[legrand198]

Finally got most of my vintage motor bits and pieces together, 327 block .030 over ( replacing mine that was cracked) , balanced 283 crank, corvette rods, arp rod bolts, 12 /1 pistons. ported camel hump heads, 202/160, screwin studs, pushrod guides, dual spring valve springs, chromemoly pushrods.
My question - it came with a stock z 28 solid lifter cam 485/485 but the lifters look marginal and should be replaced, my choice is to go with either the edge orfice lifter or I can get a 2nd stage offroad cam and lifter set for the same price.
Other factors - 780 Holley on a hirise intake, 1 5/8 headers, 3in mufflers 3.5 inch side exhaust, accel dual point distritutor.
I would like to see 400 plus out of it and instead of my previous 6000 redline , have moved it up to 6500 with a 500 rpm overrun.

Your thoughts on using the bigger cam Please.

 

[oger]

Are you linited to factory cams? The second design off road is a lot of cam for anything. the power is there at 8000rpm with a lack of any low speed torque. A 305{301+.030} with a 6500rpm max power requirement needs very little cam to work correctly. You might laugh but the old 097 will run very well to 6500 and has a wide torque band that should work well in you type of racing. If you can use after market cams give them a call they make better stuff than the factory for your type of racing.

 

[SY1]

Legrand,
Your post reads like you're standing in my garage looking at my 332 that's on the engine stand. It's a small journal with 12.15:1 forged TRWs, -140 off road cam, Smokey Ram cross ram, ported 461 heads. Hedman Husler big tube headers and Accel dual point with tach drive. Next to that sits a box of brand new 302 forged pistons I just got from Smokey Yunick Estate. I'm thinking about getting the 283 crank and doing the same as you are.

Here's what I would do with your 301. Definitely run more cam than the stock cam. I like the -140 off road cam because it has so much overlap with your 12:1 set up it won't detonate nearly as much as the stock cam in an 11:1 motor. It pulls much harder and sounds incredible compared to the stock 302 cam. I wouldn't run the edge orrifice lifters unless you are running roller rockers. They reduce the oil flow to the valvetrain and I think you'll want all you can get with the stamped steel rockers. Consider going with 1.6 rockers as well. I've done this and it results in .539" lift and .123" valve to piston clearance with the .380" dome GM forged pistons. Good choice to go with a chrome moly pushrod. Anytime you run higher compression it aggravates pushrod breakage especially on the exhaust side due to the valve timing.
ARP rods bolts are a must and I assume since you've got a small journal you bought the pro series wave locks. They're much stronger than the standard ARP wave locks and I think it's all they offer for the small journal. Your Corvette rods are the only concern. I run the 67 small journal rods and I know its the weak link in the motor. I'd like a good set of Eagle H beams. Check your rods at the big end. If the flange at the crank bore has a perfectly round lip to it, I'd look for some 327 small journal rods. They have extra material and you'll see the differnce with two humps at the flange line. These are stronger than the 283 rods and are the strongest small journal rods made by Chevy. I know a lot of guys that ran the 283 rods and had problems in the 301 because of it's high rpm potential. Crane makes a single spring with a damper that fits in the stock spring pockets without maching and is good to .580 lift. Your dual springs should work fine, just make sure you don't have to have the spring pockets machined. Make sure when they machine your heads for the screw in studs they remove enough material to run guideplates under them. The book "How to Hotrod SBCs" lists what needs to be milled off for screw in studs with and without guideplates, but the dimension is wrong. I milled mine myself and ended up needing to change my pushrod length to correct my geometry problems. I don't know whose screw in studs you are using, but they are all different dimensions and lengths and throw off the milling needed. ARP I have found to be the best overall for strength and how they are designed.
Here's what I learned about screw in studs, nobody talks about the differences, but they are significant and will really effect things. Length bottom of base hex to top of stud GM=1.59", Summit= 1.74", Dorman=1.75", ARP=1.75", bottom of base to start of threads GM=.806", Summit=.960", Dorman= .949", ARP=.952", hex base bottom to top of radius on top of base (interference with rockers limits area) GM=.281", Summit=.352", Dorman=.419", ARP= .395", base thickness GM=.231", Summit=.219", Dorman=.296", ARP=.211". ARP ranks #1 for clearance in the first and last dimension, GM ranks best for clearance in the second and third. I choose ARP for strength and the fact the studs come machined already for posi locks nuts.

Your 780 Holley will work fine, I'd go with a mechanical secondary. Use deep groove pulleys because you are going to find you run a lot more RPM than 6500. All the 302s I've run start making power at 4 grand and pull hard to 7500 or 8. I've never broken one running them to 8000 and above, I can't say that about 350s I've run to 6000.

Good luck, sorry to ramble on. You can email me if you want more info, my profile has my email address in it.
Dave

[This message has been edited by SY1 (edited 12-23-2001).]

 

[SY1]

Just read oger's post and he is right. I should mention if you plan ondriving on the street a lot the off road cam can make things a lot of work, especially without power steering and a 4 speed, you've got your hands full. There is not much power below 4000, but above that hold on. If you want to run to 6500 there are a lot of better choices for cams

Regarding the screw in studs the problem I had after milling my heads to the books specs that I mentioned was the rockers set too low on the studs, so I needed to mill the heads further than the book said. I corrected this with +.100" trick flow pushrods and ARP studs. They had the thinnest hex base which helped on my rocker interference problem. Actually in hind sight running the rockers further down the studs should create less stud flex.

 

[davidpozzi]

If you are going to run below 7000 rpm's for durability. Take a good look at the solid lifter short track cams. A cam rated for 2500 to 6500 will peak about 500 rpm's higher in a 302 and still give some good torque off the corners, and for when you aren't quite up to full rpm's when in "traffic".
I experienced the second design GM race cam in a road race 350 and iron heads pocket ported. The thing revved to 7500 EASILY. Torque was suprisingly pretty good.
Be very careful with upper end oiling. If you don't restrict oil to the upper end somehow, your bearings will be wiped out due to oil starvation. I would either use the edge orifice type lifter with no restrictor in the oil galley, or piddle valve type with block orifice restrictors. Use aftermarket grooved rocker balls. The factory GM Z/28 valve covers had drippers cast into the bottom of the cover to drip oil right onto the rocker balls.
David

[ 10-05-2004, 08:33 PM: Message edited by: davidpozzi ]

 

[pdq67]

You know my comments, but I liked my little Duntov in my junk 301. But it wasn't a real good "ball's-out" engine like yours.

Just be sure that your springs are up to the task b/c I think the kiss of death to most 302 engines was valve float, not throwed rods!

As my friend Allen said years ago, his '69 sounded awesome at 7000 rpm coming across the bottom with his dumps opened!! He said at 140mph. I think he had 3.73's instead of 4.10's?? pdq67

 

[legrand198]

Thanks guys - I am going with the original cam, and the edge orfice lifters. Since we have such a short course I figure the additional grunt off the corners will make up for the lack of power over 6500. I won/t even get into 4th gear at my local track and in third only on the straight.Thanks for the advice.