GEARMAN69

The 393859 286/286 cam .472/.472 from the 67-69 442 400 4 spd and 70-1/2 350 L74 4 spd does anyone know the actually @ 050 duration and LSA ? I have not had much luck searching for it, mostly just find the same old list all the OEM thats shared everywhere. With the "308" cam being like 232-234 range @ 050 I was thinking the 286 cam may be around 210 @ 050 but thats just a guess. Thanks

GEARMAN69

For comparison if Pontiac duration was rated similarly then the HO 288/302 was 212/225 so 286 is 210 ish ?

BlackGold

393859 cam specs:


IVO: 30 BTDC
IVC: 76 ABDC
EVO: 78 BBDC
EVC: 28 ATDC
Intake CL: 110 ATDC
Exhaust CL: 118 BTDC
Lobe Separation: 114
Duration: 286/286
Overlap: 58
Valve Lift: .472/.472


Sorry, I don't know the duration at .050". But for reference, the 328-degree W-30 cam with .475 lift has been measured by numerous people to exhibit about 244 or 245 deg duration at .050". You can probably assume the ramps are similar and extrapolate from there.

GEARMAN69

Thanks man, the 114 helps. I picked up a used one out of a 68 442 4 speed . I might attempt a measurement of it with a degree wheel and my dial indicator/ magnet base. I just have not done it before. I am pretty curious of the true hp of this cam in the 70 L74 assuming the 310 hp actually occured with the tiny 250/264 .400 cam in the 68-70 310 hp 350s before the mid year change. Knowing the W31 was well under rated and exceeds 350-360 easily I wonder if thr true HP of the L74 4 speed with this cam was also 325 hp except accurately rated ?

BlackGold

You're referring to the 1970 L74 engine, but I think you should be more specific and call it the QB code engine. "L74" by itself doesn't mean much -- it depends on what other options the car has:
L74 = QV (and later QB) code for SM.
L74 = QN code for AT exc AC.
L74 = QP code for AT w/ AC.

The QB code was the one introduced mid-year for manual trans 4-bbl 350 cars. Here's how it differed from the previous QV code engine:

The 1970 Engine Assembly Manual calls for identical parts used throughout these two engines with the following exceptions:

Cylinder Head Assembly:
QV = 405584 (used on all other 350 exc W-31)
QB = 408187 (unique to QB)
Note that these Head assemblies were "loaded," including valves, springs, etc. The only difference between these two was probably the springs.

Carburetor:
QV = 7040250 (used on all other 4 bbl 350 exc W-31)
QB = 7040253 (unique to QB among 350s, but also used on TU 455)

Camshaft:
QV = 400084 (used on all other 350 exc W-31)
QB = 393859 (unique to QB)

Spark Plugs:
QV = R45S
QB = R44S (unique to QB among 350s)

The 1982 Olds Parts Illustrated Catalog lists only three differences between the QV and QB carbs:

Primary Jets:
QV (7040250) = 7031970 "70" (.070")
QB (7040253) = 7031969 "69" (.069")

Primary Rods:
QV (7040250) = 7040701 "52C" (.052" tip)
QB (7040253) = 7040699 "48C" (.048" tip)

Secondary Rods:
QV (7040250) = 7033658 "AT" (.0667" tip)
QB (7040253) = 7033655 "AU" (.0527" tip)

Note that the QB carb is jetted significantly richer on both the primaries and secondaries.

It wouldn't surprise me if the QB was higher horsepower than advertised, as you suggest. Then again, it didn't have the higher compression and hand-picked parts of the W-31.

GEARMAN69

Yeah I should be more specific as QB and my cowl tag is third week of January 70 on my 4 speed Rallye so I will have to assume it came with the upgrade QB engine.

GEARMAN69

Leaning towards leaving my heads stock when I build my QP engine to close to original QB specs since i got the right cam. I will not leave the pedestal setup though. Probably run Ford 1.7 rockers with studs so I can lash it out how I want. My pistons are the correct 6 cc dish forged TRW ones so now just a matter if I leave the small valves or not is my only other decision as I am going to retain the stock exhaust manifolds and just have a upgrade mandrel bent 2.5" dual exhaust kit. I also got an M20 instead of M21 to go with the original 3.91 so when I run my 26x10 slicks on it my gearing will be better off the line. Hoping to get some solid 13's out of the stock cam and stock manifolds. I know some stock QB cars have ran low to mid 14's at 95-96 MPH on street tires so curious what I can get.

Fun71

I have often wondered about that. In '72 the 350 had 4 different ratings, with single exhaust, dual exhaust, 2bbl, and 4bbl. So why no such ratings for the various flavors of 350 from '68-70, especially when we know there were different camshafts in the 4 speed versions?

Back in the very early 80s I used to race against a friend's '71 Supreme and my 70 Supreme would just barely edge him out at the top of 1st gear. Both cars were 350-4bbl and had 2.56 rear gears but his was rated 260 HP (GROSS) / 200 HP (NET) and mine was rated 310 HP (GROSS). If I really had 50 HP more than him there should have been a much larger difference in acceleration. Also, I can't see how there was 50 HP more based solely on a difference in compression ratio of 1.75 points, so I have to wonder about that 310 HP rating claim.

GEARMAN69

I have finally began my engine teardown and build and did buy the Ford 1.7 roller tip rockers and 3/8 studs but also the big S/S 2.07 1.71 valves so my #6 heads are gonna get that and some porting but will run the used but correct 286/286 .472 original 68 442 4 speed cam I got that is used but in good shape but boost lift with the 1.7's to around .490-.500 ish lift and have a good zero lash adjustment for rev's. No plans other than a minimum head surfacing and no decking so those forged 6cc OE replacement pistons should be around 9.5:1 actual. I may dyno the engine with and without exhaust manifolds (w good mandrel bent 2.5" down pipes) versus some full length headers if I can borrow some. Would like to see what I get. Thinking September maybe it will be ready ? IDK

VC455

Gearman, if you are still interested in the 0.050" cam duration of the 393859, I was a cam designer in a previous life and I can give you some guidance.

The advertised/0.050" numbers have been published for the W-30 and W-31 cams by the companies that make clones. For the W-30 they were 328°/244° and for the W-31 they were 308°/234°. We can start with those numbers to make an estimate.

If I were the Olds cam designer in that way back time before computers came to the affordability level for corporations, I would use the same acceleration and deceleration ramps on every cam because those were proven to provide long life and quiet operation. Between those ramps, I would keep the same valve opening rate because it was proven to not cause warranty problems due to edge loading on the lifter. And, fortunately, the distance traveled (lift) is about the same among these three cams--that removes that variable from our calculation.

So if we accept those assumptions, and compare the published vs. 0.050" between the two W cams, we see that when the published changes 20°, the 0.050" changes 10°. Therefore given the published of the 393859 being 286°, simple proportions gives an 0.050" duration of 221°.

joe_padavano

Unfortunately, you don't know if the aftermarket cams have the same opening and closing ramps as the factory cams. Typically the aftermarket cams will have more aggressive ramps, especially if they are designed for NHRA stock classes. This will increase the 0.050" duration from that of the stock cams.

VC455

Joe, you are correct.

I compared aftermarket cams and used data from ones that had the shortest o.050" durations.

joe_padavano

Got it. Not an unreasonable approach, given the data you have.

GEARMAN69

Thanks guys, I still have yet to assemble that short block but will over the winter with that original cam I picked up. Maybe I will buy myself a degree wheel and figure it out. I have a magnet base and dial indicator I use for gear setups. I still think the advertised GM numbers Olds had would be pretty close to the Pontiac ones. like the 308/320 RAIV comparison to the 308 W31 the Pont is 231 and Olds is around 232-234 and the 328 W30 being about 244 and the Pont 320 being 240 so I still bet the 286 is closer to 210-214 but I would not mind if it was closer to 220. That is close to the range of a dual pattern cam I plan to swap to later and see the improvement on the track one day. Like a old Dual Energy Comp 275 219/233 110

fasteddy

I wanted to share this cam sheet from Supercars unlimited for the 393859 Cam.


Pat

starfire65

This is a report from a Cam Pro Plus camshaft checker for a cam that I'm installing in a 68 350" it was NOS and unopened when I got it. Ran it on the checker to see what the specs were. Advertised is 286/287 from the factory.
The LSA calculates out to 114.5 with 61 degrees overlap as I checked it as installed in the motor with a degree wheel.

GEARMAN69

Thanks Guys ! 215/217 @ 050 from SCU ! close to my estimate

olds 307 and 403

Very close to the custom Mark did for me, slightly less duration, a bit more lift and a 110 LSA for my custom Erson vs the 112 supposed LSA for the factory cam, according to Supercars Unlimited. I thought all factory cams had wide LSA numbers, the 114 LSA number seems more likely.