[74c20]

So my question is can you use them together. My valve springs I have right now are "Z28 valve springs" what I have seen is people saying flat tappet springs are to hard on the roller lifters but I'm trying to match a cam that requires the same lift or can handle those springs? Thank you

 

[2001Blazer4x4]

Flat tappet springs are not strong enough for roller lifters. Roller springs are too strong for flat tappet lifters. Both have to do with weight of the heavier roller lifters.

Sent from my moto g power using Tapatalk

 

[BogiesAnnex1]

Two big issues are rollers are heavier than flats and cam designs between

1. Roller lifters weigh about twice a flat tappet lifter. Roughly about 200 grams installed compared to 80-90. part of this is the roller and part is the alignment mechanism.

2. Here though with the cam you have to be careful of the lift rate. There are two dimensions of duration that play into this that is the duration between zero and .050 lift. The older Z28 flat tappet cams use a lot of duration in ramps between zero and .050 where more modern cams and especially rollers whack the ramp duration about in half or more resulting in a lot more jerk load on the valve gear including the springs. Insufficiect spring pressure with these roller cams let’s the closing valve bounce on its seat.

Bogie

 

[74c20]

Okay so looking into stock vortec cams just because of price and I can get stock rollers and from what bogie has already said in another thread I can drill out my bosses for the stock spider tray so my plan right now is getting a stock cam stock springs stock lifters used but still good dog bones with a gm cam and gm lifters for a somewhat stock setup but my setup is somewhat stock I think. I have dart heads ss iron eagle 76cc chamber with an eagle rotating assembly bored .30 over flat top 4 valve relief pistons. The reason behind me thinking of doing a stock cam is because budget but what do you think bogie?

 

[ericnova72]

There is quite bit of overlap for valvespring applications.
Mid and upper end of range flat tappet spec is the same as base and mild level hydraulic roller.
Same on the range for upper level hydraulic roller swap to mild solid roller.

What hydraulic roller do you have in mind??
Probably more importantly, do you have the valvespring part number??

 

[74c20]

There is quite bit of overlap for valvespring applications.
Mid and upper end of range flat tappet spec is the same as base and mild level hydraulic roller.
Same on the range for upper level hydraulic roller swap to mild solid roller.

What hydraulic roller do you have in mind??
Probably more importantly, do you have the valvespring part number??

I am open to any size cam preferably something closer to a stock 96-98 Chevy truck. Something that's budget minded. The valve spring number I have on the heads are vs-380 melling

 

[ericnova72]

According to Melling specs, that is just a stock flat tappetvalvespring, not a "Z28" spring.

 

[74c20]

According to Melling specs, that is just a stock flat tappetvalvespring, not a "Z28" spring.

Oh okay sorry I had them tested before I installed them for height checking and the machine shop checked the spring pressure and said they measure out to a Z28 spring.

 

[95 Truck]

Ok, I am illiterate to this subject, but I started reading up on it. I found a conversation on this subject, on a different forum, that Mr Jones of Jones cams was involved in. What I learned, is there is no roller cam spring vs a hydraulic cam spring, it all boils make sure your spring is sized correctly for your cam specs.

here is link to other form

https://www.speed-talk.com/forum/viewtopic.php?f=1&t=41142&sid=77df80ad9d1972a92bc62f49550f14d9&start=15

 

[BogiesAnnex1]

When you get down to what the OP is doing; that is using the stock timing L31 Vortec cam is pretty mild it is roughly equivalent to the pre 1987 standard production 305, 327, 350 cam.

In this cam’s heyday, depending on compression ratio, this produced between 250 and 300 horsepower from a 350. In the L31 96-2000 these are rated about 250 hp which is consistent with the cam timing in the not high performance 350 before SMOG requirements reduced compression ratios into the high 7’s to low 8’s.

So I think his Z28 springs using a production timed L31 roller will be just fine.

Bogie

 

[johnsongrass1]

85 seat and 200 open I wouldn't do it that way.
120 seat and 300 open is about where I'd be comfortable.

 

[55_327]

So I think his Z28 springs using a production timed L31 roller will be just fine.

I agree. I have a set of stock L31 springs in my shop somewhere, and I'd bet they don't have as much seat pressure as the PO's so-called Z28 springs. Those GM roller cams were not all that aggressive. Even the 196/206 RamJet cam has a seat duration around 278/288.

 

[74c20]

When you get down to what the OP is doing; that is using the stock timing L31 Vortec cam is pretty mild it is roughly equivalent to the pre 1987 standard production 305, 327, 350 cam.

In this cam’s heyday, depending on compression ratio, this produced between 250 and 300 horsepower from a 350. In the L31 96-2000 these are rated about 250 hp which is consistent with the cam timing in the not high performance 350 before SMOG requirements reduced compression ratios into the high 7’s to low 8’s.

So I think his Z28 springs using a production timed L31 roller will be just fine.

Bogie

so the lift on my cam is 204 int/ 214 exh at .50 lift. The cam I was looking at that is also a melling and is a stock replacement is 191 int/ 194 exh at .50 lift. Would that still be okay with those springs?

 

[55_327]

Check this out to get a basic understanding of duration and lift:

 

[BogiesAnnex1]

A half inch lift is worthy of investigation, that is quite a bit more than the stock Vortec cam.

The spring you cite, the Melling VS-380 is just a stock replacement spring of pretty low pressures of 84 psi to 204 open at .045 inch lift. .45 inch is their recommended max lift point occurring with the spring compressed to 1.25 inches high from a closed install height of 1.7 inches. At a fully open point there needs to be a sum of coil to coil clearances adding to .050 inch. If you add .050 inch to .450 inch range of function of the installed spring this is .5 inch and your cam lifts to .500 inch lift so on paper the springs you have are at coil bind, they can’t be operated that way.

I don’t have that spring around so can’t check real measured numbers for you but on the face of it unless you can come up with measures, I’d say you need different springs or a different cam.

Bogie

 

[BOOT77]

If you get an aftermarket cam, ask that cam manufacturer for recommend springs. Then set those springs up at the recommended install height.

 

[74c20]

I did find the springs that go with the cam kit just hope that I don't drop a valve changing them🤣🤣 thank you guys for the help

 

[95 Truck]

??? I thought you have the heads off?

there are many safe ways to do it with heads on engine

 

[74c20]

??? I thought you have the heads off?

there are many safe ways to do it with heads on engine

No my bad for not saying that.

 

[U_Boat]

All technical mumbo-jumbo aside, if you float the valves with roller lifters, you will pound out the needles in the rollers and that's it for the engine. (that's why there are bushing roller lifters - they wear out before needle bearing rollers, but don't grenade if you float them).