[Kent535]

Hi guys, im going to put in a 351W engine in my 87 Mustang in less then a month and already ordered most of the parts for the engine. The only main purchase is the Cam. Before i order i need to clear up on the size in which will work in the application. The motor will be stock with the exception to a edelbrock performer intake, BBK performance Headers, and a 600cfm Holly performance carb. My question was what is a safe Cam duration and lift to get without causing any problems?
I was looking at a Thumper cam by comp. Here are the specs.
Would i run into any problems?

Lift type: Hydraulic Roller Lifter
RPM range:1900 to 5600
Valve timing:0.006
Lobe Separation:107°
Intake Centerline:102°
Intake Valve Lash:Hyd.
Intake Duration:283
Intake Duration@.050"lift:227
Intake valve Lift:0.531
Intake Valve Lift:0.332
Exhaust Valve Lash:Hyd.
Exhaust Duration:303
Exhaust Duration@.050"lift:241
Exhaust Valve Lift:0.515
Exhaust Lobe Lift:0.322

[thisguysride]

That cam will work and you like it alot. But make sure you have strong springs to match it or youll get valve float. Also stick with the stock ratio rocker arms. If you change that youwill really need to measure your clearance.

[Kent535]

Originally Posted by thisguysride That cam will work and you like it alot. But make sure you have strong springs to match it or youll get valve float. Also stick with the stock ratio rocker arms. If you change that youwill really need to measure your clearance.

Thank you for the fast reply! so just to sum it up, get the Strong springs to match it and keep the stock rocker arms that came with the 351W motor correct? How aggresive is the cam in terms of sound?

[ryanw]

ask comp cams what springs they recomend for that specific cam. they will give you a part #

[69fastback]

That cam will be SUPER lazy in a stock motor. Depending on what 351W you have, it won't be anymore than 9.5:1 compression in stock form, and that cam has a lot of overlap. It's going to want at least 10.5:1. You won't like that cam in town, or anywhere for that matter. You don't have enough intake or head to get it to the RPMs it's going like, and not enough compression. With stock heads and a performer intake you need a much smaller cam. Is it a flat tappet motor, or roller motor?

[Kent535]

Originally Posted by 69fastback That cam will be SUPER lazy in a stock motor. Depending on what 351W you have, it won't be anymore than 9.5:1 compression in stock form, and that cam has a lot of overlap. It's going to want at least 10.5:1. You won't like that cam in town, or anywhere for that matter. You don't have enough intake or head to get it to the RPMs it's going like, and not enough compression. With stock heads and a performer intake you need a much smaller cam. Is it a flat tappet motor, or roller motor?

The motor is a flat tappet motor, I guess the cam i listed sound too much towards the performance side. So Could you recommend a good cam that would be great for my application? Thank you.As for the RPM the motor will only see up to 45000 RPM.

[69fastback]

It's the overlap and duration in that cam that will kill you. It just wants compression.


This cam will make good power, and have good manners, yet still sound good.

COMP Cams CL35-242-3 - COMP Cams Xtreme Energy Cam and Lifter Kits - Overview - SummitRacing.com


If you stepped the intake up to something like a Weiand Stealth, you could run the XE274H, and it would help a lot. Call Comp and ask them.

[69fastback]

This one could be an option too.


COMP Cams CL31-238-3 - COMP Cams Xtreme Energy Cam and Lifter Kits - Overview - SummitRacing.com

[Kent535]

Originally Posted by 69fastback This one could be an option too. COMP Cams CL31-238-3 - COMP Cams Xtreme Energy Cam and Lifter Kits - Overview - SummitRacing.com

Can both of those cams be used with the existing springs, rocker arms etc. that are going to come with my 351w motor?

[69fastback]

Any time you change a cam, you need to buy matching springs. Springs are very important. Another thing you may have to consider is your rocker arm studs. Yours are probably press in studs, and the general rule of thumb is that any cam over .500 lift will have spring pressures that will pop the studs out. A machine shop can put screw in studs in for you, and if you're using roller rockers, you'll need guideplates. When they put the screw in studs in, they need to machine the thickness of the guideplates off of the rocker stud pedestal to keep the geometry correct.

I know that sounds complex, but does that make sense? If you just put the guideplates on, and don't machine the pedestal, that makes the rocker sit that much higher, which will afftect geometry. Too bad I cleaned out my shop here a while back, and sold a bunch of stuff. I had a set of 351W heads that had all this stuff done, and I would have sold them to you real cheap. I think I got $50 for them. I had a basically stock 351W with a Weiand Stealth and a XE274H, and it ran pretty well. Very good low/mid power.

[Kent535]

Originally Posted by 69fastback Any time you change a cam, you need to buy matching springs. Springs are very important. Another thing you may have to consider is your rocker arm studs. Yours are probably press in studs, and the general rule of thumb is that any cam over .500 lift will have spring pressures that will pop the studs out. A machine shop can put screw in studs in for you, and if you're using roller rockers, you'll need guideplates. When they put the screw in studs in, they need to machine the thickness of the guideplates off of the rocker stud pedestal to keep the geometry correct. I know that sounds complex, but does that make sense? If you just put the guideplates on, and don't machine the pedestal, that makes the rocker sit that much higher, which will afftect geometry. Too bad I cleaned out my shop here a while back, and sold a bunch of stuff. I had a set of 351W heads that had all this stuff done, and I would have sold them to you real cheap. I think I got $50 for them. I had a basically stock 351W with a Weiand Stealth and a XE274H, and it ran pretty well. Very good low/mid power.

My dad is saying anything over a .500 lift is to extreme for what I need, because I would have to put stiffer springs, hardened push rods etc. he was suggesting I go the route where I just buy the cam and lifters and use the pushrods, rockers and springs that came with the motor. What do you think?

[69fastback]

You won't need hardened pushrods, but you absolutely will need new pushrods. You can not change a cam profile and not change pushrods, not matter how small a cam you put in. And no one can tell you what length they wil be. There are just too many factors, so you HAVE to measure for it. The process is simple, and of you get to that point, we can help you out here. You can use the rockers, if you don't have to go to screw in studs, but the best option always costs more money. Screw in studs, and roller rockers are a better choice. Do you know anything about the spring you have? Stock? Miles? Anything? I would really suggest changing them if you swap the cam. It's really a necessity, regardless of the cam. Springs are not one size fits all.


Typically with any cam swap, you'll need springs, and pushrods. Always.

[69fastback]

And remember too that there's a lot more to a cam than lift. Timing events make up the cams personality.

[Kent535]

Originally Posted by 69fastback You won't need hardened pushrods, but you absolutely will need new pushrods. You can not change a cam profile and not change pushrods, not matter how small a cam you put in. And no one can tell you what length they wil be. There are just too many factors, so you HAVE to measure for it. The process is simple, and of you get to that point, we can help you out here. You can use the rockers, if you don't have to go to screw in studs, but the best option always costs more money. Screw in studs, and roller rockers are a better choice. Do you know anything about the spring you have? Stock? Miles? Anything? I would really suggest changing them if you swap the cam. It's really a necessity, regardless of the cam. Springs are not one size fits all. Typically with any cam swap, you'll need springs, and pushrods. Always.

The springs would be stock and im assuming new since the block is remanufactured? So really what im looking at now is a cam under .500 lift. I use the new lifters that come in the Cam kit, New Springs NOT the ones from the remanufactured 351, and New pushrods with the size i need for the new cam correct? so all i really have to replace when i get the 351W are the springs and pushrods at the bare minimum correct?

[69fastback]

Yes. If you go with this cam COMP Cams CL31-238-3 - COMP Cams Xtreme Energy Cam and Lifter Kits - Overview - SummitRacing.com your studs would probably be ok, and you could likely get away with just springs and pushrods.

Make sure your heads have stud mounter rockers instead of pedestal mount. 351 heads could be either.

[Kent535]

Originally Posted by 69fastback Yes. If you go with this cam COMP Cams CL31-238-3 - COMP Cams Xtreme Energy Cam and Lifter Kits - Overview - SummitRacing.com your studs would probably be ok, and you could likely get away with just springs and pushrods. Make sure your heads have stud mounter rockers instead of pedestal mount. 351 heads could be either.

Thank you for the help! i appreciate it ill go with that.

[69fastback]

No problem. Just to get more input, I'd call Comp and tell them your plan, just to see what they say. It really doesn't make much difference I guess because if you call and talk to 5 different people, you'll get 5 different answers. That's what sucks about Comps tech line.