65Z01

In the past I've read on the Forum that full roller rockers are noisy so I was expecting to realy hear from my new 1.6:1 ProMagnums.

I just started her up and took her to operating temp for the start of break-in. Much to my surprise it was even quieter than before. Hmm, maybe I had some valve train wear before. Anyway, I had set the new Comp Cams springs seat pressure at intake/exhaust = 90/105 lbs seat pressure. Then I cranked em all to 3/4 turn past 0-lash.

If all continues well this week I'll get the results at Raceway Park next weekend. Based on Dyno2000 data with an increse in lift of 0.030" and in duration of 2deg, I expect to see 15-20 HP gain with a push in top end breathing. Since my shift points are now at about 4500rpm I may need to manually shift her to see these numbers. The exhaust note seemed a little louder, which is a good sign.

Thanks again to all who helped with this "little" project.

scorp508

Excellent!! Waiting to see the results. How did the valve covers turn out?

65Z01

Yea, me too. I'm anxious to finish the break-in and oil change so I can try her out on the street

I got the valve cover emblem and two cans of GM silver paint from MAD. After I machined the innerds of both valve covers (totally removed all drip tabs and flattened the sides of all mounting bolt pillars) I sanded the exteriors and applied several good coats of paint to each valve cover. They not only fit well now but are looking fine too.

88L98

did you go 1.6/1.6 or 1.6/1.5? if you went with the dual 1.6's, did you notice any difference in idle sound? id put the rockers on even without the power gain if i got a lumpier idle.

65Z01

Sorry I foregot to mention the idle. I had a set of 1.60:1s and 1.52:1s ready in case the idle was too lumpy.

Well the idle was so smooth that I now have a brand new set of 1.52:1s for sale. With my stock cam the 1.6s on intake & exhaust are smooth as velvet.

So TPIS data on 1.6s at the exhaust giving a rough idle is in question, at least on an '88 L98. Guess you'll have to go with a cam change to get that lumpy idle.

vettenuts

I think their test was on an 85 with cast iron heads. Not sure what makes that different, but from all the reports from people who have done this swap it does seem to be different.

-=Jeff=-

I also think that test was also with the ZZ9 cam specifically too

65Z01

They mention a stock '85 350 for the 1.6 rollers on the intake but just say that in "another test" 1.6s were tryed on the exhaust with no improvement and idle quality suffered.

So the difference in cam profile could account for their loss of idle quality.

Actually, with my cam, DYNO2000 showed the greater improvement would come from the 1.6s on the exhaust.

65Z01

I had read a review of Dyno2000 and Drag2000 earlier this year that had good things to say about both. Although neither is "perfect" they can be useful in some situations. I guess the simulation accuracy depends on the combo and the type of mods.

Right now HP gain is the biggest question for me. TPIS got a 13hp gain from the 1.6 rollers and mentioned another 4-10 hp from going to 7/16" rocker studs on that '85 350, so I think 15-20 hp gain is not too much to anticipate. If it is 15-20, I should be able to "feel" that on the street.

BobMachus

Do the roller rockwers just bolt right on? DO they need guidplates, etc installed? Is there any machining necessary? Please give a quick synopsis of RR installation. Thanks, Bob

JAKE

I tried it both ways with a ZZ9 cam and it DOES make a idle quality difference with 1.6s on both intakes and exhausts.

I suppose it's because the ZZ9 has such a wide spread between intake and exhaust duration - about twice the norm - that causes the idle to suffer slightly.

Jake

M2001

Hey Bob,

On my car, I replaced the stock 3/8 inch rocker studs with 7/16 studs made by ARP. Then I bolted in the Comp Cams Pro Magnum 1.5 rockers. To make room for the full roller rocker arms, you'll need to do one of 2 things. Either mill the stock valve cover drip taps off or buy new valve covers. I optioned for the later and bought a nice set of Billet Specialty valve covers. By the way, if you decide to use your stock valve covers, the polylocks on the rocker arms may obstruct the valve covers from fitting properly on the heads. The Billet Specialty valve covers are about a 1/4 inch taller and fit with no problems at all. You do lose an oil fill cap and you'll have to use a short piece of 5/8 inch rubber hose as a spacer on the valve cover for the PCV valve to fit but it was no big deal to rig up. Then you'll have to install harded push rods along with harded guide plates to complete the job. The job is not that tough but it will cost you a few hours of your time. I had set the valve preload to one full turn from zero lash. Some say that's too much valve preload but, that's what the Corvette service manual recommended.

h rocks

Bob, it's easy and an excellent DIY project that will help you get a better understanding of what goes on under the valve covers. I installed a split set of GMPP 1.6 / 1.5 self aligning roller rockers last summer. I've just gone to a full set of Crower stainless 1.6's with hardened push rods and guide plates. Not a difference that's discernable on the street, and I haven't been to the dyno yet.

If anyone want's my GMPP split set contact me. (They only have about 1500 miles on them.)

65Z01

Bob, my story is similar to those above.

Since I'm trying to get more revs before valve float I opted to install 7/16" ARP studs, along with the ProMagnums and hardened guide plates and pushrods. You have to discard the stock guide plates since they aren't hardened.

Midway into the project I decided to replace the valve springs too (108k miles). This gave me an excuse to discard the stock oil shedders, steel retainers and locks for the much lighter Ti retainers and machined locks. I also replaced the toasted rubber O-rings at the top of the valve stems. Then I found that the installed height of the new valve springs didn't give enough seat pressure so I got a variety pack of shims and shimmed the exhaust .050" and the intake .060" to get around 100lbs of seat pressure and nearly 280lbs open pressure (springs are 400lb/in). Of course I measured each installed spring height and checked for coil bind.

I not only completely removed all drip tabs from the valve covers but also ground flats on both sides each bolt post to assure clearance bettween the covers and the ProMagnums.

I applied a small amount of Comp Cams light break-in lube on each end of the pushrods, inside the rocker arm pockets and on the tips of the valves.

Since CompCams said to go 1/2 turn past zero lash and the GM Shop Manual said to go 1 turn, I compromized with 3/4 turn. That way I wouldn't be too far from the desired optimun .030" lifter preload.

Finally I sanded my "brown" valve covers and gave them several coats of MAD silver valve cover paint, with a wet sand between coats. Today I installed the new Corvette emblem on the left cover.

I cranked the motor for a short while with the dist and injector fuses pulled to check for any "strange metallic sounds" and to pre-lube the topend. Then I fired her up with no brackets nor the serpentine. After that test passed I reassembled the front end parts, pulleys and the serpentine and began the 30 minute break-in period.

I destroyed both valve cover groumets getting them out and had to fashion two temp subs from some old heater hose. I suggest you get a new set from GM before starting the project.

Even though I had researched the project before hand, there was still quite a learning curve involved and I came to the Forum several times for help. Like all my first time projects the next time it will be a piece of cake. Though I'd do the job again myself, I am curious as to what the flat rate would be at say a Chevy dealer.

h rocks

What's the consensus on the Crower "recommendation" to go to a .050" longer pushrod on their 1.6 RR's? I'm wondering if they suggest that to insure that you get max lift with a hyd. roller lifter, or if their geometry is different? Is this something that could/should be done on all 1.6 RR"s?

Chris@SD

Denny,
Wow!!!
The 7/16" stud WILL give you more HP at high RPM due to valvetrain stability and less flex. You will not gain a few HP all the way up, only at high RPM...

If you only got 30 HP from a set of LT4 GTP heads, something else was wrong with your car!!! Your tuning was off, vaccuum leak, something. I have never seen a gain that little off of ANY GTP heads.
I understand you have spent a lot of time on the dyno, but so have others. There is the possibility that everyone here is right! Just because you did not see the HP from a mod does not automatically mean that no one will...
As for the review of desktop Dyno, I have seen a bad review of everything ever produced since the 18th century! There are also favorable reviews or all those products also. Just because it was written in a magazine does not mean that it is gospel!

I once read a review that said 1 3/4" headers did nothing over the stock manifolds on the new computer controlled cars and that they were worthless. Then they started tuning for the modification and realized that they were actually picking up GOOD HP numbers! If everyone would have just agreed with that first review that Headers were junk, I just can't help but think that we would all be running a little slower now...
Now I am sure you are going to post that Headers gave your car 0 HP and I cannot dispute that, but I just don't believe it either...

-=Jeff=-

quote from TPIS
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:[/color]<HR><font face="Verdana, Arial" size="2">The ZZ-9 and the Super Profile L-98 cams are designed to run with the stock stamped steel rocker arms. When you are ready you can add roller rockers - 1.6 intake x 1.5 exhaust will add 12 HP. 1.6 x 1.6 is worth another 4 HP. You lose a little idle quality but it's still a good idle. [/color][/QUOTE]

this makes me think the 1.6/1.5 idle question is more geared towards the TPiS cams specifically.

Jeff

65Z01

h rocks, Crower geometry may be different. Comp Cams recommends that you observe/ measure the roller travel across the valve stem tip and use an adjustable pushrod measurement to get the best pattern.

Denny, Chris, I too am skeptical of mfg HP claims and realize that Dyno2000 has limitations (it's strength is in relative numbers). Dyno2000 shows the HP gain at higher RPM with an extension of useful HP range. It is by extending the useful RPM that I expect the 7/16" studs to "add HP". This is also why I feel that I need to extend my shift points to take advantage of enhanced upper RPM breathing and valve train stability.

With my 700R/4 and gears I'm not trying to build a motor that revs to 7000RPM, though I am trying to extend the useful range some. In the 1/4 mi it spends most of the time in the mid ranges with the next most important area being the upper end, so these are the places to put my $$.

BTW, track data from a '90 Vette 6-speed with #113 ported heads with improved valve train (TPIS Stage II, with roller tips and 3/8" studs) showed a gain of nearly 3MPH up top and .4 sec off the ET. Though not normalized for weather conditions, this indicates about a 30PH improvement in later stages of the buildup.

65Z01

Those are some mighty impressive numbers!

The benefit from 3/8" to 7/16" studs is generally accepted as valid by a number of recognized engin builders; the debate is as to under what conditions. Here my numbers are from the admittedly selfserving "Insider Hints". They do post dyno results to back up many claims though. And indeed I've noticed that most mfgs state numbers in "gains of up to...." terms. I believe I will only see these gains when I can take advantage of more revs before shifting.

As soon as I get normalized trap speeds I will know the real deal with my current setup and the numbers will be posted here. You can see from my sig and site that I have kept some valid records on results of mods, though usually done in convenient groups.

Chris@SD

I am just trying to say, because something works for one does not mean that it is going to work for everyone. Because something did not work for you does not mean that the product is automatically junk. Not trying to get in a pissing match, just wondering why the negative attitude on a LOT of your posts.