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robertob
 Post subject: Help with cam choice
PostPosted: Mon Oct 29, 2012 9:32 am 
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Now that Erson seems to be gone, MP cams are not available and Comp doesn't have a good reputation it seems like cams are now 'roll your own' for the slant.

I don't have a problem with that but I need to know what to tell the cam grinder (Delta probably) to grind onto my core.

I am building a 225, standard rod length and standard .060 pistons, larger valves, very mildly ported & de-shouded CC, decked block for true 9.5:1 static CR, offy 2x1 or maybe super six intake, 904 with stock converter, 3.25 rear.

The last slant I built used a stock cam and intake and I always wished it breathed better. My goals are roughly 140-160 hp at the wheels based on the performance of a stock '02-'05 WRX.

I don't want a rough idle.
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Doc
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PostPosted: Mon Oct 29, 2012 9:41 am 
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FYI...
Erson is not "gone", they moved to a different location.
I puchased a few of my special Slant Six RDP "street performance" cams from them a couple of months back, those cams were at my door in a week.

"Rolling your own" cam grinding boils down to 3 things:
Selection of lobe "masters" from the ones the grinder has. (this is the hardest step)
Designing the grind. This is mostly about picking "lobe centers".
Calculating some of the cam event points so you can estimate DCR... and set your compression ratio to match the cam and fuel you intend to use. (the intake closing point is the most important cam event to know)
DD
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Dart270
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PostPosted: Mon Oct 29, 2012 11:06 am 
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I would say get the Erson 280/270 cam or possibly the Oregon 234/226 cam for more rump. The former has worked well for several mild/medium performance street car folks. Spend time on head porting for biggest gains.

Lou

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robertob
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PostPosted: Mon Oct 29, 2012 11:26 am 
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Thanks guys, I appreciate it. I called Erson this morning and no answer or no return call so I assumed they were out of slant six cams since the move & sale, etc.
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robertob
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PostPosted: Mon Oct 29, 2012 11:44 am 
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I was looking through some old threads and think that I am building something like your 'recipe' Lou, but with milder intake and a rebore.
Quote:
Here, I give a recipe for what I would do to make an honest 200+ crank HP with a used assembled shortblock like Phil's (160 psi cranking on all 6). I successfully did this (200 HP - original Project V motor) with a junkyard shortblock w/o full compression on all 6, a good head, and 8.7:1 comp.

- Mill head for 9.5:1 comp
- 234/226 @ 0.050" Oregon cam or 280/270 Erson cam, degreed at 99-101 (can use silent chain or double roller) Safest to use regrind OEM cam, although I'm not sure any Ersons have wiped out oil pumps
- 1.70/1.44 Engnbldr valves, new guides
- 340 springs and retainters
- port work, mostly on the bowls and knock down guides
- reuse stock oil pump if pressure is good, and put in 1-2 washers under relief spring to bring PSI up to 55-60 @ 2500+ RPM
- stock balancer, rocker gear
- baffle oil pan at least to the rear and make sure pickup sits on the floor and near the center of the pan. If engine not out, just use it as stock and see what it does on hard accel (oil press gauge blips down? baffles...)
- Offy 4bbl intake with one of these carbs: Holley 500 2bbl, 390 4bbl, or Edel 500 4bbl
- headers to 2" secondaries into Flowmaster Y pipe under trans X member and then into 2.5 single out the back
- recurve dist for 10-15 deg initial advance, 28-30 deg final (mech), and 45-50 final with vac (cruise)

If this is badly ported/tuned/assembled, it should make 180 HP, if well ported/tuned/assembled, 220+ HP? Head porting is biggest unkown, besides care of assembly, in success. This should get you around 16 flat in a 3300 lb car (Volare wagon) and have smooth idle and be totally streetable.

I will be building an aluminum engine to nearly these specs in the near future.

Hope this is helpful!

Lou
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robertob
 Post subject:
PostPosted: Mon Oct 29, 2012 11:49 am 
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Just to clarify that is cam number 346 with .476/.479 lift... I've used Delta before but don't have a problem with Oregon.
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Dart270
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PostPosted: Tue Oct 30, 2012 4:58 am 
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Yes, cam #346 from Oregon. Make sure to check springs for bind or hitting valve guide tops as this cam is on the edge for 340 springs. Should be fine, but good to check...

Lou

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robertob
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PostPosted: Tue Oct 30, 2012 10:22 pm 
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Thanks Lou. I'm tempted to go smaller than that though, it just seems like a lot of cam for what I plan to do. But maybe slants need more?
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kielbasa
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PostPosted: Tue Oct 30, 2012 10:57 pm 
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You should see what aircooled vws need. My motor has .689 lift and 274degrees @.050.
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Dart270
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PostPosted: Wed Oct 31, 2012 6:16 am 
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The 280/270 Erson cam will suit you very well, then. That is fairly mild for a 225. The long stroke and small bore and smallish valve size relative to displacement are conducive to larger cams than standard V8 motors. Yes, the 234/226 will be a bit lumpy.

Lou

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Doc
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PostPosted: Wed Oct 31, 2012 9:09 am 
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Lou and I are usually on opposit ends of the cam choice debate...
I tend to use less cam, he tends to use more cam.
It simply comes down to personal choice.

If you are more concerned about smooth idle, high manifold vacuum readings and having lots of low speed throttle responce w/ torque, lean towards a "smaller" cam.

If you want the engine to rev high and make maximum power, with super strong mid range power, go with a "bigger" cam.

Either way, what ever cam you select, "run" the DCR numbers so it works with the gas you intend to use.
DD
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robertob
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PostPosted: Wed Oct 31, 2012 10:26 am 
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What DCR should I be shooting for to use mid grade or high octane gas? I guess I should be careful here because right now I'm living in Colorado at 5000 feet, so I could go much higher. But if I move back to CA (we still have a house there) the engine's not going to like it. So I guess I should plan for a DCR that will allow 91 octane at sea level and then I can probably use 87 octane (CO mid-grade) up here.
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kielbasa
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PostPosted: Wed Oct 31, 2012 10:29 am 
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I really like my ocg#125 but its very small
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Mike_64_Valiant
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PostPosted: Wed Oct 31, 2012 12:20 pm 
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This is one of my old posts but D.I. answers your question down at the bottom.


http://slantsix.org/forum/viewtopic.php ... ompression

Just do a search on this site for DCR or Dynamic Compression and tons of info comes up.
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robertob
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PostPosted: Wed Oct 31, 2012 2:25 pm 
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Thanks I just did that and found what I wanted. I'm going to shoot for 8.0 at sea level and accept the loss up here.
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