I have searched and searched. Trying to find "back to back" dyno results from a stock cammed L31 and then with the Hot cam.

Wanting to see how much HP/TQ gain with just the cam swap.

 

Given that you can't exactly do that, as significant head work of some sort or other is required to accommodate the lift which exceeds the capabilities of the heads, it's a bit hard to characterize. It also depends on the remainder of the induction system; what intake system, exhaust, etc. is used. And of course, whether the rockers are changed from 1.5 ratio to 1.6, as the cam is designed for.

For a carbed setup like yours, and using the simplest head modification (LS6 springs, Comp 787 retainers, .050" offset keepers... I personally don't feel real fuzzy about the Alex's or "ghetto grind"), I'd expect to see about something in the neighborhood of 30 - 40 HP of gain, mostly in the form of moving the peak torque & HP RPMs up about 1000 - 1200 RPM. Peak torque value will remain about the same, just its RPM moved up; the torque below 3000 RPM will be lower, and significantly lower below 2000 RPM. A non-stock torque converter will make a YUUUUUJJJJE difference to the overall outcome. It's considered a fairly good match of cam to motor.

 

 

That's what I figured. I'm 52 and an old car guy.

The magazine articles that have done this swap claim an "unrealistic to me" 60-70 hp gain. They do all of the mods necessary to the heads to allow the lift. Also better induction system and exhaust. But then compare it to the advertised hp rating of 255, with the stock restrictive induction system and exhaust. Of course that is true, but I was looking for a more "apples to apples" comparison. Like dyno the stock cammed engine with the same improved intake and exhaust system. Then do a before and after comparison. But, that probably would not make a good article for the magazines. Lol.

30-40 hp from a cam swap seems more realistic. Thanks guys.

 

Yerbasic magazine article always seems to have lots of fine print...

"We had this [exotic part cast in 95% virgin nonobtanium alloyed with 5% purest irreplacium] left over from last month's cover project laying around so we threw it in", "vendor XYZ donated their newest top-of-the-line [thing that is 10 times the cost of its nearest equivalent] for us to evaluate", "sent it to our friends at [NASCAR / NHRA / SCCA / ASCS / WOO engine shop] for their finest massaging that they gave us for free", etc. etc. etc. ad nauseam. RARELY, if ever, is it just a straight-up apples-to-oranges single-variable A/B test.

No cam swap in any stock motor is going to give you 70 HP. That's fantasy (aka magazine article) land. Even 30 - 40 is pretty aggressive, and is only available because you have ALREADY done all the supporting mods. Assuming of course that they're all done properly and well, and there aren't any other hidden bottlenecks lurking somewhere in your package, like crush-bent 2¼" "true duals" (2 coffee stirrers aren't necessarily any better than one drinking straw) or the like.

 

I recall reading in GMPP literature the ZZ4 longblock gained over 30hp with the HotCam swap. But reality is what you got is what you get. Every combination is different to varing degrees. Only your own Dyno testing is gonna prove expectations.
The Hot Cam is a budget cam that perfoms well in many sbc engine combinations. But what your asking is to predict the future with 1% accuracy. Ain't nobody here has that much dyno experience. All you gonna get is a lot of best guesses.

 

 

EXCEPT a stock F-car LT1 cam is a 20-30 hp gain in a Vortec compared to the **** poor wimpy cam it came with that is also advanced 5°.

Compared to the factory Vortec cam a LT4 Hotcam in a Vortec with a good intake, headers and exhaust is an 80-100 hp gain at the crank.

The Marine 350s use a slightly hotter cam than the truck grind and make 320 hp. The factory truck 350 Vortec engine with headers and a decent 4bbl makes about 290 hp. A hotcam makes about 380-400 hp in one.

I have seen cam only LS engines and modern Hemi engines gain 100 hp. My 2006 Ram made 285/301 to the tires with headers, tuning and the stock cam. Ran a 9.5s 1/8 mile. I put a 212/212 @ .050 Comp Cam in it, reprogrammed the PCM, made 360 hp at the tires and 350 TQ. Ran an 8.90 with no other changes.

The Vortec heads flow about as well as the early LS heads do and are begging for some more lift and duration to let them breathe.

GMs SPO 350 is a Vortec 350 with a cam slightly smaller than the Hotcam and stamped steel rocker arms. It is rated at 357 hp. I guarantee you could put better valve springs (LS6 w/Comp 787 retainers) on it, swap to 1.6 roller rockers, and swap to a better intake than the low rise GM dual plane used in GMs testing and get 380-390 hp out of it.

 

 

 

 

The airflow is absolutely there. With 906s cut for 2.02/1.60s and no porting I hit 272 rwhp through a 4L85E in 2nd gear and GM 9.5" 14 bolt with the GM 395 marine cam and 1.7 rocker arms. That was with a marine 350 intake which still struggles above 5,500. That was ~360 hp at the crank and it peaked at 5,100 rpm. Marine cam is on 196/206 @ .050 and it is 3° advanced. My setup was basically a Ramjet 350 with 2.02/1.60 valves, a slight compression bump, higher ratio rockers (1.7 vs 1.6) and an intake with longer runners.

 

 

My stock M56S made 378 hp and 390 tq on the same dyno in 4th gear. 1:1 5th gear hit the dyno's 165 mph speed limiter before it hit peak HP. Stock M56S also went 12.7 @ 108 mph at 4,500 lbs. Same car with a 2° timing advance, HPS silicone intake tubes and K&N filters made 390/410. Same car with the non monitored post cats deleted, 2.5" dual exhaust with a X pipe and magnaflow magnapack 3" race mufflers made 428/434. At 428/434 it ran a traction limited 12.2 @ 112.

A fresh stock L31 4bolt crate engine with crap flowing hecho en mexico heads in a cutaway van RV that I tuned with a marine cam and shorties being the only mods made 240 hp/300 tq through a 4L80E and 10.5" 14 bolt.

FWIW 2.02s only pickup 6-8 cfm under peak lift. The port stalls at high lifts above about .500" and they are worth nothing there. I used them because the heads needed the valves and seats cut anyway. The 2.02s probably did not make a 10 hp difference. On the otherhand the Assault racing 205cc heads I have on there now would probably have come close to 400 hp at the crank with the tiny marine cam and 1.7s. They flowed 265 cfm @ .450 and 272 cfm @ .500" through a 2.02. The marine cam is .488/.511" lift with a 1.7 rocker. The reason I say probably is I pulled the marine cam and put a 215/224 @ .050 cam cut on a 110 lsa with the 1.7s giving .578" lift on both sides in when the assault heads went on. With a heavily ported marine intake it pulls hard to 6,200 rpm. I now see 360+ gms/sec airflow at 6,000-6,200 and have 30 lb/hr injectors at 90% duty cycle. I am feeding it 430-440 hp worth of fuel. I have been considering putting an edelbrock proflow intake on it but it runs hard as it is and swapping that intake would be pretty involved.

The 6.2 has good flowing heads but the ports are big block sized and they are lazy. I put stock 5.3 heads on the last LQ4 6.0L I setup. It made 400 rwhp with an Elgin 220/224 cam on a 112 lsa through a TH375 in 2nd gear and 8.5" 10 bolt. Speed engineering shorties and an edelbrock carb intake with a 750cfm carb.

 

Kinda what I was going to say. It drives well, has a pleasant idle sound and is easily tuneable. I'll go a step further and say why even screw around with the hot cam? Since we know there are better cams out there in the same duration at about the same price point and you will have to change springs anyway why not just get the better cam. After I personally ran it and saw the dyno results of my engine against other nearly identical engines with only a cam change I just can't recommend it anymore.

 

What were the other cams and what was the results. Please that with us.

 

I've been on these boards for 15 years and had that 355 out for at least 5 years so you'll forgive me for no longer having a particular thread about a cammed 350 bookmarked. I know what my 355 made and I recall seeing the dynos other members posted of their HSR or carb'd 350s using the XE or XFI lines by comp with an intake duration in the 218-224 @ 050. I was making ~325 wheel horsepower (with a T5) and other guys were posting ~350 wheel horsepower.

 

 

Well OK you don't recall dyno numbers for particular cams but if your claiming better cams I'm sure the OP would like to take a look at them if you would identify them. And since your saying for nearly the same price as a Hot Cam then I would like to look at them to for my LT1 build. You left us hanging not know what better cams are out there for the same price as a Hot Cam.

 

Having messed with multiple TPI engines I do not buy the 226 hp out of a cammed TPI at all. I was over 240 with a factory LT4 cam and 305 TPI heads and gained close to 50 hp swapping to ported vortecs and an unported 3817 base. I have had several TPIs over 280 hp to the wheels with stock runners.

 

Unless it's project that I am going through or just went through I usually can't offer specifics like part numbers, old threads or links to dynos of a particular combo. I offer guidance and direction and leave it at that. I'm not paid to be on this site (the website is the one making money here, I'm only allowed the privilege of posting here) so I honestly don't put much effort into backing up what I say, I'm more take it or leave it. I usually don't (unless you're a friend or have helped me in the past) go back and search for part numbers, old threads or articles to link to because in the amount of time it would take for me to find it, you also could find it.

 

 

What are the L31 cam specs?

 

L31 Truck
191/196@ .050, .414/.428" lift, 111 LSA, 106 ICL

L31 Marine
196/206@ .050, .431/.451" lift, 109 LSA, 106 ICL.

 

Thanks. (I don't suppose the advertised duration values are available?)
I'm going to run a DynoSim comparison and see how this shakes out.
I'll do a little more digging and am looking for the factory rated L31 HP numbers. I've found ratings from 250 to 350 HP from the same source so there's a lot of misinformation out there to sort through.
Seems 255 is about the most commonly stated value.

 

L31 Hot Cam

L31

Looks like peak torque RPM moves up from 2000 to 3500. Peak HP RPM from 4000 to 4500 with an increase of 57 HP.
I could have spent more time profiling the L31 for a better match to the factory specs but this gives an idea of what a computer generated result might be. All else being equal other than the cam.

 

Stock Vortec cam is about 259/263 @ .006 from my degree wheel. The Marine cam is slightly smaller on the intake. Marine cam is 256/264 @ .006. With 1.6:1 rockers the 395' Marine cam used in the Ramjet 350 makes about 350-360 hp. The Marine cam has a higher lobe intensity than the truck cam.

Are those numbers through stock manifolds? A Vortec 350 with a dual plane manifold, 600 carb and 1 5/8" long tubes makes right at 290 hp.

The GM 330 hp crate engine is a L31 with a 212/222 @ .050, 112 lsa flat tappet cam and a high rise dual plane. Climbs to 357 HP according to GM with the 215/223 @ .050 151' roller cam. That cam is .473/.473" lift. 108 LSA and 109 ICL.

 

I would have preferred using advertised and .050" lift values for the program. That way the ramp intensity can be adjusted to better suit the real world.
But this seems to lend some cred to the results suggested above.

 

FWIW my 1997 Express van was factory rated at 245 HP @ 4,600 and 335 TQ @ 2,800. Put down 185 RWP and 250 RWTQ through a 4L60E in 2nd gear and a 3.42 geared 8.5" 10-bolt. Spinning all the accessories including the clutch fan it was probably right at 22% driveline loss. After tuning it went 200 RWHP and 278 RWTQ with everything else stock. Went from a 17.8 to a 17.3 in the 1/4 at 5,800 lbs. With a LT4 factory cam, 1.6 rockers, shorty headers and a S10 converter it ran a 16.3. Stock tune was very rich and only had 22-24° of timing at WOT. Negative timing values at lower rpm and very conservative advance rate until it hit very high rpm.

Factory LT4 cam with 1.6 rockers is 282/277 @ .006, 203/210 @ .050, .476/.479" lift, 115 LSA, 116 ICL. It pulled HARD in my heavy Express van with the GM S10 converter stalling about 2,700-2,800 rpm. Shorty headers combined with the vans dual 3" exhaust piping to the muffler and 3" factory cats surely helped. I also had a heavily ported lower intake and the BBK 80mm throttle body. The LT4 cam lowered the dynamic compression ratio and let me run the more normal 32-34° of timing and I was able to bring in 26° by 2,400 rpm and 30° by 2,800 with full advance of 32° in by 3,400. In catalyst overheat with the air/fuel ratio at 11.5:1 my tune would bump the whole timing table 2° above 2,800. I know for a fact comination was in the 300-320 hp range.

Also keep in mind with stamped steel rockers they will never see the actual 1.5 ratio. In reality they are 1.42-1.48 ratio and will make the lobe intensity as seen at the valve even lower.

 

For the record:
86 IROC-Z (3700 lbs) with this engine:
353: 4.020” x 3.48”
10.05 SCR / 8.08 DCR
670 Holley
RPM Air Gap
Vortec heads (unported). Decked .006”. 63 cc (?)
Comp XR276HR. 276/282, 224/230, 110 LSA, 106 ICL, 64 ABDC IVC
Cranking pressure 185-190
700R4 w/ 12" converter and 3.27 rear gear
12.78 @ 105.1 / 8.088 @ 83.94 1.71 60’
Dynojet 280 HP/280 TQ
That's a pretty **** poor drag racing chassis but the engine was healthy enough. Maybe 370 HP depending on how you want to calculate driveline loss. That dyno run was in little d however the dyno technician said he was seeing the converter lockup in the graph (which I find unlikely as the 4th gear apply switch is part of the TCC circuit) but that was the result.

 

It looks like you and I have a similar mind. Over the summer I picked up a L31R for my truck. I put in LS6 springs and 787 retainers and then stabbed a SP350/357 cam. Topped that with a simple jegs manifold and a sniper EFI.

That engine is absolutely nuts. Snappy, gobs of torque, and tons of power. Even with stock rear gears I took out a 5.3 swapped C10...and I still had the engine I pulled in the bed.

 

I had that cam in my Express van with 1.6 rockers and the 2.02/1.60 valve 906s that were milled .020" and installed on a L31R HD with .016" compressed head gaskets. Right at 9.6:1 compression. Pulled my 6,000 lbs travel trailer down the road at 70 mph with ease in overdrive at 2,700 rpm. 5.13 gears and a 4L85E with 31.5" tall LT265/75R16s. With the L31 marine MPi intake and thorley tri-ys it was no slouch either. I set my WOT shifts to 6,200 rpm and Tow/Haul WOT shifts to 5,500. Sounded absolutely wicked above 5,000 rpm with the exhaust cutouts open as well and the only sound muffling being the high flow cats. Playing with the shift points to get them right I actually turned that engine 6,500 rpm a few times and it never stopped pulling until the 6,500 rpm rev limiter closed the DBW throttle body. I only limited it to 6,200 to be a little more conservative on the factory bottem end.

I swapped in a custom roller with almost identical specs but alot more lift when I put the 205cc assault racing heads on it. With 1.7 rockers I am running a 215/224 cam, 110 lsa, 106 icl and .578" lift.

I currently have the assault racing heads at Lloyed Elliots getting some work done to them and have a chinese stealthram ported up to swap on it. Looking for 480+ HP out of the 350. I put new rod and main bearings in the engine along with a full length windage tray. I am going to twist it 6,500 rpm or kill it trying. The thing I have yet to buy is the $$$$ EFI connection DBW LT1 throttle body.

 

 

Thanks for the replies.