I'm running a 302 Ford with B303 cam and 1.7 roller rockers. I'm getting valve float at 5500 rpms, and am thinking that it's probably the valve springs. What kind of springs would be a good replacement. I'd like to get 6000 or 6200 out of it.

 

I'd call the cam manufacturer for that info. Isky was really helpful when I was putting mine together. They confirmed that my rockers and valve springs would work with their cam.

 

Call PAC...... I've had a few bad experiences with Comp's valve spring breakage.

 

What kind of lifters are you running? Stock ones will float at that rpm. Check out the factory numbers on them.

 

How do stock lifters cause float? In the Ford world, are the OEM's way heavier then the aftermarket units or something?

 

I am running stock roller lifters and a Ford Racing B303 cam. Thanks for the replies.

 

Comp cams p/n 986-16 will accommodate up to .560 lift and 6000 rpm.
This is the spring they recommend for most of their street cams unless you go past the .560 lift. Just like too little spring pressure will cause valve float, too much spring pressure can cause problems too, such as collapsed lifters, bent pushrods, and worn cam lobes.

Use steel retainers, p/n 740-16. Or upgrade to p/n 795-16. These are 10 degree retainers, superior to the stock 7 degree.
Locks would be part number 611-16. Upgrade is 614-16. These are 10 degree locks.

Sounds like you have typical 5.0 stock springs. Hopefully you’re not using the stock retainers as the exhaust springs are probably close to coil binding due to the short installed height combined with the 1.70 rr & B cam.

 

Just because you've changed cam doesn't mean you've increased the RPM capability of the motor !!! You've changed RPM performance Range of the motor. If you have not changed rods, pistons, crank.....bottom end of the motor you'd better keep RPM in the stock range or you're gonna damage the bottom end. Most street cams are designed to offer good low end torque and horsepower from around 1500 to 5500 RPM when used with improved intake and exhaust systems. With otherwise stock motor you're "over camming" when using cams designed for above 6000 RPM and actually losing low end torque and horsepower. BEWARE !! Consult tech support for parts supplier for info on proper parts for intended use for best results.

 

The stock HO 5.0 is rated to 6250 rpm. Rob's not attempting to exceed the stock rpm capability. He's experiencing what a lot of 5.0 motors go thru even on a stock high mileage 5.0 motor. Your right about the designed power range of most street cams but they would still be able to rev to stock red line without experiencing valve float. It's one thing for a cam to get lazy beyond it's rated power point but you don't want to risk piston to valve contact due to valve float prior to reaching the 6250 rpm fuel cut-off point.

BTW Rob, Jim's conversion is almost complete. We'll have have to have a 1st state V8 miata get together when he's done.

 

I've seen a few stock bottom ended 5.0's launch at 7200 and shift at 6800.

 

That's absolutely amazing !!!!! There aren't too many modified motors that can do that !!! Absolutely AMAZING!!!! If loaded up with proper bottom end parts.....hell they should run to 10,000 !!! NASCAR builders need to know this info since their motors will only rev to about 9,000 !!!

 

You do know every time you post, you make it more clear you don't have a clue what your talking about.... Correct?



Wow....... I've been hanging out on MT.net a little too long......

 

I do know BS when I see it. Why do people like you want to post a bunch of crap that you know is just that. Boy, I've been building race engines longer than you've been alive.....stop posting crap that's gonna hurt some unsuspecting guy who doesn't know better and really believes in such crap as stock 7000rpm launches..please

 

Tony, thanks for the info, I'm gonna look into the comp cams setup. I figured the stock 5.0 HO should rev a little better than 5,500. The power is still building and all of a sudden float occurs. Yeah, I think we all need to get together soon, maybe even get Jason and Manchester Miata there too. Guys play nice now, opinions are like a$$holes, everybody has one.

 

A get together would be great. I hope my input helped. I don't want to discourage anyone. I have found over the years the manufacturer's tech lines are incredibly helpful. I couldn't guess how much time, money and headaches they have saved me.

Someone else posted that the red line of your engine is 6200 but what's really important is to look at a dyno printout to see where you're getting optimum horsepower and torque. Then depending on your usage decide which cam grind will give you the most of what you're looking for. Most street motors use a cam which will give strong lowend torq building along with Hp as rpm increases. This type of cam will also produce enough vacuum to allow your power brakes to work without modification. Drag racers want a flat torque curve so the engine will pull all to way to red line (no problem when you're running with your foot to the floor). Road racers usually like torque and horsepower in mid-range building all the way to red line. Another consideration in all of this is what rear gear to use. Again, your manufaturer's tech can advise you there. A cam with a power range of, for example, 3000 to 7000 rpm my sound great but you're car will run like a dog until you get the rpm up into the performance range so you'd want a big gear like 4.11, 4.56,etc. to get the revs up quickly.

There's a lot more to this stuff than just bolting on a buntch of parts....everything has to work in conjunction to optimize performance.

Good luck, God bless !!

 

I just post observations from spending years at a high performance automotive school watching instructors and students put stuff on the dyno's just to see if they'd survive, followed by a few years at a shop who had cars on the dyno daily.

With proper flow, the stock bottom end will hold 7k...... actually, according to the dyno operator I was talking to, he's had one of his old high nickle content block's with stock guts in it up to 7900rpm a few times on accident without creating a vented block or two 4 cylinders......

Have you tried mating that LT1 block up to your LS1 transmission yet?

 

Requires adapter kit. Weir Hot Rod Products supplys everything needed.

 

There is a guy named tim that works at accurate machine in newport. He is the man when it comes to 5.0 motors I just got a spring set up from him and its sweet. There are a lot of variables needed to be measured in order to get the right set up.