cam questions

cgrey8 · Post by **cgrey8** » Mon Jan 05, 2009 7:32 pm

I would recommend the 1.7 rocker upgrade over an F303 upgrade just because it's easier. And yes, they sell 1.7 rockers for stock heads. In fact, that's a rather common upgrade for stock engines since 1.7 rockers will improve the performance of stock cams too and can be installed easier than a new cam can be.

One thing I would like to stress is you can't compare cams purely by duration and lift. You have to analyze all 3 components, duration, lift and lobe separation before you can make any SOLID assumptions about the cam behavior. Although most cams, especially those listed as being "street legal" are going to have a fairly good manners that compare to a stock tune...not what you are looking for. But if you really want an idea as to how a cam is going to affect your engine as compared to what you already have, you need an engine simulation software. Engine simulation software is really good for helping you determine the affects of one cam vs another or one head vs another. Even though engine sims can't tell you for sure exactly what HP and Torque output you will get with a particular build, they can get you in the neighborhood AND are excellent for helping you compare different engine components like cams. So in your case, you could run a sim of your engine with the existing E303. Then run another sim of your engine with 1.7 rockers. Then run a 3rd sim of your engine with the existing rockers, but using a different cam. That way you could see what the HP/Tq affects are by a 1.7 rocker upgrade vs a cam upgrade.

Dave · Post by **Dave** » Mon Jan 05, 2009 7:56 pm

Chris,
Are you suggestng I get of my butt tommorrow and run a couple for him? I might just do it for myself to see just how close that XE-264-HR I got does compared to the dyno tests. Bad thing about that program is that it doesn't take into consideration of the different head designs. Guess I'll check for myself.
Dave

v8ranger · Post by **v8ranger** » Mon Jan 05, 2009 8:02 pm

Its funny you say that, I forgot I have a desk top dyno program. Its been so long since I used it I forgot I had it lol. Will changing to a 1.7 change the idle also, or will that stay the same as it is now??? I just want a cam thats more beefy and has a little more lope in the idle.

cgrey8 · Post by **cgrey8** » Mon Jan 05, 2009 8:28 pm

Dave, the pain of removing all the crap in the engine, the cost of the gaskets, and don't forget the cost of the coolant and oil. I was at Walmart looking at oil. I hadn't realized how high the price of a quart of oil had gotten since this summer. Even the cheap stuff was well over $2/quart. Just last year the Walmart cheap oil was just over $1/quart. And Mobil1 was over $6/quart.

And I was suggesting he get the software for himself, but if you just want to do the comparison for him since you have that software, I'm sure he'd be appreciative. I'd be curious to know which would be the better move 1.7 rockers using the E303 vs an F303. My money is riding that the E303 with 1.7 rockers will be the winner. The E303 with 1.7 rockers will be slightly lower duration, but it makes up for it with a higher lift and a slightly faster ramp rate. The F303 has about 5 degrees of cam advance built into the grind as compared to the E303 which will give it a slight low-RPM advantage.

My prediction on the outcome of the simulation is the F303 may actually have a slight torque advantage at the lower RPMs because it has that cam advance ground into it...about 5 degrees advance as compared to the E303. The E303/1.7 rocker combo should hang right with the F303 in the RPMs that matter if not exceeding the F303 thanks to the higher lift and no cam advance. At the top-end where HP starts falling off, it gets unpredictable. If it wasn't for the cam advance, the F303 would fall off slower than the E303 because of the wider duration. But cam advance causes the high RPM HP production to roll off faster than it would normally. So yeah, this will be a really interesting comparison.

Here's a site that has both the E303 and F303 cam specs. Assume stock cam ramp rates for both cams, 1.84"/1.54" valves, and I have no clue how the software takes into account carb intakes vs tuned port injection intakes.

V8Ranger, yes the 1.7 rockers will affect the idle. Upping the duration via the higher rocker ratio will do that. And in fact I'd actually expect the 1.7 rockers to have a bigger affect on idle than the F303 would. The cam advance in the F303 is probably there to help smooth what would be a terribly annoying idle without it.

v8ranger · Post by **v8ranger** » Tue Jan 06, 2009 4:21 am

Well then I think thats what I will do. Just replace the 1.6s with 1.7 rolloers. I did find some new ones for $165

http://cgi.ebay.com/ebaymotors/ws/eBayI ... &viewitem=

Do you think these are ok? You guys have been awsome.....You dont know how much I appreciate all your wisdom. I have worked on cars all my life but when it comes to the tecnical crap, im lost, so thank you all so much for your exspertice in this.

cgrey8 · Post by **cgrey8** » Tue Jan 06, 2009 6:40 am

Wow, they aren't even stamped steel. They are true aluminum roller rockers with pivot bearings. I didn't know they were that cheap even on eBay! That in-and-of itself is a nice upgrade for the engine. The fact that they'll be upping your ratio to 1.7 and saving you from having to install another cam makes them doubly nice.

Just make sure you get them setup right. I don't have a whole lot about valvetrain geometry knowledge and "how" you setup an engine being I've never had to do it before, but I do know there's something to it and doing it right reduces wear on your valve guides. I also always hear that the stud-mount rockers are easier to setup than pedestal mount for some reason, but I don't exactly know what the reason is. What I have read is the intention of the task is to get the roller tip to touch as close to center of the valve as possible AND reduce the sweep it makes across the valve stem tip. As the rocker plunges the valve down, the tip moves outward away from the mounting point of the rocker. But somewhere in the middle of the plunge, the tip touching the valve stem starts moving back again. When the geometry is setup correctly, the surface of the valve stem that is rolled on is as centered as possible and is as thin as possible. Some sweep is unavoidable, but the pros seem to believe you can get it really minimized if you are diligent and spent the time AND money. I think the main reason they say this is part of what adds to valve guide wear is the resistance the spring is creating and since the spring creates max resistance at full lift, you want as little "angle" being pressed on the valve as possible and to do that the rocker must be pressing on the valve dead-center. The less sweep you have and the more centered over the valve stem you have the sweep, the less wear you put on the valve guides because the majority of the rocker pressure is being exerted on the spring, not on the valve at that point. The centering of the sweep is the #1 thing to get right so you don't wear out your valve guides in 20kmiles. But I don't know how important the narrowing of the sweep is on engines that rarely see 6000RPMs, get regular oil changes, etc. But valvetrain geometry setup is one of the things the pros dog the cam companies for because the cam companies give "generic" direction on how to do a setup that most people can follow and it works for most people's applications. Here's what some serious pros over at SpeedTalk have to say about valvetrain geometry:
Valve/Rocker/Pushrod Geometry
If the subject is at all interesting to you, read through the thread, but I warn you it does get a little boring and tiring because so much of what they are talking about are things the average person doesn't have the time or money to deal with. And also keep in mind these guys are building 10,000RPM engines, not street performance engines or daily driven engines. To go to all the trouble they describe for a daily driver would have serious diminishing returns.

v8ranger · Post by **v8ranger** » Tue Jan 06, 2009 7:51 am

I am hoping they are a direct replacement, but we all know thats not always the case. I would think they are but I will see. I do have shims if I need them but I wouldnt think so. Do you think there will be any peoblems with valves hitting the pistons with my setup if I put these on? I wouldnt think so anyway, but cant hurt to ask.

cgrey8 · Post by **cgrey8** » Tue Jan 06, 2009 8:23 am

That's always a potential, but I doubt it. I've heard of plenty of people running 1.7 rockers with the E303 and not having a problem. I'd think if there was a problem, it would be a more known issue since the E303 is probably the most popular performance cam out there thanks to its flexibility.

See, the E303 is your generic, all purpose cam upgrade from any stock cam.

It works as a 100% direct stock replacement while reusing stock valve springs.
It's 50 state legal.
It's an OK cam for aftermarket heads.
It works well with superchargers and turbos.
And the performance increase it gives isn't too shabby as compared to a stock cam.

Most people that use the E303 are quite happy with the results so it is really hard to hate the E303 for what it was designed for...being a generic all purpose cam. But because it is so generic in design, it leaves a lot of potential on the table for optimizing. For example:

If you want better low-RPM grunt for towing or 4x4 use, you can get MUCH better that the E303 with other cams designed for that, but these cams won't hold the HP in the higher RPM range as well as the E303.
If you want more street performance (1500-5000RPMs) with better fuel economy, you can get that from other cams too, but you better have the stock valve springs replaced to handle the higher lift and faster ramp rate this type cam will demand.
If you want a cam designed to optimize aftermarket head flow potential for absolute max HP on the strip, you can get that too with aftermarket cams, but you won't likely be able to use this cam with a stock head even with aftermarket springs and you won't likely want to drive this cam to work everyday or just to go get groceries since driveability and emissions are likely to be the sacrifice here.

The catch is, each of the more specialized cams optimize their area while sacrificing the flexibility of working in many other possible combinations. The flexibility of the E303 is both the beauty and the ugly because the E303 doesn't optimize anything except flexibility of use which in your case you'll be making use of by putting 1.7 rockers on.

v8ranger · Post by **v8ranger** » Tue Jan 06, 2009 2:09 pm

Well I bought the 1.7's so we will see what happens. I am also in the middle of changing over my cable clutch to hydrolic. I will have to post some info and pics of how I did mine ( if it works ) lol. After 5 years of having the cable I am finaly changing it over lol. Might as well do it now while its winter and im not driving it so I have plenty of time for screw ups lol.