Ok guys let me start by givin you a base line to compare.

My car had the same opty spark for 149k miles. Ran smooth except for one time it began backfiring and missing badly that turned out to be a cracked inside insulator on #1 spark plug and I also found a puncture spark plug wire.

Just recently the car developed a very slight misfire. If it wasnt for my ES tranny mount that transfers every move of the engine in the cabin I would have never noticed. It was that tiny. The Long term fuel trims had slowly deteriotated and were are about 112 to 117 at idle and about 120 to 124 on cruise at 65 mph. The short term trims were about the same.. 124 or so..
Had new tr55s in and did nothing... I notice lots of oil in the from of the engine and over the opty spark... The back on the intake was leaking too.. I figured it was time for some new gaskets..

This is the work done in the car... New Timing Chain...New Opty Spark... New intake, timing, oil pan Gaskets. New Valve stem Seals... OEM for intake and exhaust (diff seals for each).

I found #8 rocker wearing out at the Rocker to Pushrod conecting point due to poor lobrication... so I figure Lifter change Time!!!.

More work done to car... New Scorpion 1.7 roller rockers, New Studs 7/16 size, Beehive Ovate Valve Springs, Locks, Keepers, GM Guide Plates Plus New Water Pump, Opty Spark, Alternator and new timing cover to water pump, to opty Spark, to crankshaft seals were put in place. **Note** When I removed my Intake manifold to my horror the bolts that hold it in place were loose!! I did turn them all by hand... I would say it would have about 2lbs of torque so essentially the manifold was just place over the engine... That would explain why my vacum had dropped to 17 inches at idle with stock cam.


Anyway after the work was all done here are the initial results:

Intake Vacum went up to 23 inches!!
slight misfire is now gone... smooth very smooth
Mass Air flow at Idle dropped from 7 to 5 Grms/sec
RPMs went up at start up then corrected by the Idle Air Meter (motor?)
Learned Idle meter possition dropped from 30 steps to 0 steps!!
Engine Idle speed is perfect although the above statement...
Great Throttle response compared to the previous engine health.
More more Power no doubt about it. Engine feels willing and efortless.
Lots and Lots of Valve Train noise.
After the Valves/lifters were ajusted again noise is half now but still noisy
OEM Valve covers went right in without mods... something fishy about that.
The car takes off like a JackRabbit yet above 3k RPms still feels stock powered...
Maybe the dirty air filter has something to do with it.. CAI on its way
The long term fuel trims are between 128 and 132 idle and 128 cruise..
Short term fuel Trims are in between 128 and 132 idle and 128 cruise..
Engine Temp @ idle goes up quickly to 160* but then from 200 to 221 takes much longer than before. by the time the first fan comes on its been easily 15 minutes. My ambient temp here was mid 70*s.


In short my biggest improvement were Idle quality, Long term fuel trims basically perfect, more power down below but I have a dirty air filter so I am yet to do a Logged WOT run for High RPMs comparison, Way better Idle Vacum.

Cons... Noise. The friggin thing sounds like a freight train with the valve covers off. Lifter pre-load was adjusted twice since it took but two minutes for some rockers to become loose.... Not the Poly locks though.. they were solidly in place.. something gave way and loosened up the rockers. On the second round of ajustment they all held just fine till now. I am in the break in process.

With 5 miles on the new combo I cant wait to end the heat cycle break in process and then spin the **** out of her and see what shes made of now!!!

Guys with questions please post.. I will answer the best I can.


Marvin

 

Which springs, 26915 or 26918?
Which spring seats?
Which retainers and locks?
What was your installed height?

If you set your lash at 1/4 to 1/2 turn, don't worry about the extra
valve train noise. The roller rockers just sound that way. Mine sounds
like a singer sewing machine convention (compared to stock). I'm in the
middle of a spring change (to 26918s) and everything looked great when
I pulled the covers. Lash was 1/8 and all the poly locks were tight. Bottom
line is that roller rockers are just noisy.

 

26918 springs
63-648-16 valve locks
63-4501-16 Studs
787-16 retainers
installed height?? Whats that? I didnt check
Lash with new lifters dry was set at 1/4....
Lash after engine fully warmed up set at 3/4 but it felt too tight.
I will redo the lash when the lt4 covers arrive back to 1/2
Spring seats are the same that were in the heads.
14011051 Gm Guide pushrod plates

Marvin

 

Thanks for the info. Your installed height will probably be somewhere
in the 1.75"-1.76" range, which is fine.

 

so you didn't have to change the stock spring seats? i thought the seats would have to be changed to support the 918's

 

I didnt have to change the stock spring seats. My beehives went in just a bit snug but then seated perfectly. I did read a post of a guy whose Beehives did not completely seat on the seats.. I think he has a picture showing the spring about 1/2 millitimer off the seat but mine are seated just fine. I tested all of them by the way.

Marvin

 

Did you have to change pushrods for proper geometry?

 

I used the same length of pushrods but are now the hardened type. I dont take my car to the track. I am sure a longer pushrod would be perfect for High RPMs and I will eventually swap them for better longer ones. if you see my posts I was told I should be ok with the stock length. I am assuming its pretty close to perfect.

Also the Roller Rockers were very noisy at the begining and now with over 400 miles on them they got pretty quiet... to the point where I dont even hear them in a quiet nite. Kinda fishy if you ask me cause I thought they would always be loud. they only sound I hear from inside is the sound of the pushrod rubbing on the guide plate.. well thats what it sounds like. No clickings and no other sounds can be heard till I open the hood only then I can hear then clearly with the stock valve covers

Marvin

 

Thanks, I have 7.250 length pushrods from Crane. I will try those out with the Scorpions 1.7 roller rockers. I will do a geometry test before and after.

 

What is max lift for those springs?

 

How do you check what your installed height is? And how do you check for proper valvetrain geometry? Some Scorpion rockers might be in order this summer!

 

These rockers sound awesome! Where did you buy everything? what are the part # for the rockers? I going to go this route.

Lift on a stock cam is .447 intake and .459 exhaust correct? So the new lift # would ,507 intake and ,520 exhaust, are these # correct?

 

Simple math, take the lift of the factory cam with the 1.5 rockers, and divide that number by 1.5, then when the answer comes up, multiply by 1.7, voila , your new lift. Be sure you get the right springs and pushrod length, dont kid yourslef. ALso, the LT4 Hot Cam springs from GM are only about 30 bucks for a set. GM does allot of R/D,so I bet they are good enough for your app with factory cam and 1.7 RR's. Steve

 

Cool, I was thinking of running those springs.

Now, how do you determind the correct lengthof the pushrod?

 

Go to ComP Cams website. They have a really good article on checking the geometry. Basically, you use a sharpie marker and mark the top of your valve stem, where the rocker rolls on it, then you install the rocker, with proper adjustment, then you turn the motor over a couple of times. Then you remove the rocker and look at the top of the valve and see where the rocker rubbed off the marker. You want it to be as close to the center as possible.
With 1.7 RR's, you are moving the point where the pushrod touches the rocker(that little cup it pushes into) closer to the rocker stud. SO, since it is going further away from a 1.5 , you will probably need longer pushrods. If your heads are stock etc, no shaving of head, you can probably get away with a stock pushrod. BUT, It is cheap insurance to verify the right geometry, as you could break something in the valve train, which could be pretty bad. A few minutes of work, a 20 dollar tool to test it, and it could be a big saver in your pocket book.