Cam Shaft Mystery 5.0L

[Jim Dewar]

I would like to build a stock short block with 165 AFR heads and a 650 Demon carb.on a Airgap manifold.
Has anyone built this combo with success?
My concern is which cam to purchase for piston clearance.
I get very mixed recommendations from different suppliers.
I need advice from a camshaft wizard!

Jim /ubbthreads/images/graemlins/confused.gif

 

[Brett James-McCall]

Why don't you speak to AFR, they were very helpful when I mailed them. They will give you advice if you tell them what you want. (It'll probably be a Comp Cams cam thoough)

Brett

 

[Jim Dewar]

Thanks Brett,
I spoke with AFR and they were very shy about how much camshaft to recommend because of piston clearance.
They do recommend Comp cams, so I called them, they were reading to me from a script. At this point I thought I might post and see what you guys might know.
Regards,
Jim

 

[Adam C.]

General rule:

If it is a stock late model 5.0L block with valve reliefs in the piston tops and the heads have inline valves (pretty much all but twisted wedge) with 1.94" intake valves, you can run up to an X303 cam (224 deg. in. 224deg. ex. @.050", 0.54" lift on 112LSA)

Heads with inline valves and 2.02" intake valves usually require notching the pistons further. The twisted wedges can run 2.02" on a stock block with the X303 cam however, due to their relocated valves.

 

[Lynn Larsen]

James,

I relatively sure that the cam you chose can be accomodated by the pistons you chose. You can specify the reliefs you need based on the head/cam combination and desired compression ratio. Now as to cam choice; depends on how your are going to use the car and the rpm range that you want you sweet spot to fall in. Once you've decided this aspect, you should be able to go to Comp or other well known cammers and provide the runner lengths, header lengths, displacement, etc., etc. and they should be able to give you a cam profile.

As an example, I had speced a 347 ci motor with 4.125" bore and 3.25" stroke, Roush (EFI) intake, AFR 205 heads, GT40 exhaust (1 3/4" primaries), 3K-7k rpm range, mostly street car with occasional track days. The cam recommendation was a comp cam solid roller (for rpm requirements) with right at .600 lift on intake/exhaust, duration in 230-240 degree range and 110 degree LA. Like everyone, I wanted my motor to idle like stock and run like a NASCAR motor. This grind should give an idle the I can live with on the street, plenty of torque down low (it had >300lb ft across the board) again for street driving, but also continued to make power right through 6500 rpm. Max HP was calculated at just a hair over 500 very near 6k rpm. The gearing of your transaxle will also come into play here. I am using a Porsche and, as a result, want my power a little higher in the rpm range than most American performance motors.

I am going from memory here because my main computer's hard drive crashed last night and I can access the exact numbers at the moment. But, these are very close.

Lynn

 

[Bill Musarra]

James,
Your choice of cams will probably fall along the manufacture's recomendations. I have collected articles over the last several years onarticles from door closing mechanisms to which is the best crate engine.
In some of the articles they tell you exactly what they used and how it worked. Granted some of the engines built were for dyno only, but what I have found is that you can use the stock pistons(as long as they have valve reliefs) on just about any cam out there. I have seen from just using GT40 heads up to AFR225 and HP figures from 275 to 600. MM&FF mag did an excellent series on the "Ultimate Guide to 5.0 Cylinder Heads" that lasted through about 6 issues. They used engines that were detailed throughly and I think used Comp cams in all.The early articles were on the 302's and finally worked up to the 427's(heavily mod 351's). They started with the stock heads, then progressed through the different flow sizes up to the monster 225's, with each level used at its optimum size engine.(165,185 on 302's 205 on 351's etc.) the only disaster they had was when they went to a 418 engine and were running 12.0:1 compression and a wild 264/268 race roller camshaft. While using the AFR 205 they noticed the power to be off and when checked, they had bent a few valves. They were in a hurry to meet the publishing deadline and didn't check the piston to valve clearance.(something every engine build should include). These engines were putting out over 600 HP.
What this diatribe is leading to is that you should consult the various parts manufactures and see what they suggest. Then research the various mags like MM&FF or Popular Hotroding(Engine Master's Series) for what they might have done with your combo. Check with the different engine crate suppliers and quiz their tech guys on your choice of equipment with their particular engines to see what they have to say. There is a lot of info out there and a lot of people with the knowledge(outside of the forum). Just ask around. Most of these guys are happy to give you their views and opinions.Regardless of what you use, tell them how you plan to use it and be sure to check the clearances twice before you fire it up.
Bill

 

[Jim Dewar]

Thanks for your replies,
Mr Christian,
Would you recomend the ford cams?
When you refer to "up to an x303", this I understand to mean all under but not including an x303. So I should select one of the lower cams?
This engines primary use will be for street performance and some moderate track use.
Regards,
Jim

 

[Ron Earp]

Hi James,

If you're using the stock short block and Airgap you're looking for a fairly mild to medium combo. I would just purchase a X303, as one suggested, and use it. It'll work well and provide what you want without a lot of hassle, guessing, etc. You might, if you try, get a little more power with a lot of selection but that isn't written in stone. I'd used this combo, not with an air gap, but with the Performer RPM and it did well, making about 304 rear wheel hp if I remember correctly in a 85 Mustang (not mine, a buddies I helped wrench) with a 650 Eldebrock carb. That is about 330-340 crank hp, not bad at all for the small amount of cash spent. Just my 0.02.

R

:Correction above - I've used this before, not that I wouldn't use an Airgap. I think the AirGap is a good manifold and I prefer it over the others they make.

 

[Jim Dewar]

Hi Ron,
I'm following your advice on easy build from an early post and having great fun! Sounds like good advise.

Jim

 

[Adam C.]

[ QUOTE ]
Would you recomend the ford cams?

[/ QUOTE ]
For a mild engine they are fine. Notice that all of the FMS alphabet grinds (B E X F Z) have equal duration for intake and exhaust. Many will try to steer you towards a cam with longer exhaust duration than intake. For well balanced heads (intake to exhaust flow), and the engines that these cams were ment to be in, there simply isn't any power to be had with asymetric grinds. So the FMS cams are a good choice for mild engines with hydraulic roller lifters.

[ QUOTE ]
When you refer to "up to an x303", this I understand to mean all under but not including an x303

[/ QUOTE ]

This actually includes the X303. I used it as the example because it's properties are relatively well known. Basically you can be pretty sure that this cam will work without piston to valve clearance isues. If you change any of the parameters in the "more perfomance" direction, i.e. increase duration, decrease the LSA, increase the lift, then you may have interference issues.

That said, you would probably do fine with the X303, or the E303 for that matter. There is little performance difference between the two, but the E is emmissions legal to boot, if that is a concern. There is no problem with selecting another brand of cam, so long as they have similar specs as the these.

 

[Howard Jones]

Adam, I have a question. I have a B303 cam in a SVO 302, 9to1 motor. After looking over the cam specs in the ford motorsport catalog it looks like that the B cam and the X cam are pretty much the same except lift, B=.48 X=.54. The head I have has 1.6 rocker ratio arms in it . If I went to 1.7 wouldn't I end up with about the same lift without changing the cam? This way I could kinda get a 2fer. Roller rockers and a cam upgrade.

Thanks for the real engineer stuff, it helps a lot.

Oh Jim, A 302 roller cam motor rebuilt with 9 to 1 pistons, 165AFR's with roller rockers, X303 cam, and the 650 demom/ airgap would be a very nice road going motor and would make something in the neighbohood of 350-390Hp. That's plenty. Don't forget ignition, I am using a all MSD setup, small cap billit, 6AL box, and SS coil. My advice keep the motor simple to start with and sort out the rest of the cars systems.

 

[Jim Dewar]

Thanks Guys,
All of your info is very helpful and I hope you will let me call on you again!
Jim

 

[Adam C.]

[ QUOTE ]
wouldn't I end up with about the same lift without changing the cam?

[/ QUOTE ]

Correct, the overall result will be similar. Be sure to get a shim kit and set the preload properly, and that you get the correct bolt-down rocker arms for the svo heads because they are pedistal mount.

Adam