Author Topic: Cam for my 1969 302ci  (Read 5575 times)

pjbizjak

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Re: Cam for my 1969 302ci
« Reply #15 on: May 22, 2019, 02:36:21 AM »
I recently installed the Comp cam version of the 30/30 in my 68 z/28 302+. Sounds great but haven't road tested it yet. Currently in the paint shop.
Pete

X33RS

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Re: Cam for my 1969 302ci
« Reply #16 on: May 23, 2019, 02:07:31 PM »
Seems even the so called repop copy cams are tinkered with a bit.  I have one here in a box that was bought 25 years ago and even then they were changing the specs.  I found out later it's actually advertised as a copy of the 30-30 but they ground it with 2 more degrees of advance than the OE cam had.   Guess they believed even then they could improve on the characteristics of the engine, and when I had the guy on the phone a couple years ago he confirmed they were trying to build a little more low end torque in the engine.  Oddly they still advertised it as an OE cam.

I couldn't help but wonder after that phone call that cam companies are likely still doing this today, and wouldn't surprise me if they are doing them with slightly different lobe profiles then before.  I doubt any of them have the lazy GM lobes and really wide LSA's with little advance that the OE cam had.

One of the things we did on my cam, since it was a custom deal that would only mimic the original in lift and duration only, was to use a lobe profile that had a soft closing ramp, similar to the GM cam design, so it was easy on the seats.  It also has a late opening exhaust in an effort to build more torque.  A tight lash was also something considered mainly for stability and longevity.   Explained straight from Harold,  "With tight lash the pushrod hits the same spot in the rocker, reducing shimmy, which effects spring life.....  Very wide-lash cams cause the pushrod to hit all over the place, and the resulting vibrations/shimmy is translated to the valve and spring."
  Some other things I did was to nitride the cam, and also run a solid lifter with an EDM hole that shoots pressurized oil right on the lobes.  All done in an attempt for longevity.

I've shied away from the solid rollers in street engines.  They require quite a bit of spring seat pressure to control the valves, more so in engines like Pontiacs or BBC's that have heavy valve trains in them.  Not so much in a SBC but still more spring seat pressure than I care for in a street engine.  What happens over time is usually a lifter eats itself if you drive it enough.   We had this very thing happen on my fathers engine.  Most aggressive solid rollers in a street application typically have 240-260 lbs. seat pressure.  His was 240.  We even used the very expensive Crower bushed rollers with pressurized oiling on the rollers.  After 6,000 street miles one lifter ate itself, taking the cam with it.  Have since switched this engine over to a hydraulic roller.  Typical aftermarket hydraulic rollers use about 150 lbs. seat pressure and around 400 lbs. open.   

crossboss

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Re: Cam for my 1969 302ci
« Reply #17 on: May 23, 2019, 03:58:14 PM »
Most OEM camshafts are ground 2-4 degrees retarded for emissions. What the aftermarket does is grind the same cam 2-4 degrees advanced to achieve some low end torque, and gain back some performance improvements. I also agree, an aggressive solid cam for a street/mild performance set up is really not worth the extra hassle. Heavy spring pressures, radical lobes, small base circles, can result in premature failure on the valve train….IF not watched/maintained carefully. With modern hydraulic rollers, you get the best of both worlds…reliable performance, relatively low maintenance, and RPMs. That said, anyone who wants the 'correct' cam will go with the OEM solid lifter version.
Just another T/A fanatic. A new project in the works.

X33RS

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Re: Cam for my 1969 302ci
« Reply #18 on: May 23, 2019, 08:13:05 PM »
That said, anyone who wants the 'correct' cam will go with the OEM solid lifter version.

Agree, and even though I was confining myself to rules when I did mine at the time, I still would have put a solid flat tappet cam in the engine if I were free to do what I wanted.  Very doubtful it would have been OEM and most certainly nothing off the shelf,  since lobe profiles today have come a long way, but it would be a solid flat tappet none the less, because I don't want to get away from the nature of the engine and what it was intended for.

crossboss

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Re: Cam for my 1969 302ci
« Reply #19 on: May 23, 2019, 11:03:01 PM »
That said, anyone who wants the 'correct' cam will go with the OEM solid lifter version.

Agree, and even though I was confining myself to rules when I did mine at the time, I still would have put a solid flat tappet cam in the engine if I were free to do what I wanted.  Very doubtful it would have been OEM and most certainly nothing off the shelf,  since lobe profiles today have come a long way, but it would be a solid flat tappet none the less, because I don't want to get away from the nature of the engine and what it was intended for.



Absolutely correct. When I vintaged raced my T/A car, the rules 'required' us to use a solid lifter (a special larger radius tappet) experimential grind within the 'specs' of the rules concerning lift and duration. Yes, it was quite radical with 636 lift, 338 degrees duration, with a lobe center of 104. Idle quality was at 2,500 RPM….not street able for most guys.
Just another T/A fanatic. A new project in the works.

janobyte

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Re: Cam for my 1969 302ci
« Reply #20 on: May 24, 2019, 12:31:59 AM »
Guys head's probably spinning now, lol.

We run a hydro roller in the Anglia, .610 lift, 308 duration. Custom grind for the application, all the specs are in a folder out in the shop. Love it. Shift points 7400, responsive as a variable drill motor. No "hit", smooth idle, good vacuum. Hp/torque crosses at 5500, lines run parallel post. Builder went with heavier springs then the Dart's. No valve adjustments with the sun reflecting  off the chrome,,in the pits.

That being said, I'm keeping the old school Comp. hydro in the 302. With,gasp, Rhodes lifters. Same lift/duration as the 30-30. Doesn't "slam" the valves like the 30-30. Choppy idle, good vacuum, advertised float at 6500, however began laying down around 7200.

So,,all depends what you are doing with the car. Mild cruiser, making alittle noise, sleeper, or are you running a 14:1 with a set of .208's. Sounds like x33 has the set up, but, that's the package he had in mind, to suite his( and his wife's, who daily drives it) needs.
68 Z/28  born with: 302, drive line, etc..

janobyte

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Re: Cam for my 1969 302ci
« Reply #21 on: May 24, 2019, 01:06:43 AM »
Somewhere on here I have a copy of the cam card posted.
68 Z/28  born with: 302, drive line, etc..

Stingr69

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Re: Cam for my 1969 302ci
« Reply #22 on: May 24, 2019, 12:48:37 PM »
I am running a 302 with a Crane 113841 solid flat tappet.  Has .050" open and close points that are very close to the LT-1 cam specs but somewhat faster ramps and higher lift.  Third time using it.  Needs 130# seat with 350# over the nose for best RPM performance.  3000-6800 basic RPM range, valve float at 7400 per Crane.  PAC 2600 springs will do it and fit stock valve spring pockets.  Whats not to love?

I am putting a 355 together with it now.

 

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