

bobzilla said:

I'm also currently running 400+tw all seasons pumped to 50psi and not wide and fat race slicks. so the nascar comparison is a bit moot. 

They probably handle about the same at the limit, but the limit comes at ~2-3x the speed.

In reply to Knurled. : I understand a lot of people want that rough idle Lopey sound because they equate the sound with power.   While that may have been true 20-30 years ago it sure isn’t now  

None of them have listened to a recent NASCAR engine which has a fairly smooth idle  Same with formula 1 or the cars racing at LeMans.  

In reply to frenchyd :

yeah, and 58 times out of 59, that rough, lopey idle doesn't even portend great power.  My neighbor has a mid-80's GM pickup he uses as a lot truck/ back 40 bang around toy (yes, I love my neighborhood ).  The thing sounds evil as hell- but it barely idles, stalls, and only faintly chirps the tires from a get-go.  I think it may just be running on 7 cylinders.  

In reply to volvoclearinghouse :

so it's like the engine I have now. 

frenchyd said:

In reply to Knurled. : I understand a lot of people want that rough idle Lopey sound because they equate the sound with power.   While that may have been true 20-30 years ago it sure isn’t now  

None of them have listened to a recent NASCAR engine which has a fairly smooth idle  Same with formula 1 or the cars racing at LeMans.  

 

Then you mostly understand incorrectly. Most people want that rough idle because they like the sound of a rough idle. It sounds cool, and if the cam is supported by the appropriate mods it can and should be equated with power.

The fact that modern engines are capable of making good power and idle smoothly is due to a number of things, but mostly cylinder head technology allowing the use of shorter duration cams with wide lobe centers, very little of which is applicable to Bob's small block Chev motor. If he wants to make big power he's going to have to tolerate a rough idle. His choice of a mild performance cam with reasonable duration in the mid 220's on a roller profile will idle ok, but still be lopey under 1000 RPM

In reply to Suprf1y :

Correct. I'm not dealing with an LSx here. I'm dealing with late 50's technology still. 

bobzilla said:

In reply to volvoclearinghouse :

so it's like the engine I have now. 

Are you my neighbor?  ;-)

In reply to volvoclearinghouse :

I think its just all neglected SBC's. They'll run well past the point they shouldn't. 

If you want a big, fat powerband and you've got good flowing heads, run as much lift as you can take advantage of flow-wise and in a range you can still keep the valvetrain in one piece.  And with a roller cam, you can get a cam with pretty fast lift rates, allowing you to run a lot of lift without crazy duration.  

In the Jeep, I'm running these heads (scroll down the page a bit for flow numbers): http://immengines.com/indyimmironheads.html, around 9.5:1 compression, airgap intake, 1 5/8 tri-y headers and this tiny little cam with 1.7 rockers (compared to 1.6 stock, so .512" total lift at the valves): http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=659&sb=0

It pulls almost as well as stock down low, idles like a stock engine, but if you wind it up it doesn't start to fall off until you're past 5500 and even then it falls off pretty slowly.  It'll pull right to the limiter at 6100 pretty nicely without a big dropoff (nothing like the cliff that the stock setup fell off at 4800 or so).  The good heads / mild cam with lots of lift combo leads to a nice, wide powerband (but a bit less peak power than a bigger cam would give). 

In my case, with 360 cubes of displacement and the stuff listed above, I should be somewhere in the 350 - 380hp range (based on other people's dynos plus a run through engine analyzer).  Going a little bigger on the cam than what I run should get you right around 400hp at the crank given good heads (and still provide a well behaved engine).  You've got more compression, so that'll let you go a bit bigger on the cam before the low end gets soft and the idle gets too rough and should give a little more power for all other things staying equal.  

In reply to bobzilla :

A friend of mine is fond of saying that GM engines will run poorly longer than any other engine will run at all.

I  had a '77 Suburban back in college with a 350 SBC.  Drove it around for months feeling like something was a little off about it, but it would still pull 75mph up hills and so I didn't worry too much about it.  One day, I pulled the valve covers and found that one of the pushrods was bent and that valve wasn't opening at all.  And based on the mushrooming that was going on there, had been like that for quite some time.  

Man did it run great after I fixed that!

In reply to Suprf1y :

The problem is, they want the sound, but they don't appreciate that the sound is because the engine is choking on its own exhaust and is barely running, with all of the drivability issues that come from that.  Fouling plugs, no brake vacuum, need a very loose converter if automatic, can't cruise at low RPM/load if manual, and so on.  (Have a car here with a 383 Chevy and a MothrThumpr cam or whatever it is called.  Guess what?  3 inches of vacuum at 1000rpm in gear, with a 3000rpm stall converter!)

I'd love to do a V8 with a mild cam and MS3, and see if setting up a rotational idle that tapers off as you open the throttle would give the same sound...

In reply to Knurled. :

It seems modern cat-back exhausts do a pretty good job of emulating that lopey-cam idle sound with an otherwise bone-stock EFI V8. 

So, one of my best friends has a 69 mustang with a 351 Cleveland. Has the massive 4V heads, an 850 holley and a cam so large that that I've seen mountain ranges that look small sitting next to it. He is a "bottom of the last page" camshaft selection type of person and I've watched him make some collosal mistakes. I don't want that. I'm not trying to wring every last pony out of this engine. Just making a solid power band sbc that makes pretty noises to go with it.