350 rebuild questions.

Discussion in 'Small Block Tech' started by Juze86, Nov 9, 2015.

  1. Juze86

    Juze86 Well-Known Member

    My is total timing is 36, all in at 2800rpm. Vacuum canister gives 10. I've tested tougher springs and without vacuum advance and that made no change for that noise.
     
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Have you tried 34* or even 32*?
     
  3. Gary Farmer

    Gary Farmer "The Paradigm Shifter"


    The Crower level 3 cam uses a 112* lobe separation angle. If the intake center line is set to 108* (or 107.5*, close enough), it's advanced (not by you; the cam sits here by default). Crower puts the bolt holes on the front of the cam in a position that the cam will be set to this if the timing marks are aligned to no advance, no retard ('straight up') on the timing gears.

    This is what is referred to as 'advance built into the cam', and can cause some confusion.

    So even though your timing marks may indicate no advance or retard is there, the cam itself will be sitting at a 4* advanced position by default.

    If it was sitting on 112/112 intake/exhaust centerlines, the cam is sitting at a true 'straight up' position.



    Getting to the noise, it's possible it's detonation as Larry suggests, particularly when only heard at a certain RPM.

    OR it could be valve/lifter noise that is only heard at those RPMs because of the incidental resonance that can be detected given other circumstances, almost like how exhaust 'drone' is loudest at certain RPMs because of wavelength resonance.

    Pinging (detonation) sounds different than lifters/valvetrain. If you have a trained ear (or find a mechanic buddy who does?), have more than one person listen to it and get more than one opinion on it.

    Didn't you say earlier in your thread that you were having some valvetrain noise? Check clearances and pushrod lengths.

    36* timing is a little heavy; most here will say 32* or 34* is ideal, but your compression is low enough that some more ignition advance could be safely used with proper octane.

    If I recall, octane there converts to 91 for your 'regular' and 93 for your 'premium' as it would be here in the states. Even if you used the regular there, it should still be enough for your dynamic...but I could be wrong. Your exhaust setup provides some very good scavenging, but detonation from this wouldn't occur until higher RPMs if this was the cause.

    Also make sure your plugs are correct.

    Also make sure your flexplate on your engine isn't cracked. This will cause some clacking at certain RPMs. You said it was a Chevy TH350. Make sure everything's aligned properly and you're using a BOP converter.

    Isolate where the sound comes from and go from there.

    Others here will give advice on this too. There are a lot of very knowledgeable people on this site.
     
    calvinv8 likes this.
  4. Juze86

    Juze86 Well-Known Member

    Yes I had lifter noise (or same noise than now) before engine build up, but then I heard it on all rpms. I have TA adjustable pushrods, they are not rubbing to heads and preload is double checked to 0.02. Flexplate is new and also confirmed it is not cracked. I dont believe engine is pinging because like I said I've tried with tougher springs for centrifugal and without vacuum advance. My plugs are NGK UR4.
     
  5. alec296

    alec296 i need another buick

    Seems odd to detonate so low in rpm range as that's still trans convertor slip. I'm going to say it could be a cracked flexplate/loose bolts/torque converter issue. Atleast confirm there is no problem there
     
  6. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Could also just be unrealistic expectations as to level of valve train noise. I have heard some quiet original engines that have never been apart. With a longer duration higher lift cam, some noise may be normal. If it is really tapping away, sure, you have to investigate. Since getting my aluminum heads, my engine has always been a little noisy when fully warmed up. This has been the case with both my motors. I can't hear it over the exhaust while driving. Roller rockers also make some noise.
     
  7. 8ad-f85

    8ad-f85 Well-Known Member

    Still entirely possible depending how the curve comes in, I see this often too. Very true on the flexplate.
     
  8. Juze86

    Juze86 Well-Known Member

    Flexplate is checked. I hope it's just normal noise like Larry said, but I have pretty loud exhaust and I can still easily hear it while driving. Street testing continues in next spring, we had our first snow already here.
     
  9. 8ad-f85

    8ad-f85 Well-Known Member

    It's been mentioned already but I've had some noisy Chev/BOP adapter plate swaps. You can feel and hear just before they seem to loosen up.
     
  10. Gary Farmer

    Gary Farmer "The Paradigm Shifter"


    As a point of reference (and very interesting), I ran a simulation with the exact same specs, adjusting the static compression to match the dynamic compression with this cam's settings, only I used the FM cs647 cam and came out with 425.5 ft. lbs. and 323.5 hp at the same RPMs as the Crower level 3 simulation with 4* advance. So the Crower level 3 gives .5 ft. lbs. and 9 hp more.

    Those silly simulators.

    As for the Crower level 3 cam, putting it in a 'middle ground' @112/112 I/E shows a larger difference between these two, not so much on torque, but horsepower (but then, retarding the OEM cam a bit narrows the gap again).
     
  11. 8ad-f85

    8ad-f85 Well-Known Member

    Being that it's a chassis dyno, maybe look at the torque #'s to see how far past peak torque it's close to that figure.
    That might indicate things like potential calibration or very slight slippage issues.
    The shape of the tq curve itself would lend useful.
    More importantly is how it drives, of course. :)
     

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