5,7 tbi roller rockers

[eran tomer]

hello
surfing this site i came across the roller rockers tune concept, but remained with some unanswered questions :
can they be installed without the valves touching the pistons?
does it take replacing the pushrods etc.?
does the pcm need to be modified?
what is a "full" rockers as was mentioned couple of times?
what is a good brand?
and what's the benefit providing i got the vortec fuel pump?
thanks

 

[Erik the Awful]

can they be installed without the valves touching the pistons?

Yes. I have roller rockers on mine, and I'm running .515" lift with flat top pistons. Still, it's a good idea to check before you fire the engine. Put some silly putty on the piston, set the head on the block, and spin it through a cycle and see how thin the putty gets spread.

does it take replacing the pushrods etc.?

Typically, no. On engines with fixed rockers, it's common to have to change pushrod length or change lash caps. Our rockers are adjustable. You do need to check for pushrod clearance in the head. A 1.6:1 ratio moves the pushrod closer to the upper edge of the holes the pushrods pass through in the heads.

does the pcm need to be modified?

It shouldn't. The difference between non-roller and roller rockers is only a horsepower or two. If you rev to 7000 you might see five horsepower. If you also move up to 1.6:1 ratio rockers you're gaining about 5 horsepower across the rpm band, which should be within the capability of the stock tune. 1.6 rockers do nothing to increase your duration or change your lobe separation angle. It's simply a 7% increase in lift.

what is a "full" rockers as was mentioned couple of times?

There are roller-tip rockers, and there are full-roller rockers. The roller-tips have been dyno proven to be nearly worthless compared to the expense. Full roller rockers have roller bearings in the tips and in the fulcrum. It's a situation where you shouldn't deal in half-measures. You either need full rollers or you don't.

what is a good brand?

If you want some quality 1.6:1 stamped rockers, these Elgins have been suggested.

Elgin Stamped Steel Rocker Arms 1.6 long slot; Late model; self-aligning

KMJ Performance

www.kmjperformance.com

Proforms are cheap. I used them on my engine, but I'm also running beehive valvesprings, which don't have a ton of spring pressure. Knowing what I know now, I would have gone with the Elgin rockers above. I wouldn't trust them for 7000 rpm operation, which is what justifies roller rockers over stamped rockers. Skip 'em.

Scorpion and Crane are supposedly pretty good, and not horribly expensive.

Harland Sharp is the gold standard of roller rockers, and they charge gold prices.

and what's the benefit providing i got the vortec fuel pump?

First, you have to understand that the factory stamped steel rockers aren't actually 1.5:1. It's more like 1.48:1, and at high rpm they flex to about 1.45:1. If you have a mild motor, they're good and dirt cheap. Failures are really rare, which can't be said for aluminum rockers.

If you're not building a 7000 rpm motor, get some longer-slot stamped 1.6:1 rockers and ensure your pushrods have clearance.

If you're building a 7000 rpm motor, buy quality full roller rockers.

 

[PlayingWithTBI]

^^^This plus keep in mind there are self guided rockers and non-guided ones which need guide plates AND hardened push rods like chromoly. I have the Proform 1.6 rockers and with my aluminum heads and guide plates, I used a push rod length checker to order the proper lenght hardened push rods.

1.6 rockers do nothing to increase your duration

Actually they do but, it's minimal. They increase duration @ 0.050" because they get to that a little sooner.

 

[Frank Enstein]

I have been answering these questions for the better part of 3 decades.
There are a lot of misconceptions and bad info from "my buddy". We'll get back to him in a minute!

Unless you have installed a camshaft with .480" lift don't waste your money.

The factory cam has very little lift and the higher ratio rockers would do very little for a bunch of money.

Maximum lift on the cam has nothing to do with piston to valve clearance.
At max lift your piston is more that halfway down the bore.
The valve overlap which is tied to lobe separation, cam phasing, and duration @.050" lobe lift are the salient factors.

Anytime ANYTHING is changed in the valvetrain assume the pushrods are the wrong length.
The closer to stock your combination is, the less likely the pushrod length will need to be changed.

Roller tips weather or not they have a roller fulcrum (full roller) are pickier about pushrod length due to the small radius of the roller tip of 3/16" to 1/4" vs the nearly flat 36" radius of the stock stamped rocker arm.

An investment cast roller tip or a full roller rocker will have accurate ratios vs. any stamped rocker.

Cylinder heads on a small block Chevy 1987 and newer need Self Aligning rockers unless pushrod guide plates are used.

Piston to valve clearance must always be verified. Again the closer to stock the less likely you are to have any issues.

O.k., Now back to "my buddy" he shouldn't be allowed tools and if you find him fix him up with my ex-wife!

 

[eran tomer]

it's too complicated, I'll skip this.

how about just putting a tuned tbi like this:

46mm PORTED 5.7L TBI Package Deal 650CFM | eBay

THIS IS 650CFM! 46MM TBI /Adjustable Reg Cover. TBI are known for leaky throttle shafts. 5.7L TBI as described above and below. There are multiple casting numbers used. Not all the TBI units have all the available vacuum ports as shown in the photos.

www.ebay.com

along with the vortec fuel pump, otherwise stock engine.
will i gain anything?

 

[Erik the Awful]

Actually they do but, it's minimal. They increase duration @ 0.050" because they get to that a little sooner.

I keep reading that, but that would require a change to the cam and lifters. The lifter still hits the rise in the cam at the same time, and it's measured at .050 cam lift, not .050 valve lift. A larger ratio doesn't increase the duration, it just ramps faster. If there's a relationship here that I'm missing, please educate me.

 

[L31MaxExpress]

I keep reading that, but that would require a change to the cam and lifters. The lifter still hits the rise in the cam at the same time, and it's measured at .050 cam lift, not .050 valve lift. A larger ratio doesn't increase the duration, it just ramps faster. If there's a relationship here that I'm missing, please educate me.

Duration increases at the valve where it DOES make a noticeable difference. I gained about 15 hp from 1.6 full rollers on a TBI 350 with a performer rpm intake under a 454 TBI and thorley tri-ys.

 

[Frank Enstein]

Duration increases at the valve where it DOES make a noticeable difference. I gained about 15 hp from 1.6 full rollers on a TBI 350 with a performer rpm intake under a 454 TBI and thorley tri-ys.

What he said!

It doesn't add duration it just acts like it does. Going from a 1.5:1 rocker to a 1.6:1 rocker feels like you've added 2 to 5 degrees @ .050" depending on the cam grind.
The more radical the opening/closing ramps the more you will notice the change.

A higher ratio rocker on a modern cam lobe that wasn't designed for the higher ratio (like a Comp Extreme Energy or a Thumpr) can cause valvetrain instability and a loss of power if not outright engine damage.
Higher ratio on a 1980's cam is no problem.

When in doubt ask your preferred camshaft vendor.

 

[JeremyNH]

The Ramjet uses full roller 1.5s for 345HP/396tq. The HT383e uses stamped steel 1.5s for 323HP/444tq. Cam and heads are the same. But HP = K x (torque) x (rpm) where K is a fixed number so the only way that works is for the Ramjet to hold torque for a few rpm beyond where the HT383e runs out of breath. What little the rollers provide the Ramjet in added HP must take place far beyond the rpm band where most of us would find it useable. And the higher developed torque over the full operating band will result in higher energy delivered (i.e. acceleration) over the same operating time so the HT383e will outperform the Ramjet by any reasonable definition of outperform. That's engineering physics and there isn't any way around it. Point is I don't think a peak HP number is a relevant metric since it only represents one point on the power band and if full rollers only serve to push that number a little higher without changing the total developed torque it isn't something a driver will feel. A race car maybe where rpm is always high. But a street truck? Nope.

With regards to ratio though the Ramjet did have a period where it used 1.6 full rollers instead of 1.5s and iirc it developed 351HP/400tq. That is apples to apples on ratio only and it does show a slight improvement on performance using a low rise cam. I've read where the higher number was throughout the RPM band but I've never seen a chart to trust so only hearsay.

 

[L31MaxExpress]

The Ramjet uses full roller 1.5s for 345HP/396tq. The HT383e uses stamped steel 1.5s for 323HP/444tq. Cam and heads are the same. But HP = K x (torque) x (rpm) where K is a fixed number so the only way that works is for the Ramjet to hold torque for a few rpm beyond where the HT383e runs out of breath. What little the rollers provide the Ramjet in added HP must take place far beyond the rpm band where most of us would find it useable. And the higher developed torque over the full operating band will result in higher energy delivered (i.e. acceleration) over the same operating time so the HT383e will outperform the Ramjet by any reasonable definition of outperform. That's engineering physics and there isn't any way around it. Point is I don't think a peak HP number is a relevant metric since it only represents one point on the power band and if full rollers only serve to push that number a little higher without changing the total developed torque it isn't something a driver will feel. A race car maybe where rpm is always high. But a street truck? Nope.

With regards to ratio though the Ramjet did have a period where it used 1.6 full rollers instead of 1.5s and iirc it developed 351HP/400tq. That is apples to apples on ratio only and it does show a slight improvement on performance using a low rise cam. I've read where the higher number was throughout the RPM band but I've never seen a chart to trust so only hearsay.

The Ramjet difference is straight ratio change. Full roller reduces friction and that is worth even more. There is a reason the LS engines use factory roller trunions and the newer 4.3s had the same style. Moving from a friction causing 1.42 stamped to a 1.6 full roller realizes torque gains everywhere. My 350 TBI even idled more smoothly.