it it worth running a shorter duration solid flat tappet?

[1980Buick]

Comparing two off the shelf grinds as an example:

Comp 270 H magnum
Comp 270 S magnum

For a motor example, typical back yard 350

[lefty o]

for the typical backyard built 350 where a guy just stabs the cam in and doesnt bother to degree it, may as well run the hydraulic.

[1980Buick]

Ok not THAT backyard maybe . Just a typical build

[GARY C]

I can't see a benefit, they are both 224 @.050 and 135 @.200 with a .313 lobe lift. I guess it is just a matter of do you want to do valve lash on occasion.

[GARY C]

Ok not THAT backyard maybe . Just a typical build

I guess it depends on what one considers typical, for me that would not be a solid flat tappet motor. For me if a hyd flat doesn't fit the bill the I typically go solid roller. Everything in between seems to be a more costly compromise. My cross over point would probably be in the mid to upper 280's seat duration.

[rustbucket79]

Go with the hydraulic, cheaper (lifters) no valve adjustments and no worries about pressed in rocker studs pulling out. (Not certain that would actually happen)

[plovett]

I don't think you can compare a hydraulic and solid, "apples to apples", in terms of duration.

They measure advertised duration at different lifts and I think that affects everything. Bottom line is to get a similar rpm range you generally need a solid to have very roughly 8 degrees more duration @ 0.050" compared to a hydraulic. So you might need something like 232 degrees duration @ 0.050 on the solid to have the same rpm range as a 224 @ 0.050" hydraulic.

JMO,

paulie

[RCJ]

I believe plovett is correct. I have that comp 270 solid in a 64 chevy with a backyard 350.Runs good with very good throttle response

[RevTheory]

I believe plovett is correct. I have that comp 270 solid in a 64 chevy with a backyard 350.Runs good with very good throttle response

I'm in this camp as well. I ran the 270S in a 350 in a heavy Blazer with 35" tires. I ported the crappy smog heads and the exhaust ports cleaned up really well. The cool thing about the solid Magnum cams is they have a wide range on lash settings so you can fiddle around with it and see what you like best. Every time I tightened up the intake and loosened the exhaust, I was rewarded with a smoother idle, more vacuum and more butt-dyno power. I think (it's been 15 years) I ended up at something like .016" on the intake and maybe .024" on the exhaust.

I've never run the 270H so I can't compare the two. I just know the 270S ended up being a pretty cool, old-school cam with a bit of a "tuning window."

[CamKing]

I don't think you can compare a hydraulic and solid, "apples to apples", in terms of duration.

They measure advertised duration at different lifts and I think that affects everything. Bottom line is to get a similar rpm range you generally need a solid to have very roughly 8 degrees more duration @ 0.050" compared to a hydraulic. So you might need something like 232 degrees duration @ 0.050 on the solid to have the same rpm range as a 224 @ 0.050" hydraulic.

JMO,

paulie

Correct. Because of the difference in height between the hydraulic ramp of the hydraulic cam, and the lash ramp of the mechanical cam, the mechanical cam needs to be 4-8 degrees longer at .050", to have the same power curve

[mag2555]

What year 350 ( compression ?) and what rear gears are or will be in the car?
I have a lot of time in on the Isky 270H mega Cam in a 9.2 to 400 motor and with everything the same but with only 8.5 comp and 2.73 gears the car was pretty soft below 2300 rpm with a TB350.

Where talking a 3650 lb car here.

[Stan Weiss]

I can't see a benefit, they are both 224 @.050 and 135 @.200 with a .313 lobe lift. I guess it is just a matter of do you want to do valve lash on occasion.

Gary,
If these are the two lobes. Then the difference shows up when looking ATDC values.

5201 270-4 224 135 .3130 .069 .057 .470 .501 .532

6017 270-3 224 135 .3120 .064 .054 .468 .499 .530

Stan

[GARY C]

I can't see a benefit, they are both 224 @.050 and 135 @.200 with a .313 lobe lift. I guess it is just a matter of do you want to do valve lash on occasion.

Gary,
If these are the two lobes. Then the difference shows up when looking ATDC values.

5201 270-4 224 135 .3130 .069 .057 .470 .501 .532

6017 270-3 224 135 .3120 .064 .054 .468 .499 .530

Stan

Do you think there would be any measurable difference in power?

[1980Buick]

It's out of a 1974 Chevy C50 truck. 175hp factory rating.
Seems like a dished piston 882 headed motor.

Flat top pistons
Import heads either Flotek or ProMaxx (buying bare)
Cam
RPM Air Gap or equivalent
Carb

Trans either a TH350 or a Muncie M20

3:1 gears in a 9"

Going in a longbed 58 Chevy Apache that is manual steering, brakes

Note I am totally open to cam suggestions. I figured if a solid will give me a meatier power band it would be worth it

[CamKing]

I can't see a benefit, they are both 224 @.050 and 135 @.200 with a .313 lobe lift. I guess it is just a matter of do you want to do valve lash on occasion.

Gary,
If these are the two lobes. Then the difference shows up when looking ATDC values.

5201 270-4 224 135 .3130 .069 .057 .470 .501 .532

6017 270-3 224 135 .3120 .064 .054 .468 .499 .530

Stan

Do you think there would be any measurable difference in power?

The mechanical cam would peak about 200 rpm sooner.