Solid roller lifters worth it in a street car?

[drdano]

For that combination you'd want a lot of midrange, so I'd be looking at a Comp Cams high energy street roller profile.  Their lobe 1476 has duration of 244@ .050", and .641" lift with the FE rocker ratio.  Advertised duration is 288.  I'd probably use that lobe on both intake and exhaust, with a 110 degree lobe separation, and degree the cam in so the intake centerline is at 105.  This will give you about 8:1 DCR, which should be safe for pump gas with your iron heads and still make good power.

One thing I would be careful of is a guess on your static compression ratio.  Get the data on that, don't just trust what your machinist says.  Have the chambers cc'd so that you know their volume, and get the data on the pistons so you know how many ccs are in the eyebrows or dish.  You need to be confident of your compression ratio if you are going to pick the right cam.

I cc'd the heads tonight and they came in right at 74cc.  I'll be running Felpro 8554 head gaskets. 

[jayb]

By my calculations that chamber will give you a 10.07:1 static compression ratio.  That assumes that the pistons are zero decked; if they are not, the CR will go down if they are in the hole a little at TDC.

[drdano]

I tried checking the zero deck, but don't have a super good method for it.  My dial indicator doesn't have the correct base to swivel from the deck to the piston reliably, so I used the straightest steel rule I had and feeler gauges carefully.  Looked like less than .005" checking in various spots...and even that could be the edge of the rule chewed up a tad from use.

What measurement are you using for the compressed thickness of the 8554 gasket?  .051?

Using the Dynamic Compression calculators online I see a full point drop when calculating in the 5000' elevation given all other factors are the same.  I assume installing the cam in the advanced position with my timing set would help make up for this assuming the cam isn't already ground advanced?  If it is ground advanced, would advancing it again be advisable.

Sorry for all the questions, this is new territory for me and I'm eager to learn this stuff. 

[jayb]

I figured .041" thickness for the gasket.  You are correct that advancing the cam will increase the DCR, by closing the intake valve earlier and allowing the cylinder to build more pressure.  I don't see any reason why you couldn't advance a "pre-advanced" cam even further, provided you had adequate piston to valve clearance.  Of course you may run into decreasing power levels just from advancing it too far if you aren't careful.  I wouldn't go much past 104 for the intake centerline.

FYI the DCR calculation I run does not figure altitude into the equation.  I can see where it will have an effect though, so maybe you should pay attention to those online calculators.  You might consider cutting the heads or using a thinner head gasket to increase the static compression ratio, rather than advancing the cam farther than 104.

[drdano]

For that combination you'd want a lot of midrange, so I'd be looking at a Comp Cams high energy street roller profile.  Their lobe 1476 has duration of 244@ .050", and .641" lift with the FE rocker ratio.  Advertised duration is 288.  I'd probably use that lobe on both intake and exhaust, with a 110 degree lobe separation, and degree the cam in so the intake centerline is at 105.  This will give you about 8:1 DCR, which should be safe for pump gas with your iron heads and still make good power.

Pulled the trigger and ordered the hydraulic roller this evening.  The lobe ended up being very similar to what you suggested above, 242@ .050" and .633" lift with a 110LSA.  Thanks again for all the info, really appreciate being able to bounce endless questions off an expert.

[4twennyAint]

However, for a ~425 HP target, I have to ask, is the cost of a roller worth it?  I'm hoping to hear a bunch of YES answers just so I don't have to fear the break-in of a flat tappet.   We are building 428 CJ for the silver Fairlane and want a powerful low-end punch.  Figuring a roller profile would offer the faster cylinder fill = more low end...

Thanks

 

[jayb]

For the cost of the roller, you will have an additional $250 or so in the cam, another $300+ in the lifters, plus better springs.  You will get more area under the curve and will get more torque all across the power band with a roller.  But you certainly don't need a roller lifter to make a 425 HP 428; a mild solid flat tappet cam like a Comp 282S is easily capable of delivering that horsepower, along with excellent low end and mid range torque.  Whether or not the roller cam setup is worth the extra money for the extra torque is pretty much up to you, but at that overall power level its going to be a pretty mild roller.

Why not shoot for a higher HP target, like 500 for example.  Then your roller cam would really deliver, and would still make gobs of low end and mid range torque, plenty to fry those street tires at any speed.  Just a thought...

[4twennyAint]

AGREED (you know, being able to talk with guys like you and Barry is really cool).  The thing here is this is dad's car, and he's had the 500+ hp 427 that spit trannies and 9 inch parts all over the road.  He thinks a mild 428 and C6 will be fine,a s he remembers his all stock 69 Torino SCJ drove easy and was very hard to beat...back in the day.  But I know better now - in the neighborhood are a Coronet 440, a Yenko clone, newer Vettes - so he'll suddenly wish he did more when those matches come up. 
Your book is AWESOME (as is Barry's) but you guys never mention the vacuum signal these engines had.  So the magic I need this camshaft to perform is to get a +.030 428 with Barry's Probe pistons (~9.8 :1) and CJ heads (maybe Edy's - more here next thread) to get to 450+ HP but still have proper vacuum for brakes and a near stock convertor.  A stroker crank would be great bu the already had the 3.98 crank turned .010...

[jayb]

OK, well then you probably want to hang around 228-234 degrees of intake duration at .050" lobe lift to keep the vacuum usable for brakes and so forth.  Again a 282S would work, but if you went with a roller of about the same duration you would get the benefits of more area under the curve and more torque. 

I guess your dad can always add some nitrous to handle that 440 Coronet