Advice on this little cam wanted. - Team Camaro Tech
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post #1 of 27 (permalink) Old May 7th, 04, 05:47 PM Thread Starter
 
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Please comment on a solid cam like this for my about 9.75 to 1 CR., 283 motor with no more then a Holley 600 on a Performer along with a set of cheap four tube, long 1.625" headers.

Heads will be -601's with 1.60" exhaust valves and cut down about .030" to get me up to the compression I want using the .015" shims and stock, four notch, cast flat-tops..

250/260 advertised duration, 104/104, and say maybe .450" lift, (after lashed), with 1.6 ratio rockers??

I'm looking for comments on the 104/104 thing vs a more normal, 110/106 or 108/106???

pdq67



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post #2 of 27 (permalink) Old May 7th, 04, 06:24 PM
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I don't think a 283 would like that cam one bit. That is a typical high grunt cam for 8.0 to 8.5-1 267's and 305's in high geared/heavy vehicles. I think it would ping like crazy and have no power above 4K rpms. Look at the crane compu-cams...they have several just like this with ridiculously tight lsa's to make those little smog motors stronger on the low end.
In my limited experience with 283's, they like a wide lsa and a small duration. My 1st 283 was in a '64 el camino. It was a bone stock 2bbl 195hp engine with duals and glasspacks. It came stock with the old 300hp gm cam and 9.25-1 compression. For its size, it pulled great from idle to 6K (I accidentally pegged my 8K tach once ) and sounded pretty nice. It had a 3 speed stick and either 3.31's or 3.55's in it. When I was driving back and forth to Dallas from Durant, OK, I had to run at 4K on the highway to keep up with traffic...and it still got 22mpg. I later installed a performer intake, 600 holley, and a 268 high energy cam. It sounded awesome, but totally lost all torque under 3K, and lost a bunch of fuel economy. I think you would want something like a performer type cam...or even the good ol' 097 you always talk about.

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post #3 of 27 (permalink) Old May 7th, 04, 06:31 PM
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Now that I think about it, I bet another cam that would work great would be the gm L-69 305HO cam. It is something like 202/206, .403/.415, on a 115 lsa. Chevy used them in 9.5-1 305's on pump gas and they run pretty darn good...especially when you take all the smog stuff off of them. If you look at any of David Vizards books, he always says that the longer the stroke, the tighter the lsa you want. Working that the other way, a short stroke should want a wide lsa.

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post #4 of 27 (permalink) Old May 7th, 04, 06:59 PM Thread Starter
 
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Why then does D2K say it has almost a flat torque curve from 2 to 5 grand??

2000 = 341
2500 = 349
3000 = 355
3500 = 360
4000 = 362
4500 = 358
5000 = 335

And hp peaks at 356/357 at 6000 and 6500rpm. And at 8,000rpm, D2K say's it's still making 300hp!!

Seems it should be a dandy cam??

And I dearly love the old -097 but this time I want to max. lowend and midrange grunt so am looking for the highest and flatest torque curve I can find which this little bugger seems to make.. And being a solid it will still be able to rpm way up there...

pdq67

PS., and I know it's just D2K too... And Looking back, I honestly think my junk 301 had about 10.5 CR. or so due to the small heads and half domed pistons..



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post #5 of 27 (permalink) Old May 7th, 04, 08:07 PM
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I think DD2000 is being WAY optimistic on that torque curve. I mean, 341#'s of torque at 2000rpms out of a 283? I don't think so. And it probably would do ok with a bunch less compression, but that tight 104 lsa is going to build a ton of cylinder pressure with 9.75-1 compression, even in a little 283.
It sounds like you are trying to do something with a 283 that is going to be next to impossible, which is cool, but I honestly don't think you'll be happy with it. That tight of an lsa is going to fall off the power curve HARD, and with the small duration it is going to happen early. What kind of .050 durations are you looking at? I'll run it thru EA3.0, which to me is a lot more believable.

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post #6 of 27 (permalink) Old May 7th, 04, 08:57 PM
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Ok...I made some guestimations on your engine. Stock b/s 283, 9.75-1 compression, stock 305 heads with 1.84/1.60 valves, a aggressive 250/260 (seat timing) solid with .459/.457 net lift (assuming .020/.022 lash and 1.6 rockers), performer intake, 600 carb, 1 5/8" headers, and a 1000cfm exhaust. Like you said, it does make a very flat torque curve...from 2000-4500, then it falls flat on its face. Torque peaks at 3K and drops from there. Hp peaks at 5K and also falls off a cliff. It also predicts that it will have 230+ psi cranking compression (race gas territory with iron heads), and I usually find that it predicts about 10psi low. It also predicts that the engine will be quite inefficient. Power peaked at [email protected], torque peaked at 292 [email protected]
Then, I "swapped" cams to a 097 with 1.6's. It did make less torque under 3500, but then took off and blew the 1st cam away. It predicted 40 more hp at peak, and peaked at 5500 where it was making about 53 more hp than the 1st cam. Torque peaked at [email protected], hp was [email protected] Cranking compression was 181psi...doable on pump gas if you are a sharp tuner.
Next, I used a standard -929 gm hydraulic with 1.6's. This was interesting. It made only 10#'s less torque at 2000, even at 2500, and kept increasing to a peak of [email protected] rpms...making more torque than the 1st solid at everything above 3K. Hp peaked at [email protected], with a gradual dropoff to 5500, then it too nosed over. This cam beat the 1st solid handily, but cranking compression is still too high at 204psi.
Next, I used a performer type hydraulic with 1.6's. Compared to the 250/260 solid, this cam was down about 30#'s at 2000, even at 3200, and pulled away from there on up. Same with the hp, with a peak of [email protected] Still too high at 197psi.
Comp 270s w/1.6's...blew the 250/260 away at anything over 3200, and gained 50+hp at the peak. Still too high on the cranking compression.
I also ran the L69 cam with 1.6's. There was a slight torque loss at 2000 (about 15#'s), about equal at 3K, and pulled away from there, gaining about 35hp at the peak. 190psi.

Take these with a grain of salt, but the program seems to agree with me...cranking compression is going to be insane with the small cam and very tight lsa. A -929 with 1.6's seems to be about the best compromise here, but the compression is still a bit too high.

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post #7 of 27 (permalink) Old May 8th, 04, 02:07 AM
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Intersting idea Paul. I agree with Travis about the power band on the 250/260 cam . . .

The only thing though -- why do we think the Comp 270s would build too much cylinder pressure? Pat Kelley's DCR calculator predicts a 7.95:1 DCR. That should make roughly 180 psi cranking pressure. Just about perfect?

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post #8 of 27 (permalink) Old May 8th, 04, 02:39 AM
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That kind of threw me off too. For an iron head small inch motor, I would have thought the 270s would have been a good match for something in the neighborhood of 9.75-1. I do know that with the XE268 in my truck, and 9.4-1, it makes either 7.78 or 7.88 DCR (I can't remember exactly)...and it cranks a solid 180psi. EA3.0 predicted 170 for my combo. Based on other known engine combo's the cranking compression numbers seem to be pretty accurate. Besides, if you think about it, that cam is [email protected] lashes at .020 (or is it .022). The cam is going to be actually smaller than its rated seat timing becuase of the way comp rates them. I still haven't figured that one out yet.

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post #9 of 27 (permalink) Old May 8th, 04, 05:40 AM Thread Starter
 
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Question

I see where you guy's are coming from and I remember driving my Mom's new '65 el-cheapo, 300 four door Chevelle, three on the tree, 195hp/283.

I put a cheap tach on it and the little -929 cam would go above 6500 before valve float after I lashed her a schosh early Sat. afternoon to go play that evening.

I dearly loved my junk 301 with the -097 but want something that comes on earlier b/c it was a real dog coming out of the hole with my 3.31's but once "up on the pipe" ran like Jack, the Bear!!!

After it's all said and done, didn't Pat K. figure that the -097 solid was more a 270 cam then the usual 287 I always read it was in my Wolverine Blue Racer cat.?? And it sure isn't what GM said it is when rated more modern......... And it is 110.5/108 too?????

Maybe the L-69 cam in a solid with more lift would be a dandy?? But comparing it to the old -097 at 228/230 vs 202/206 sure seems that there is one heck of a jump???

I like Harold's three smallest original UD solids I saved for historical stuff but am really torn between high rpm and low to medium grunt like my big motor to make it explosive off the line even with 3.31's. (If a little motor can be made explosive??)

Anybody have any real old spec's on small cams b/c it seems to me, they would fit in great now b/c they were made low lift, but wide LCA and lazy timing or are the computer cams about the closest I'm going to get like Compu-cam and the 256 and 262 Isky Supercams but on 112 LCA's??

I really want a solid cam b/c I will rpm her when I get the urge just like I did my junk 301!!

If I don't plane the heads, I should be right at 9.31 CR. per Ross's compression ratio calculator and using -4 cc valve notches. I just figured 9.75 CR. would be ideal for the small chambers and gas nowadays along with a decent really small solid torque cam???

Why would this combination differ all that much from the high compression, flat-top piston, small chambered motors people say we can run on 87 octane gas??

Please offer more comments.

Thanks.

pdq67



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post #10 of 27 (permalink) Old May 8th, 04, 11:07 AM
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I don't think it would differ from your average "high compression, flat-top piston, small chambered motors people say we can run on 87 octane gas"

The only difference IMO is that it is scaled down a little. Scaling a good combo down works!!!! This is exactly what we did with my friends 327 !! We took my 383 combo with 11:1, and a 294s and modeled his 327 to fit.

We just used the 282s (straight out of my 383 BTW) and ran 10.3:1 compression. It could have used another half point but its tough to build compression in a small motor with 64cc heads, but 10.3:1 is enough for an 8:1 DCR. This little 327 is a screamer and runs 12.5's @ 106-107 in the quarter and it idles a lot like my 383 (maybe a little milder).

I think the same basic combo scaled down a tad would work for your 283 build. You won't need a 300cfm head either --- maybe only 210-220 and a 170cc runner for a real hot 283 that runs to 6500. The 270s cam fits right in there with the rest of your parts IMO and would probably have that same 2500-6500 power band.

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post #11 of 27 (permalink) Old May 8th, 04, 11:07 AM
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PAW P/N 10341 - 264°Duration/246°@.050", .471" Lift, 108°LC's, .030" lash.

Just a cool little solid cam. Never tried it but it just looked interesting when I threw it on DD2K once for a giggles.

-Mark.
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post #12 of 27 (permalink) Old May 8th, 04, 11:07 AM
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When it comes to running high compression, no 305 head is your friend. They suffer from the same chamber design as all other smog castings. For example, a friend of mine runs a flat top piston 355 with ported 416's (305HO heads off an '84 monte carlo) with the stock 1.84/1.50 valves, an old 214/224, .442/.465, 112lsa hydraulic, headers, decent exhaust, performer intake, q-jet (then later a 600 edelbrock), all in a '72 chevy truck with 3.73's. His engine makes 180psi cranking compression, same as mine with my vortecs and XE268. His pings like mad on anything less than 93 octane...I use 89 octane in mine, and I even have 3.08's, and mine is about 1/2 second quicker in the 1/4 mile. No amount of tuning would completely get rid of the ping in his engine, short of retarding the timing so much that it run like crap.
You'd be hard pressed to ever make a 283 have massive low end grunt...the laws of physics are just not in your favor. Consider too that the general rule is to add 8-10*'s to a hydraulics .050 numbers to get a comparable acting solid. Isky has some small solid lobes...how about a 256 advertised, [email protected], .425 lift, or the next step up which is a 260, 216, .425. IMO a 283 does not need a dual pattern cam (a few degrees would be ok though). There simply isn't enough cylinder volume there to saturate a typical small block exhaust port under 6K or so. Most smog 305 heads actually have a pretty fair exhaust port...especially with just a bit or short side radius blending and bowl blending.
I don't have time to run some small solids thru EA3.0 right now. I had to go get a 13/32" drill bit to finish installing this funky march power steering bracket. Back to work!

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post #13 of 27 (permalink) Old May 8th, 04, 12:08 PM Thread Starter
 
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Travis,

That's what is good about the 305HO, -601 heads b/c they have double-hump bathtub chambers!! (I just got a set of -601's to play with too so once I get them cleaned up, I will cc all three areas for us to know at least what my set cc's at..)

The 305HO, -416 heads have "squared-off", smog chambers so are less eff. then the old double-hump heads, imho..

I was looking for a set of 305 vortec heads that were 58 cc's but don't know what I need as far as casting numbers go if indeed they are even made..

BUT, I really don't like the idea of the Vortec specific valve covers and intake tho, but that's just me..

And stingr69 thanks for the heads up on the little PAW solid cam.. It does appear to be VERY aggressive with an intensity of, yikes!!, 18!!!!, tho..

I guess I need to drop some coin and get updated Isky and PAW cats.

Keep the good advice coming everybody b/c I bet if gas keeps going up like I bet it will, there will be more 283's dug out from under the shop/garage work bench's and put to high gas mileage use!! Imho...

pdq67

PS., it's funny b/c my junk 301 never knocked ast all and I ran the cheapest gas I could buy way back then, even if it was leaded regular!!

And again figure it was above 10 to 1 CR.......



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post #14 of 27 (permalink) Old May 8th, 04, 06:03 PM
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I've got 2 pair of -601's (1 set is in excellent shape), and a pair of -434's. The 434's are the early 305 2bbl heads with the smaller 1.72 intake valve but a standard 1.50 exhaust. These are 63cc heads.
You know, I was considering building a mild little 283 to drop in my nova. Even with its 3.73's I bet I could get 20+ mpg out of one easily enough. But, just a few minutes ago, I just fired up the "new" 388 with open headers. It sure would be hard to give up a 100+ inches now.

I'll play with EA3.0 some more and see if I can't find you that perfect little solid cam. What kind of car is this going in, gearing, tranny/convertor, etc? What kind of idle quality and power range are you looking for?

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post #15 of 27 (permalink) Old May 8th, 04, 07:04 PM Thread Starter
 
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Don't know yet b/c it might go in a P/U for my son or even back in my car at some later date when/if I get tired of feeding my 496.

My car's an early, (Dec. '66), '67 SS/RS, M-20 and 3.31's and about 25.5" to 26" tall tires.

I would really like to drop it into a '64 Duece Coupe four speed with some 3.73 gears but you know how that goes..

Yes, please play with it some more if you want to..

And thanks..

pdq67



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