Author Topic: Cam Choice  (Read 14292 times)

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Cobra1

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Cam Choice
« on: November 17, 2012, 08:26:35 PM »
I'm new to this forum but have read it with interest. It seems like there's a alot of very knowledgable people here. Wanted to get a cam recommendation for a 427 SO. So I called two companies.

Its for a 427 SO
4.25 Bore
3.78 Stroke
10.5: CR
93 Octane
Stage 2 Edelbrock Heads
4 speed
3.54 Rear
2500lb car
26" tires

Solid Roller Cam
Webers
6500 rpm max
Mostly street use


Cam A: 243/243 @ .050"
            .624"/.624"Lift
             114 LCA

Cam B: 253/261 @ .050"
            .690/653" Lift
             114 LCA

I was a little surprised by this so I decided to call a few more companies. (Seven total) And the answers were just as varied. Some were from the low to mid 240's. Others from the low to high 250's. Now there can only be one right cam. So which is it? Are there two different philosophies here?? When I asked the companies about the larger cam "why so big?" the answers varied from "those are good heads" to "its a light car" to "need a large cam to bleed off compression for pump gas"
Those with the smaller sizes said those sizes would perform better on a street application.

Now its certainly complicated by the fact that Webers "like" less overlap or a wider LCA. Also , further complicating things, 4 of the cams were Dual Pattern and 3 were single pattern.

Would like here everyone's opinion.



           

jayb

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Re: Cam Choice
« Reply #1 on: November 17, 2012, 08:40:30 PM »
It would be helpful to have more info on the cams, specifically the advertised duration on the intake and the amount of advance ground into the cam, if you are going to install it straight up.  These are the numbers used for DCR calculations.  On first glance you don't have the compression to support some of the larger duration cams, but again it will depend on seat to seat timing.

Also I'm not sure I agree that there is only one right choice.  Different cams will give you power in different RPM ranges.  Where do you want to make the power?  Do you have a horsepower target?
Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC

   

plovett

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Re: Cam Choice
« Reply #2 on: November 17, 2012, 08:45:17 PM »
There is not one right cam.  Of the two I would go with cam 2 in such a light car, but that's just my opinion.  10 different drivers should have 10 different opinions.

JMO,

paulie

Drew Pojedinec

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Re: Cam Choice
« Reply #3 on: November 17, 2012, 08:58:47 PM »
Maybe I'm just ignorant, but with a 6500rpm ceiling on the street, why not go with a hydraulic roller?  I mean, if you were going to the track and running the engine way up high, it'd make lotsa sense.  I'd think in a car that light, just about any 427 ought to be retardedly fast...

Cobra1

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Re: Cam Choice
« Reply #4 on: November 17, 2012, 09:08:26 PM »
Jay,

I wasnt given advertised duration figures. TBH, I thought cam manufacturers were moving away from advertised duratio to sort of compare "apples to apples" as it were. But I could be wrong....I'd like to peak around 6000-6200 rpm and shift around 6500-6600. As for horsepower I think 550-580 is doable. Its such a light car I'm sure I'll scare the hell out of myself....

Drew,

Rregarding the hydraulic roller, honestly this is a weekend car. Something to have fun with and tinker around. I'd like to take it out on the track (road racing) maybe once a year. I've also read alot of negative things about hydraulic roller cams. I know they are supposed to be maintenance free but I don't mind adjusting the lash a couple of times a year...

hotrodfeguy

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Re: Cam Choice
« Reply #5 on: November 18, 2012, 01:01:42 AM »
Just curious but why not the 4.25 stroker crank and make it a square engine? Then you could go with a juice roller and still make just as much if not more @ 6k as you would with your combo now all day @ 6500.
Not kicking your build cause I already did the 4.25" purchase and am going the 4.5" route, after looking at Jay's rod clearing for the cam. For a 65 Mustang witch is way light also.

Cobra1

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Re: Cam Choice
« Reply #6 on: November 18, 2012, 08:32:08 AM »
Hotrodfeguy,

I knew someone was going to ask me this. If I was driving a Fairlane or Mustang I wouldn't hesitate to go with a 482" but in a 2500lb car its not going to take alot to get going. I can tell you I've driven a 289 Cobra with a 347" and had to change my shorts afterwards! I've spoken to a few engine builders about this and got agreement. Lighting the tires in 3rd gear at 100mph shouldnt be a problem.

jayb

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Re: Cam Choice
« Reply #7 on: November 18, 2012, 09:46:25 AM »
Jay,

I wasnt given advertised duration figures. TBH, I thought cam manufacturers were moving away from advertised duratio to sort of compare "apples to apples" as it were. But I could be wrong....I'd like to peak around 6000-6200 rpm and shift around 6500-6600. As for horsepower I think 550-580 is doable. Its such a light car I'm sure I'll scare the hell out of myself....


Can you look up the cam specs online and match up to the specs you have?  DCR calculators require seat to seat duration numbers; if you plug in the .050" numbers to the spreadsheet I gave you, you'll get the wrong answer.

The 427 sideoiler dyno mule in my book made about 580 HP at 6400 RPM with the Webers and a Comp Cams 308R roller, which is 312 degrees seat to seat, 262@.050, and .674" lift.  That was also a pretty sophisticated short block with a lot of low friction tricks that were probably worth at least 20 HP.  That engine also had 10.5:1 compression, which was a notable compromise with that cam, because the short block had been put together for Engine Masters and 10.5:1 compression was mandated by the rules.  DCR on this engine was only 7.1:1, so more compression would have picked up some power on this engine. 

Bottom line on this is that if you are stuck at 10.5:1 compression, you will need a pretty big cam, like that Comp roller, to get to your horsepower target.  I'd guess that to get to a reasonable DCR of 8:1 or so, you will end up with a much smaller cam, which may preclude reaching your horsepower target.

If possible, I'd consider going to a higher compression ratio, or going to more cubes.  It is much, much easier to make the horsepower target you have in mind if you alter those two variables.  Otherwise, you could revise your horsepower target down, because even a 500 HP 427 will yank that 2500 pound car around pretty well... 8)
Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC

   

Cobra1

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Re: Cam Choice
« Reply #8 on: November 18, 2012, 03:51:16 PM »
JayB,

I agree. I think a smaller cam, say something in the 240-245 range might work. What do you think?

Mike

Cobra1

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Re: Cam Choice
« Reply #9 on: November 18, 2012, 04:38:51 PM »
Jay,

Excuse the previous post; I misunderstood your question. Maybe go up to 11:1? Or try a 244/250 or 240/245 cam. I saw the combination Barry R ran on his 2007 EMC entry. I'd like to do something similar. It seems the powerband on that engine peaks at 6500rpm (or higher). If I can have it peak at say 6100-6200rpm and shift at say 6500-6600 that would be great. I'm thinking 10.5-11:1 CR as I'd like to run pump gas. 93 octane. I'd like to go with a nice set of Edelbrock heads. Stage 2 (if you want to call them that). Blair Patrick, Keith Craft, Kuntz, Survival, etc. Barry made 659hp on his combo with 10.5:1 and a 252/252 solid flat tappet so I think 550-600 is doable. Yes the Webers will max out about say 6000 rpm but I think I can get some airflow back with a few little tricks like profiling the throttle shafts, flared velocity stacks, etc. If not open up the throttle bore to 51.5mm. What do you think??

afret

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Re: Cam Choice
« Reply #10 on: November 18, 2012, 05:24:55 PM »
If you want to hit the DCR target of around 8 as Jay suggested and still run a decent size cam,  Lunati has a solid street roller cam with 255*/263* at .05 lift  and 285*/293* at .02 lift (advertised).  Lunati a .390 lobe and a .400 lobe for either a .686" or .704" gross valve lift.  This would give you around 8.1 DCR with the cam ground with a LSA or 110* and installed 106* ICL.  If 108* LSA and 104* ICL, the DCR will go up a bit to around 8.25.  This cam is from a line similar to the Comp XE solid street roller lobe family and will work with the same valve springs that work with the XE cams like the Comp 943 for a 1.9" seat height or the Comp 955 for a 2.0 seat height.  According to UD Harold who designed the Lunati lobes, it's supposed to be an improvement over the Comp XE series.   Somehow a Cobra would be missing something without a solid lifter cam.   :)


Cobra1

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Re: Cam Choice
« Reply #11 on: November 18, 2012, 06:03:33 PM »
Afret,

I agree regarding going with a solid roller. Like I said its a weekend car. I want it to be a little hard core. I'd like to run a DCR of at least 8.5. In Barry's FE book, he says Cobra's can get away with a little higher static compression due to there light weight. Say 11:1.

The 255/263 sounds a little big for my RPM range. What do you think??

My427stang

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Re: Cam Choice
« Reply #12 on: November 18, 2012, 06:08:11 PM »
I run 8.33 DCR in a heavy 70 Mustang, no issues if you have a decent quench, it'll run on almost anything. I wouldnt go to 8.5, but I'd be very happy between 8.1 and 8.35-ish

I also ran a 250 solid flat tappet in the car when it was a stock stroke 427, it did fine and is WAY heavier than your setup

I also like the idea of narrowing the centers and running it on 105 or 106 ICL.  Webers don't like reversion, but with the cam up at 105 or 106 it'll do fine

I think a 294 advertised / 250s at .050 intake lobe, timed for an 8.2:1 DCR would work out great for you.  Pick lobe seperation based on how much lope you want, but realize the small motor will like tighter centers more than wide ones


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Ross
Bullock's Power Service, LLC
- 70 Fastback Mustang, 489 cid FE, Victor, SEFI, Erson SFT cam, TKO-600 5 speed, 4.11 9 inch.
- 71 F100 shortbed 4x4, 461 cid FE, headers, Victor Pro-flo EFI, Comp Custom HFT cam, 3.50 9 inch

Cobra1

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Re: Cam Choice
« Reply #13 on: November 18, 2012, 06:17:38 PM »
Mystang,

I like your combination. Doesnt seem to far off from mine. I think a DCR of 8.5 or maybe a touch higher is doable with such a light car BUT I have no proof...I'd like to hear other thoughts.

Is a 250 duration on a solid flat tappet the same as a solid roller??

What I was told with Webers is keep the overlap down. Either a small cam or a wide LCA, 110-114. Again, I'm not a Weber expert, just what I was told.

Does an individual runner setup like a bigger cam? Does a lightweight car like a bigger cam?? Again want to keep the power band under 6500-6600 RPM.

jayb

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Re: Cam Choice
« Reply #14 on: November 18, 2012, 07:03:41 PM »
A solid at .050" is the same as a roller at .050"; both are measured at .050" lobe lift.  And I would agree that you want more overlap with the Webers, and I think the drivability issues of a bigger cam are not as pronounced in a lighter car.

Here's what I would suggest:  Go to 11.2:1 static compression, and get a Comp Xtreme Energy Street Roller cam, with lobe 4875 on the intake and lobe 4876 on the exhaust, set up at 112 LSA and 108 for the ICL.  You can go to the Comp Cams web site to download their lobe catalog for all the specs, but the 4875 lobe is 286 advertised duration, 248@.050", and will be about .672" for gross lift.  The 4876 is 292 advertised, 254@.050", and about .678" for gross lift. I think that combination will give you a broad power band from 3500-6500, and peak around 5800-6000 RPM, and you will come very close to your horsepower target with that setup.  The heads should flow in the 300 cfm range on the intake and 220 cfm on the exhaust to make everything work.
Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC