Vintage 302 chevy.

Discussion in 'Engine Combos and Dynometer Database' started by rjs89ia, Feb 16, 2016.

  1. rjs89ia

    rjs89ia Active Member

    Ironically the pistons are sold out and on back order for 3-4 weeks. The good thing is that they're in demand and people are out there building these small cube engines. So I shouldnt have to worry about them being discontinued for a while.
     
  2. Loves302Chevy

    Loves302Chevy "One test is worth a thousand expert opinions."

  3. Grumpy

    Grumpy The Grumpy Grease Monkey Staff Member

  4. rjs89ia

    rjs89ia Active Member

    Whats everyones definision of polished?
    Mirror finish or smooth?

    Those are the ones. Sorry I should have linked them. You can get them in a variety of configurations throughout the internet but CNC is by far the cheapest. I think i found where you can even get them by individual pistons from UEM can't remember for sure. They seemed very decent and once I receive them I'll get some good pics and post them so others that might be looking at them can see more than just the sales pic. They have them marked as shipped and will be drop shipped from kb so maybe they managed to find a set in their stock.
     
    Last edited: Sep 7, 2017
  5. Loves302Chevy

    Loves302Chevy "One test is worth a thousand expert opinions."

    Is this correct Grumpy?
     

    Attached Files:

  6. rjs89ia

    rjs89ia Active Member

    That cam looks like it would be more streetable than the one I have. I don't think it would enjoy my spring pressure. It would probably work better with a single carb manifold given the lower rpm range.

    I was told that even my cam wouldn't take full advantage of the intake I have.
    20150609_225023_zpss5rentjt.jpg
     
  7. Loves302Chevy

    Loves302Chevy "One test is worth a thousand expert opinions."

    I can see a lesson from Grumpy in your future.
    Your heads cannot take full advantage of that camshaft. Too BIG.
    You will also need an ultra-lightweight valvetrain.
     
  8. rjs89ia

    rjs89ia Active Member

    From my research on the cam it's original 1969 and apparently was a popular camshaft among racers during that era. I don't think they had any better small block heads so I shouldn't have any worse breathing (rpm) problems now than they did then with the same cam. The angle plug 492's were one of the best available in the mid 70s behind the slightly larger 292's and my ports are not stock by any means. I think I said this in an earlier post I would love to have AFR's or Darts but that's not what I'm after in this engine and I feel the gain wouldn't offset the extreme cost. If I were building a 355 or 383 I wouldn't hesistate to invest in the better heads.
     
  9. Loves302Chevy

    Loves302Chevy "One test is worth a thousand expert opinions."

    In the past, they had to over cam those engines because of the limitations of the heads.
    Now we have the opposite situation of excellent flowing heads which allows a much less radical camshaft.
     
    Strictly Attitude likes this.
  10. rjs89ia

    rjs89ia Active Member

    So I should still be fine with the long duration of this cam then. I can always change it down the road. My biggest goal is to see how it performs with the original combination.
     
  11. Grumpy

    Grumpy The Grumpy Grease Monkey Staff Member

    yes it should be interesting to see the results

    http://garage.grumpysperformance.co...eption-has-changed-over-time.8379/#post-29224

    http://garage.grumpysperformance.com/index.php?threads/z28-1st-2nd-design-cams.4463/#post-11732

    http://garage.grumpysperformance.com/index.php?threads/the-cross-ram-intake.623/#post-1657


    Standard 302 (30-30) cam, P/N 3849346
    Casting #3849347
    254 duration @ .050" (intake & exhaust)
    .485" lift (with 1.5 rockers)
    114 deg. lobe separation
    Exhaust Max lift @ 116 deg. BTDC
    Intake Max lift @ 112 deg. ATDC

    First Design Off-Road cam, P/N 3927140
    Casting #3927141
    Intake 257 duration @ .050" (333 advertised)
    Exh. 269 duration @ .050" (346 advertised)
    Lift: .493" intake, .512" exhaust
    Intake Max lift @ 108 deg. ATDC
    Exhaust Max lift @ 116 deg. BTDC

    2nd Design Off-Road cam, P/N 3965754
    Casting #3965751
    Intake 248 duration (324 advertised)
    Exh. 267 duration (334 advertised)
    Lift: .512" intake, .535" exhaust





    back around 1969,we used to buy those CHEVY cams for $47 each at the Chevy parts counters,
    matched lifter sets we $38 they sounded great,
    but they were designed for road racing not drag racing,and we found that there were better designs for drag racing cams
    but we soon found the faster cars were running a CRANE 110921,
    in heavy cars with 3.90:1-4.11:1 rear gears and for lighter cars with a 4.56-4.88:1 rear gear the 110981 and 110921
    (back then they were called something else, before crane changed their part numbers)
    [​IMG]
    [​IMG]
    if your convinced you need a hydraulic lifter cam this crane 110711 gives reasonably good performance in a 10.5:1-to-11:1 compression 383 built to similar specs
    [​IMG]
     
    Last edited: Sep 9, 2017
  12. Loves302Chevy

    Loves302Chevy "One test is worth a thousand expert opinions."

    Grumpy, would it be safe to ASSUME, as in the case of SBC camshafts for example, unless actually specified for a
    certain size engine that the rpm ranges called out on cam cards pretty much are directed towards 350 ci engines?
    I have read in the past for each 1/4" change in stroke that the rpm range will shift by approximately 400 rpm.
    Looking at the 110921 cam card above, min rpm is 3200, max is 6800, and float is 7600. If this is for a 350 (3.480 stroke),
    let's round to 3.500 for discussion, then if used in a 302 (3.000 stroke) the numbers would then shift to 4000 min,
    7600 max, and 8400 float - all things being equal. Of course there are many other variables.
    I'm just trying to do an apples-to-apples comparison here.
    What are your thoughts on this?
     
  13. Loves302Chevy

    Loves302Chevy "One test is worth a thousand expert opinions."

    Let's start a pool on estimating how much vacuum this engine will pull at idle.
    I'll start - 3" at 1500 rpm, if it can even idle that low.
     
  14. Grumpy

    Grumpy The Grumpy Grease Monkey Staff Member

    that crane 110921 flat tappet solid lifter cam, is an older design with lower ramp acceleration rates than some modern cam lobe designs , yes theres several dozen similar flat tappet cam designs.
    it was designed to work well in 327-350 engines,
    that were being modified for performance,and maintain good valve train control.
    originally, this was and remains a very effective crane cam design.
    its lobe design allows good valve train control as long as the correct spring load rates and valve train geometry is used.
    but Ive used it in 302-406 displacement engines, and Ive found it provides excellent power.
    I think you will find that the power band in a 302 will be higher than it would be in a 350 built to similar specs ,
    but I don,t think theres a 100% reliable way to exactly say if its operating at 3200-rpm-6800-rpm in a 350,
    that its power band will jump 400 rpm higher in a 302 or 400 rpm lower in a 383,
    and yes that will be the trend but its not going to hold 100% exact, mostly because theres thousands of potential part combos.
    just changing the heads, compression ratio, intake manifold and header designs alone would easily have a huge effect and thousands of choices
    and yes most power bands assume youll use it in a 350 simply because thats one of the most common displacements available
     
  15. rjs89ia

    rjs89ia Active Member

    Interesting.

    I'm sure the vacuum is going to be crap on this engine. It will be a dog until it gets above 4-5k rpm.

    I had to consult in my crane cams guy on the power range vs stroke question. Its understandable but still confusing at the same time.
     
  16. Grumpy

    Grumpy The Grumpy Grease Monkey Staff Member

    keep in mind CRANEs engineers seem to be much more concerned with predictable and consistent valve train stability and engine durability,
    rather than sacrificing durability and stability for potentially gaining an extra 4-5 peak hp, for bragging rights , under the theory, I,ve always proposed,
    "you need to finish a race with the engine in good shape ,
    RATHER THAN,
    building a dyno queen ,that makes the best power peak for an hour or two."
    Verifying your engines clearances, and rocker geometry, and use of A rocker stud girdle and high quality roller rockers go a long way towards maintaining valve train durability
    [​IMG]
    [​IMG]
    first CHECK CLEARANCES AND GEOMETRY WITH THE PROPER MATCHING CHECK TOOL(THE ROCKER STUD SIZE ,LENGTH AND DIAMETER,MATERS)and you damn sure want the correct push rod length and rocker geometry and clearances
    [​IMG]

    the higher rocker ratio increases the effective acceleration rate of the cams lobe ramp, being transmitted to the valve so the higher ratio tends to cause valve control issues at a lower rpm level UNLESS the valve spring load rates increased to compensate. this allows a greater area of lift or open port area so the engine will tend to run better in the mid rpm range, generally making it well worth while as the mile duration cam can use the extra lift and duration at the valve.



    http://garage.grumpysperformance.co...i-reasonable-sbc-race-combo.13289/#post-69274

    http://garage.grumpysperformance.com/index.php?threads/cam-help-for-new-383-build.13099/#post-68275

    http://garage.grumpysperformance.co...er-rockers-and-stud-girdles.12208/#post-59297

    http://garage.grumpysperformance.co...s-on-valve-spring-pressures.10268/#post-41364
     
    Last edited: Oct 13, 2017 at 1:37 PM
  17. rjs89ia

    rjs89ia Active Member

    Pistons finally showed up today, Icon IC803. Old arias pistons are on the left for comparison. 20171011_175030-3559x2002.jpg 20171011_175038-3559x2002.jpg 20171011_175047-3665x2062.jpg 20171011_175101-3665x2062.jpg 20171011_175154-3665x2062.jpg 20171011_175255-3665x2062.jpg 20171011_175716-3665x2062.jpg
     
  18. Grumpy

    Grumpy The Grumpy Grease Monkey Staff Member

    the newer ICON pistons appear to be much better quality,
    the new piston, also appear's to be forged and lighter in mass,
    while the other piston appear's to be cast or hyper-eutectic
     
    Last edited: Oct 12, 2017 at 9:08 AM
  19. Loves302Chevy

    Loves302Chevy "One test is worth a thousand expert opinions."

    Be sure to assemble at least one cylinder to see if the new pistons will contact the heads.
    Use clay or play-doh. You will need to rebalance the crank because the new pistons are
    certainly lighter than the old ones, and you don't want to discover that you have to do
    some grinding after the rebalance is already done.
     
  20. rjs89ia

    rjs89ia Active Member

    I have to assemble all four corners and take measurements to see where the block is as far as being square. These piston domes are considerably smaller than the old ones my only concern right now would be the exhaust valve clearances during the exhaust stroke as this piston has a higher profile on the exhaust side than the old piston. Not sure if you can see the lip in the pictures or not.

    Anyways I still need to order the rods from grp and thats probably going to be a while still to see if they have any christmas deals or till tax time.

    I might send the crank out to be undersized as theres a few grooves that didnt polish out and I'm very nervous about any stress risers in the crank. Anyone got anything to say about grooves? I can get some pictures if needed.

    I bought a really nice pressure washer today I'll have to make up a thread on that in the tool section. Also been doing some body work on the chevelle, I'll have to start a thread on that too.
     

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