1.6 Roller Rockers...Fit Under Stock Valve Covers?

[RubyDropTop]

Hi guys -

Does anyone know if 1.6 roller rockers will fit without a problem under the stock valve covers of an LT1?

Thanks in advance.

 

[vms4evr]

Use self-aligning rockers. Replace the springs and retainers also. You will have to grind your drip tabs down because the 1.6 will hit them. If you just went to 1.5 RR then they are supposed to clear and you can retain all your original hardware.
I haven't done it yet but it's on my list. If you search this forum you'll find more info on it.
Graham

 

[Hib Halverson]

1.6 rockers, with the self-aligning feature, were OE on LT4s so they'll fit. GM sourced the roller rockers from Crane.

In fact, you can buy a LT4 rocker kit from GM that makes just that conversion.

Use the LT4 rocker covers.

 

[sothpaw]

I have had this done on my car.
No, the 1.6 RR from the LT4 will
not fit the LT1-- you have to machine
the valve covers for adequate clearance.
This was a surprise to my Corvette-only
speed shop, but that's the way it is.

--I would think if you replaced the valve covers
with LT4 valve covers, then you would not have
to do any machining or have anyone else do that.

Andy

 

[RubyDropTop]

Glad I Asked...

Okay, does anyone know about how much LT4 valve covers are going to cost me? And will there be any problems with the valve covers themselves fitting on the LT1?

sothpaw - did you realize any performance gain from this conversion? I've very curious about what you think about changing the rockers over from a performance standpoint. Thanks.

 

[Vettelt193]

I have done roller rockers in different combinations... I like the mixed set the best... that is 1.6 intake, 1.5 exhaust... use the self aligning rockers, made by crane cams... The reason why I like this the best is for multiple reasons... 1) if you go 1.6 all around, you may have to change the springs too... some LT1's can take 1.6, and some can't... I would advise just changing the springs if you go to 1.6, because it is a pain to do the job twice (which I have done on multiple LT1's... it is also a pain to change the rockers, find it doesn't work, then try to find valve springs while the car is apart!) The problem with the springs is always on the exhaust side... I have never had a problem with the intake side. You can actually buy a mixed set from one of the big parts companies (if you want me to look it up let me know and i can figure out which one it is)... a second reason for the mixed set is the power curve... The full set of 1.6's will raise your peak HP RPM... this means you will make more HP, but you have to get the engine to a higher RPM to use it... This also means you will lose some of the low end grunt... I don't know about you, but I use from idle to 2000 RPM 95% of the time... this is where you may feel the slight loss of power... The good news is the decreased friction from the roller fulcrum usually compensates for it... (to make a long story short, you shouldn't lose power at the bottom if switching from the stock rockers because you gain HP from reduced friction, the down side is you don't gain power, which is the reason for doing it in the first place) Going with the mixed set gives an all around good mix though... It gives a boost on the top end and bottom end... reduces friction (more HP, better gas mileage, lower oil/engine temperatures)...

--Now that you have read all that, you have to make a decision... I am taking a wild guess based upon your car here... you use it for 'spirited cruising'... if this is the case, go for the mixed set.... if you like to go racing alot, go for the 1.6's all around... if you like the low end of your car best, stick with the 1.5's all around (but still switch to the rollers!)


--The LT4 valve covers should fit, but are not worth the money... The factory vette covers are made of carbon fiber and are very expensive... I would just cut off the drip tabs on your covers, if you want to keep them to put back to stock form, buy an aftermarket set, it will save you lots of $$.

--on a side note, manufacturers of rocker arms are starting to develop decreased rocker ratios for the aftermarket... why? because a lower ratio increases low end torque, which is the get up and go power of engines... Auto manufacturers on the other hand know that Horsepower sells cars, so they try to make high HP numbers.... it is much easier to make high horsepower numbers when your engine makes power up high, not down low...


If you (or anyone else) wants any more info on tuning LT1's feel free to let me know... This is my specialty since I have done it way too much!

 

[RubyDropTop]

Thanks Everyone!

Thanks to everyone that has replied to my question, I really appreciate the insight that many of you can offer to those of us that are not as "mechanically inclined".

I'll be starting this project in the 1st week of August, and am really looking forward to it.

 

[vms4evr]

Bob,
That's interesting. I didn't know you could buy a split kit of 1.6 intake, 1.5 exhaust. I'd be curious what company you are referring to. When I looked at Crane and a few others I saw the complete 1.6RR or 1.5RRkit. The Gold Race "Self-Aligning" Extruded Narrow. But no split kit.
It was recommended that you change all springs so I'm curious why you can get away with your factory springs on the intake side.
Someone had also mentioned to me that on the 92 it would be a good idea to change the rods because they weren't really up to the increased lift and spring pressures from the 1.6RR setup. I believe GM changed the rods in the LT4 and they are more durable and will live with 1.6RR. Please enlighten me... :cool
Graham

 

[sothpaw]

Ruby,
I don't know if the LT4 covers would fit,
I would think so. LT1/4 is the same engine,
LT4 just has different heads, cam, RR, ? springs,
rods.

But you might just get the LT1 covers machined
like I did.

Yes, by doing 1.6 all around, I realized about a
11 rwhp gain. This is a dyno result. I did a dyno
8 months after I bought the car (266 rwhp) and then
after the RR change (277rwhp). Now, I also added a
K/N to my stock box and a hypertech chip, but I doubt
that either of these changes helped at all. The chip
may even have hurt, in which case the RRs do more
than 11 rwhp.

I do race the car so I think 1.6 all around was the right thing.
?I didn't get charged for springs or rods, car has run great
for over 20k mi, with some racing, I assume it's all ok.

A

 

[rrubel]

Vettelt193, in a split ratio set, is it better to have the 1.6's on the intake or the exhaust? I've heard differing opinions.

I'll soon actually have a split set of CAT roller rockers for L98's for sale. I had to buy two sets and split them myself . Anyone who's interested let me know... These are 3/8" stud, non-self-aligning.
[RICHR]

 

[Vettelt193]

I think it is much better to do 1.6 on the intake, 1.5 on the exhaust... I will get back to you all on the company that offers the split set (it is a big parts company that splits up a set of crane cams rockers for you, so you don't have to buy both sets then try to sell the other set yourself)

 

[intruder9]

That's all good info for LT1's....

But what about the poor ol' lonely and forgotten L98?!

Love that torque on the bottom end!

Have a cat-less Borla exhaust, Superchip chip, K & N Filter w/ modified cover and a set of ported and polished Aluminum Heads are on their way!

Looking to port the intake plenum and install big-tube runners and possibly a 58mm throttle-body (might not need it yet) and shorty headers (will hook right up to the existing exhaust w/ no mods).

Any suggestions for this type of set-up while the heads are out of the car?!

 

[Vettelt193]

You said you love the low end torque of the L98. I would be very careful of what you are doing with the engine... all of the airflow mods you are doing will raise your peak RPM and HP, at the expense of low end torque. Also, a 58mm throttle body is probably too big for your application stick with the 52mm throttle body... It supplies enough air for most modified engines and it will still eliminate the bottle neck that the factory 48mm throttle body creates.

As far as rockers go, it depends on what you want... higher peak HP at higher RPM, or better low end torque... Since you like the torque side of things, I would go with the full roller rockers, but keep it at the factory 1.5:1.

while the engine is apart you may want to do a cam? You can find some excellent cams out there, but you need to make sure you are getting what you want... most aftermarket cams go for mega HP at high RPM... I would call around and ask for a high torque cam if that is what you are looking for.

 

[intruder9]

Thanks for the response, Vettelt193!

Will be more careful what I wish for!

 

[Vettelt193]

intruder, from gainesville?? are you a gator? do you go to the raceway there? I have been trying to get down there for some time now to run my Vette