Aluminum Roller Rocker considerations

[bigsteviejoe]

What do you imagine the gain would be by successfully installing custom made, needle bearing and balanced roller rockers for Vin C motor that are at spec? More aggressive 1.6 (safe bet?)? Or even a more aggressive 1.7?

HP gains at an expenense to fuel economy(the hotter ones)? From what I got from the GNX site I believe the rocker arms are 1.55, is that the same for the VinC? Is this bolt on efficiency?

I found a place the would likely make them for the VinC.

Would a V6 benefit greater from roller rockers than a 4 cylinder since they will effect 2 more cylinders?

Harold Sharp is the place, the website is in my FYI HOTRODDER post from earlier.

[Guest]

At spec? Something on the order of 10rwhp at best. On some small blocks, ZERO gain was seen, but I personally think these are flukes.

Changing the ratio of the rockers may cause a ton of other problems unless done very carefully.

First, you are most assuredly going to have to re-tune the computer. Not only are you adding lift, but you are also adding duration.

Have you checked valve/piston clearance with the higher lifts? Having to buy new pistons with valve reliefs would be pretty expensive...

Will the springs lock up (go solid) at the higher lifts? Generally, springs are designed to work within the range of the stock lift, and not much more. The swap could require new springs... LS1's used to break springs constantly with higher lift cams, until the aftermarket finally got their stuff together.

Another option on the valve springs would be to identify the differences between the higher lift GN cam valvesprings and those in VinC and see if they will work. Should be pretty easy for any reputable shop to do (material, height at rest, compressed height at max lift, compressed height at zero lift, solid height, spring rate, open force, closing force, I.D., O.D.).

What about pushrods? Can the stock pushrods take the higher forces involved?

You also have to remember that adding ratio will cause a greater tendency to float a valve, which would be bad. There will also be added valvetrain stress due to the fact that the motor will now want to spin to higher revs.

Would probably want to check for prices on new retainers, locks and valve guides at the same time.

Honestly and truly, a pocket-porting job on the heads would probably be your best bet for the same amount of money and or better power gains without a ton of aggravation.

Then again...

You could do both...

I would imagine a streetable 3800 could touch 230-250rwhp with the normal hot-rodding tricks and a good tune.

[padgett]

a: the documentation I've seen indicates a stock ratio of 1.6:1

b: believe the SII went to roller rockers

c: might be of benefit in conjunction with a broad range of changes but doubt that the ratio *by itself* would do much.

Really want to get BB tuned in and some tests run as a baseline first. That has a more agressive valve profile than just going from 1.6 to 1.7 would cause.

That said, the head intake passages, exhaust passages, throttle diameter, exhaust system, and air fitler/passages are pretty much maxed out for the existing "C", would need to improve all to get any meaningful effects.

[2seater]

Higher ratio rockers do have the effect of giving you more cam and all the cautions about coil bind are certainly valid. This is an old trick to get some gain without tearing into the engine. There is a big advantage in moving the valve more rapidly as the time it is at a desirable opening and flow rate is increased. It is also a good way to find out if you can use more cam. If the rockers do help, the results could be duplicated with a revised cam profile. The valve springs should be checked to see if there is enough travel left to increase the lift. The base valve strength isn't as much of a concern unless greatly increased revs are the goal, but, if they are old and tired, I would at least have the spring pressures checked. I can't find the measurements I made when I rebuilt my engine but if memory serves, the minimum valve to piston clearance was approx. .110" with increased piston height of .050" and have no valve to piston interference problems. There is essentially no valve overlap with our mild cams so the valve is almost closed at tdc. Any idea of the cost? Is this a roller tip as well as the fulcrum? I do know the Series II roller rockers will not work in our engines unless the pivot point is moved.

[Guest EDBSO]

The guys on the GTP pages with SC3800s are trying this. Many posts about valve train failure followed some times by catastrophic engine failure, Geometry is off also. Done right they are installing competition cams, valve springs, retainers, pushrods and longer rockers and a bit of fairy dust and they still are failing. GTP Note piston to valve <span style="font-style: italic">issues!</span> Some have been able to get it to work.

[bigsteviejoe]

I'll check on prices. I should have something by mid Saturday. These roller rockers have roller tips. The website is www.harlandsharp.com.

[Guest]

I'd really like to know how much of a gain can be had from a home pocket porting job.

A big porting job is going to beg for more cam, but just cleaning up the bowls, a port match and a polish might do wonders.

[Guest]

...just 2¢ more. When i checked out the 1.6 ratio roller rockers i got from Competition Cams ® they fit right in my rear wheel drive 3.8 Monte Carlo. Yes, there was definately a performance gain. Don't quote me on this ...but i believe the increased fulcrum of the 1.5 - 1.6 ratio caused a .030" increase in valve lift. This is a rear wheel drive vehical just like te GNX's. i discussed this a couple years ago with Hal. Our Reatta's are front wheel drive and won't accept these same roller rockers. The 3.8 was re-engineered with the valve heads compacted inward so....it was concluded that the 1.6 or > could not yet be found for this trick on the Reatta. The only caveat was to determine if the increased fulcrum would cause the pushrods to scrape the exit hole in the head casting. i've heard "chamfering" (or rounding) the top of the hole can usually take care of this problem ....but i saw there was plenty of clearance on the RWD 3.8.

......so far my greatest gain has come from removing the tapered air intake tube that connects from the air-cleaner box to the radiator baffle and replacing it with thin walled 3" PVC (which fits right in the hole) and a rubber sleeve. This was probably a greater increase than the so called, "fast-chip ®" trick.

nomad

[Guest EDBSO]

This is scheduled to be my winter project. Don't know what the gain might be.

Excellent guide PDF.

HTML guide

[2seater]

I tried measuring the stock rockers to verify the ratio but it is a little difficult as determining the exact point of valve contact and the center pivot can only be estimated. The stock rockers are listed as 1.6:1 ratio and they do measure pretty close to that. One small advantage to the sliding tip on a stock rocker is the ratio actually increases slightly as the valve is opened and the contact point moves outward. Not a great advantage, but there is some. Of course the friction probably eats up any ratio advantage over a roller tip. There is a drop in roller pivot conversion made for Ford rockers which use a similar shoe type pivot slide as do ours. They are also 1.6:1 rockers from the factory. If I could find one, rather than a whole set, I wanted to investigate if this was viable improvement. If I had been thinking ahead when I rebuilt my engine, I would have had the rocker mounting machined flat and install screw in studs for a truly adjustable valvetrain. This would make installing a different cam with a possibly different base circle, such as a regrind, easier to set as desired.

I did port my engine and it is a tedious project but kinda fun, (winter project per EDSO). I regularly do this to small engines such as lawn mowers and snowblowers. You can actually hear the difference after the ports are cleaned up. Even though the cam and valves are not changed, any reduction of the friction in the flow is beneficial. How much gain from porting is hard to quantify without a flow bench or dyno. Even if the gain is minimal, it's a good project and you have at least a subjective pleasure from making an "improvement". Plus, you'll be all set for that new cam

[bigsteviejoe]

Sorry I have nothing yet. I was going to call, but they aren't open. I'm waiting on an email.

[bigsteviejoe]

Okay the unofficial price is. . . $30 US a roller rocker, bolt on & not adjustable. They've done a few 3.8 litre motors before. Its pretty much definate that there would be a 10 (my guess) to a very pessimistic 15hp gain. The website shows 15-40hp increase. They claim to make the finest. increase in hp just going with OEM spec. Check out the website www.harlandsharp.com.

No choice in color.

vfnfiberglass is looking at some photos for a reatta hood & decklid. They also do carbon fiber. If anyone has good photos of trunk, or any other photos (mine are all low perspective and I can't find a good pic to use from ebay), could you give me the UBB or URL code so I can post to their chat.

[2seater]

Lessening friction is a good thing, but it does seem optimistic to gain a lot with rockers only, especially at the stock ratio. Of course the big advantage is you don't really have to tear into the engine, but for that price you can get all new lifters, reground cam, valve springs and a gasket set. The down side of that is a lot more work, although changing the cam is the big gain. I do not want to sound negative and I do appreciate the work looking into this conversion.

[bigsteviejoe]

Thats cool. I just look at it as bolt on efficiency and enhancement. I think their would be real gain. Maybe less gain since there are less valves.

One place where the 3800 wins hands down! Less valves.

Just another thing to enhance a new cam once that comes around.

[2seater]

There you go, get both! Now if we had solid roller lifters, we could limit the oiling to the top end and gain another small efficiency. That pesky non- adjustable valve train gets in the way of that.I need to look at the oil flow diagram to see if this would leave more for the bearings, which would also be a good thing.