DSKRALL

How difficult is it to install GM's L98 roller cam in an L98 block that was originally designed for a flat tappet cam? I expect it's a real production.

86 silver bullit

if my memory serves me right..you will have to install an aftermarket lifter set up. there are no bosses in the ends of the lifter valley to accept the roller lifter brackets

corvette1990

Here is what I have experienced with the new style Roller Cam in my L98. First is that the bolt holes where the timing chain bolts to is alot different. So you will need a different timing chain setup. Next you will find that roller cams require roller lifters. That means a retro fit kit to hold the roller lifters in place. (good news is they make them, see summit catalog). Then the Roller lifters are longer than regular lifters, so the pushrods must be shorter roller types. Then there is the cam gear different alloy issue, that you probably have to get a updated distributor gear to match the cam. I am sure i will get corrected on some of these issues or confirmed. Good luck. Chris :flag

vader86

Lingenfelter says you just have to install a kit, without having to have any serious block work done. Others say you do have to have the block tapped for the new lifters.

Unless you have a pre-87 block, you dont have to worry about this problem.

JAKE

It's not all that difficult to install if you are familiar with screwing on your engine. Now that I'm of "advanced age" I tend to divide a cam swap into two days. CompCams and probably others, have a video showing you exactly how to degree it if you opt to go that way. They may have a video on how to do the basic swap too, give 'em a call.

Since you have a flat tappet block you just need what is called "retro-fit" parts.

Here're are the parts I used when I swapped to a roller in a 350 flat tappet block:

Hydraulic roller cam (comes with assembly lube)

Retro-fit hydraulic roller lifters

Shorter, hardened pushrods (use a pushrod length checker (the inexpensive kind will work fine) to establish the correct length, but the new pushrods will usually be about 1/2" shorter than the ones you're running now

A new Timing chain set which comes with the 3 piece Torrington bearing set - CompCams, Crane and others sell them; get a double roller type

Roller thrust button to limit forward movement of the camshaft

Valve springs, retainers and locks designed for the camshaft you chose.

A new distributor gear is recommended; it'll be of the same type (iron) that you're running now NOT THE ALUMINUM/BRONZE TYPE, which won't last long.

Screw-in studs and guide plates if your heads don't already have them.

Some of the hydraulic roller cams call for .100 longer pushrods, so be sure to check with your cam manufacturer.

Roller rocker arms are recommended too.

Give CompCams a call on their toll free number and they will give you all the correct part numbers and prices. It will add up!

Hope this helps.

Jake


[Modified by JAKE, 11:08 PM 12/24/2003]

CFI-EFI

There is not a whole lot to be gained, subbing in a stock L98 roller cam for a flat tappet. All the above advise is good advice. Maybe I can help clarify the issues, and offer an unmentioned alternatve. There are several points of concern.

The first, is that the lifters cannot be allowed to rotate in their bores. The simplest (and more expensive) route, is retrofit lifters. Roller cams have been used in racing engines for years. It is the hydraulic roller that is the more recent developement. Retro fit lifters have a bar between the pairs that keep them from rotating. The factory roller lifters have two flats machined at the top of their bodies. A plate fits over the tops of a pair of lifters and prevents the lifters from rotating. That (anti-rotation) plate simply drops over the tops of the lifters. Inorder to keep that plate from being tossed off, there is a "spider" that bolts into the valley of the block. This spider has 8 legs. Each leg reaches out and contacts the center of each plate. The (relevant) difference in a "roller cam block" and a conventional block, is the boss, cast, and drilled and tapped in the valley to bolt the spider to. You CAN drill and tap your non-roller block to accept the spider. This allows the use of the less expensive OE roller lifters. Either aftermarket (retro) or OEM cams can be run with either, aftermarket or OEM lifters.

The lobes on a flat tappet cam are ground with a slight taper, front to rear. This is to promote lifter rotation and causes the cam to be pushed to the rear of the block. With no such taper (and therefore thrust) on the roller cam, the cam has to have the end play controlled. That is the purpose of the aforementioned thrust bearing and button. Also, the (OE) roller cams have a different nose that takes a different cam sprocket. With a stock L98 cam you can simply use the stock roller cam timing set, and a kit available from the aftermarket to control the endplay of a roller cam in a non-roller block.

Roller cams are often ground on billet cores and require a different distributor gear. Check with your cam supplier as to what works with their cam. Even different offerings from a single supplier have different reqirements.

The last, "must" is push rods. Roller lifters are taller than the conventional flat tappet lifters. Also, I believe the OE and retro rollers are different lengths than each other. Match the push rods to your lifter selection.

There CAN be many other considerations, such as proper valve springs, geometry, etc. But they are more basic modification concerns not necessarily "conversion" concerns.

There you have it. A ton of typing, for what turns out to be a reasonbly simple conversion. Not knowing what you, or other readers, may bring as prior knowledge, I thought some expaination was in order. Good luck, and...

RACE ON!!!


[Modified by CFI-EFI, 10:13 AM 12/25/2003]

Dale1990

To help clarify the above description, here are two pics from my 90's lifter valley showing the plates and the 3 attaching holes for the "spider" (very appropriate name BTW)


And a pic of the spider:


- Dale

CFI-EFI

A picture is worth a thousand words. Thanks, Dale.

RACE ON!!!

DSKRALL

Thanks to everyone for their tremendous replies. David

tjwong

Just be aware that what the Professor show inside his engine is for a 90 model year engine that was GM equipped for roller cams. These parts cannot be used in your engine that was not originally equipped for a roller cam. As you can see in the picture there are guides that hold the roller lifters in place so that the rollers remain in one position on the camshaft lobe. The block has to be machined for these guide plates, otherwise they cannot be used. Also the hold down plate has holes drilled and tapped in the block to bolt down that lifter guide retainer plate. Your block will not have these bolt holes. Insted you will need the "retro-fit" roller lifters that will be paired up and held together with a tie bar. This tie bar holds the lifters in proper alignment to the cam lobe.

65Z01

DSKRALL, instead of having the block machined to retorfit a roller cam you could install an agressive flat tappet cam along with 1.6:1 or even 1.7:1 RRs. These would give you more agressive valve lift beyond the limits of the cam.

You would likely need to have the heads machined to open up the push rod guide slots used in earlier heads. But then you chould also put some $$ into having the heads pocket proted and worked to increase the benefit of the cam.

CFI-EFI

tjwong,
That is correct. Did you read my second paragraph? I stated: If you have any doubts, Dan Plett has posted pictures of his 400 that he converted to OE roller lifters. And it doesn't look like it has to be a machine shop operation. Good luck, and...

RACE ON!!!

JAKE

My only thoughts is that to drill and tap will necessitate disassembling the engine to clean out all the cast iron shavings.

Making sure that everything is perfectly aligned is another concern for me.

Seems like a lot of work for no gain.

Here's my thinking: He's got to buy the parts anyway, whether stock type or retro-fit; so why go through all the trouble of adapting the block for the factory-type roller camshaft?

Am I missing or misunderstanding something?

Jake

Curveit

Jake...factory lifters are about 1/2 the cost of aftermarket.
I wonder about those figure 8 retainers, around the lifters. There's enough clearence for them?

:chevy

tjwong

Sure I would like to see a picture of how it was done. I am always open to new ideas, especially one that would save $$$ and make life easier. My only concern would be drilling and tapping the retainer bolt holes. As the bosses that are cast in place on a late model roller block are directly on top of the lifter oil passage if I remember right. Plus as you can see from a previous post with pictures the bosses actually stand off about 1/4 to 3/8" from the top of the block oil passage. It would seem to me that it would be much easier just to use the retro-fit lifters with the tie bars. But of cost was a issue I can see doing whatever it takes to save the $$$ :)

ben73

I have done this also on the 383 I am currently building. Cost is the main motivation. Here in Australia, a set of link bar hyd. roller lifters costs about Au$1200.. I did the conversion with the factory parts for under Au$300 :D :D

SBNova

I am about to do this mod myself. I just bought all the factory roller parts (lifters,retainers,"spider",pushrods and a factory cam for $65) and I am going to do the retrofit. I will be using an aftermarket cam and probably new pushrods, but the rest will be GM. I have a few blocks lying around- 283,305,350 and 400 and although Im sure they are the same I willl test each one to see how the retainer "figure8 thingy" fits. I can try to do this in the next few days and I will get some pics to show all the results if interested. The drilling/tapping of the valley isnt a concern for me, as is the height difference of the factory "stand-off's". Spacers could easily be fabbed if needed, and thead sealant used on the bolts. I could even spot face the area around the hole and use a simple gasket if I feel its warranted.

CFI-EFI

It would seem to me it would be much easier just to order an assembled engine, ready to drop in. Easier still, to just send the car off to someone, to do it all for you. Not all of us have unlimited budgets.

Here is a link to Dan's 400 engine site. There are two or three pictures of the OE lifter installation in the non-roller, 400 block. http://www.swko.net/~lionsden/400sbc.htm It looks pretty straight forward, to me. Good luck, and...

RACE ON!!!

JAKE

Sure, but once you factor in the cost of the parts and extra work needed to run a factory type setup, what have you really gained?

Aren't the lifter bosses different in a factory roller cam block? How do you mount the spider?

I just went through sometime similar building a 434 using a new BowTie block and just getting the correct lifters was a nightmare.

Jake

Jake

jbbiggs

The factory roller lifters are to tall for the pre roller block, the oil slots in the lifter come clear out of the lifter bore on lift no matter what base circle you have on the cam. it would probably run for a minute or two til the motor seizes from no oil pressure. You can use GM 4 cyl lifters but it's a hassle to find them, I recomend retrofit lifters from crane or comp cams.