Sizing Exhaust header Site

[tri-power 250]

This is a pretty good website for header sizing: http://www.centuryperformance.com/exhau ... g-137.html

Ken

 

[Buddy Rawls]

they seemed to omit a critical piece of the puzzle; the valve events. The valve events are what dictate when and how fast the doors into and out of the cylinder are opened or closed. The inlet (total intake system) and outlet (total exhaust system) parameters are seen as a restrictions to the pumping volume of the cylinder. The way those restrictions are addressed in terms of the motor's ability are thru the valve events. This is what dictates the need for earlier/later, quicker/slower, narrower/wider, etc/etc valve events. It has nothing to do with horsepower or usage, but everything to do with the air exchange of the cylinder and inlet and exh.

A quick look at a P-V diagram for a 4 stroke engine demonstrates that the motor is all about pressures and volumes (obviously, P-V), and those absolutely controlled by the doors into and out of the cylinder; the valve events.

The reason a particular header test (diameters) or exhaust system sizing works or not is not because of some innate ability of the header or muffler. Its because the motor's output is due to the whole combination, not simply the exhaust. The scenarios where a smaller header works better are going to end up in cases where the exh valve events are too early or wide to begin with, therefore the smaller tube provides a better match to the door (camshaft) operating the cylinder volume. It matches the opening and closing better and provides proper velocity.

The point is not to say that certain header diameters are good or bad, or that they are linked to a type of usage or hp. The point is to say that the whole engine combination works as a system. You cant build a whole custom motor with this and that, then simply add the headers based on the usage or horsepower. If you are going to use any sort of analogy of exhaust sizing to horsepower atleast use some of the formulas that equate inlet flow capability to 'horsepower potential'. This way you can atleast approach an exhaust size that is based on the inlet capability of the motor, which is miles more valid than usage or horsepower.

the Centruy site says "Example: If you have a stock engine up to about 350 cubic inches, and producing about 300 horsepower installed in your street rod that is going to spend most of it's time going stop light to stop light, all you need is a 1-1/2" primary tube size header."

However, I have seen times when a 1 3/4 header on this essentially same 350 outpaced the 1 1/2 header across the whole rpm spectrum, significantly (incl off-idle response). Why? the valve events and displaced cyl volume required a larger exh cross-section to benefit the motor. Was this a 7000 streetracer motor? no, a truck motor with a small cam that made peak hp around 5300 as I recall, but no exh biasing in the cam events and a it had a relatively narrow LSA (108). What would the same motor have done with a cam having 5-10 degrees more exh, than the intake, and a 112 LSA. My guess is the 1 1/2 or 1 5/8 header would have produced the best response. The issue is, it wasn't the headers, but rather the whole engine combination that produces the output.

With custom camshafts, the exhaust parameters are very much (or better be) in the total picture. Why it doesn't work in reverse, in the articles or guidelines, befuddles me.

a good case in point is 4V cleveland head on a small cid motor (ie 302 boss). To say a 302 cid that is making about 300 horsepower (in factory form and tune) with an inlet capability in the 270cfm range needs to use a 1 1/2 header makes no sense. With 270 cfm on the inlet side paired up with the 130-150 cfm of the 1 5/8 long tube header with typical bends and such, is going to cause lots of problems. even with a cam change to account for it, the motor will need lots of compression to counteract the very weird exhaust events it will need. Even Ford recommended a 1 7/8 or 2" header for a stock bolt on (with appropriate exhaust sytem and mufflers). A 1 7/8 header will enable a flow capability near 200 cfm, which believe it or not ends up being around 75% E/I (versus about 50% or less with the 1 1/2's or 1 5/8's set-up) and the motor runs quite well. Its not about usage or horsepower, its about whole package: what does it need. The 50% E/I ought to be enough to diffuse the argument, and not even touch on the valve events whatsoever.

In the cases of the little sixes, wide lobe separations and exhaust biased cams are nearly everytime going to favor smaller exhausts. Its not the exhausts' fault, its the overall combination.

the narrower LSA's and non exh biased cams (such as the old clifford stuff) are likely going to favor increased exh flow capability.

You can certainly follow guidelines of sites like that, but you have to always keep a card in your back pocket that tells you, you cant take this stuff at absolute face value without seeing the whole picture. What were the engine's parameters, the total picture, when the one component out performed another? thats where the story and the truth are, not in the component itself.

 

[Frankenstang]

In the cases of the little sixes, wide lobe separations and exhaust biased cams are nearly everytime going to favor smaller exhausts. Its not the exhausts' fault, its the overall combination.

the narrower LSA's and non exh biased cams (such as the old clifford stuff) are likely going to favor increased exh flow capability.

Buddy, would it be fair to say, based upon what you've described, that it is relatively 'easy' to over-size the exhaust sytem (going too big)?...and/or would this explain some of the 'perceptible' low end torque losses some have reported when enlarging their exhaust system?

Are there certain measures or specific numbers for the LSA's and exh bias where enlarging the exhaust system becomes a real necessity? Or certain LSA's and durations below which you'd not advise over-sizing the exhaust? I'm still trying to get all this exhaust info to sink into my brain, so hope my questions make sense.
Thanks in advance

 

[Buddy Rawls]

The answer to your question is simply, it depends; what cam, what is intake capability. If these motors have a history of not responding well to an exhaust system and header installation, then I would say you already have your answer; it is easy to over-size the exhaust. But like I said, its not the "header or exh system fault", its the whole combination not responding. saying a 200 six does not like a certain diameter is what is incorrect. Saying a 200 with xxx head and xxxx cam, etc, etc does not like a certain diameter is the correct perspective to address it.

I answered the question with far too much rambling, so I deleted the bulk of the post and focused on the question.

 

[Frankenstang]

The answer to your question is simply, it depends; what cam, what is intake capability. If these motors have a history of not responding well to an exhaust system and header installation, then I would say you already have your answer; it is easy to over-size the exhaust. But like I said, its not the "header or exh system fault", its the whole combination not responding. saying a 200 six does not like a certain diameter is what is incorrect. Saying a 200 with xxx head and xxxx cam, etc, etc does not like a certain diameter is the correct perspective to address it.

I answered the question with far too much rambling, so I deleted the bulk of the post and focused on the question.

Thanks Buddy! I understand the reason to qualify the response with "it depends", but it makes me kinda wish I saw your "rambling" response However as a for instance to further the discussion, if for example, one looks at the stock 200's cam specs (taken from Classic Inlines Tech Specs):

Either:
---Duration.....Intake Open......Intake Close......Ex Open......Ex Close......Overlap......Valve Lift
A)252/256.........7...................65.................55............21.............28.............348
B)256..............28..................48.................76.............0..............28.............372

And, if I've calcluated the LSA's for both correct : they would be:
A) ((252+256)/4)-(28/2)=113 LSA
B) ((256+256)/4)-(28/2)=114 LSA

So assuming each of these stock cams were used with the same head & carb (i.e. same log volume cfm and same carb cfm)...the better way to ask my question might be:
Is there something in particular (given the information above) that would tell you one of these cams "has more exhaust bias" or something about their slight difference in LSA's that would tell you one would benefit more than the other (or one would suffer more than the other) from exhaust enlarging?

I hope this make sense. Trying to make this example as much apples to apples with the main variable in this case being the cam (keeping all other things equal). I guess I'm searching for the 'tipoff' or 'key' in this example, that indicates one cam could benefit or be hurt more by exhaust sizing?

Alternatively stated: Would it have more to do with the slight difference in the LSA's, or the timing of valve events, or difference in durations? Some or all of the above?
I probably need to do a lot more studying on cam tech, but wondering if in this simplified example there is a clue for exhaust needs.

Thanks for any and all advice, insight or explanation you can offer, and again hope this makes sense given my limited understanding. It just seems some of the anecdotal "seat of the pants" data reporting that 'torque was lost when exhaust size was increased', leaves something to be desired.

 

[Buddy Rawls]

...However as a for instance to further the discussion, if for example, one looks at the stock 200's cam specs (taken from Classic Inlines Tech Specs):

Either:
---Duration.....Intake Open......Intake Close......Ex Open......Ex Close......Overlap......Valve Lift
A)252/256.........7....................65.....................55............21.............28.............348
B)256..............28....................48....................76.............0..............28.............372

And, if I've calcluated the LSA's for both correct : they would be:
A) ((252+256)/4)-(28/2)=113 LSA
B) ((256+256)/4)-(28/2)=114 LSA
...

yes, those are the LSA's (atleast based on what you can see in the seat events).

The intake and exhaust centerlines for the 252/256 cam are 119(ICL) and 107 (ECL) ---(113 LSA)
the intake and exhaust centerlines for the 256/256 cam are 100 (ICL) and 128 (ECL) ---(114 LSA)

those cams, per those specs, are so far different from each other it is wild. surely that cant be correct, but if it is correct, I would stick to my guns regarding the motor not requiring exhaust help in the valve events. For sure, the 252/256 has really stifled the exhaust with its 107 degree exh centerline, which is good. But, the intake activity is also really delayed (at 119 int centerline) which is bad; there is no way good "power making" cylinder fill can be occuring in a restricted motor with such small and late intake valve activity.

given the two cams,
I would lean towards advancing the 252/256 to acheive a true straight up 113/113, or as close as possible. Granted the exhaust timing may not be working as well for you, but there may be some better cylinder pressure and low/mid response.

the 256/256 has a better lobe layout, but the LSA is a tad wider, at 114, and with the stock positioning, the exhaust is insanely early. If this were a truly optimized cam for the motor, I would be inclined to think the exhaust is severely hampered, but then why close it so early. Based on the flows, I am not sure this is the case. The motor may be losing alot of torque capability with this cam; and an increase in exhaust flow capability (headers, system, etc) likely kills it. For this one, I would retard it to around a 110/118. intake activity still pretty good, but the exhaust will be moving out to where it needs to be.

the LSA on both cams really needs to be narrower. Atleast with the 240/300, the cam is not really too far out of whack. It could stand to have signiifcantly stronger ramps, but in a stock factory application that does hurt durability. But the small Ford six camshafts look pretty off. I suspect that cam changes in general, see lots of gain; and a proper cam turns it in to a whole different motor.

 

[xctasy]

Ken,Buddy, Robert, this post is gold.

There is an old saying by Jack Braham when he did some consulting work for the Aussie Triad mid engined car in 1984. In a Modern Motor article he said "You start with your combination built up and ready put into production, then you test and optimize it. There is no other way." Transfering that maxim, one can only consult on an existing package, then then suggest if advancing or retarting a stock cam angle setting will work. That's the true science-meets-art of cam selection. All we want is to get the cam making good pressure to yield torque where its wanted.

Firstly, due to the cam to rod clearance issues, all should be warned that the little 200 is effectively an interferance engine. When we recomend a course of action, sometimes its an invalid option due to the rod hitting the camshaft.

Secondly, What hasn't changed is that stock standard 3.3 power ,despite the profile changes, is about 67 corrected rear wheel horse power, 1965 to 1982. Carb, cam, exhast, emissions, ignition, head, valve sizes. But between those periods, every single component changed.

Thirdly, cam optimization is likely to be the best way to yield good power and torque. Ford spent most of its time regigging cam profiles with no apparent change in specified power. But some 200's through the years are dogs, yet others are really a lot stronger than there rating. I use a 1982 3.3, and it runs a heap better than its 87 hp net at 3600 rpm because it has a reworked cam profile which teams up brilliantly with a 2.79:1 diff and 1650 rpm stall ratio auto. But it still gives only 67 rear wheel horsepower corrected.

All little Ford Six cams varied wildly from the stock 240 or 252 or 256 degree call names. Ford used generic cam profile for its engines. 240 for pre 1965 egines, then 256,264, 268 profiles,and a brace or really specialised Cobra Jet/Boss/K-code Inlet and exhast profiles which only saw duty on FE's, small block Windor, 335, 385. Although collectively there might have been a 240 degree at lash profile for an early 200, the intake and exhast profiles could be clocked widley. Ford really did a huge amount of fiddle work,and a so called 125 or 120 hp early 200 six could have had a vastly differnt cam spec to what it should have. Later 3.3's and 4.1's had crazy changes, assumaby to pass the fed sniffer test.

First, Clean Air Act, then local California and then finally the more virilent Federal Motor Vehicle emission testing protocols probably forced Ford engineers to use the stock profile but clock the lobe centers and factory timing chain sproket. The last 3.3 liter FMV emission upgrade in 1980 resulted in a wierd cam profile which stiffled mid range power.

The website information for SAE blueprinted cam profiles I've seen shows that Ford engineers optimized the stock 200/250 profiles about 8 times from 1965 to 1980.

 

[Buddy Rawls]

...then you test and optimize it. There is no other way." Transfering that maxim, one can only consult on an existing package, then then suggest if advancing or retarting a stock cam angle setting will work. That's the true science-meets-art of cam selection. All we want is to get the cam making good pressure to yield torque where its wanted. ....

No disagreement with that whatsoever. However, the point at which you call a combination optimized may be where are thoughts may differ. First and foremost, an engine is an engineering and math quantifiable system. Depending on the tool/s used, the level of optimization might be simply an optimum fuel sytem/ignition system tuning, camshaft alignment or lash experimentation of an existing combination which may not be anywhere near optimized, as far as flows, velocities, displaced volumes and cylinder pressures are concerned, but the tuning, at hand, simply cannot be improved upon any more. Or on the other side of the coin, it may be a detailed look at inlet and outlet cross-sections, and their parameters in terms of flow quantity, flow quality, velocity, and valve events and ramp rates, in relation to displaced cylinder volumes. This is the perspective I look at the engine combinations. From this point optimization is baselined, AND THEN the real world testing becomes the slight modifications to completely vamp the combination. Even at that point it may be another camshaft (or even 3 more), after testing lash response or rocker ratio, or a host of other seemingly small effects that can make a huge difference, or other peripheral components. It may be that the lash exeperiments were indicating a decreased flow potential/capability on the inlet or outlet may be beneficial. on and on and on.

My comments on cam positioning are based in math modeling of the inlet and outlet parameters versus the displaced volumes. IT is very hard to argue that a restricted motor can benefit from lazy and delayed intake valve events and early exhaust valve events. The math bares this out, just as real world bears this out. Based on that premise, as well as cam calcs and customers, aggressive early intake and very delayed exhaust (the quantification is dependant on the amount of exhaust restriction) are what is required, be it racing or towing. The ford 252/256 cam is a awesome example of this, with its extremely delayed exhaust events centerline at 107 degrees, but the likewise delayed lazy intake events just simply do not provide a good cylinder fill. The cam simply needs a narrower lobe separation angle (period). Likewise the 256/256 as well. But in this case, they rocked it way to the other side. The intake events are pretty nice, but the the exhaust events centerline is way way too early at 119 degrees. It too simply needs a narrower LSA. The small six cams would do better if utilizing the valve events of the 240/300 cams ~265/265/110, installed at 110/110.

You made a statement regarding using valve events to get the torque placement where you want it. Actually the torque peak is dependent on port velocity and cylinder fill. In optimum conditions, the valve events do not necessarily control where this occur, they either allow it to occur or they penalize it by attempting to rewrite the torque peak rpm. The valve events can add cylinder fill earlier, which can increase some torque and fill the lower end of the power curve (giving more usable area under the curve- better torque, better shift recovery, etc). Or they can do the opposite. But each time it can be a penalty in reference to where the motor geometry is wanting to go. There is absolutely nothing wrong with wanting a motor to run counter to its geometry (that is the whole point many times), but that is a different kind optimization. That is an acceptance of an ill matched combination, and optimization of whats there, within the constraints of the inlet/outlet/cid/rpm/etc. Those are the scenarios at which the corrective paths may run counterintuitive to the norm. The end result is often that the previously thought intuitive paths must have been incorrect becuase they did not apply in the specific case. This is often the end thought process after testing severely out of whack combinations. The previously thought intuitive "path" is blamed instead of the engine combination itself and its response to the change. In reality, those counterintuitive paths were actually the real world application of the intuitive paths, but the engine combination itself was masking the end outcome, making it look like the intuitive path was incorrect.

We cannot take an extremely non-optimized combination and apply typical techniques of optimization. Their face-value global application does not work, because there are other pieces of the puzzle that may be dominating the situation. For example retarding a camshaft can actually bring the motor closer to optimization and the actual rpm peaks and top rpm decrease. This is counterintuitive because retarding a camshaft is globally thought to raise peaks. What if the cam was so far out of whack thats its response was completely masked by other flow problems in the motor.

In the statements referenced concerning the only reality is in the real world testing does fit this thread to a tee. However, there are parameters that are 100% addressible and easily calculated pointing the direction (or trend ) things need to go. This puts the optimization at a higher level, and at that point things can make a lot more sense. The best way to address the changes, outside of the math, is to step back, observe, and say there are no real guidelines, no absolutes, all responses come from test results, with the specific combination at hand. As is the case that Jack Braham (I assume Brabham) references; it is absolutely 100% correct. However, the math and engineering can reveal a different story. They can demonstrate the trend to follow, and testing therefore becomes a tuning exercise of confirmation (or failures) with minor turns and joggles. An accurate math model is required.

 

[xctasy]

Wow.

Cam timing is indeed the heartbeat of an engine. Thanks for that. I understand that development is therefore not a closed loop, and that there is out side math and engineering input which can give clues to a better combination. I've worked on

I'd like to share and feed into and elaborate on how downgradeing duration and exhast spec , while optimizing valve lift can raise power and torque a whole 9 percent in two I6 applications. Or how optimizing independent runner EFI calibration verses the best 2-bbl 500 cfm carb set-up can yield 9% more power and torque. To get 9% from just optimizing and reworking the basics of a factory six cylinder performance egine isquite something. The first engine is based on a triple carb 1971 XU1 GTR spec item, which made 190 hp gross at 5300 rpm, and took a 2500 pound car with close ratio M21 four speed maunaul to a 15.8 second quarter mile, and 125 mph top speed. Actual power was 142 hp net. The second started out as a 1985 142 hp port EFI 3.3 six which did 16.7 to 17 second quarters and 115 mph in a larger 3-stage auto 3000 pound car. Despite 14 years, the first engine and second produced the same flywheel horse power but this first needed a 308 duration cam, the second a mild 264 degree cam. When each engine modifed to the specs included, power or the first went up 78%, and the second went up 56%, and quarter mile dropped almost 3 seconds for the EFI six. So 15 years of developement allows a streetable 280 degree cam engine to eclispe older engine tunes.


Getting back into the exhast part of modification or optimization model, I've seen some astounding things over the years regarding six cylinder engine exhasts and cams. See the following 1.26 lb-ft per cubic inch Holden six cylinder engines. Engine specs span 500cfm 2-bbl, triple SU HS6 1.75", and then factory Independent runner tuned port efi. Power and torque are equal at 5252 rpm, so they were picked to simplify the torque and power calculations.

If you look at the flywheel net data on two 202/3.3 liter L6 Holden engines, you'll most likely see exactly what is happening. But what I will say is that the first five dyno tests on a 9 port head engine just optimized the exhast, putting in a milder solid cam with less duration but more lift, and better lash and intake refinments, 8.6% more specifc power was made. Went from 210 hp at 4750rpm to 254 hp at 5250 rpm. Stock cam was an XU1 HX cam with 308degrees duration. The Waggot E3 was less duration, more lift. The exhast? Downgraded from tuned length tube headers to a single dual outlet iron exhast header with an iron divider added. Second test on the 12 port indictes just how hard it is to optimize a TPI engine when compared to an optimized 2-bbl L6. EFI yielded 18 hp more from an extra 250 rpm, but no specifc power increase. 22 lb-ft or 9% more torque. No change in exhast or to the 280 degree cam.

If you'll take a snap shot of the rather odd way I've contended with increasing BMEP (iMEP, bMEP, fMEP, or in my case Maximum out put cylinder filling and inertial ramming in this post is covered by an Aspirations Index based on likey power that a cross section of different but optimized four stroke engines can likely produce), then you'll see that the timing of the inlet opening verses exhast closing has profound impacts for higher specifc hp per cube six cylinder engines in the 200 cubic inch area. See a post from back eightyears ago when I was looking a drawing straightlines between basic low specific out put Detroit OHV production engines to NASCAR/AVESCO/AustralianTouring Car Championship style engines. I still use this approach as an optimization litmus test. You'll no doubt have read that the likes of David Vizard often look for key performance indicators, like asking if your two valve per cylinder engine makes 1.39 lb-ft per cubic inch (a BDA Cosworth 4 valve per cylinder key performance indicator of about 207 lb/in2). I look at how low the AI value is trending. If its 3630, such as an Australian Vee Eight Super Car Organisation AVESCO canted valve port EFI Windsor might produce (305cid*7500rpm/630hp net= 3630), its state of the art. A 1986 600 mile GroupA race car with 4-bb 725 cfm Quadrajet equiped Holden 304 gave 462 hp at 6700 rpm, which is 308*6700/462=4409 with just a Wade 169 cam with about 276 degrees duration. 15 years before, the three leading 1971-72 contenders ran three special combos. A 1971 Bathurt 600 mile racer ran a 780cfm 3514V HO GT engine which gave 350 hp at 5800 rpm for 5833 with a 300 duration solid lifter cam. Difference is just how optimized the cam was in those 15 years of development. An independent runner 3 times 2-bbl DCOE45 265 cid canted valve I6 gave 296 hp at 5300 rpm in 1972 with a 306 degree cam. AI ratio was 4744. A 202 XU1 Torana with three 1.75 CD 175's gave 216 hp at 5500rpm, for a 5144 AI ratio. These were dyno net figures by engine builders Webb, Leonard and Tate. So that's AI index, which isn't really BMEP, but Maximum Output verses revs and capacity.


Anyway,the post is here. viewtopic.php?f=5&t=5554&p=38262&hilit=+how+aussies+build%2A+#p38262

 

[Buddy Rawls]

Your factored relationships are essentially an inlet capability versus displaced cylinder pumping volume ( CID and rpm) relationship. You have established a criteria or fudge factor to address the actual port velocity issue (which is super important to the process), which is critical to the big picture. One end of your spectrum is very restrictive motors ran at high rpms (extreme port velocities), the other end of the spectrum is very flow capable inlet inlets running at low rpms (slow port velocities). I do not use multiple curves based on the level of modification, I go straight for the actual inlet and outlet parameters in comparison the displaced cylinder 'pumping' volume using a single set of equations, regardless of the build level. Three quick examples, using your A? relationship, in my direct experience (camshaft customers) are an FIA 289 build that mapped to a 4550 AI, a 360 cid outlaw street car (nat asp) that mapped to around 3600 AI, and a stock headed 125cc 289/302/E7 head on a 306 that ran around 5700 AI . I have never used such a rating system, but it is cool to see how it fits in your criteria.

Interesting read on the link regarding exhaust experiments. However, without the flows and cross-sectional areas of the inlet system, exhaust header dimensions, and valve events, it is pretty futile for me to draw any conclusions.

As far as Vizard's stuff is concerned, there are some liberties often taken in the books that are not conveyed in the final text. A big one I recall is the LSA relationship versus CID. What is not clarified in the write ups is that the inlet parameters are held constant as the CID is increased. This shows the relationship of the exh positioning relative to the intake getting narrower as cid increases. In reality what is happening is that as the CID increases the engine combination becomes more and more inlet restricted (inlet velocity is increasing). It's only a function of CID if the inlet capability is held fixed; this extremely important issue is sort of left out of the literature altogether early on, and only latest book revisions attempt to address it. The cid versus LSA is too easily argued by simply looking at the 500 cid pro-stock motors running 114-119 lobe separation angles. Once again, its a function of flow parameters in relationship to the displaced volume.

Anyway, I don't want to be considered hijacker, since this thread was essentially an exhaust thread. To me you simply can't look at one without the other, which is exactly where I started my first reply to the thread.

when it comes to valve event stuff and intake/exh interaction, I really enjoy it and I am a sponge when it comes to different methods. Thats why I spent the better part of 10 years (88-98) developing my own math for it. By knowing the many avenues I took (with a lot of wrong turns from reading articles and books), it enables me to pick out the avenues and methods that others are taking. It does not make me an authority by any stretch, but it does make me very observant.

 

[The_DropOut]

So this thread has been a very awe inspring read so far. But it does me no real good, for I dont have the tools, funds or time (10 plus years) to experiment with these facts.

I was looking for any cam for my 200ci motor. There were several companies who offered a very limited choice. I read as much as I could absorb and then I made an educated guess on which cam would serve me best. I went for a Schneider Racing Cams 256-H grind.

Its stats are:
...........VALVE LASH.....VALVE LIFT.....DURATION.....CAM LIFT.....DURATION @.050" CAMLIFT
INTAKE: .000__________ .420________256________ 280________204
EXHAUST: .000________ .420________256_________280________204

It also says OPEN:260/280 CLOSED:90/100 OUTER: 68044 LOBE SEPERATION: 112 DEGREE INTAKE 110

Some of these stats done mean anything to me due to my lack of experience.

I wonder if you guys could coment on this cam or other cams available to the avarage Joe and explain what kind of performance to expect or how to size their exhaust headers based on store bought cams.

Thanks.

 

[bubba22349]

Check out this link it might help your understanding of cams some it also lists many of the cams that are available for the small sixes. than you need to decide what type of use you want out of the car too IE a Daily Driver, weekend cruiser, a combo street and race or race etc and the other parts combo you will be using with it. Good luck

http://www.classicinlines.com/SelectCam.asp