Timing for SP '70 350?

Discussion in 'Small Block Tech' started by MrSony, Nov 30, 2017.

  1. MrSony

    MrSony Well-Known Member

    I have it set now at 10*btdc with a TA HEI. 22* of advance all in by 3400 according to TA. They recommend 12* initial, but I set it at 10 as the engine supposedly has 10.25:1, and all I can get is 91 octane. I've read on here that the SP actually has only about 9.5:1. Any validity to this? Stock everything, other than an 800cfm qjet (17058241, '78 sbb), .040 headgaskets, crower level 3, lifters, and new springs. The dish on the pistons seemed shallower than the "10:1" 340p pistons I've seen on the net. Playing with a compression calculator, going from 5cc to 10cc is a .8 difference in compression. Anyway, any input is appreciated.
     
  2. alec296

    alec296 i need another buick

    Get that timing in by 2800 if you can.
    My calculator shows about 9.2 compression.
    Here are the specs I got from my SP.
    .058 below deck, about 10cc dish in piston.
    58 cc head. My felpro gasket used measured.043. Fairly confident at 9.2-9.3 you should be fine with 91 octane. It’s cool out now so you can run it up some. You will know if you need to adjust as it gets warmer. Rear gear and converter can affect what engine will tolerate also
     
  3. Mart

    Mart Gold level member

    That advertised 10.25 was using the .020 thick steel shim head gaskets. You lost comp by running the fel pro .042's.
     
  4. 8ad-f85

    8ad-f85 Well-Known Member

    Maybe do a compression test for crank psi and try to find a way to relate that from other builds.
    You'll have to do plug readings or maybe make up some kind of listening device or gauge using a knock sensor to better assist determining if it can take the timing before your 3200.
    Sometimes the cold doesn't vaporize fuel as well and they still knock.
     
  5. LARRY70GS

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

    Yeah, advertised compression is always inflated. Yes the TA HEI has 22* of mechanical advance. Make sure you set your initial timing with the engine idling as slow as possible. You want to make sure the weights are fully retracted so there is no mechanical advance at all when setting your initial. Checking the total advance just takes a few minutes longer, and hopefully, you are doing that as well.
     
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  6. MrSony

    MrSony Well-Known Member

    Why was the compression number inflated? Was it buick trying to 1 up the others? Or just bean counters wanting a high number, and the engineers just went "what? No.". Something to that effect?
     
  7. LARRY70GS

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

    If the engine was zero deck, it would be at the advertised compression ratio. With manufacturing tolerances of the day, it was safer to engineer the deck height to put the piston in the hole some. That enabled the owner to blueprint the engine when it was rebuilt. The last thing the factory needed was a piston above deck on the assembly line. That is my understanding anyway. Someone will correct me if I am wrong.

    BTW, I doubt this was a Buick only thing.
     
    Last edited: Dec 3, 2017
    Gary Farmer likes this.
  8. wovenweb

    wovenweb Platinum Level Contributor

    Everyone was doing it. Most performance engines from Pontiac were at 10.75 compression ratio in theory during the '67-'70 era. Early sixties stuff was as high as 12.0 I think.
     
  9. 8ad-f85

    8ad-f85 Well-Known Member

    Nothing's off limits if it sells cars.
    It isn't any surprise that specialty engines intended to dominate racing classes (intended to promote sales) were made at the 500 quantity to meet the rules of a 'stock production vehicle', and put in select vehicles.
    Also if it's listed that way, the sanctioning body will let you blueprint it to factory specs (as mentioned).
    The compression number seems to mystify people like a power laden catch phrase, with the consumer barely aware of how 'high compression' works with the overall package to make power.
    Look at how many people here are pressured to spend a ton to raise their compression .7 or their stage 85 cam won't work.
    "Oh, yeah? Well The new xxx has 14-1"
    (Jaws drop...)

    :D :D :D
     
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  10. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    Seeing how the sbb had so much deck height, I suspect there was a pushrod length issue and the supplier of those made them to long! Earlier blocks had around an extra .030" of length and the later blocks had around double that or some times even more!

    I would guess the bean counter fix for the to long already pushrods was to machine less off of the deck, less $$ for machining and more than likely a discount on the wrong length pushrods? When they tried to correct the length for the later engines when the pistons were re-designed I suspect that they went longer with the pushrods instead of shorter like they were supposed to!

    Bean counter fix again was to cut even less off of the deck and make the pathetic compression even more pathetic than the neutered 8:1 the emission police demanded back then!

    That gives us 2 iterations of an engine platform that was less than stellar from the factory and probably why the sbb 350 is so overlooked to this day!
     
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  11. Gary Farmer

    Gary Farmer "The Paradigm Shifter"

    The Buick 350 responds very well to compression increase, no matter which components are chosen.
     
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  12. MrSony

    MrSony Well-Known Member

    I was wondering, does the procedure for installing the distributor start by putting #1 at TDC (0* on the balancer), put in dizzy with the rotor pointed at the #1 (or just before?) terminal, fire it up, THEN turn the dizzy (while running) to get the initial timing (10btdc, 12, etc), or do you drop it in at whatever you want it at, and then adjust it to your engine's preference? On both of my 350s, I did it the 2nd way. Either way the engine should end up at whatever it needs, right? There's no right or wrong in my mind. It runs, that I do know.
     
  13. 8ad-f85

    8ad-f85 Well-Known Member

    Tangent aside...
    If you have enough cam that needs a lot of initial timing, you aren't going to have an easy time firing it up at all with zero initial.
    I think all that would be accomplished is the cam lube would wipe off, the carb would flood and backfire, possibly start on fire, dilute your oil, etc. etc.
    Extremely counterproductive.
    10-15* would be much safer if worried about it actually starting.

    Don't guess, start with a good idea where it will need to be.
    It's fine within a few degrees of final settings.
    Don't give yourself so much to panic over at first startup beginning with zero.
    It can't possibly help to set zero vs (16*?) when you can choose either as easily...except when it's meant to be at 6* initial.

    For first firing and cam break in it will run fine with a little extra timing and much less worry over the extreme exhaust heat, which could be a concern on restored or any vehicles having perfect wiring looms and factory gadgets that could melt.

    There's no right or wrong way, but there are risks involved with way too little.
    I bet the procedure to start at zero was the simplest way to 'foolproof' when almost every car on the road had between zero and 8* initial timing.
     
  14. sean Buick 76

    sean Buick 76 Buick Nut

    You need to confirm it’s on the compression stroke of number one.. pull the number one plug, stick a wine cork it it then you will know you on the right stole when the cork pops line up TDC. Otherwise you could be on the exhaust stroke.
     
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  15. MrSony

    MrSony Well-Known Member

    Yeah, it's on compression.
     
  16. MrSony

    MrSony Well-Known Member

    Thanks for the input everyone. The engine is running as of Sunday night. Runs good and strong. Initial as of now is 10*, haven't had time to mess with the distributor weights and springs, but will do when I get around to it.
     
  17. sean Buick 76

    sean Buick 76 Buick Nut

    I like to pull the number 3 plug out and inspect it for signs of detonation. Number 3 seems to run the leanest.
     
  18. LARRY70GS

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

    There is no difference between those two procedures, timing is timing. The distributor body can be in a number of positions relative to the rotor. 10* of timing for instance, would be the same regardless of the position of the distributor. You read about guys thinking they have the distributor in on the "wrong" tooth. The fact is, if you can move the distributor and adjust the timing to what you want it at, then it isn't on the wrong tooth. If you go to adjust the timing and you run out of rotation before you can get the timing you want, then putting it in on another tooth would give you more rotation. You can run out of rotation if the vacuum canister hits the BB bypass hose, or the canister faces the driver's side of the car.
     
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