[Cliff R]

Something to consider with the cams above is that the solid's advertised duration is at .015" , the HR most likely at .006". It's still a smaller cam even though it sports more .050" duration, and the engine saw it as a smaller cam if you look at how much power it left on the table and it quit 300rpms earlier in the rpm range.

I still want to point out that it was sent here with an engine to assemble, we didn't pick it. It was chosen by one of the big names in the Pontiac industry as a replacement for the OF cam at much less cost.

I'd also add here that you are looking at the best dyno run of the day, the first pulls weren't even 500hp and barely 500tq. We had to pull out ALL the stops to get the numbers shown on that dyno run.

Anyhow, just another lesson learned with these things that most folks never get to do. The only way the test would have been better if we could have ran both cams in the same engine on the same day, but at least we used the same dyno and dyno operator.......Cliff

PS: I couldn't post dyno runs of the OF cam, they got lost when our last hard drive crashed......

[blykins]

Great numbers Paul, and a great looking torque curve due to the shorter LSA. I use a lot of 109-110 LSA cams on street engines and with the right lobes, you can have power and vacuum too.

[blykins]

There seems to be two underlying themes here that keep getting passed around: a long LSA is superior, and an SD OF cam trumps all. I'm not at all saying the OF cam is a flop but the fact remains that no one has shown an apples to apples test yet.

Showing dyno sheets of a grossly under spec'd cam then replacing it with an OF that's 10+ degrees larger, both seat and .050", while having more lift, etc., absolutely proves not one thing, other than you make more hp with a bigger cam!

If you want apples to apples, order 3 of the OF cams, one on 108 LSA, one on 110, and one on 112. Measure manifold vac on each and dyno the engine.

[PAUL K]

Originally Posted by blykins

Great numbers Paul, and a great looking torque curve due to the shorter LSA. I use a lot of 109-110 LSA cams on street engines and with the right lobes, you can have power and vacuum too.

Thanks Brent! When you need that "glue your eyeballs to the back of your skull" torque, it's usually found with the correct lobes and a tighter LSA.

[Cliff R]

"Showing dyno sheets of a grossly under spec'd cam then replacing it with an OF that's 10+ degrees larger, both seat and .050", "

The flat solid sports more .050" timing and probably more seat timing at .006" since the advertised on the cam card is at .015" tappet lift.

Once again the OF cam is 289/308 at .006" seat timing, 236/245 @ .050" on a 112 LSA.

The flat solid we used was 281/289 @ .015" seat timing, 244/252 @ .050" on a 110LSA.

Here's a question for the highly educated and opinionated folks following this thread. So a customer calls you up and says he just grenaded his fresh 455 on the dyno using the XR276HR cam and wants a cam recommendation. It's got 250cfm #96 "D" port heads, 9.5 to 1 compression, and zero deck height. He wants a hydraulic roller cam, what cam/specs would you recommend to him?........Cliff

[PAUL K]

Originally Posted by Cliff R

"Showing dyno sheets of a grossly under spec'd cam then replacing it with an OF that's 10+ degrees larger, both seat and .050", "

The flat solid sports more .050" timing and probably more seat timing at .006" since the advertised on the cam card is at .015" tappet lift.

Once again the OF cam is 289/308 at .006" seat timing, 236/245 @ .050" on a 112 LSA.

The flat solid we used was 281/289 @ .015" seat timing, 244/252 @ .050" on a 110LSA.

Here's a question for the highly educated and opinionated folks following this thread. So a customer calls you up and says he just grenaded his fresh 455 on the dyno using the XR276HR cam and wants a cam recommendation. It's got 250cfm #96 "D" port heads, 9.5 to 1 compression, and zero deck height. He wants a hydraulic roller cam, what cam/specs would you recommend to him?........Cliff

Do we figure out why the engine blew first?

[slowbird]

I'd recommend OF, lol

[blykins]

Originally Posted by Cliff R

"Showing dyno sheets of a grossly under spec'd cam then replacing it with an OF that's 10+ degrees larger, both seat and .050", "

The flat solid sports more .050" timing and probably more seat timing at .006" since the advertised on the cam card is at .015" tappet lift.

Once again the OF cam is 289/308 at .006" seat timing, 236/245 @ .050" on a 112 LSA.

The flat solid we used was 281/289 @ .015" seat timing, 244/252 @ .050" on a 110LSA.

Here's a question for the highly educated and opinionated folks following this thread. So a customer calls you up and says he just grenaded his fresh 455 on the dyno using the XR276HR cam and wants a cam recommendation. It's got 250cfm #96 "D" port heads, 9.5 to 1 compression, and zero deck height. He wants a hydraulic roller cam, what cam/specs would you recommend to him?........Cliff

I'd find out what he's driving, what the rear gears are, what trans, what gas they want to run, if they need vacuum, what they want it to sound like....the list is extensive.

[71 T/A]

I spoke to Cliff about my 9.5:1 461 and he said that the Stump Puller HR I use was the correct choice for the 268/223 ported 62 iron heads. He said I didn't have enough compression for the OF cam.

[Cliff R]

"Do we figure out why the engine blew first?"

The 455 Super Duty engine we're working on here seized two pistons, and the rest weren't too far behind them. They were older forgings and from what I can remember they require quite a bit of skirt clearance compared to modern alloys.

I suspect that the older pistons in conjunction with running a tad lean at full throttle led to it's demise. The carburetor had some issues and I'm certain it was lean at full throttle as the float was clear on the bottom of the bowl, the lowest float setting I think I've ever seen to date on a q-jet.

Not sure how it ended up there, and it didn't have a high flow N/S assembly installed either, so quite likely at the power level of this engine it wasn't keeping up on hard runs being fed only by a stock mechanical fuel pump.......Cliff

[catc]

Awesome Horsepower and Torque Paul ...and on a 109....sweet.......

[PAUL K]

Originally Posted by 71 T/A

I spoke to Cliff about my 9.5:1 461 and he said that the Stump Puller HR I use was the correct choice for the 268/223 ported 62 iron heads. He said I didn't have enough compression for the OF cam.

268 cfm heads should be able to make some good power. Do you have any track times?
If you're happy with the camshaft and it's performance then it was the correct recommendation.

[PAUL K]

Originally Posted by Cliff R

"Do we figure out why the engine blew first?"

The 455 Super Duty engine we're working on here seized two pistons, and the rest weren't too far behind them. They were older forgings and from what I can remember they require quite a bit of skirt clearance compared to modern alloys.

I suspect that the older pistons in conjunction with running a tad lean at full throttle led to it's demise. The carburetor had some issues and I'm certain it was lean at full throttle as the float was clear on the bottom of the bowl, the lowest float setting I think I've ever seen to date on a q-jet.

Not sure how it ended up there, and it didn't have a high flow N/S assembly installed either, so quite likely at the power level of this engine it wasn't keeping up on hard runs being fed only by a stock mechanical fuel pump.......Cliff

The domed TRW pistons called for .005 piston to wall clearance, we usually set them at .0055-.006. They are heavy but pretty rugged. They're made out of 2618 material, featured 1/16, 1/16, 3/16 ring pack and had the full float option. Back in the day they were a pretty good piston.

[PAUL K]

Originally Posted by catc

Awesome Horsepower and Torque Paul ...and on a 109....sweet.......

Thank you, Sir!

[Cliff R]

We replaced the domed pistons with Ross flat tops on Eagle H beam rods, full floating.

I've been associated with one Super Duty and one HO 455 that used domed pistons in them to get the compression up to 9.5 to 1 or so, and had zero luck with either one of them as far as tuning for pump gas and making acceptable power with "normal" timing/fuel curves in them. I just don't think that's a good way to go with one of these engines.........Cliff

[blykins]

Originally Posted by Cliff R

We replaced the domed pistons with Ross flat tops on Eagle H beam rods, full floating.

I've been associated with one Super Duty and one HO 455 that used domed pistons in them to get the compression up to 9.5 to 1 or so, and had zero luck with either one of them as far as tuning for pump gas and making acceptable power with "normal" timing/fuel curves in them. I just don't think that's a good way to go with one of these engines.........Cliff

Flame travel issues probably.....harder to propagate across a big old piece of aluminum sticking up in the way.

[67GTO4SPEED]

Originally Posted by blykins

There seems to be two underlying themes here that keep getting passed around: a long LSA is superior, and an SD OF cam trumps all. I'm not at all saying the OF cam is a flop but the fact remains that no one has shown an apples to apples test yet.

Showing dyno sheets of a grossly under spec'd cam then replacing it with an OF that's 10+ degrees larger, both seat and .050", while having more lift, etc., absolutely proves not one thing, other than you make more hp with a bigger cam!

If you want apples to apples, order 3 of the OF cams, one on 108 LSA, one on 110, and one on 112. Measure manifold vac on each and dyno the engine.

While I agree with everything you say here, the fact is a lot of well known builders and cam manufacturers recommend these smaller cams. When I started building my engine, Comp themselves recommended the XE274. Another well known Pontiac builder recommended that cam as well, saying "the 274 is pretty much as big as you will want to go with a Q-jet and manifolds." It's since been proven over and over to me by people here that you can make more hp with a bigger cam, and still have better street manners with a wider LSA. The reason people seem to be hanging on to that premise is because they've seen what actually works, and works well.

I hope you or somebody else will do some back to back dyno tests. I'd for one would love to see any brand cam, by anybody, that offers more power than any current offering out there, as long it provide the same kind of vacuum numbers and streetability. I have bought almost everything for my engine except the cam and pistons.

Tell me what you'd recommend for my car:

'68 428 block, will need to be bored .060"
'73 455 nodular crank .010"/.010" OR '68 428 crank - I can go either way
6.625" Tomahawk I beams rods
I had KB hyper dishes, but sold them. I will buy Autotec dish pistons.
#16 D-ports, ported to flow 265/208 by Steve Magnotti, cc'd at 76cc
2.11/1.77 Ferrea RAIV length valves, valve job by Steve Magnotti
ported '68 iron intake, modified like Cliff's
'73 800 cfm Q-jet - will be built by Cliff. Car has functional Ram Air.
2.5" RA manifolds, Pypes 2.5" X-pipe exhaust.Terminator mufflers.
Muncie M21 - will be TKO 5 speed after restoration is paid for
3.55 posi
Car weight should be around 3850 with me in it.

I'm looking for as much power as I can get with my parts, while be stock appearing under the hood. I don't mind a fair lope, but I need vacuum for brakes and the car has A/C.

Until proven there's something better otherwise, I'm leaning toward Dave's OF cam.


Flow charts for my heads.

[goatman65]

Originally Posted by PAUL K

Thanks Brent! When you need that "glue your eyeballs to the back of your skull" torque, it's usually found with the correct lobes and a tighter LSA.

I would like my eyeballs glued to the back of my head. lol. Send me one of those cams.

[blykins]

Originally Posted by 67GTO4SPEED

While I agree with everything you say here, the fact is a lot of well known builders and cam manufacturers recommend these smaller cams. When I started building my engine, Comp themselves recommended the XE274. Another well known Pontiac builder recommended that cam as well, saying "the 274 is pretty much as big as you will want to go with a Q-jet and manifolds." It's since been proven over and over to me by people here that you can make more hp with a bigger cam, and still have better street manners with a wider LSA. The reason people seem to be hanging on to that premise is because they've seen what actually works, and works well.

I hope you or somebody else will do some back to back dyno tests. I'd for one would love to see any brand cam, by anybody, that offers more power than any current offering out there, as long it provide the same kind of vacuum numbers and streetability. I have bought almost everything for my engine except the cam and pistons.

Tell me what you'd recommend for my car:

'68 428 block, will need to be bored .060"
'73 455 nodular crank .010"/.010" OR '68 428 crank - I can go either way
6.625" Tomahawk I beams rods
I had KB hyper dishes, but sold them. I will buy Autotec dish pistons.
#16 D-ports, ported to flow 265/208 by Steve Magnotti, cc'd at 76cc
2.11/1.77 Ferrea RAIV length valves, valve job by Steve Magnotti
ported '68 iron intake, modified like Cliff's
'73 800 cfm Q-jet - will be built by Cliff. Car has functional Ram Air.
2.5" RA manifolds, Pypes 2.5" X-pipe exhaust.Terminator mufflers.
Muncie M21 - will be TKO 5 speed after restoration is paid for
3.55 posi
Car weight should be around 3850 with me in it.

I'm looking for as much power as I can get with my parts, while be stock appearing under the hood. I don't mind a fair lope, but I need vacuum for brakes and the car has A/C.

Until proven there's something better otherwise, I'm leaning toward Dave's OF cam.


Flow charts for my heads.

Compression ratio? Also, I'd need to know which way you are for sure headed on the displacement. There's 22 cubes difference between the two and it makes a difference on duration choices.

Thanks for including that you'd be switching to a TKO. There is a little strategy involved in this as well, as you have to pay attention to which OD you choose. The TKO 600 is available in both a .64 and a .82 OD. If you pick the .64, you have another variable to add to the cam specs, as it's possible to get the dreaded "buck" if you pull the engine down too far with a load on it. With a heavier car and a 3.55:1 rear, I'd personally recommend the .82 OD.

Nail the variables down and I'll be happy to give you my recommendation....FWIW.

[Cliff R]

One thing to keep in mind here with this cam and LSA topic is that a back to back dyno test will NOT tell the end user if the engine will successfully manage pump fuel. One is actually quite likely to see higher peak power (torque) with a smaller cam or cam on a tighter LSA.

What we have seen here, and continue to see is that these "small" cams and/or cams on tighter LSA's narrow up the power curve, and peak torque is a higher number and/or occurs earlier in the rpm range. This is why these cams often make the engine "feel" very responsive and fools the user into thinking they are making more power.

What no one touches on is that when you make peak torque earlier, narrower power (torque) curve, and more of it, the octane requirements are considerably greater. This simply happens because cylinder filling (cylinder pressure) is improved in the lower rpm range, where engine damaging detonation is most likely to occur.

As rpms increase, the events happen much quicker, and cylinder pressure is never as high as it is at peak VE, it actually falls off as engine speed increases. This reduces octane required as rpms increase.

I have seen this many times, as I've probably tuned more engines than most who will read this. The absolute WORST engines I've had in here to custom tune were 455's with the XE268 or XR276HR cam in them.

I also get more emails from folks who are having all sorts of detonation, running hot/overheating issues with fresh 455 builds who are using those cams, and even had a few (for what reason I will never understand) install the XE262 cam in a 455 with 9.5 to 1 compression, another used a Summit 2800, and one even used an XE256 cam in one.

ALL of those engines are giving the owners so many issues they are not able to successfully run them on pump fuel.

I love DIRECT results, and stories that reflect them. Couple of years ago a well known Pontiac engine builder who posts on this site built a 455 for a customer with pretty low compression down around 9.2 to 1. He selected and used a Comp XE262 cam in it.

Our only contribution to the engine was the carburetor. The owner absolutely HATED everything about that engine, and we got the carb back here in short order. The carb was flawless, even ran it on my car and it would tear your head slam off and "glue the eyeballs to the back of your head". Sent it back, same thing, pings everyplace, running hot, overheating, and WAY down on power.

The owner actually wanted to trailer the car here for a cam change, as I told him that that cam was not a good choice and causing all the issues with the engine. He ended up finding someone closer to do a cam swap to a larger cam on a wider LSA. Power was immediately restored and end of the issues........FWIW.......Cliff