[1971WARBIRD]

Originally Posted by Formulas

Didnt the stock SD 455 have less compression or the same with more seat to seat valve timing ?
How bad can the 2802 be in this guys combo?

have you ever read the HO or SD threads in the 70-73 firebird section?they were talking about how the HO455 out powered the SD on the dyno.one of the guru's that really knows this stuff talked about how the smaller cam in the HO was better for the compressions those 2 motors were running.the 2801 is a close match to the HO cam with more lift where the 2802 is close to the cam in the SD with more lift.by the way,HO's came with 3.42-3.73 stick or 3.08-3.42 auto,and the SD came with 3.42 stick and 3.08-3.42 auto.either one could blow the tires off on the street,the 455's have that much torque.

just ran both thru the desktop dyno with 8.2 compression;2801 cam made 482lbs torque at 2500,the 2802 was 444 at 2500.2801 made 357 hp at 4500,where the 2802 made 373 at 5000.in round numbers the 2801 had about 30+ lb more torque across the board at a lower rpm than the 2802,where the 2802 had 15 more hp at a higher rpm.with the 2.73 gears he will be using the lower rpm's more than the higher.thats why they talk about making the whole combo work together.

[goatless]

Originally Posted by 455z4ever

Hey Goatless! Weren't you in an HPP shootout?? Just read it last night and your combo sounds very familiar!

Yup. Here's the link- http://www.highperformancepontiac.co..._4/benson.html

FWIW, I also ran this car with 3.55 gears and surprisingly the 60 foot, ET and MPH all stayed the same! The revs on the highway were a little more annoying though. One thing that I do believe could be hurting this combo is that it could be running out of fuel on the top end.

[Formulas]

Warbird.. No i havnt read that post.. Ive run the 2801 in a 350 just seems bizzare that a 2802 is to much for a 455.. The 2801 wasnt much in my 350.. Oh well

[lust4speed]

Our 2+2 with the 2802 cam was also in an HPP shootout (September 2007). Here's the link: http://www.mickbatson.com/images/HPP/HPP_Article.html

[1971WARBIRD]

Originally Posted by Formulas

Warbird.. No i havnt read that post.. Ive run the 2801 in a 350 just seems bizzare that a 2802 is to much for a 455.. The 2801 wasnt much in my 350.. Oh well

no,it's not that it is way too big,he may love the way it runs,just with the parts he has the 2801 may be a better fit.like i said earlier i ran one just with more compression(9.2) and more gear(3.08) and think it would have ran better if i had alittle more converter and gear(3.23-3.42).

my 2802 had a nice lope to the idle,more than likely the 2801 will be dead smooth,so that may be what makes up his mind.

by the way,what compression,gears and such were you running in the 350?i think that is close to the cam the factory ran in the 350 HO's.

[screamingchief]

I've been trying to stay away from 455z4ever posts because he seems to prefer I do such,but I just cant let some info pass without discussion.

Originally Posted by 1971WARBIRD

the 2801 is a close match to the HO cam with more lift where the 2802 is close to the cam in the SD with more lift.by the way

Lemme start by saying I'm not trying to step on any toes here,but IMHO the 2801 cam is not even remotely "close" to the factory 068/H-O cam folks,and those that perpetuate said theory are looking at the topic from a narrow set of criteria.

Further I am certain they are not looking at the complete specs & valve events on those two cams,and by repeating that common misunderstanding they are leading anybody who bothers to listen to them astray.

With 10° less total overlap and an intake closing event that is 14° earlier than the 068 cam,the 2801 cam is nowhere near the 068 cam in terms of "size".

Even the 067 cam bests the 2801 on those same aspects,but only by a very slim margin,the 067 has only 1° more total overlap,and the intake closes about 6° later than the 2801.

So truth be told the 2801 is much more closely comparable to the 067 cam than it is to the 068 cam,I would call the 2801 cam a good standard 4bbl style replacement cam in lieu of the 067,but I would hesitate to call it a performance cam myself.

You cant just look at the advertised and .050" durations and decide you "know" any given cam,it just does'nt work that way,a cam designer can use many tricks to make those numbers almost meaningless,whether they intend to do so or not.

Same deal with LSA's relationship in all this.

And lift,well dont even get me started...

And do note the same sort of disparity exists when comparing the 2802 cam to the factory SD cam.
(BTW the SD uses the same specs as the 744 RA/MT cam uses,except the SD cam uses the smaller distributor gear)

The 2802 (59°) is down 17° of total overlap to the SD/744 cam (76°).

And the 2802 intake closes 13.5° earlier than the SD/744 cam closes it's intake valve.

The 2802 does'nt even best the 068 in those two respects (total O/L & IC/ABDC),but that 2802 cam is in fact a much closer "comparison" to the 068 cam than the 2801 cam is.

So you should understand why I must debate the validity of comparisons of those "factory" cams to those summit "clone" cams,the common specs on all those cams are very misleading for the less studious consumers/users.

In the factory cam terms,each jump up of roughly 10° (+/-) or so of total overlap represents the next "step-up" in terms of performance levels.

Factory cam total overlap:
067/4bbl = 54°
068/H-O = 63°
744/S-D = 76°
041/RAIV = 87°

The 2810 has 53° total overlap.
The 2802 has 59° total overlap.

And by looking at the valve timing events and overlap numbers instead of the "popular" advertised specs that is all much easier to see.

Now dont get me wrong,I'm not saying overlap is everything here,but ignoring it is certainly not a wise idea either,the factory cam designers certainly did'nt ignore it,fact is they used it to their advantage,the way the factory pontiac heads were designed these engines are very overlap responsive.

And valve timing events show a lot as well,and a fella must be sure to look not only at the .050" valve events,but the "advertised" valve events as well.

Originally Posted by 1971WARBIRD

have you ever read the HO or SD threads in the 70-73 firebird section?they were talking about how the HO455 out powered the SD on the dyno.one of the guru's that really knows this stuff talked about how the smaller cam in the HO was better for the compressions those 2 motors were running.

The merit of the factory cam comparisons refered to in 1971WARBIRD's post is night and day as opposed to his comparing the "factory" cams to the summit "clone" cams.

The differences between the 068/H-O cam and the 744/SD cam are indeed valid,the guru was likely aware of this,and one can easily see why the slightly milder H-O cam would outperform the "bigger" SD cam,especially in a lower compression ratio engine,of which neither cam was designed or optimized for.

Both cams used wide LSA's for broad powerbands,so neither cam likely gave up a bunch in terms of overall RPM range,so this is just another example of a "torquey" powerband upstaging a more "peaky" powerband.

Simply put the added 13° of overlap and a few degrees more duration @ .050" with the 744 based SD cam was just not enough to overcome the DCR boost the earlier intake closing the 068/H-O cam added to those H-O engines,with a bit more static compression ratio and a higher RPM operating range,that situation would have surely changed.

Now some thoughts on the topic at hand.

I would expect the 2802 to have a slight edge over the 068 cam in a lower compression engine,mostly because the 2802 closes the intake earlier and does'nt give up all that much in the overlap department compared to the 068 cam,sure the 2801 cam will "feel" better at lower RPM's compared to those two "bigger" cams,but it almost certainly will not match those two "bigger" cams in peak output,and likely will result in a slower ET than the 2802 or 068 cams would have,especially when the drivelines are optimized for each given cam.

I would use the 2802 without any serious concerns in a lower compression,moderately geared 455 based combo,were it a 400,I would likely take a little more time with that decision.

The 744 style cams with the added overlap and later IC events would make even more power than those two cams (2802/068),but almost certainly the 744 based engine combo would need/benefit from a slight bit more compression ratio,more gear and a mild stall convertor for best results.

If ya'll wanna see the valve events for any/all these cams,feel free to lemme know,I'll take some time and type them out for you guys to peruse.

HTH.

[Will]

SC - at what lift points are you comparing your overlap figures?

If you are using the advertised duration numbers, are you sure that Pontiac and Summit rate their advertised durations at the same lift? If they are not the same, how does that affect the comparison? Isn't the fact that manufacturers never standardized on a lift point for advertised duration numbers the reason we use the .050" lift point as a standard among all cams?

Yes, I know that only looking at .050" numbers has it's problems as well, especially since Pontiacs are very responsive to valve acceleration rates off the seat below .050" lift.

And, while I agree with you that overlap and intake closing events are very important in how the cam will behave, you can't simply discount duration, especially not when we're talking differences of 10 degrees or more at .050".

The reason I blabber so is that seeing how the 2802 actually performs in engines and comparing it to the 068, I would say that the 2802 is indeed more similar to the 744 than the 068. The 068 has a pretty dead smooth idle with excellent torque right off idle and doesn't pull hard past about 4800-5000 RPM depending on the size of the engine whereas the 2802 has a bit of attitude to the idle, is softer on the bottom end and will pull to 5000+.

In short, if we have to compare the summit cams to factory cams then I would agree that the 2801 is similar to the 068 in performance and the 2802 is similar to the 744, regardless of what the numbers on paper may say.

[Larry Navarro]

Throw another variable in the mix, these valve lifts haven't been brought up in reference to duration and how it affects cam charateristics.
valve lifts:
pontiac cams(excluding the RA4) = .406" lift

summit 2801 = 0.442 int./0.465 exh. lift

summit 2802 = 0.465 int./0.488 exh. lift

[1971WARBIRD]

hi SC.not worried about my toes,they get stepped on all the time .i was trying to keep it simple,quess i was just getting way too general with my comparisions.i hadn't pulled the overlap specs,but you are right they are a big part and should have been included.i've always compared cams by .050 lift like alot of other people and it's taking time to try to learn what you are explaining.

when it comes to my engines i have a couple guys i call and use their ideas.it's funny,but so far they are coming up with bigger cams than i thought would work.i'm using more compression,flow,and gears in my cars thou.

back to the question he asked,which cam do you think would work better in a 8.2 compression 455-2.73 gears-auto car?the 2802 or the 2801?

[Thomasmoto]

I would "at least" put a numerically higher rear gear in. IE 3:23 or 3:42 and I would get a higher stall converter as soon as I could- I ran a 10" nitrous converter once, but it really didn't stall that much- I think most converters are liberally rated on the high side.
Just my .02.
David

[P455]

My '67 Lemans has the 2802 in a 462, street ported SD Performance 6X heads shaved to 9.5 compression, Hughes GM2500 converter, 3.23, locker. Idles nice with just a hint of lope, pulls nice to 5400 rpm, runs 12.8's.

[Bumper]

Originally Posted by Will

SC - at what lift points are you comparing your overlap figures?

If you are using the advertised duration numbers, are you sure that Pontiac and Summit rate their advertised durations at the same lift? If they are not the same, how does that affect the comparison? Isn't the fact that manufacturers never standardized on a lift point for advertised duration numbers the reason we use the .050" lift point as a standard among all cams?

Yes, I know that only looking at .050" numbers has it's problems as well, especially since Pontiacs are very responsive to valve acceleration rates off the seat below .050" lift.

And, while I agree with you that overlap and intake closing events are very important in how the cam will behave, you can't simply discount duration, especially not when we're talking differences of 10 degrees or more at .050".

The reason I blabber so is that seeing how the 2802 actually performs in engines and comparing it to the 068, I would say that the 2802 is indeed more similar to the 744 than the 068. The 068 has a pretty dead smooth idle with excellent torque right off idle and doesn't pull hard past about 4800-5000 RPM depending on the size of the engine whereas the 2802 has a bit of attitude to the idle, is softer on the bottom end and will pull to 5000+.

In short, if we have to compare the summit cams to factory cams then I would agree that the 2801 is similar to the 068 in performance and the 2802 is similar to the 744, regardless of what the numbers on paper may say.

I have to agree. A buddy has a 2802 in a 400 and there's no way it's similar or even close to a 068. Crunch numbers all you want, anyone that's ever ran one of these can tell you how similar the 2801 is to a 068 and the 2802 to the 744.

[455z4ever]

Hmmm.. the proverbial 'can of worms" as always ... maybe I'll just step up to a gm6 converter later.. I'm really wanting to use this as an all around cruiser and keep the revs low so the 2.73 posi in the car now stays.. Had a 412 in the car and it turned 2300 at 60 and did damn good on mileage (around 21 on trips). I was hoping to use the low end grunt of the 455 to keep the fun factor up with a gas pump friendly rear ratio.. I must admit though... I love the cam sound at idle and am willing to trade some torque for that and to let the 7.5" rear live a bit.

P.S. thanks Warbird for the "dyno time" !!

[455z4ever]

Hey Warbird... Can you advance that 2802 cam 4 degrees in your dyno sim and post those results?

[1971WARBIRD]

hp-369@4500-368@5000......torque-452@2500-456@3000-452@5000. (+4 degrees)

hp-386@4500-389@5000......torque-468...-470@5000.these numbers are if you bump the compression up to 9.0.

your numbers may not be exact to this but it should show the difference that changes make.you lose a little hp but gain torque when you advance the cam.this was run on a 455-stock 6X heads-dual plane intake-800cfm carb-small tube headers with open exhaust-2802 cam advanced 4 degrees-8.2 compression-then 9.0 compression.

it would not be cheap,but you could always run an overdrive trans to keep the 2.73 gears but have the better first gear.

[BVR421]

I agrree with SC on the timing difference, at first glance the summit cams seem the same as factory but not really.
Real world experience: 2802 in a 428 9-1 in a big fat 63 with 2.69 gears. th400/stock convertor
No lack of low end according to the shredded Michelins. Later swapped to GM2500 convertor and 3.64 gears. That really brought it togather. I would have no hesitaion about using a 2802 in a street 455. Likewise a factory spec 068 (Melling?) I have another 455 with a factory 041 and would not want that cam in any street car. Not even if propped up with leaky lifters.
(It would have been fun when I was young and didnt know any better) LOL

[Bumper]

Originally Posted by BVR421

I agrree with SC on the timing difference, at first glance the summit cams seem the same as factory but not really.
Real world experience: 2802 in a 428 9-1 in a big fat 63 with 2.69 gears. th400/stock convertor
No lack of low end according to the shredded Michelins. Later swapped to GM2500 convertor and 3.64 gears. That really brought it togather. I would have no hesitaion about using a 2802 in a street 455. Likewise a factory spec 068 (Melling?) I have another 455 with a factory 041 and would not want that cam in any street car. Not even if propped up with leaky lifters.
(It would have been fun when I was young and didnt know any better) LOL

The 068 or the 2801 doesn't need a 3.64 gear to wake up a 428! The 2802 needed more gear & converter , as would the 744 or a similar sized cam. No way you would need converter and more gear with a 068 or a 2801 in a 428 unless you're running 8:1 or <.

[hobbygto65]

I know this might be a dumb question but what brand of cam are guys talking about?

[1971WARBIRD]

Originally Posted by hobbygto65

I know this might be a dumb question but what brand of cam are guys talking about?

no,not dumb.summit.summit sells 3 cams with their brand on them,2800,2801,2802.i've ran a couple that worked pretty good.not sure who grinds them.

[screamingchief]

Originally Posted by hobbygto65

I know this might be a dumb question but what brand of cam are guys talking about?

Brands I would rarely ever use...

I really dont even know why I bothered to get involved in this topic???

I could give a rats a** about these summit or factory cams,,,to many better choices out there to loose any time arguing these cams merits.

Use whatever ya'll choose,makes no difference to me...