Author Topic: Roller cam suggestion  (Read 7652 times)

Offline JoeF

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Roller cam suggestion
« on: April 13, 2010, 06:59:29 AM »
I'm planning to build a Pontiac (400 based) stroker for my '67 GTO.  The car will be 99% street driven and the primary goal of the build will be max performance WITHOUT giving up street manners.  The car has PS, PB and AC.  It's a TH400 auto and I'll probably strap a Continental converter to it.  Rear gears are 3.42 posi.  What  are some good roller cam choices to look for?  Either solid or Hyd is fine.

Offline Cliff Ruggles

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Re: Roller cam suggestion
« Reply #1 on: April 14, 2010, 03:52:42 AM »
Joe, what cylinder heads are you using, and what compression ratio?....Cliff

Offline JoeF

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Re: Roller cam suggestion
« Reply #2 on: April 14, 2010, 04:11:53 AM »
Cliff,

I'll either use my existing 670's with a dished piston or, if I find a cheap set of 6X's, I'll pick them up and use those.  I'm looking for something that will work with 89-93 octane and iron heads.  I plan to shoot for the 9-9.5 range on the CR unless you think I can manage something higher.  I'll have the block zero decked and some light port work done.

Edit: Forgot to mention I'll be using RA manifolds
« Last Edit: April 14, 2010, 04:14:03 AM by JoeF »

Offline Cliff Ruggles

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Re: Roller cam suggestion
« Reply #3 on: April 18, 2010, 04:07:38 AM »
If you are going to end up around 9.5 to 1, choose the roller cam just as if you were choosing a flat tappet cam.  A very good place to be with a 400 Pontiac engine at that compression ratio is around 220-224 degrees intake duration, with about 6-10 additional degrees of exhaust duration.  LSA should be 112-114, with the ICL 108-110.

Avoid cams with short seat timing events, and "tight" LSA's....Cliff

Offline JoeF

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Re: Roller cam suggestion
« Reply #4 on: July 02, 2010, 04:03:23 AM »
220-224 for a 400.  How much more duration for a stroker (462)?   I'm thinking something around 230/236 would have great stret manner and vacuum in a 462.  (SD stump puller?)

Offline Cliff Ruggles

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Re: Roller cam suggestion
« Reply #5 on: July 05, 2010, 12:41:10 PM »
For the 455's, cam selection once again is base on the static compression ratio, use of the vehicle, gearing, converter stall, etc.

I like cams around 230 @ .050" on a wide LSA for 9.5 to about 10 to 1 compression.  We have a custom hydraulic roller grind that we use here that specs out at 230/242/112, with .361" lobes.  We've used it with several sets of KRE aluminum heads in 455 builds around 10 to 10.4 to 1 compression with excellent results.

Another very good choice is the "Old Faithful" grind from SD Performance, specs out at 236/245/112.  It like a tad more compression and a bit more stall speed, but still a very mild cam in a 455 build.  I use this cam in my own 455 that pushes my Ventura nearly into the 10's in full street trim....Cliff

Offline JoeF

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Re: Roller cam suggestion
« Reply #6 on: July 06, 2010, 09:26:53 AM »
I'll be using iron heads, so I think I'll be shooting for 9.0-9.5 on the CR.  Is that too low for either of those cams? 

Offline Cliff Ruggles

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Re: Roller cam suggestion
« Reply #7 on: July 08, 2010, 03:48:47 AM »
Running more compression allows for more camshaft, all else being equal.  The compression ratio (effective) is determined as much by the cam as anything else.

The problem I've seen in recent years when it comes to this topic, is that folks believe there is a perverbial "brick wall" at 9.5 to 1 SCR with these engines.

My old 455 managed 10 to 1 for years on 87-89 octane pump gas with iron heads.  That same engine wen on to run a few more years with aluminum heads at 10.5 to 1. When pulled down for inspection, the bearings and pistons were in perfect shape.

My new engine is 11 to 1 on a steady diet of 89 octane fuel, and pushes my car nearly into the 10's in full street trim.  It would be a "turd" at 9 to 9.5 to 1 compression with the cam I'm using......Cliff

Offline JoeF

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Re: Roller cam suggestion
« Reply #8 on: July 08, 2010, 05:17:52 AM »
I know that you've succesfully managed higher compression ratios than most.  I also know that it doesn't happen by accident.  If I recall correctly, there is a list of 20 or so things that you do (that many people don't do) that enables you to move up the compression ladder.   I certainly plan to zero deck, but beyond that, what types of "mods" make sense for a nice torquey street motor?  CVMS will probably build the motor, so Jim's philosophy will come into play at some point, but I really like your approach to Pontiac builds am curious to hear what cam you would use given the relatively modest goals.   

Offline jamesF

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Re: Roller cam suggestion
« Reply #9 on: July 08, 2010, 08:38:19 AM »
That will be an interesting decision regarding the cam.  Especially if you are building a higher compression motor.

I too would like to hear Cliffs key factors in building a 10.0 -1 engine that runs well on 89 octane.

Cliffs build is proven to work. Whats the recipe buddy?
I know on my build I did at least 2 or 3 things he has described.