mcm95403

I see that Scorpion makes 1.7 roller rockers for the SBC. I'm wondering if anyone has tried them on a "stock" L-98. I realize I would need hardened pushrods and guide plates since they aren't self-aligning rockers, and new springs of course.

The 1.7's would give me .468/.485 lift from the stock cam without excessive cost or work, so unless someone knows of serious issues this could be interesting.

I did already e-mail Scorpion, just curious what the forum thinks.

cv67

Pushrod length?

imo too agressive on parts

GREGGPENN

I posed this question 2 or 3 years ago. No one said they'd done it on an L98...only LT engines.

FWIW, I thought it might be interesting to see what AFR heads would do with a stock cam and 1.7 rockers. That's because the mid-lift numbers are so good (especially on 195s).

That said, I do know 1.65's have been run. If I were you, I'd play it safe and use those. (Keeping in mind that the 1.65's were used on an auto-x car vs long-term street trials.) What would you lose with .05 less ratio?

mcm95403

True, I doubt it would be a difference you could feel. I was looking at the amount of work do do the swap and this would really only be adding the guide plates unless there is a problem somewhere else.

If I decide to go with less, I'd just get the 1.6 self-aligning rockers and be done with it.

mcm95403

Nevermind - I just saw that these are standard width and won't work with the center bolt heads.

Another incorrect listing for parts from Summit.

rklessdriver

They will work with centerbolt heads/rocker covers.

You may have to trim the center support brace on those stamped steel rocker covers but they will fit.
Will

mcm95403

Will they fit with my stock magnesium covers? If not maybe some aftermarket cast covers would be better?

65Z01

I installed ProMagnum 1.6s in my '88 L98 and had to grind down the drip tabs as well as narrow the bolt bosses.

If you are going to hi lift RRs see if you can get the ones for 7/16" studs. You will need to unscrew the studs anyway for guide plates and 7/16" will give a little less deflection at high lift.

Plus, while "in there", do the valve seals too.

GREGGPENN

You did notice he's got an L98 with 113 heads -- not an LT1, right?

mcm95403

I don't think I've ever done rockers on a center bolt head engine. I've done them on the standard heads. Being a previous die-hard Mopar guy, I gotta say that Chevy rockers suck to deal with - too bad there isn't a good shaft mount system for these heads. I can just imagine the fun of trying to adjust the passenger side while the engine is running.

Yeah, I'd do the seals too. I did hear back from Scorpion and they also suggested getting .080" wall pushrods to limit deflection.

I really want something that is bolt-on. I don't mind dealing with the drip tabs but if I have to start grinding anything on the head that's where I draw the line.

GS4-LT1

Doesn't Jessel make a shaft rocker setup for SBC???

rklessdriver

Aftermarket rocker covers are probally your best bet. The stock Mag covers are really low profile and if I remember correctly the center supports are very chunky, not to mention cutting off the drip tabs....

This is what I think you'll need:

Scorpion 1.7 rockers
7/16 studs
Real guide plates
Correct valve springs (GM LT4 spring kit is good)
Correct length hardened pushrods
Aftermarket rocker covers
Rocker cover gaskets
Valve seals (might as well while your in there)


Yea I know.

There is no physical difference in the 113 and the LTX heads (on top). The only problem is going to be the springs won't support that much lift and clearance issues with the rocker covers.
Will

Black89Z51

Are scorpion rockers self-aligning?

GREGGPENN

They make both...
http://www.summitracing.com/search/M...orpion+rockers



FWIW: I think my final decision not to run 1.7's was [my perception of] the extra stress on the lifters. Since higher ratios have less and less leverage to depress springs, 155# springs + anything higher than 1.6 didn't seem like the best option...at least for longevity. Plus, buying an aftermarket cam with more overlap was an advantage too.

USAsOnlyWay

I think 1.7s on my motor added 5hp on a simulator. Not worth it. You'd probably be OK with the 1.7s just because the stock cam is small but then you wouldn't want to run them when you finally put a decent cam in there. I just don't think it would be worth it honestly.

Nathan Plemons

I'll just throw my $0.02 in here. I BELIEVE, although I may be wrong, that I was the first one to try 1.7's on the LT1, at least on this forum. I have been running the same rockers for 9 years and 41,000 miles with absolutely no ill effects.

According to my gas mileage record, I actually gained 1.3 MPG and I have a dyno proven gain of 14rwhp and 11ft-lbs of torque.

I am running ARP 7/16 studs with factory length trick flow single piece hardened push rods, comp cams guide plates, scorpion rockers, comp cams pro mag lifters, with very large double valve springs.

In my book this has truly been a win-win modification. But, there are a few things about it. Before I did it I was fully aware of the flow numbers of my cylinder heads and I knew there was a lot more airflow to be had if I could go with the higher lift. I also knew that my valves springs could easily handle the extra lift and pressure. It was an experiment for me that turned out well. It worked so well that I tried a set of 1.8's, and actually lost power. Although I still had plenty of spring and there was more airflow, I had reached the point of diminishing returns in terms of internal friction. Basically I lost more to drive the 1.8's than I gained.

Will you see the same results on a stock head on a TPI car? Not likely. My 1.7's gained me more power at every point along the power curve. The reason? It allowed more air into the engine at every RPM and my intake was more than capable of flowing it. On a TPI car, it's whole problem is that it runs out of breath at RPM. You'll probably see some low to mid range increase but you will likely run into that TPI breathing barrier a little bit sooner.

I had the good fortune of being able to do back to back dynos with my car so I could quantify my gains. I would love to know what it does for your car, but if you don't have the ability to dyno and / or tune for the changes, I don't really know how you're going to quantify it. The butt-o-meter is notoriously inaccurate.

mcm95403

If I needed to change the valve covers to get these to clear, that would be fine - as long as I can find some that I like and that will fit without causing problems.

From what I've seen, picking up 10-15 RWHP with the 1.6's is quite common. I don't know of the improvement would be much more than that with the 1.7's. The 1.6's would be a fairly simple upgrade, but would still beed the springs, valve seals, and to do it right, should get the stiffer pushrods as well. That only leaves the difference of the cost of the rockers, the guide plates and getting the 7/16" studs. If I picked up a reasonable amount of TQ and HP with the extra lift, it would be worth it but if not the 1.6's would be the way to go.

Maybe someone here has a version of the desktop dyno software that will allow for figuring this out and will take a stab at it. I tried it on my old version but getting the cam numbers and intake flow numbers right was a problem.

65Z01

That was my thoughts too so I used a static method. It was time consuming but worked out very well...

Nathan Plemons

That's generally a futile effort. There are too many variables that the software cannot take into account to give you any meaningful information. In fact I believe it told me I would gain power with my 1.8's....

4th Gen Camaro valve covers will clear the 1.7's with virtually no modifications, this is what I use, simple black understated.

Nathan Plemons

I figured out a way that seems to be foolproof and is very quick. Doesn't work with new lifters though, they have to have been pumped up at least once.