I'm starting this thread after reading everything I can find through the search about 1.7 RR rockers for a stock LT1 motor. I would like to keep this thread focused on installing 1.7 rockers with a stock cam. Many of the other threads get confusing due to information being added on what the 1.7s would mean after a cam swap, and I'd like to keep that from happening here.

I'm hoping to get clarification and just more knowledge in general before I start ordering parts.

Just to clarify, to install 1.7 RR in an LT1, they must be non-self aligning and use guideplates with hardened pushrods. I've read this is because nobody makes a self-aligning 1.7 ratio RR for the LT1. Anyone know otherwise?

I have read MattysTA's 1.7 RR Install post all the way through, and really appreciate the information given. This install used Scorpion rockers. Are these the only option for 1.7s on an LT1?

Parts which are a given for this setup:

• 8 - GM guideplates: p/n# 14011051
• 2 - Intake Valve Guide Seal Kits: p/n# 10212810
• 2 - Exhaust Valve Guide Seal Kits: p/n# 12564852

I plan to swap out the rocker studs for 7/16" studs. My research tells me the stock studs are already 7/16" in the head, and 3/8" on the rocker side. So upgrading to 7/16" should be a no-brainer. A member posted good luck with ARP 7/16" studs with p/n# SCP 1026, but I cannot seem to locate this anywhere. I searched through summitracing and just don't know enough about valvetrain stuff to identify the proper studs to get. I know I need the right depth to use with guideplates, but am not sure what that depth is. Some help here would be appreciated.

From what I've read, a 1996 stock LT1 cam has the following lift numbers:

• Stock cam with 1.5 = .447 & .459
• Stock cam with 1.6 = .477 & .490
• Stock cam with 1.7 = .506 & .520

After reading all of the other 1.7 threads, it seems there are several options for springs.

• 987 Springs (good for .600 lift)
• Lt4 Springs (good for .550 lift)
• isky 235d springs (good for ??? lift)

Does anyone know the lift #s for the 235ds? From what I've read, the isky springs will not fit the stock head without replacing the seats and adding spacers (anyone confirm/deny this?). This makes me want to stay away from them.

Looking at the lift numbers with the 1.7s, it seems the LT4 springs would be plenty. Is this true? Should I go with the 987 springs anyway, and if so, will they fit without modification? Will having .520 lift on a spring capable of .600 cause any issues?

I believe the stock pushrod length is 7.200". (non hardended in the 1996). Can someone please confirm this for me?

The largest concern people seem to have with the 1.7s is valvetrain geometry. I have read you can check geometry by using an adjustable pushrod and checking the wear pattern on the valve stem. I've also been told there is a formula which can be used to determine the proper pushrod length to use for a given setup. Of course, most of the pushrod debate issues are quickly clouded with responses which start discussing non-stock cam numbers. So I guess I am looking to determine if changing the rockers and leaving the stock cam will require a non-stock length pushrod.

Thanks to anyone who can offer some insight here. I know lots of individuals are considering this exact same upgrade (keeping the stock cam), so hopefuly others will benefit as well.

Thomas.

 

I would like to know about the pushrods as well, as I dont plan on doing a cam swap for a while.

 

Stock pushrod length: 7.200"

LT4 springs: .525 if I'm not mistaken

LT4 springs should handle the 1.7s. Hopefully I'll be installing the scorpions this summer. Harland Sharp also makes 1.7s.

 

Have fun, my car fell off hard on the top end, i would go with something bigger than the lt4 springs. 1.7rr are too aggressive .521 to .525

I dont think the lt4 springs are stiff enough, JM2C


Note- I had to clearance my valve covers , the rockers would hit the top of the valve cover, as well as the sides of the bolt supports

Other than that, i love my 1.7rr

 

So LT4 springs are good only up to .525 and not .550?
I'll have to check out the Harland Sharps, thanks for that.

Roadtrip,
Did you have the Scorpions installed? What springs are you using now? Are you using the stock length pushrods?

You say it fell off hard at the top end. I assume this was with LT4 springs, and you were most likely getting valve float. Did you fix this issue by swaping to something like the 987 springs?

Thanks guys,
Thomas.

 

Not enough cash is a down fall of mine.

Ya, i had the scorpions.

I just put on a new set of lt4 springs for the bolt-on record, i should have gone with some Iskie's but i didn't.

Stock pushrods with stock cam are fine.

I just put a cam in my car with the 1.7rr, and i had to go to 7.350 pushrods. Im running the comp 918's now for a big cam.

good luck with the install

B-rad

 

Thanks for the info.

I assume you mean stock pushrod length is ok, but I will need either hardened or chromeoly, right?

Here is what I've got for a parts list so far. Anyone care to comment? I could definitely use all the help I can get!

• Scorpion Rockers SCP1026 http://www.flatlanderracing.com
• Comp Cams Hardened Pushrods ENG-7808-16-Comp http://speed-eng.com
• Comp Cams 987 Springs 987-16 http://www.flatlanderracing.com
• 10* Steel retainers (Dont have a part number as I can't determine which ones I'll need)
• Stem Locks (Dont have a part number as I can't determine which ones I'll need)
• Valve Seals 10212810 & 12564582 http://www.gmpartsdirect.com
• GM Guideplates 14011051 http://www.gmpartsdirect.com
• ARP 7/16 Studs ENG-134-7103-ARP http://speed-eng.com
  
• I am also debating on getting the LT4 Vavle Covers (12552321 & 12552322 from http://www.gmpartsdirect.com) and modifying them as shown in This Page

Does this list look ok?
How can I determine which retainers and locks will work with the rest of this setup?
If I am only going to be turning stock RPMs, is there any reason to spend the extra $$ on titanium retainers instead of steel?
Will those ARP studs work with the guideplates? Doesn't the stud need to be a bit shorter if you are using guideplates?

Also, I read somewhere that an LT4 knock module is not enough to filter out false knock with this setup. I saw a comment about putting a resistor in line with the knock module wiring. Anyone have more information on this?

Thanks again for your input, I really appreciate it! Hopefuly I'll be ordering the parts this week

Thomas.

 

Just an update, and a bump in hopes of more information from you guys.

I just ordered everything in my list above except the Scorpion rockers. I called Scorpion to ask some questions before ordering. I spoke to a guy named Harold who told me the SCP1026 rockers would not fit in the stock valve covers (which we already knew), but I've decided to get the LT4 covers with supporing hardware anyway; so no problem there.

He told me the pushrod length will be different due to the 1.7 ratio being obtained by moving the pushrod cup on the rocker closer to the rocker stud. He agreed the best way to determine the correct size is to mark the valve stem and check the wear pattern. The change may be so minimal the 7.20 length will work; but I'll check it anyway during the install.

He also told me, when they build race motors with these rockers, they sometimes have to port the head a bit so the pushrod doesn't rub against the casting; due to the added angle of the pushrod from the cup being moved. I hadn't considered this. Anyone who has the Scorions care to comment?

Another thing he suggested is, to verify the pushrod doesn't bottom out on the guideplate when a full revolution is obtained. He said, due to the pushrod cup being moved on the rocker, some guideplates need to be opened up more to accomidate the added angle of the pushrod.

I'm feeling more and more confident in this 1.7 install now. Lots of research and part numbers later, although it is getting a bit pricey! Almost makes me wonder if I should have just gone with 1.6 SA and spent the extra $$ on some other upgrade ..... but naaa, just having the rarity of 1.7's in an LT-1 will make it all worth it LOL!

Thomas.

 

PLEASE let us know all the details on the install. I am fixing to get a good sum of money and I would LOVE to do this! I'm glad that you started this thread for installing them on a stock cammed LT1.

 

This is very interesting.... especially since something in the valvetrain of the T/A let go . I was told that I may have had a rocker "back off" and drop? If I have any rockers messed up, I might go with a 1.7 setup.

I am running 987-16 springs right now with the cam below. Does this look like a good setup for 1.7's?

 

The 987-16 springs are dual coil and supposed to be good to .600 lift.
I was told by Speed Engineering, conical springs (like the 918s) are favorable; but the 987's should be fine for my stock cam setup maxing .520 lift on the exhaust with the Scoripon 1.7s.

Do you know what your lift numbers are now, and what ratio rockers you currently have?

Thomas.

 

I will have to check when I get home for the cam specs.

 

The added lift of a 1.7 rocker would make more power the higher you rev, especially with the roller tip, wouldnt it? Was your loss of high end power due to valve float?

On the grand prixs guys would run Comp Cam 1.7s for an aftermarket rocker and had incredible success. Why would you need a different length pushrod unless you are mounting the rocker on a pedestal and increasing the height of the whole rocker itself. Also, what is a Guide Plate? The grand prix never mentioned anything aftermarket for rockers other than stiffer springs, lifters, valve seals. No mention of pushrod length unless an aftermarket head gasket was used.

 

Isn't the Grand Prix an overhead cam setup? If so, the rocker rides right on the cam itself, so no need for pushrods.

On the LT1, the cam is not overhead, and therefore a pushrod is used to span the distance from the cam/lifter to the rocker arm. A guideplate is a plate which bolts onto the rocker stud and has a stand off to keep the pushrod aligned therefore keeping the rocker from twisting side to side. Stock rockers on an LT1 are self aligning, and do not need guideplates. If you upgrade to a rocker which is not self aligning (NSA), then you need to add guideplates and go with hardened pushrods.

Thomas.

 

You kidding me, the 3.8 V6 is always and will always be a pushrod engine. If I were to dig into an overhead cam engine, id be lost instantly. The Rockers for the L36 and L67 (grand prix NA and FI engines) both have pedestals they are mounted on. Is that the same thing as a guide plate?