Don Terrill’s Speed-Talk

Hi, I have a question that I can't seem to find much info about. I have found loads of info about Hydraulic vs Solid difference's, but not much comparing Solid Flat Tappet vs Solid Roller. It has always been my thought that a Solid Roller will have better vacuum and street manners than a solid flat tappet of similar size and lobe seperation, when used in the same application. Is this correct? Here are the two camshafts I'm comparing... .. what would the difference in idle characteristics, vacuum, and street manners be between these two camshafts?

1.) Ultradyne Custom Solid Flat Tappet

288/301@.020" Adv. Duration
255/267@.050" Duration
166/176@.200" Duration
.360"/.3677" lobe lift
112* Lobe Seperation
106* Intake Centerline
.020"/.024" Valve Lash

2.) Comp Cams Custom XE Solid Street Roller Lobes 4877/4878

298XSR/304XSR@.015" Adv. Duration
260/266@.050" Duration
181/187@.200" Duration
.392"/.398" Lobe lift
112* Lobe Seperation
108* Intake Centerline
.012"/.016" Valve Lash

The application is a Street/Strip 3800 lb 1978 Trans Am with TH400, 9.5" 3500 stall converter, and 3.73 gears. Not driven daily, maybe 2000 miles a year.

461 Cu. In. Pontiac
4.250" Stroke/ 4.155" Bore/ 6.700" Rod
Ross Flat Top piston .005" in the hole
Cometic .030" Head Gasket
.035" Quench
10.9:1 Compression
Kauffman Racing D-Port Aluminum heads 325cfm
Kauffman Northwind Intake
Fitech 1200PA EFI 30012
1 3/4" Hedman Headers/ dual 3" exhaust/ Dr Gas Xpipe/ Dynomax Ultraflo 17229 mufflers/3" tailpipes

What would the difference in Idle Characteristics, Idle Vacuum, Street Manners, and Power Capability be between the two above camshafts?

Thank You

Just too add another for comparison, here is a third Camshaft that's a possibility....

3.) Comp Cams Custom XE Solid Street Roller Lobes 4876/4877

292XSR/298XSR@.015" Adv Duration
254/260@.050" Duration
176/181@.200" Duration
.388"/.392" Lobe lift
112* Lobe Seperation
108 Intake Centerline
.012"/.016" Valve Lash

Ok. Both of the roller cams are going to make more power. But, the flat tappet cam could likely have a little better idle manners. I think any of three will have "decent" driveability in that cubic inch.

Hi, I have a question that I can't seem to find much info about. I have found loads of info about Hydraulic vs Solid difference's, but not much comparing Solid Flat Tappet vs Solid Roller. It has always been my thought that a Solid Roller will have better vacuum and street manners than a solid flat tappet of similar size and lobe seperation, when used in the same application. Is this correct? Here are the two camshafts I'm comparing... .. what would the difference in idle characteristics, vacuum, and street manners be between these two camshafts?

1.) Ultradyne Custom Solid Flat Tappet

288/301@.020" Adv. Duration
255/267@.050" Duration
166/176@.200" Duration
.360"/.3677" lobe lift
112* Lobe Seperation
106* Intake Centerline
.020"/.024" Valve Lash

2.) Comp Cams Custom XE Solid Street Roller Lobes 4877/4878

298XSR/304XSR@.015" Adv. Duration
260/266@.050" Duration
181/187@.200" Duration
.392"/.398" Lobe lift
112* Lobe Seperation
108* Intake Centerline
.012"/.016" Valve Lash

3.) Comp Cams Custom XE Solid Street Roller Lobes 4876/4877

292XSR/298XSR@.015" Adv Duration
254/260@.050" Duration
176/181@.200" Duration
.388"/.392" Lobe lift
112* Lobe Seperation
108 Intake Centerline
.012"/.016" Valve Lash

I don't usually comment on threads like this, but it's almost impossible to answer all your questions. the 299XSR will likely produce the most WOT horsepower above 4000rpm or so.

1) The Ultradyne lobe is "unsymmetrical", the opening even is delayed. You would need to know IVO/IVC and EVO/EVC at lash.
2) Comp advertises their duration at .015", Ultradyne at .020".
3) A hyrdraulic cam is usually moving by .004-.006" lobe lift.

The only way to compare this is to know what they all are at zero lash and what the actual events are.

The extra 15 degrees of .200 duration on the SR cam on the intake is going to show up as power in my opinion. Especially on that size motor.

Thank You both for the responses... here are the Valve Events for each camshaft....

1.) Ultradyne Solid Flat Tappet

Advertised Duration@.020"- 288/301
Duration@.050"- 255/267
106* Intake Centerline
112* Lobe Seperation

Valve Events on the Seat Rated@.020"

I.O.- 38.0* I.C.- 70.0*
E.O.- 88.5* E.C.- 32.5*
Overlap- 70.5*

Valve Events@.050"

I.O.- 21.5* I.C.- 53.5*
E.O.- 71.5* E.C.- 15.5*
Overlap- 37.0*
____________________

2.) Comp Cams XE Solid Street Roller

Advertised Duration@.015"- 292/298
Duration@.050"- 254/260
108* Intake Centerline
112* Lobe Seperation

Valve Events on the Seat Rated@.015"

I.O.- 38.0* I.C.- 74.0*
E.O.- 85.0* E.C.- 33*
Overlap- 71.0*

Valve Events@.050"

I.O.- 19.0* I.C.- 55.0*
E.O.- 66.0* E.C.- 14.0*
Overlap- 33.0*
____________________

3.) Comp Cams XE Solid Street Roller

Advertised Duration@.015"- 298/304
Duration@.050" 260/266
108* Intake Centerline
112* Lobe Seperation

Valve Events on the Seat Rated@.015"

I.O.- 41.0* I.C.- 77.0*
E.O.- 88.0* E.C.- 36.0*
Overlap- 77.0*

Valve Events@.050"

I.O.- 22.0* I.C.- 58.0*
E.O.- 69.0* E.C.- 17.0*
Overlap- 39*

Hope this helps!!

Basically on face value ,,
Cam #1 best vac and street/low rpm manners.
Cam #2 my 1st thought for best power
Cam #3 may out power 2 but a little more CR would make me say it will outpower cam 2.

All sound like fun on the street.

Did I miss what trans?What rear gear?Power brakes?Those will make a diff if your going to drive it.Tom

tjs44 wrote: ↑Wed Apr 25, 2018 9:33 pm Did I miss what trans?What rear gear?Power brakes?Those will make a diff if your going to drive it.Tom

1st post !

Thanks,old eyes!Tom

Thanks guys! I found out what the Seat Duration@.020" is on the bigger Solid Roller, so now we can compare it agaisn't my current Solid Flat Tappet, which is also rated@.020"..... so here are the Valve Events and Overlap comparison between the two....

Comp Cams XE Solid Street Roller

Seat Duration@.020"- 289/295
Duration@.050"- 260/266
Duration@.200- 181/187
108* Intake Centerline
112* Lobe Seperation

Valve Events on the Seat Rated@.020"

I.O.- 36.5* I.C.- 72.5*
E.O- 83.5* E.C.- 31.5*
Overlap- 68*

Current camshaft for comparison


Ultradyne Solid Flat Tappet(current cam)

Advertised Duration@.020"- 288/301
Duration@.050"- 255/267
Duration@.200"- 166/176
106* Intake Centerline
112* Lobe Seperation

Valve Events on the Seat Rated@.020"

I.O.- 38.0* I.C.- 70.0*
E.O.- 88.5* E.C.- 32.5*
Overlap- 70.5*

So, judging by the overlap, it looks like the Solid Roller could have better street manners than the flat tappet, and the roller has 15* more duration@.200 on the intake and 11*more on the exhaust @.200, so I would assume there would be a substantial difference in power between the two as well?

The flat will always have a faster action because of its smaller size.. Frankly, I see people having more issues with rollers then flat tappet... I know for a basic fun street motor, flat tappet with low compression and cubes is the way I like to go.