valvetrain/lifter questions out of ignorance

[rrubel]

Ok. I'm getting ready to order the rest of what I need for my engine upgrade and I'm getting somewhat contradictory/confusing answers from parts places. Herewith are a series of questions, in no particular order, that hopefully people here can answer...


1. Converting flat tappet cam to roller lifter cam. I have the cam. I need a conversion/retrofit kit. TPIS sells one for $425; was told you need to drill the block and it's not worth the hassle. LPE sells one (Comp Cams, I think) for $499. Straight plug-n-play, apparently. Pricey, though. The GM Performance Parts catalog, though, lists a roller lifter kit that they claim, with new pushrods, will convert a flat tappet engine to a roller one. Price? $275 list, $207 discount. And $38 list for the pushrods. That's half the price. Anyone have any experience with this kit, or any other conversion kit?

2. When are pushrod guideplates *required*? Hardened pushrods in aluminum heads? Does it hurt to use guideplates when they're *not* required? Or only if one is using hardened pushrods, regardless of head material?

3. What length are stock pushrods? Are roller pushrods and flat tappet pushrods the same length? I'm getting conflicting data on this one.

4. Are the timing chain/gears different from early L98's to later L98's? Was told the cam gear is a different size, but wasn't told what year they switched or what I'd need to do to correct for that.

Think that's it for now. Thanks in advance...
[RICHR]

 

[-=Jeff=-]

Lets see if I can help

for your flat tappet non-roller block you will need these:

1
there are the retrofit roller lifters that are paired for each cylinder. they have a bar to keep them form spinning in the bore. I have not had to go through this yet, so I don't know which is the right set-up give us part numbers from each place and someone will check. The OEM in 87-later blocks used little figure 8 ring that kept the lifters from spinning and a spider plate that bolted to the block and kept the figure 8 keepers in place

2
As I understand it, Hardened pushrods and Hardened Guideplates are only needed if running non-selfaligning rockers. If you have Selfaligning rocker you will not need Hardened guideplates or hardened pushrods. Now some vettes (I know the 89 for sure) had non-hardened guideplates and they were used to keep the pushrods in place during assembly only.

3
I know on a late model roller block the pushrod standard length is 7.200" not sure on the older style. (Again I have not had to deal with that yet)

4
The Timing sets are different, but it is not a matter of size, but how it bolts to the cam. on the 87-newer 1pc rear main roller blocks the Cam is locked in with a plate to keep it from walking forward. I think you will need a cam button. Also the nose of the Cams are different. I heard you cam use an 87-later roller cam in a early block and use the later style timing chain but you will need a retro cam kit. I think Lingenfelter will know what you need for that, or maybe even TPiS

hope this helps

 

[rrubel]

Got most of the questions answered by a Jeb Burnett on "the other Corvette forum":

"I'm going to simplify this whole process. In order to convert a non-roller application to a roller cam you will need:
1) Camshaft (obviously), here's where you may run into a "little" situation. Late model cams for roller cam blocks have a stepped nose design. While you "can" use this it makes it a little more difficult. A standard nose is best.
2) Retro-fit roller lifters. Crane, Comp, etc... They will be the tie-bar style and they ARE NOT CHEAP (there's only two mfg's worldwide for these pieces and they have a similar collusive monopoly as the oil companies). Simple, go to your local speed shop and tell them you need either Crane p/n 11532-16 or Comp 853-16.
3) Cam thrust button. Moroso, Crane, Comp, Milodon, you name it there are many varieties. I prefer the roller type. Make sure you get the right button for your particular timing cover though.
4) Timing set. Cloyes True-Roller double set is the only way to go IMO. Get the correct piece for your camshaft nose type.
5) Pushrods. As others have already stated you will need hardened pushrods if you use guideplates (non-self aligning rockers). However, they are under a pretty good amount of stress so it's always good to use hardened ones anyway. As for length if the heads haven't been decked considerably and you're not running longer valves you will probably stay with a stock length pushrod. Go buy the cam mfg's recommendations based on your combination or if you want to be as anal as I am go get an adjustable pushrod length checker and check the geometry to be sure.
6) Rocker arms...Six of on half-dozen of the other here... Your GMPP rockers are manufactured by Crane and are the same as their "Gold Race" models which are excellent pieces. I suspect they are also self-aligning."


I'm trying to figure out what he means by a "stepped" nose. I may have to just go to a parts store and look at camshafts side-by-side. Also, still can't get an answer as to whether the GM roller lifters that GM *claims* can be used to retrofit actually have the tiebars.

Jeff, your post explains why the guy at TPIS kept talking about "spider plates". I think he wasn't aware of the tie-bar retrofit kits, even though that's specifically what I was asking him about (they sell one; not sure of brand).

Is the standard pushrod length 7.2" or 7.724"? The GM catalog says the latter, but 7.2" sticks in my mind as well. Now, if I'm using guideplates I HAVE to use hardened pushrods, but it seems to be OK to use hardened pushrods WITHOUT guideplates as well.

Time to visit the garage and look at the camshaft I'm installing. LPE had an 87-ONLY version of this shaft, as well as an all-roller-years version. Pretty sure mine is not the 87-only one by virtue of its age, but who knows...

Thanks for the info.
[RICHR]

 

[-=Jeff=-]

Is the standard pushrod length 7.2" or 7.724"?

I thought 7.2" was for standard OEM roller motors and 7.724" was for Flat tappet. I don't know if that is true though

 

[-=Jeff=-]

Attached is a picture of the nose of a 'Step Nose' Cam

 

[8388]

I don't know to what extent your mods are or type of heads, base circle on camshaft, block decking etc. etc. But before you order a set of push rods, I would check the geometry 1st. You can achieve this with a push rod lenght checker. If you don't get this right you will experience premature valve train wear.

 

[bossvette]

I purchased a complete Isky retrofit Hydralic roller cam and kit, the parts were all matched and work well together, the only downside was I had to get my heads machined for the larger dia dual valve springs which came with it still running strong three years later.

 

[rrubel]

Jeff, thanks. I have a step-nose cam...

Also, according to more that I'm reading from the GM Perf Parts book, GM Perf Parts "Heavy-duty" pushrods "can be used with all conventional hydraulic and mechanical flat tappets and most aftermarket roller lifters. They cannot be used with hydraulic roller tappets installed in 1986 and later small-block V8 ... engines."

They also list two types of pushrods for use with factory roller tappets - one for guideplate use and one for without.

8388, explain more on checking the pushrod length, please... Heads right now are stock cast iron L98, nothing has been shaved AFAIK. Plan to install Trick Flow street/strip heads. In-going camshaft is LPE 74219.

Bossvette, I bought the cam that's designed for the intake I wanted (Accel SuperRam). LPE sells a separate hydraulic roller retrofit kit, but wants $500 for it... GM has something they CLAIM does the same thing, and it can be had (discounted) for under $200. Hence my questions...

Heads I'm looking buying at come with dual valve springs already, which is something else LPE was recommending.

Thanks.
[RICHR]

 

[bossvette]

Do not know what the GM setup is but remember hearing about something to retrofit rollers into early blocks, the key is to maintain alignment of the rollers to the cam surface.
You could use aftermarket lifters like Jeff posted and the matching pushrods, comp cams sells a set reasonablely priced in summit just make sure you get the pushrods for the lifters you use.

 

[8388]

Any time you go with aftermarket parts, the factory tolerances are removed. If your going with Trick Flow heads I would definetely recommend checking the rocker geometry, especially if 1.6 rockers are going to be used. If the push rod lenght is not correct, the rockers will not ride correctly on the valve stem, and if it's severe enough, it will put unnecessary stress on the valve guide.

 

[sothpaw]

Pushrod length is an issue.

I had to replace mine because I think the heads were decked a little to much and also, I'm not using a stock head gasket.

Yeah, hardened pushrods w/guideplates are best. Don't forget, you're going to need good, stiff springs for that cam. It's VERY important to find out what springs you are getting and whether they are right for your set up.

The spring issue is why I got the heads&cam from the same guy. I wanted him to do all this for me. He used springs that the cam manufacturer doesn't recommend on the website. Dual springs are stiffer. Also, with the stiff springs, the 7/8" rr's w/studs are better with your high rpm cam.

 

[rrubel]

LPE makes a decent recommendation on the springs specifically for this cam. Also, for the L98, 3/8" studs are fine. The engine just doesn't live at the RPMs yours does. If I get much over 5500 and still have power, I'll be surprised. All the people at Lingenfelter said 3/8" was fine.

Talked to Comp Cam's CAM TECH 800 support line today. They suggested I wait until everything is together and then measure using one of their adjustable pushrods. Sound familiar? They (and Crane) sell a specific length for using their roller retrofit kits with 1.5 RR's, but the tech guy wasn't sure about 1.6's.

Anyone got a pair of those adjustable pushrods I can borrow sometime over the winter?

[RICHR]

 

[bossvette]

you could make your own by cutting a stock pushrod in half and drilling and tapping for a fine thread set screw, just make sure you cut the legnth down some to accomadate the lock nut

 

[8388]

Anyone got a pair of those adjustable pushrods I can borrow sometime over the winter?

[RICHR]

I made my own, it's not too hard, but I let someone borrow it and never got it back. When you do go to check it, the lifters have to be filled with oil, so that you can get an accurate reading, as the lifter travels around the lobe, this is important. Also the verification needs to be done with what ever rocker ratio your planning on using.

 

[-=Jeff=-]

LPE makes a decent recommendation on the springs specifically for this cam. Also, for the L98, 3/8" studs are fine. The engine just doesn't live at the RPMs yours does. If I get much over 5500 and still have power, I'll be surprised. All the people at Lingenfelter said 3/8" was fine.

Talked to Comp Cam's CAM TECH 800 support line today. They suggested I wait until everything is together and then measure using one of their adjustable pushrods. Sound familiar? They (and Crane) sell a specific length for using their roller retrofit kits with 1.5 RR's, but the tech guy wasn't sure about 1.6's.

Anyone got a pair of those adjustable pushrods I can borrow sometime over the winter?

[RICHR]

Yep, I agree on measuring the Valve train geometry.

As for borrowing a set I have a set that are around the 7.7" length, they were too long for my set-up (7.2") let me know when you need them and you can borrow them if you want.