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HT 383 pinging?

Discussion in 'The Garage' started by Sparky, Dec 4, 2003.

  1. Sparky

    Sparky 1/2 ton status

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    So I built myself the GM HT 383 (just used the same parts), and I have a little problem with pinging. Typical chevy mid throttle pinging. Only does it if the truck is warm and or it is hot out. In other words, when the motor is pulling in hot air under the hood.

    I was wondering if anyone else out there has the GM performance parts 383, and if they have problems with pinging on 87 or 89 octane? Seems to make no difference for me, and 93 is too expensive.

    I have a stock rebuilt Q-jet and a "performanc" HEI. Its one of those summit racing HEI distributors. It has a pretty quick mechanical advance. Full advance by around 3000 rpm if I remeber right.

    Any body have any good suggestions about how to fix the problem?

    I was thinking about building a cold air intake. comments?

    I could retard the timing, but that would hurt performance.

    I could get one of those adjustable vacume advances, but that would hurt gas mileage.

    Anyways, just looking for ideas.


    Thanks

    Ryan
     
  2. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Welcome to CK5.

    What compression are you running? What heads? How thick are your head gaskets? How much deck clearance does that engine have? What size cam are you running (please give as many specs as possible). What rig is it in? Are you towing? What trans? What rear gear ratio?

    Full advance by 3,000 RPM is fine, that's what I run, no problems

    Cold air intake or whatever you want to call it will not help this problem but isn't necessarily a bad idea unless you're getting into deep water or something.

    Retarding the timing may help, but I don't think your problem is in your mechanical curve.

    Getting an adjustable vacuum advance canister isn't going to give you worse fuel mileage if you're currently having knock issues. Nothing could possibly make your fuel mileage worse than detonation if your engine is well tuned otherwise. I think you need to seriously re-consider this option. I run tons of base timing, all my mechanical is in by 2,800, I run full vacuum at idle, and I still have no detonation issues.

    Either way, if you have a stroker motor with small chamber heads, lots of compression, a lot of quench distance, and a small camshaft and 87 octane, you're going to have detonation, although we can help you work most of it out if you include some more info other than that you attempted to copy the GM mill that I'm not familiar with.

    Either way, welcome to CK5. This is a great group here. If you don't mind, provide us with as much info as possible so we can try to help you as best we can.
     
  3. OrangeCrushK10

    OrangeCrushK10 1/2 ton status

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    Hmmm... sounds like you're running a bit too high of compression for Regular pump gas. Once the temperature is getting too high in the combustion chamber it is preigniting.

    Getting a cold air intake may or may not help. While you'll be getting colder air you will also be running higher compression as cold air is naturally more dense than hot air. And on a hot day the problem would return.

    One possible fix for this would be to buy an extra thick copper cylinder head gasket. It would very slightly lower compression and is pretty easy and not too expensive considering the cost of high performance cylinder heads or a new set of pistons.

    Or buy a high flow water pump, better fan, and large aluminum radiator to upgrade your cooling. Lowering your engine heat would fix the problem.

    Personally, I think I'd just fork out the extra $2.00 per tank and get the 91+ octane. But if you're really set on cheap gas, but keeping your performance up, go with upgrading your cooling system.

    Just my two cents.
     
  4. Topdown

    Topdown 1/2 ton status

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    welcome to CK5...

    If I remember right, the timing curve on the HT383 is 10 @ 800 and 32 total at 4000

    From the sound of it, your advancing too fast through the throttle range and need to put in a little bigger spring or a little smaller weight to slow the advance.

    -Ryan
     
  5. OrangeCrushK10

    OrangeCrushK10 1/2 ton status

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    Oh-yeah, and welcome to CK5!
     
  6. Bullet

    Bullet 1/2 ton status

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    I have a similar engine and I fouled up once and put 87 in it and it ran like crap. Your easiest solution is to try the 93+Octane, its what I run 90% of the time and it runs like a champ. Try and retard the timming too.

    By the way, are you a Texas A&M aggir by anychance? I'm located in Abilene /forums/images/graemlins/thumb.gif
     
  7. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    One possible fix for this would be to buy an extra thick copper cylinder head gasket. It would very slightly lower compression and is pretty easy and not too expensive considering the cost of high performance cylinder heads or a new set of pistons.

    [/ QUOTE ]

    That is not a solution. Increasing quench distance is going to make it run like crap and detonate even more than it does now.

    It may just be jetted too lean and that's why it's knocking. I'd like to see him hook us up with more specs before I comment further.
     
  8. OrangeCrushK10

    OrangeCrushK10 1/2 ton status

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    [ QUOTE ]
    [ QUOTE ]
    One possible fix for this would be to buy an extra thick copper cylinder head gasket. It would very slightly lower compression and is pretty easy and not too expensive considering the cost of high performance cylinder heads or a new set of pistons.

    [/ QUOTE ]

    That is not a solution. Increasing quench distance is going to make it run like crap and detonate even more than it does now.

    It may just be jetted too lean and that's why it's knocking. I'd like to see him hook us up with more specs before I comment further.

    [/ QUOTE ]


    How would that make it run bad? /forums/images/graemlins/shocked.gif It's a pretty insignificant change overall, mainly effecting the compression. Still, I wouldn't think enough to screw up the drivability? Am I missing something important? /forums/images/graemlins/confused.gif


    At any rate, I would agree that more info is needed to say what could be wrong.
     
  9. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    [ QUOTE ]
    [ QUOTE ]
    One possible fix for this would be to buy an extra thick copper cylinder head gasket. It would very slightly lower compression and is pretty easy and not too expensive considering the cost of high performance cylinder heads or a new set of pistons.

    [/ QUOTE ]

    That is not a solution. Increasing quench distance is going to make it run like crap and detonate even more than it does now.

    It may just be jetted too lean and that's why it's knocking. I'd like to see him hook us up with more specs before I comment further.

    [/ QUOTE ]


    How would that make it run bad? /forums/images/graemlins/shocked.gif It's a pretty insignificant change overall, mainly effecting the compression. Still, I wouldn't think enough to screw up the drivability? Am I missing something important? /forums/images/graemlins/confused.gif


    At any rate, I would agree that more info is needed to say what could be wrong.

    [/ QUOTE ]

    Yes, you're missing something very important. Detonation is affected a ton by how flame travels in the combustion chamber, and increasing the distance from the op of the piston to the bottom of the head, by using a shim, a thicker head gasket, or otherwise, is generally bad idea and will make an already bad problem worse.

    There are many theories to ideal quench, but .039-.045 is generally accepted everywhere I've read.

    I'd be more than willing to bet he's got 10+ compression, a small cam, and .060-.080" of quench already. Adding a .021" shim would make an already bad problem worse.

    Ever wonder why most '80s Chevy engines had .020" steel head gaskets? Did you know that composite type Fel-pro that you see most often is twice as thick?
     
  10. Sparky

    Sparky 1/2 ton status

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    Here is the specs on the motor

    Horsepower: 325 hp @ 4500 rpm
    Torque: 415 ft lbs. @ 3500 rpm
    Compression Ratio: 9.1 to 1
    Block: Cast Iron 4-Bolt, 4.000" Bore
    Crankshaft: Forged Steel, 3.800" Stroke
    Heads, Chamber Size: Vortec, 62cc
    Valves (I/E): 1.940"/1.500"
    Camshaft, Lift (I/E): 0.431"/0.451" Hydraulic Roller
    Dur. @ 0.050" (I/E): 196/207 degrees
    Intake: Aluminum Dual Plane


    web page

    The only difference between that motor and mine is the intake. I have the edelbrock intake as opposed to the gm intake. Everything down to the head gaskets is identical. Dont know the quench distance, but I trusted the engineers at GM on that one. I literally got a parts list for that motor and bought exactly the same partnumbers.


    Tranny is a TH350, still have the stock 3.42 axles w/ 35inch tires /forums/images/graemlins/shocked.gif Supprisingly enough, it doesnt seem to knock in first gear when I first take off. Mostly does it in 2nd and 3rd gear. Especially at low RPMs (below 3000).

    Plugs look very normal. Motor has about 10,000 miles on it. Coolant temp never gets over 190. I could keep it lower by changing the thermostat if yall think that will help. Already have a BIG 4 core radiator.

    GM claims it will run on 87 octane.

    Thanks again, Sorry it took me so long to get back to yall.


    Ryan
     
  11. Sparky

    Sparky 1/2 ton status

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    Oh yeah, I was thinking the carb was jetted to lean too. Like I said, its a stock q-jet, and the motor has aprox. 325 hp and 415 ft*lbs.


    ryan
     
  12. Stroked72Blazer

    Stroked72Blazer 1/2 ton status

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    [ QUOTE ]
    One possible fix for this would be to buy an extra thick copper cylinder head gasket. It would very slightly lower compression and is pretty easy and not too expensive considering the cost of high performance cylinder heads or a new set of pistons.



    [/ QUOTE ]

    Hot Rod magazine does this all the time and this is recomended to them by shops like ET Shop. If you don't know who ET shop is just ask any NHRA member.
     
  13. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    [ QUOTE ]
    One possible fix for this would be to buy an extra thick copper cylinder head gasket. It would very slightly lower compression and is pretty easy and not too expensive considering the cost of high performance cylinder heads or a new set of pistons.



    [/ QUOTE ]

    Hot Rod magazine does this all the time and this is recomended to them by shops like ET Shop. If you don't know who ET shop is just ask any NHRA member.

    [/ QUOTE ]

    Copper head gaskets are fine, that's exactly what my buddy runs in his top fuel drag boat. Trying to get .080" quench by using a super thick head gasket or stacking them is no good though.

    Either way, it shouldn't knock at 9.1:1. That is a really small cam though...even smaller than the smallest Comp Xtreme 4x4. That motor needs more cam. With all that stroke it should be able to keep its torque with a slightly bigger bumpstick that will seriously help power.

    I'd double check the simple stuff. That engine really should run fine as-built.
     
  14. Triaged

    Triaged 1/2 ton status

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    I'm with Tim on this one (doesn't happen often /forums/images/graemlins/grin.gif)

    Quench makes a huge difference in the octane requiments of a motor. Increasing the quench distance will not do much for the detonation and will hurt power.

    Personally I think the problem is the advance curve. How much total advance are you running? Vortec heads don't need as much timing as other/older style heads due to a more efficient chamber design.

    What cc is the dish on the pistons?
     
  15. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    Personally I think the problem is the advance curve. How much total advance are you running? Vortec heads don't need as much timing as other/older style heads due to a more efficient chamber design.

    [/ QUOTE ]

    I'm pointing more towards vacuum advance than too much mechanical.

    Try disconnecting your vacuum advance and going for a ride.
     
  16. sandy78

    sandy78 Registered Member

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    If the timing doesn't take care of it, you may want to revisit the head gasket issue. See how thick the ones you used are. Most composite gaskets are in the .040-.050" range. Steel shim head gaskets are generally .015-.020" compressed thickness. Depending on how you prepped your block, the piston could be as much as .025" down the hole at TDC (if it's never been decked 9.025" is what the factory decks them and rotating assemblies are based on 9" deck to crank centerline if I remember right). When you add these numbers up, it is easy to get above the .040-.045" upper limit for quench. I am running approx. .029" quench on my 383 w/ a similar compression ratio with no problems. Also, in the lean/rich dept., I used an air/fuel ratio gage and O2 sender from Summit to jet my Q-Jet and it worked beautifully. Good luck!
     
  17. dyeager535

    dyeager535 1 ton status Premium Member

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    Mid throttle, are you talking about cruise?

    What kinda carb are you talking about here? Application, year, etc.?

    Do you have any "surging" at lower vehicle speeds? (assume you'd mention it, but sometimes thats hard to feel)

    Obviously check the easy stuff first, but GM carbs setup for an EGR 305 or 350 motor will run lean at part throttle, and trying to feed a 383 with a carb setup for a 350 with EGR can lead to incorrect fuel mix. Major variations in the primary rod "steps" between each engine combo.

    Just some food for thought, 9:1 with vortecs on 87 is a piece of cake.
     
    79rustyk10 likes this.
  18. Stroked72Blazer

    Stroked72Blazer 1/2 ton status

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    [ QUOTE ]
    Also, in the lean/rich dept., I used an air/fuel ratio gage and O2 sender from Summit to jet my Q-Jet and it worked beautifully.

    [/ QUOTE ]

    So what size jets did you end up with. I have 74s in now but need to go bigger just not sure how much. I don't know how much difference it makes that I have 10.7:1 compresion but I have a simular motor and was just wondering. Oh yea I think my cam is bigger than the HT 383 too. I have the Comp Extreme 4x4 254.
     
  19. Sparky

    Sparky 1/2 ton status

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    mid throttle: I mean mid throttle. Anything above cruise. Basicly light acceleration.

    carb is a non EGR, and is for a early 70s truck w/ a 350.

    no surging problems at all.
     
  20. Sparky

    Sparky 1/2 ton status

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    I disconnected the vacume advance and so far I havent heard any pinging at any throttle or RPM range.

    However, it did get real cold out so that might have something to do with it. I'll find out for sure tomorrow.

    Ryan
     

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