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Discussion Starter #1
I have a 64 1600 spider historic race car.
I’m looking to change cams for more torque and power.
Engine config:
79 mm JE pistons at 12.5:1 C/R
Large port early 105 cyl head w/o the 2 front cam cover bolts. Ported per Alfa Comp specs in the 60’s. 38mm tall intake port, 34mm exhaust port and stock sized valves.
45DCOE14’s (restored by Gordon) 34mm venturis, on a matched 105 intake manifold. 26mm velocity stacks are all that I could fit without buying curved stacks.
1600 veloce headers (I’d like to change these as well. I believe the primary tubes are too small and lengths are not optimum)

Close ratio gearbox (2.5, 1.7, 1.25, 1.0, .92) and a 4.56 locked rear end.
The engine’s current powerband is 4000-7500 (I have not revved it any higher), has not been on a dyno yet.

The current cams are regrinds from the 1970’s that I think are 10.6 Autodelta or similar to that.

I also have 2 other sets of reground “race cams” from the same era. I have not degreed them but they also look to be about approx .410-.420” lift.
I have several early 105 1600 stock cams to use as cores.

Recommendation on cams please? I’m looking for good torque from 4-4500 to 7500.
Intake (w.015" lash) [email protected] LC
0.050 213
0.070 192
0.100 168
0.150 136
0.200 113
0.250 93
0.300 74
0.350 56
0.400 25
0.415 0

exhaust (w/.017" lash) installed at 108 LC
0.050 215
0.070 194
0.100 169
0.150 137
0.200 113
0.250 92
0.300 73
0.350 54
0.400 27
0.410 0

Thanks for your help,
Dave
 

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Richard Jemison
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7,379 Posts
Cams

Your cams as "described" below are smaller than street cams. Where did you get the profiles?

Either they are just wrong, or maybe they were done using a small ball pointer on a dial caliper to come up with lift/degrees.

You cannot measure a cam lobe with such instruments. The cam follower being used to measure lift to compute duration, must be the same basic design and size as the engine`s cam follower.

If you want info on my cam designs, send me an email and I`ll send you a PDF file with them, all the Stock and Alfa/Autodelta profiles as well as competitor`s profiles I have "camdoctored". These are all full profiles of lobes.
 

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Discussion Starter #3
Thanks Richard,
I did the measurements on my assembled engine using a large degree wheel and a dial indicator on the cam follower. It was a little tricky but was somewhat repeatable.
I'm sure a bench set-up with the right size "foot" on the dial indicator would be much better.

I tried sending an e-mail but it came back with an error.
Can you help please?
Dave
 

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Dave,

I have specific experience with the 1600 and with the factory "10.6" if you want to call me at 417-849-4673. I don't understand your degree numbers though. A "10.6 measures 258ish degrees at 10-12 thou lash. It measures about 10.5mm if you use a dial caliper on the loose cam.
 

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Oops. Continuing. If you want to stay at a 7500 shift point and I f you really do have 10.6s leave one on the exhaust side, buy a fast ramp higher lift intake cam with the same 260ish duration from Richard, time the Intake LC at 102-103 and exhaust at 106-108. You will gain everywhere.
 

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Richard Jemison
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7,379 Posts
Cams

This is from a later PDF file than the one I sent you.
If your cams "are" true copies of the Alfa/autodelta 10.6 (10121 cam)
Then they are profiled in the PDF I sent. Be aware that most "copies" stray from original designs nearly all the time.

In the comparison below that will undoubtedly be mangled by the BB system, you can see the differences between old cam lobe design and modern lobes.
As well you can see the decrease in early duration from the old cams (which causes excessive overlap and reduces torque) and increases in "open valve duration (over .50 lift) that improves breathing as well as additional lift when added to the equation really improves breathing and power.
The difference in old lobe design and new lobe design can be simply described. Old designs produce peaky power at high RPM. New lobe designs produce higher and broad power bands at lower RPMs.

As for using the old 10121 type cam on the exh side it is exactly what you don`t want as an exh cam. Way too much early duration and little duration above .200 lift.


Comparison of Old cam lobe design to“modern” cam designs
#101210320001 RJR 429+3In. RJR1195+3Ex. RjR575In. RjR1291Ex. RjR 11i Ex.(for 750 Veloce )
lift .414 .438 .442 .503 .480 .358(9.1mm)
.010 345°° 295 281 310 289 304
.020 297°° 284 277 289 279 276
.040 274°° 274 262 273 260 248
.050 265°° 261 257 267 255 241
.080 246°° 245 244 250 241 230
.100 235°° 236 235 241 232 213
.150 215°° 216 217 221 212 190
.200 187°° 193 195 202 192 163
.250 164°° 173 169 175 171 130
.300 136°° 152 149 156 150 98
.350 101°° 124 122 114 125
.400 045°° 85 84 107 97
.450 81 59
.414 maxlift .438 max .442 max .503 max .358 max
 

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The dyno says that a 1600 Alfa, particularly a large port one in a full race application, for the most part could care less how fast the exhaust valve opens and closes. If there was any gain to be had from an exhaust cam change it would be from going to a little shorter duration exhaust and then very little. You will pick up torque correcting your lobe centers, some power with an intake cam change, and then some tiny little bit that might be measurable but that you won't be able to feel in the seat with an exhaust cam change. I would recommend Richards 260ish degree intake cam for a 7000-7500 rpm redline or Steve Schwitters 270 degree cam for an 7500-8000 rpm redline. Both cam options and maybe even just the lobe center correction of your existing cams will likely require additional clearancing of your Pistons if you are at 12.5:1
 

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Dave, hello, sounds like you have two good resources going for cams

I will only add that engine dyno tuning for us was the key.

Running RJR's cams, but with a small port head, jetting was the biggest change +20hp, with dist advancement good for 2-3hp each bump up as we moved toward forward on the adv curve. Ended a little over 150hp & 135 torque.
Our optimum torque is 5500-7500, but pulls flat to 8500.

I imagine you will end up similar or a little better with your carbs and head work

Peter
 
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