302 solid lift cam - Team Camaro Tech
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post #1 of 19 (permalink) Old Dec 22nd, 08, 04:48 PM Thread Starter
 
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302 solid lift cam

I noticed that the solid lift cam for a 302 single carb has a different # than the 302 cross ram cam. Does anybody know if the lift and duration are different in the cross ram cam? If so, can it be put into the single carb 302 to give it better performance?

Thanks,
John
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post #2 of 19 (permalink) Old Dec 22nd, 08, 05:28 PM
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Re: 302 solid lift cam

THE CAM THAT WE GOT THE BEST RESULTS FROM WITH THE CROSS RAMS IN THE OLD DAYS WAS THE CRANE 110921,(IT USED A DIFFERANT part NUMBER but the same specs then)

http://www.cranecams.com/?show=brows...21&lvl=2&prt=5

but it really requires about 10.5-11:1 cpr MINIMUM and 11.5-12:1 CPR is IDEAL,and a 3.73-4.56:1 rear gear and a manual trans to work really well in a 302-327

btw
http://store.summitracing.com/partde...5&autoview=sku

http://store.summitracing.com/partde...?part=OFY-5903


the offy versions still available

notice the crane cam has more lift and slightly less durration, and it pulls well lower in the rpm band and up to about 7500rpm in a properly built 302sbc

heres the factory race cam specs, it ran like crap under 4000rpm, and didn,t have any more hp up top,
270-968821
Factory ''Off-Road Special'' Camshaft
BluePrinted Mechanical Flat Tappet Camshaft
Lift: .493''/.512''
Duration @ .050'': 257°/269°
RPM Range: 4200-7000

Last edited by grumpyvette; Dec 22nd, 08 at 06:05 PM.
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post #3 of 19 (permalink) Old Dec 22nd, 08, 05:39 PM Thread Starter
 
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Re: 302 solid lift cam

well will that cam work in my stock 302 with one carb.

john
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post #4 of 19 (permalink) Old Dec 22nd, 08, 05:54 PM
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Re: 302 solid lift cam

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Originally Posted by sg1747 View Post
well will that cam work in my stock 302 with one carb.

john
Not well on the street.

Brett
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post #5 of 19 (permalink) Old Dec 22nd, 08, 06:09 PM
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Re: 302 solid lift cam

its designed for max torque over the 302 power curve and racing , not for traffic and street use., do a desk top dyno run with decent heads, open exhaust headers and 12:1 cpr and youll see the results
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post #6 of 19 (permalink) Old Dec 22nd, 08, 06:17 PM Thread Starter
 
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Re: 302 solid lift cam

does any buddy have the part # for stock 302 cam from GM. one carb
john
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post #7 of 19 (permalink) Old Dec 22nd, 08, 07:34 PM
 
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Re: 302 solid lift cam

3849346
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post #8 of 19 (permalink) Old Dec 22nd, 08, 09:03 PM
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Re: 302 solid lift cam

No such thing as a single carb 302 cam. It came from the factory with a "Duntov 30-30" cam. There were a couple of off-road that GM cams made. They could be used on a single carb 302 as well. Here are the three factory cam specs. as posted by JohnZ.

"Standard 302 (30-30) cam, P/N 3849346
Casting #3849347
254 duration @ .050" (intake & exhaust)
.485" lift (with 1.5 rockers)
114 deg. lobe separation
Exhaust Max lift @ 116 deg. BTDC
Intake Max lift @ 112 deg. ATDC

First Design Off-Road cam, P/N 3927140
Casting #3927141
Intake 257 duration @ .050" (333 advertised)
Exh. 269 duration @ .050" (346 advertised)
Lift: .493" intake, .512" exhaust
Intake Max lift @ 108 deg. ATDC
Exhaust Max lift @ 116 deg. BTDC

2nd Design Off-Road cam, P/N 3965754
Casting #3965751
Intake 248 duration (324 advertised)
Exh. 267 duration (334 advertised)
Lift: .512" intake, .535" exhaust

(Thanks to Mark C.)"

------------------
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post #9 of 19 (permalink) Old Dec 22nd, 08, 09:13 PM
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Re: 302 solid lift cam

The -140 Off-Road cam will need a minimum of 4.10s and headers are preferred. It sounds wicked at idle and will sing at RPM, but I would say it's not too favorable on the street from my experiences. Not impossible, but I would think the 30-30 or a modern variation will have much better manners.

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post #10 of 19 (permalink) Old Dec 22nd, 08, 10:08 PM
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Wink Re: 302 solid lift cam

The 140 off road cam as already pointed out requires 12:1 static compression minimum according to GM and I would not use it unless you have a good set of headers, at least 4.10 gears, preferably 4.56 or 4.88 and no power brakes. My brother and I have always run them with at least 12:1 compression and 4 series gears and no power brakes. There isn't much vacuum at idle with this cam and if you run the DZ carb you'll need a lower power valve in it or it'll want to be open at idle and run too rich. A mechanical carb is better with this set up anyway. Some guys say they run the 140 with the stock 11:1 302, most that do this comment that there is less detonation than with the 30/30. There a reason for that and it bleed off quite a bit of compression, one reason GM says 12:1 minimum static compression.

If you tune for it the cam pulls very well on a short stroke motor above 4000 rpm. But what's required to tune it makes the car less street friendly. I enjoy a first gen that's a handful to drive on the street, but most guys get tired pretty quickly of it.

GM no longer makes the 140. GM Performance Parts gets theirs from Crane Cams blueprint series. Clevite/TRW also offers the 140 grind as part number 299-1622. That's what I've got right now.

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post #11 of 19 (permalink) Old Dec 22nd, 08, 10:13 PM
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Re: 302 solid lift cam

There is no detonation with a 30-30 cammed stock 302 on 92 octane. We have been over this a hundred times.

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post #12 of 19 (permalink) Old Dec 23rd, 08, 07:44 PM
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Wink Re: 302 solid lift cam

Quote:
Originally Posted by Gary L View Post
There is no detonation with a 30-30 cammed stock 302 on 92 octane. We have been over this a hundred times.
Gary not looking for an argument to get anyone agitated. Try running 87 and compare the two cams. I know you've got yours set up and working well and have no detonation issues while maintaining the factory quench to retain your 11:1 compression.

But for many guys who have rebuilt their 302 and didn't want to deck them using a common composite head gasket of .040 drops their compression to 10.33:1 even with a .030 over bore. So these guys probably still wouldn't have detonation issues even with 87.

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post #13 of 19 (permalink) Old Dec 23rd, 08, 09:23 PM
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Re: 302 solid lift cam

No argument. Just want the record to reflect reality. I agree using 87 octane, but who would do that? I have a non-decked block (assume .020" clearance), .028" GM composite gasket, assuming 63 CC heads (not sure how many times they have been surfaced), and .030" overbore. I do not have the ideal quench, but it works just the same. The 30-30 is such a long duration cam (.050" lift can not be used here) that the DCR is like 7.2:1 and SCR is almost 11:1. That is using the 304 dur. number Pat Kelley recommends. That indicates a 84 deg closing angle! Here is what he says:

"The special case of solid lifter cams. Solid cams are usually speced at an abitrary lift value (often .015" or .020") determined by the designer to be a good approximation of the cam's profile. This lift spec is not always correct for a particular cam. The correct lift point to determine the seat to seat timing of the cam is: Lash / rocker ratio + .004". This accounts for the lash. A cam with a .026" lash (given 1.5 rockers) should be measured at .02133" (.026/1.5+.004= .02133>"). This cam lash, with seat timing speced at .020", is actually a bit smaller than advertised since the valve has yet to actually lift off the seat. How much is the question (.024" lash is the only lash that is correct at .020" with 1.5 rockers). Without knowing the ramp rate, and doing some calculations, or measuring with a degree wheel, it is impossible to know. Again, we have to use the mfg's numbers. Here is some Chevy factory cam help.

"To calculate the proper tappet lift at which to measure the seat to seat duration for a solid lifter cam:
Divide the lash by the rocker ratio and add .004".


GM 3849346 ( 30-30 Duntov ).Chevys advertised duration is 346... lash .030.
.008 ____________ 440
.010 ____________ 418
.012 ____________ 396
.014 ____________ 375
.016 ____________ 354
.018 ____________ 331
.020 ____________ 314
.050 ____________ 254
.024" is the proper tappet lift. It's not on the table. Further date points to the .024" duration being 304"


I am no expert engine builder, I just know my data point along with what JohnZ (and a couple others on TC) say about their stock 302. I am curious how many people have really taken the time to tune a stock 302 to run right. Everyone always want more power but the 302 is only going to give so much and be driveable. And mine is very driveable in town. Getting into modern fast ramp cams is a whole different ball game.

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post #14 of 19 (permalink) Old Dec 24th, 08, 01:38 PM
 
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Re: 302 solid lift cam

I guess I don't understand why somebody hasn't dial gauged a 30-30 cam at lash so we would know what it's actual seat duration should be for figuring DCR??

This need's to be done w/ the old -097 Duntov, the -178, the -140 and -754 solid cams too!

pdq67



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post #15 of 19 (permalink) Old Dec 24th, 08, 02:41 PM
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Re: 302 solid lift cam

Quote:
Originally Posted by pdq67 View Post
I guess I don't understand why somebody hasn't dial gauged a 30-30 cam at lash so we would know what it's actual seat duration should be for figuring DCR??

This need's to be done w/ the old -097 Duntov, the -178, the -140 and -754 solid cams too!

pdq67
I would bet that is where PK's number come from. Actually I bet JohnZ did that when he wrote the 30-30 adjustment paper. He did enough points to know the factory rockers are 1.44 not 1.5:1.

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