TU and F4 Camshaft Follow-on Discussion

[4 l-bodies]

pdf please.

Done!

[acannell]

okay hopefully I didnt screw this up..assume any errors are mine and not 4LBODIES lol...im a bit brain dead right now

f4 vs r5 4lb.bmp

[bakes]

Looks like that R5 is a little hotter of a cam.

[acannell]

Looks like that R5 is a little hotter of a cam.

The question I have, which nobody else seems to give a crap about, is why these cams are designed the way they are. There is intent behind them. Its no more difficult or expensive to make an R5 or an F4. So why did they make them the way they did? Why not with a little more or a little less duration or lift?

[knownenemy]

Now we're talkin'!
Great work guys; thank you very much.

Invaluable information to one selecting the right cam for their setup.

[acannell]

btw if anyone points me to or gives me a cam measurement dataset I can add it to the chart...but its gotta have as many data points or its kind of pointless

[4 l-bodies]

Looks like that R5 is a little hotter of a cam.

The F4 intake has more duration at all lifts until about .375" (on the way up to peak and down). The R5 passes it up to peak lift due to its slightly bigger lift. Most of the added duration of F4 is on the closing side of intake at low lifts. Substantially later closing of intake valve. If your keeping score, the F4 has more area under the curve than the R5 on the intake side of things.

On the exhaust the events are happening at nearly the same crankshaft degree. The F4 has a couple/few more degrees duration until around .240 lift (again, on the way up and down). R5 due to its substantially higher lift (.033), clearly has benefitted from added duration from .300 and up. From .240" to peak then back down, to .240", the R5 has more duration. So if your still keeping score, the R5 has a bigger area under the curve on the exhaust side.

Todd

[4 l-bodies]

okay hopefully I didnt screw this up..assume any errors are mine and not 4LBODIES lol...im a bit brain dead right now

Asa, looks good to me! Some people just see things clearer with charts and graphs than #'s.
Todd

[bakes]

Todd what you speculate on the rpm range of the R5 over the f4

[4 l-bodies]

The question I have, which nobody else seems to give a crap about, is why these cams are designed the way they are. There is intent behind them. Its no more difficult or expensive to make an R5 or an F4. So why did they make them the way they did? Why not with a little more or a little less duration or lift?

Asa, its not that nobody gives a crap, but very few people can answer that question. It is kind of a loaded question. None of us here are in the cam grinding business. My guess is many of these camshaft masters are from entirely different engines. For example I was researching a camshaft profile and came across one I thought looked pretty good on paper. Cam grinder got back to me and told me it was a semi mild BBC camshaft grind that some people were using for forced induction applications. We both got a good laugh from it. He said, at least it wasn't a SBC! Amen!

Even .500 camshafts, one better be checking piston to valve (belt breakage), retainer and keeper to guide/valve seal clearance, spring selection, etc. My point is you venture too far from what bolts in, and you keep narrowing the market to sell to. Yes I wish we had more choices for camshafts like just about everyone else enjoys. I'm just thankful that we have some vendors (like yourself) that are still offering new choices for us as our engines become more and more efficient. We keep building a better mousetrap, but at the same time every day the market keeps getting smaller. Its been over 20 years now since that last 2.2/2.5 NA vehicles rolled off the assembly line.

IIRC, A great deal of time and probably plenty of money in R&D was spent on the design of the original 2.2 slider camshaft. I bet one would be hard pressed to find a better design for ALL aspects ie; emissions, low and high speed performance, fuel economy, longevity, cost, etc. given the era in which it was designed and ultimately put into production.

Todd

[4 l-bodies]

Todd what you speculate on the rpm range of the R5 over the f4

Maybe because of the higher lift (and with it more duration at higher valve lifts) the R5 could potentially enjoy a bit more RPM. Hard to say though, the F4 has more duration without a doubt at lower lifts. If I were to guess, it would probably be likely very similar. How is that for a PC answer (lol)?
Both have very close to same LSA (within a degree), both have similar overlap periods (at .050). The biggest difference is the later intake valve closing on the F4 camshaft. At what point is too late of closing for cylinder filling? The other big difference is the very early start of intake and exhaust opening .006 on R5 camshafts. I know not much flow is happening at that lift, but it really effects overlap results at .006 and somewhat at .020. Are they doing this to decrease pumping losses?
Todd

[Shadow]

Great job Todd, Glad You got to do it as it's a better BtB compare. (same mtr, same guy measuring ect)

I should add that it is Very clear to me, looking at the compare info of these two cams, why the F4 is such a Good cam with Great performance gains while giving up very little on the low end compared to other cams.

No surprise that I lost practically No spool time with the Big Holset and this cam!

[dwh4784]

Out of curiosity what sort of information would point to negatives in terms of daily driver/streetability? What would a factory turbo roller look like next to these two?

[Shadow]

Out of curiosity what sort of information would point to negatives in terms of daily driver/streetability? What would a factory turbo roller look like next to these two?

Good Q's! More modeling Asa!

[acannell]

Good Q's! More modeling Asa!

I dont have detailed measurements for the stock cam ...

I guess I could measure it myself but not this week.

Or if someone already has the specs with lots of datapoints send em over and Ill put em on the chart mateys

[Shadow]

Ya know I just thought of that after typing my post.

It would surprise me if Todd didn't already have the stock roller done

[moparzrule]

This was from Todd's post earlier in the thread, not very detailed but there are some comparable specs-

Here is a couple more actual camshaft degree measurements I took years ago. This was done on uncut cylinder head, with .006 cut from deck of block to get flat. Standard .072 thick headgasket. Sorry this got compressed when I copied from MS word document. Looked great on preview until I posted it.

86 Slider turbo camshaft
From low mile 86 GLHS. No noticeable wear. # 618 casting. T stamped in end..New follower used. Zero lash.



Intake: Exhaust:
-Duration @ .020 238.5 232

- Duration @ .050 218.5 214
- Duration Advance ----- -----
-Overlap @ .050 +1 degree
-Intake centerline 110.5 Exhaust CI 104.5 retarded 3°
- Lift at Valve .430 .430
- Open @ .050 1.5 ATDC 31 BBDC
- Close @ .050 40 ABDC 2.5 ATDC
- LSA 107.5



89 Roller turbo camshaft
2.5 turbo 1. New follower used. Zero lash.

Intake: Exhaust:
-Duration @ .020 234 231

- Duration @ .050 212 209.5
- Duration Advertised ---- -----
-Overlap @ .050 -17 negative
-Intake centerline 112.5 Exhaust CI 113.5 advanced .5 degree
- Lift at Valve .433 .433
- Open @ .050 5.5 ATDC 41 BBDC
- Close @ .050 37.5 ABDC 11.5 BTDC
- LSA 113

[Shadow]

Some food for thought;

R5 advertised specs; 496/508 intake/exhaust valve lift. Actual valve lift = 490/501

............................. 243/235 duration @ .050. Actual duration = 227/219 @ .050

F4 advertised specs; 470/467 intake/exhaust valve lift. Actual valve lift = 478/468

...............................282/276 duration @ .006. Actual duration = 294/276

Now, as I said earlier in this thread, Truths were going to come out and it was Not going to be the fault of either Chris or Cindy for this. This is simply the info given by the cam grinder to the vendor and shows the accuracy/ inaccuracy of those cam grinders.

This is also the reason that all of the bickering over the years was such a total BS feast. Because people are crying foul, and No foul has been committed, only information/ misinformation from the source.

[moparzrule]

I believe chris used 1.78 rocker ratio to figure the actual lift, not 1.75 which Todd is what used to come up with that figure. The lobe lift spec he has was every so slightly different, Todd's specs with 1.78 ratio would give it .498/.509 lift.

[Shadow]

I thought he had them sent out and done? Or are you saying he gave them that ratio to use?