[darbikrash]

I’m selecting a cam for my 421 Tri-power motor, and looking for any suggestions. I called around to the usual cam companies, Bullet, Comp Cams, Lunati, etc. and of course each company had a totally different suggestion with no two the same- not even close.

Given the differences of opinion, I am trying to use simulation tools to narrow the choices down. As this is a 100% street motor, I have posted in the Street forum, if this topic is better suited to the Race Forum, feel free to move it.

There is some discussion on other forums regarding others that are using 1D simulations and calculators to select cams, and this sounds to me like a better approach than asking for general opinions.

I am using Engine Analyzer Pro to try and narrow down the field. This seems like a pretty good tool, but my use with it so far is pretty superficial, just using the HP and Torque RPM graphing, with little use of the cyclic graphing outputs (so far). I suspect much of the value in these types of simulations lies in the cyclic outputs such as intake and exhaust flow velocity, and other metrics that govern cylinder filling.

Here are the particulars of the engine setup:

-Bore 4.155”, stroke 4.0” (433 CID)
-Rod length 6.625
-C/R 9.5:1
-Ported cast iron heads (SD Performance)

Flow test @ 28"
Intake Exhaust % of intake port
Ported Cast Iron D ports, Pontiac (CFM) % of exhaust flow to intake.

Lift, inches
0.100 73.2 64.9 88.7%
0.200 148.5 122.7 82.6%
0.300 204.8 158.7 77.5%
0.400 237.9 181.9 76.5%
0.500 259.3 201.7 77.8%
0.600 265.4 219.5 82.7%

-2.11 Intake valve, 1.77 exhaust valve diameter
-Chamber volume 87 CC’s
-Flat top custom piston
-Exhaust, header, 1.75” primary, 3” collector.
-Tri-Power carbs with port matched aluminum intake
-3900# car, OD manual transmission, 3.9:1 final drive ratio- daily driver street only no strip.
-Min 14” vacuum at idle desired (Power brakes)
-91 Octane CA pump gas (10% ethanol)

Beyond these specs, I am not interested in using a roller cam, and I am concerned that a wide LSA cam is not the right direction to go for this motor.

So I’m looking for any modeling suggestions for using Engine Analyzer Pro more effectively, and any cam recommendations which I can run to see how they stack up. If there are any better tools for cam selection/simulation, that might be interesting as well.

So here is what I have so far. I have setup the Engine Analyzer Pro sim tool to include the above mentioned parameters, and setup a cylinder flow table representing the SD Performance cast iron head using the flow data for my heads provided by Dave Bisshop. For the cam, I am just using the seat duration, lobe lift, LSA, and duration at .050 and .200 lift (when available).

So far I have run more than a dozen cams, and of these three rise to the top:

- The Lunati -702 cam, 219/227 @ .050, lift .468/.489 112 LSA
- The Lunati -703 cam, 227/233 @ .050, lift .489/.504 110 LSA
- Custom Grind, David Vizard, Comp Cams Lobe # 5445, 230 @.050 (single pattern) .488 lift, 106 LSA

All cams above are HFT, and lift is at 1.5 rocker ratio.

Some solid lifter cams from Bullet were examined:

GRIND PON 276/286H112+4
DUR @ .050 221/230
LIFT .454/.454
LSA 112
INT C/L 108

and from Mike Jones:

GRIND PONT455 M73359-74359-110
DUR @ .050 248/252
LIFT .538/.538
LSA 110

Based on simulation, these solid cams did not perform as well as the two Lunati's.

And last but not least, I decided to pop for the $150 cam selection fee from David Vizard, based on all the controversial posts on Speed Talk regarding his supposed system or formula for simplified cam selection. So I sent him all the pertinents, and he came back with his suggestion. Here it is, verbatim, what $150 buys you:

Originally Posted by David Vizard

Pontiac 421 Hyd flat tappet single pattern cam spec:- Should NITRIDE !
In/ex profiles Comp Cams Xtreme Energy (P14) #5445 274/230/143/0.325 lobe lift. Grind on a 106 LCA 4 advance. (do not let the comp cams tech guy talk the customer into a wider LCA!)

This grind should deliver a minimum of 14-15 inches of manifold vacuum. More in an engine with good valve and ring seal.
[/I][/B]
Valve lift with 1.5 R/ratio = 0.487 with 1.65 (recommended) 0.536. Scorpion rockers usually deliver more than the advertised ratio so they would be worth using. DV

After I had a chance to calm down, I looked into this recommendation more closely. I called Comp Cams to get some more info on the #5445 lobe, in the hopes it was something special (it’s not, just a standard XE274 lobe) but notice that the cam is single pattern and of course the 106 LSA (LCA) jumps right out at you.

This single pattern configuration would seem to make some sense if we look at the cylinder head flow data, the exhaust flows ~ 80% of the intake, so perhaps a single pattern cam makes some sense here.


Here is a comparison graph of the top three cams I simulated, the Lunati -702, the Lunati -703, and the Vizard XE274. As Vizard recommended a 1.65 rocker ratio for his cam, I have set all three cams to this same ratio for comparison. Turns out the Vizard cam performs pretty well at least with regard to torque production- it outperforms the two Lunati's below 4100 rpm.



Here are the results tabulations, cam by cam. Note the dynamic compression ratio and the static cranking pressure for each cam are highlighted, also we can see predicted idle vacuum for each cam.

Lunati -702 HFT



Lunati -703 HFT



Vizard XE 274 Custom:



Looked at from this perspective, I would be very concerned the Vizard 274 cam would have detonation on 91 octane pump gas. Another comment would be just the general good performance of both Lunati cams, with low dynamic compression ratio and good idle vacuum.

Open to suggestions, and any insight into modeling with Engine Analyzer Pro.

[blykins]

I would have charged you $149....

Ok, there are more than a few points I look at when I choose a cam:

1. Where do you want the hp peak rpm to be? Obviously your car is heavy, but you have a manual trans and a deep rear gear, which helps out considerably. You shouldn't have to cut the duration short to help with lower rpm power.

2. You obviously need vacuum.

3. You have excellent intake/exhaust flow. High 70's/low 80's offers a really nice setup. I base the duration splits on this.

4. You have cast iron heads and 9.5:1 SCR, so I would keep the DCR under 8:1.

5. Lift can be based around the head's performance. Obviously, the flow isn't backing up on you at .600" lift, so I would aim there.

6. LSA isn't the first input that I look at, but it is important. Keep in mind that a lot of cam grinders will offer high advertised durations to help with octane requirements or to use a bigger cam, but they will widen the LSA to keep vacuum up. I feel that if you can help it, a tighter LSA is best for making torque. I've repeatedly seen wider torque curves on the dyno with tight LSA's. I'm not advocating going as low as David suggested, but 109-110 is often a sweet spot.

Computer sims aren't the end-all/be-all, but you can get an idea of what each camshaft will do. Give me a bit and I'll come back with my own recommendation for giggles.

Where would you like the peak hp to be at? 5500-5700 would be a sweet spot, IMO.

[blykins]

Forgot to ask....

What's most important to you? Peak hp? Peak torque? Average hp or torque?

[77 TRASHCAN]

I have met Jim Hand and Cliff, I know how their "spec'd" engines perform. I know how well S.D. Dave's stuff performs. I'd trust Paul K., Brent, GTOFreek, and others here to pick a cam and engine parameters.

To me David V. seems to live in another world. I've read a lot of his stuff, he's NOT the performance answer man, especially pertaining to a street/strip Pontiac powered automobile!!! Maybe in things more race oriented, sometimes...

I'd throw David V's stuff out the window, and talk to some real Pontiac experienced folks, period!!!
Computer generated engine parameters can be interesting to play with, but also have no real world comparison.
Good old fashioned machine work, proper selection of parts, properly installing them, and tuning ability are the things that make the deal. My engine builder could build a common 350 Chevy, the dang thing ran better than most could imagine, got good MPG, and w/ preventive maintenance could last a LONG time!

[tom s]

It's nice to look at all those numbers BUT as you said this is the street section and you intend to street drive it.I work backwards when trying to pick a cam for that.Where will you do the most driving?At 40-50 around town or 65-70 on the highway.If you pick too much cam and your driving is mostly at 50 you won't be able to use your OD,you will be pulling back a gear.Lots of this stuff will be trial and error if you start too big or IMO too tight of lobe.My 63 421 lemans has a Tremic and I have been down this road with our cal gas.Good luck with your choice.Tom

[TCSGTO]

Looks like you have the intake center lines straight up on the Lunati sims. Try the 112 @ 108 ICL and the 110 @ 106.

[blykins]

Originally Posted by TCSGTO

Looks like you have the intake center lines straight up on the Lunati sims. Try the 112 @ 108 ICL and the 110 @ 106.

And the 110 on a 104 as well.

[pastry_chef]

It would be more ideal to have flow values with the intake bolted on.

I dislike Comp XE lobes.

I would rather go with
Comp Dual Energy Lobe 5002
283 advertised
233 @.050
146 @.200
.320 lobe lift

For a 433 to run about 6000 RPM I would look for around 63 degrees of overlap (advertised).

For another solid flat option:

ULTRADYNE

Intake Lobe F18
280 adv
247 @.050
159 @.200
0.3500 lobe lift

Exhaust Lobe F8
284 adv
251 @.050
162 @.200
0.3533 lobe lift


I like Mike Jones, his lobes are unique and run really strong.

[blykins]

Originally Posted by pastry_chef

It would be more ideal to have flow values with the intake bolted on.

I dislike Comp XE lobes.

I would rather go with
Comp Dual Energy Lobe 5002
283 advertised
233 @.050
146 @.200
.320 lobe lift

For a 433 to run about 6000 RPM I would look for around 63 degrees of overlap (advertised).

I'm waiting to hear what the OP is putting the most stock in before I place my bid....

[darbikrash]

Originally Posted by blykins

Forgot to ask....

What's most important to you? Peak hp? Peak torque? Average hp or torque?

I think the Tri-Power is largely going to dictate this. This is of course a 2 bbl motor for 80% of it's duty cycle, when the end carbs open the cam should hit hard. I'm not interested in time slips, just a hard hitting motor when the end carbs open. I think this means average torque is the most important parameter, with an all in HP band at 5500-5700 as you suggest.

[blykins]

Try something like this...

230/234 at .050", 274/278 advertised, 110 LSA on a 104 ICL, .540"/.547".

Trying to get my daughter ready for bed so I haven't ran the numbers, but see where that puts you.

[pastry_chef]

This also might be a contender.

5800 RPM

ULTRADYNE Solid flat

1.5 roller rockers.

109 LSA - install intake at 106 centerline

Intake F9
276 adv
243 @.050
153 @.200
0.3450 lobe lift

Exhaust F18
280 adv
247 @.050
159 @.200
0.3500 lobe lift

[darbikrash]

Originally Posted by TCSGTO

Looks like you have the intake center lines straight up on the Lunati sims. Try the 112 @ 108 ICL and the 110 @ 106.

That's a good idea, I'll try that. Thanks for looking at the details.

Originally Posted by pastry_chef

It would be more ideal to have flow values with the intake bolted on.

I dislike Comp XE lobes.

I would rather go with
Comp Dual Energy Lobe 5002
283 advertised
233 @.050
146 @.200
.320 lobe lift

For a 433 to run about 6000 RPM I would look for around 63 degrees of overlap (advertised).

For another solid flat option:

ULTRADYNE

Intake Lobe F18
280 adv
247 @.050
159 @.200
0.3500 lobe lift

Exhaust Lobe F8
284 adv
251 @.050
162 @.200
0.3533 lobe lift


I like Mike Jones, his lobes are unique and run really strong.

Great suggestion, I'll try that UD lobe.

Originally Posted by tom s

It's nice to look at all those numbers BUT as you said this is the street section and you intend to street drive it.I work backwards when trying to pick a cam for that.Where will you do the most driving?At 40-50 around town or 65-70 on the highway.If you pick too much cam and your driving is mostly at 50 you won't be able to use your OD,you will be pulling back a gear.Lots of this stuff will be trial and error if you start too big or IMO too tight of lobe.My 63 421 lemans has a Tremic and I have been down this road with our cal gas.Good luck with your choice.Tom

Absolutely true. You see the LS guys make this mistake all the time, too much cam duration and tall OD gears make for an unpleasant ride at freeway speeds. How the engine behaves at partial load @ 2200 rpm is very important.

[blykins]

Forgot to mention, 140/147 @ .200". 1.65 RR.

[slowbird]

Originally Posted by darbikrash

I think the Tri-Power is largely going to dictate this. This is of course a 2 bbl motor for 80% of it's duty cycle, when the end carbs open the cam should hit hard. I'm not interested in time slips, just a hard hitting motor when the end carbs open. I think this means average torque is the most important parameter, with an all in HP band at 5500-5700 as you suggest.

The tri-power will have little effect on cam selection, it will hit hard no matter what.

[Stan Weiss]

Originally Posted by darbikrash

I’m selecting a cam for my 421 Tri-power motor, and looking for any suggestions. I called around to the usual cam companies, Bullet, Comp Cams, Lunati, etc. and of course each company had a totally different suggestion with no two the same- not even close.

Given the differences of opinion, I am trying to use simulation tools to narrow the choices down. As this is a 100% street motor, I have posted in the Street forum, if this topic is better suited to the Race Forum, feel free to move it.

There is some discussion on other forums regarding others that are using 1D simulations and calculators to select cams, and this sounds to me like a better approach than asking for general opinions.

I am using Engine Analyzer Pro to try and narrow down the field. This seems like a pretty good tool, but my use with it so far is pretty superficial, just using the HP and Torque RPM graphing, with little use of the cyclic graphing outputs (so far). I suspect much of the value in these types of simulations lies in the cyclic outputs such as intake and exhaust flow velocity, and other metrics that govern cylinder filling.

Here are the particulars of the engine setup:

-Bore 4.155”, stroke 4.0” (433 CID)
-Rod length 6.625
-C/R 9.5:1
-Ported cast iron heads (SD Performance)

Flow test @ 28"
Intake Exhaust % of intake port
Ported Cast Iron D ports, Pontiac (CFM) % of exhaust flow to intake.

Lift, inches
0.100 73.2 64.9 88.7%
0.200 148.5 122.7 82.6%
0.300 204.8 158.7 77.5%
0.400 237.9 181.9 76.5%
0.500 259.3 201.7 77.8%
0.600 265.4 219.5 82.7%

-2.11 Intake valve, 1.77 exhaust valve diameter
-Chamber volume 87 CC’s
-Flat top custom piston
-Exhaust, header, 1.75” primary, 3” collector.
-Tri-Power carbs with port matched aluminum intake
-3900# car, OD manual transmission, 3.9:1 final drive ratio- daily driver street only no strip.
-Min 14” vacuum at idle desired (Power brakes)
-91 Octane CA pump gas (10% ethanol)

Beyond these specs, I am not interested in using a roller cam, and I am concerned that a wide LSA cam is not the right direction to go for this motor.

So I’m looking for any modeling suggestions for using Engine Analyzer Pro more effectively, and any cam recommendations which I can run to see how they stack up. If there are any better tools for cam selection/simulation, that might be interesting as well.

So here is what I have so far. I have setup the Engine Analyzer Pro sim tool to include the above mentioned parameters, and setup a cylinder flow table representing the SD Performance cast iron head using the flow data for my heads provided by Dave Bisshop. For the cam, I am just using the seat duration, lobe lift, LSA, and duration at .050 and .200 lift (when available).

So far I have run more than a dozen cams, and of these three rise to the top:

- The Lunati -702 cam, 219/227 @ .050, lift .468/.489 112 LSA
- The Lunati -703 cam, 227/233 @ .050, lift .489/.504 110 LSA
- Custom Grind, David Vizard, Comp Cams Lobe # 5445, 230 @.050 (single pattern) .488 lift, 106 LSA

All cams above are HFT, and lift is at 1.5 rocker ratio.

Some solid lifter cams from Bullet were examined:

GRIND PON 276/286H112+4
DUR @ .050 221/230
LIFT .454/.454
LSA 112
INT C/L 108

and from Mike Jones:

GRIND PONT455 M73359-74359-110
DUR @ .050 248/252
LIFT .538/.538
LSA 110

Based on simulation, these solid cams did not perform as well as the two Lunati's.

And last but not least, I decided to pop for the $150 cam selection fee from David Vizard, based on all the controversial posts on Speed Talk regarding his supposed system or formula for simplified cam selection. So I sent him all the pertinents, and he came back with his suggestion. Here it is, verbatim, what $150 buys you:



After I had a chance to calm down, I looked into this recommendation more closely. I called Comp Cams to get some more info on the #5445 lobe, in the hopes it was something special (it’s not, just a standard XE274 lobe) but notice that the cam is single pattern and of course the 106 LSA (LCA) jumps right out at you.

This single pattern configuration would seem to make some sense if we look at the cylinder head flow data, the exhaust flows ~ 80% of the intake, so perhaps a single pattern cam makes some sense here.


Here is a comparison graph of the top three cams I simulated, the Lunati -702, the Lunati -703, and the Vizard XE274. As Vizard recommended a 1.65 rocker ratio for his cam, I have set all three cams to this same ratio for comparison. Turns out the Vizard cam performs pretty well at least with regard to torque production- it outperforms the two Lunati's below 4100 rpm.



Here are the results tabulations, cam by cam. Note the dynamic compression ratio and the static cranking pressure for each cam are highlighted, also we can see predicted idle vacuum for each cam.

Lunati -702 HFT



Lunati -703 HFT



Vizard XE 274 Custom:



Looked at from this perspective, I would be very concerned the Vizard 274 cam would have detonation on 91 octane pump gas. Another comment would be just the general good performance of both Lunati cams, with low dynamic compression ratio and good idle vacuum.

Open to suggestions, and any insight into modeling with Engine Analyzer Pro.

The BS over on SpeedTalk is about a different method then David use to come up with your cam specs. What RPM did you tell David you wanted Peak HP at?

Stan

[darbikrash]

Originally Posted by Stan Weiss

The BS over on SpeedTalk is about a different method then David use to come up with your cam specs. What RPM did you tell David you wanted Peak HP at?

Stan

5500 Rpm. The "128" method he uses to estimate LCA seems to be controversial over there. I understand that the paid up recommendations use COS CAM to determine the best cam. No one else has suggested a single pattern cam, given the exhaust flow numbers maybe he is right?

I'm tempted to try this cam, but I'm afraid it will ping.

[pastry_chef]

Originally Posted by darbikrash

5500 Rpm. The "128" method he uses to estimate LCA seems to be controversial over there. I understand that the paid up recommendations use COS CAM to determine the best cam. No one else has suggested a single pattern cam, given the exhaust flow numbers maybe he is right?

I'm tempted to try this cam, but I'm afraid it will ping.

For a case on the 106 LSA look here:

http://forums.maxperformanceinc.com/...d.php?t=430357

Take note of the performance.

I like David Vizard, I own most of his books.
He is most likely correct in his recommendation.

BUT going with 106 LSA *may* be taking a risk you will have lower vacuum than 14 "

Also -

Pump gas can be much like engine dynos, the chemistry can vary with different brands / locations.
Vizard ran a test and found significant power differences with different brands of pump gas.

As for Speedtalk and 128.
There are some who may very well be intelligent, but they need some counselling.
Posting scores if not hundreds of rebuttals about how 128 does not scale correctly when pushed to extremes. Not worth anyone's time!
I don't know anyone building an engine with 8 inch bore and 8 inch stroke.

A person can make their point, perhaps make it a second time, then they should move on!

[pastry_chef]

If you WILL have your can nitrided and will use lifters with an oiling hole.
Good quality rockers, pushrods and valve springs.

1.5 ratio rocker

One more:

Comp Cams Solid Flat
---------------------
GRI intake lobe 16206

277 advertised
250 @.050
162 @.200
.367 lobe lift

XTX exhaust lobe 6404

280 advertised
246 @.050
153 @.200
.347 lobe lift


110 LSA - intake at 106 centerline.

[Cliff R]

Choosing a cam for your engine will certainly be a tall order.

The trump card is requiring 14" vacuum at idle speed (750-800rpm) and getting enough cam in the engine to effectively use 265cfm head flow.

The 9.5 to 1 SCR isn't helping. I've done a half dozen 428 builds in my time and they are excellent engines, much more efficient than the 4.21" stroke engines and really respond well to tighter LSA than what we usually select for similar 455 engines.

Recently we've been involved with two 428's, both were dyno'd and both used unported KRE aluminum "D" port heads at 260cfm intake flow.

The first one we did used 74cc heads and 10.6 to 1 compression. We used a custom ground HR cam with Comp XFI lobes 236/244 on a 110LSA. It made 12" vacuum at 1000rpm and 497hp/540tq with peak HP at 5800rpm's.

The second 428 used 87cc heads with less compression and made 480hp/528tq with a HR cam 236/244 on a 111LSA. Since it ended up in a 4 speed application it has acceptable idle quality but pretty "lumpy" below 1000rpm's.

Neither one of those cams would meet your vacuum at idle requirements as they were lower at 1000rpms with more compression, and compression is a KEY player in vacuum production at idle speed.

Since you are using a flat cam, and 9.5 to 1 compression and 433cid and 265 cfm head flow a pretty "hefty" cam will be needed to effectively work with those parameters. Problem is that 9.5 to 1 compression and a big cam will result in pretty "low" vacuum at idle speed.

I'd look closely at an older Ultradyne cam that specs at 231/239/110 specs, and put Rhoads lifters on it. Use the V-Max variety and set them at .020" clearance. This might get it done, but I really don't think you'd see 14" vacuum at idle without throwing a LOT of timing at the engine at idle speed. You can always drop back to 1.5 rockers and loosen up the valve lash a bit if more vacuum at idle is needed.......Cliff