Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Engine Guru's (383?)

Discussion in 'The Garage' started by Emmettology 101, Jul 24, 2002.

  1. Emmettology 101

    Emmettology 101 3/4 ton status

    Joined:
    May 9, 2000
    Posts:
    8,126
    Likes Received:
    0
    Location:
    FL
    Engine Guru\'s (383?)

    Here's my question.

    I recently bought a friends truck with a 383.. It has a Scat crank, Manley Rods, KB Hyperu pistons, Trick Flow Twisted Wedge heads, stock 89 block, Edelbrock intake and carb... The engine was built to run an EFI.. But my bud swapped on a carb after he got tired of playing with the comp stuff. When originally built he told me it had about 10.5:1 compression. ABout 1 year after he built it, he burnt a valve and the builder resurfaced the heads. Now he thinks the compression is about 11.5:1 or 12.5:1....
    Withthe timing set where it should be it pings bad on 93(thats a given), but he retarded the timing(he says 13*) and now you can run 93 in it and have a very slight ping under a heavy load.

    My question is, is this doing harm to the engine? I know the pinging isn't good, but what about running so much retard in the timing?

    Thanks!
     
  2. Twiz

    Twiz 1/2 ton status

    Joined:
    Mar 8, 2001
    Posts:
    3,729
    Likes Received:
    0
    Location:
    Clearfield Ut.
    Re: Engine Guru\'s (383?)

    Detnation is bad news dude. Even a slight amount.
    It's ruff on parts and robs power, but it'll probably be O.K. depending on how bad and how often.

    You can richen up the carb a bit, a fatter mix will help limit detantion to a point. It might also cool off the chamber a bit.
    Run a cooler t-stat, bring the chamber temps down.
    Thicker head-gasket might lower compression to a resonable level
    Swap out the cam to one that holds the intake valve open longer - bleeding off some of the compression.

    All the "fixes" listed above are double-edged, it might limit detanation, but it's going to have some draw-backs of one type or another.
    It really needs to have the pistons swapped out.

    Running the timeing retarded isn't going to have any ill-effects that I can think of. (other than poor fuel economy, poor power, ect...)
     
  3. Emmettology 101

    Emmettology 101 3/4 ton status

    Joined:
    May 9, 2000
    Posts:
    8,126
    Likes Received:
    0
    Location:
    FL
    Re: Engine Guru\'s (383?)

    Right now the way he has it set-up, I am not getting that bad of mileage! I think it is at about 10mpg... I know I will have to swap the heads or pistons out sooner or later, just wanted to check and make sure I am not harming it more. The pinging that is happening now is not severe, I have heard alot worse. Actually it is hard to hear...

    He had thicker copper gaskets under the heads the first time, but I guess they leaked bad so he went to Fel-pros...

    Think an MSD would make matters or pinging worse?(i have one laying around that I might put on)

    Maybe I will stop on the way home and see if they'll let me put some Turbo Blue in it.... *evil grin*
     
  4. m j

    m j 1/2 ton status

    Joined:
    Dec 28, 2001
    Posts:
    4,606
    Likes Received:
    0
    Re: Engine Guru\'s (383?)

    can you post some numbers of what parts are in that engine.
    with a SBC it is real rare to get that kind of compression with common parts as they have huge CC combustion chambers
    I really doubt you gained a full 1 to 2 compression points with shaving unless you really went to town.
    if retarding the timing stopped the detonation I think you are in fine shape.
     
  5. m j

    m j 1/2 ton status

    Joined:
    Dec 28, 2001
    Posts:
    4,606
    Likes Received:
    0
    Re: Engine Guru\'s (383?)

    13 is not real retarded if that is base timing.
    back it down to 10
     
  6. Emmettology 101

    Emmettology 101 3/4 ton status

    Joined:
    May 9, 2000
    Posts:
    8,126
    Likes Received:
    0
    Location:
    FL
    Re: Engine Guru\'s (383?)

    I wish I knew! The guy who built it is a jacka$$.. My friend is not real sure either. When he comes home next I have to pick up some parts at his house that go with it and I will see if he can did up his receipts.....

    I think if I get some extra cash around Springtime, maybe I will just pull it and have someone go over it and see whats in it and freshen it up....

    The heads originally had 64cc chambers and I think it has flat top pistons in it. Not sure what he ground off the heads though...
     
  7. Emmettology 101

    Emmettology 101 3/4 ton status

    Joined:
    May 9, 2000
    Posts:
    8,126
    Likes Received:
    0
    Location:
    FL
    Re: Engine Guru\'s (383?)

    I think he is getting 13* off the balancer....
     
  8. m j

    m j 1/2 ton status

    Joined:
    Dec 28, 2001
    Posts:
    4,606
    Likes Received:
    0
    Re: Engine Guru\'s (383?)

    I dont thnk you can get 12.5 with flat tops and 60cc chambers but dont have time for the math right now...
    I think good chamber design reduces the ignition lead requirements
    back the timing until ping isnt an issue, if it is a dog then look deeper
     
  9. BigMac

    BigMac 1/2 ton status

    Joined:
    May 27, 2002
    Posts:
    397
    Likes Received:
    0
    Location:
    Fremont, CA
    Re: Engine Guru\'s (383?)

    I recently had some detonation going on in my tired ol 350. I checked the timeing , did a little tuning... am at 6 deg before tdc.. still pingin and diesling which was new....
    I took it out to the freeway and punched it. I drove from Fremont to Modesto (60 miles aprox) and used about 3/4 tank of gas. After that it ran beautiful. I was building up carbon or something babying tired ol parts...

    13 deg seems too advanced to me, but I've not tuned any hotrod motors.
     
  10. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

    Joined:
    Feb 23, 2001
    Posts:
    3,369
    Likes Received:
    0
    Location:
    Chicago, IL
    Re: Engine Guru\'s (383?)

    I'm with m_j... I just had a pair of heads milled .030 down, and the shop here told me that I would only gain .25 to .50 additional comp ratio. So WORST case, you shouldn't be over 11.0:1 if it started off with 10.5:1! /forums/images/icons/smile.gif

    What kind of 93 are you using? Crappy stuff - or something like Mobil or Amoco? There is a difference... I don't care what anyone else says! /forums/images/icons/crazy.gif

    -Dan
     
  11. Emmettology 101

    Emmettology 101 3/4 ton status

    Joined:
    May 9, 2000
    Posts:
    8,126
    Likes Received:
    0
    Location:
    FL
    Re: Engine Guru\'s (383?)

    Actually I am running Sunoco 94 in it right now..
     
  12. lizard

    lizard 1/2 ton status

    Joined:
    May 11, 2002
    Posts:
    114
    Likes Received:
    0
    Location:
    Tallahassee, Florida
    Re: Engine Guru\'s (383?)

    One of the best thing I ever did to reduce detonation was to polish the combustion chamber and relieve the edges on valve pockets of the piston.

    Think about it. Detonation is helped along by hot spots in the combustion chamber. smoothe everything out and you reduce the possibility of hot spots.

    ...
     
  13. spoolnaround

    spoolnaround 1/2 ton status

    Joined:
    Apr 8, 2002
    Posts:
    1,419
    Likes Received:
    0
    Location:
    Kingsburg Ca
    Re: Engine Guru\'s (383?)

    I never had any problem with my 383 pinging untill I put a smog legal cam in it. When I freshen it up I am going back to the cam I had.
     
  14. Emmettology 101

    Emmettology 101 3/4 ton status

    Joined:
    May 9, 2000
    Posts:
    8,126
    Likes Received:
    0
    Location:
    FL
    Re: Engine Guru\'s (383?)

    Well If I bump up the timing back to where it should be and run straight race fuel( abotu $4.30/GAL here) then the pinging would be non-existant... But at $150 a fill up, that gets a little outta hand! $30-$60 is bad enough! /forums/images/icons/smile.gif

    Last night I added some NOS Off-Road octane booster(2 cans since I had about 35 galllons). It helps and the pinging is reduced alot. Dont get me wrong the pinging isn't severe int he first palce, but none is better.
    Next fill up I am going to fill it up most way with 93/94 and then added about 5 gallons of Turbo Blue...

    Here is the kicker though. They have Turbo Blue right n town and it is $4.30/gal this year. If I drive about 30 mins I can get Cam 2 for about $3.00/gal. Doh! Supply and demand I guess!
     
  15. BorregoK5

    BorregoK5 1/2 ton status

    Joined:
    Sep 7, 2001
    Posts:
    2,457
    Likes Received:
    0
    Location:
    San Marcos, Ca USA
    Re: Engine Guru\'s (383?)

    For a quick fix, run a shorter spark plug (heavy duty, not light duty) and index it to shroud the combustion chamber. You'd be amazed at the amount of detonation control you can get doing this. Krazie87K5 pretty much nailed it on your likely compression ratio. Check for an adjustable advance kit while your at it. The 383 and 400 high compression engines usualy require one to get dialed in without full or part throttle ping.
     
  16. Emmettology 101

    Emmettology 101 3/4 ton status

    Joined:
    May 9, 2000
    Posts:
    8,126
    Likes Received:
    0
    Location:
    FL
    Re: Engine Guru\'s (383?)

    Any idea on a good NGK part number for that plug?
     
  17. skyblazer

    skyblazer 1/2 ton status

    Joined:
    Oct 1, 2000
    Posts:
    209
    Likes Received:
    0
    Location:
    Houston, TX
    Re: Engine Guru\'s (383?)

    Speaking of compression ratio, Speed-O-Motive built my bottom end. They recommended 10:1 compression with my aluminum Trick Flow 64cc heads. I run 13* initial/35* total timing with no detonation problems. Last night I did a compression test......205 psi on each cylinder. Wow, that sounds way too high to me, but the dude from Trick Flow says that thats in the ballpark for aluminum because it disapates heat quicker than iron. Anyone else get high numbers like this? Oh yeah, this is with a Comp xtreme energy 4x4 cam installed straight up.
     
  18. BorregoK5

    BorregoK5 1/2 ton status

    Joined:
    Sep 7, 2001
    Posts:
    2,457
    Likes Received:
    0
    Location:
    San Marcos, Ca USA
    Re: Engine Guru\'s (383?)

    I'd don't have an NKG to reference but the same would apply as the ACDelco reference below.

    ACDelco Heavy Duty Plug: .R44T
    ACDelco Light Duty Plug: .R45TS

    These are tapered plugs, can't remember what the Twisted Wedge use. I originally ran the HD short plugs in my 415 before the advance kit was installed, no ping, good torque but I wanted more power. I switched to the light duty and unleashed a bit more power but both full and part throttle ping as well. Once the adjustable advance kit was installed I was able to keep the power and rid the ping. Shrouding is an quick and easy way to combat a relatively non existant or very infrequent ping, for a more consitent yet slight ping the shorter plugs will do it... if not, an adjustable advance will take care of the rest and is a good idea to get a good curve anyhow and really unleash your potential. Your probably stuck with premium fuel though, the adjustable advance might curve you down to mid grade if you really needed to at the expense of some power. Consequently, a 400's initial advance is only 2 degrees, your 383 will probably be between 4 and 6 degrees.
     
  19. Emmettology 101

    Emmettology 101 3/4 ton status

    Joined:
    May 9, 2000
    Posts:
    8,126
    Likes Received:
    0
    Location:
    FL
    Re: Engine Guru\'s (383?)

    Well in the beginning I could have swore he said the compression ratio was around 11.5:1(now that I think of it) then he ground the head. My friend says he thinks the amount they ground on the head was 8 thousanths. The engine builder isn't too siwft, hell, he couldn't even remember what cam went into it.. I told my friend not to use this guy, but he did anyhow. I htink I will pull it in the spring and freshenit up, that way I will have a chance to swap in the cam of my choice and now what is in it....(and the comp ratio)
    My friend said he tried doing a compression test and it was coming up 180 on the third round...
     
  20. Supergas

    Supergas 1/2 ton status

    Joined:
    Oct 17, 2001
    Posts:
    161
    Likes Received:
    0
    Location:
    Texas Coast
    Re: Engine Guru\'s (383?)

    Sell the aluminum heads and buy a set of stock Vortec heads. That will solve several problems and will give you more bottom end. If you try to build a "race" engine with high compression you are really shooting yourself in the foot. I have a 377 that is 9.2:1 compression and makes over 400 lb ft of torque off idle (1875 RPM) that is what gets you going, not HP at higher RPM... my 2c worth /forums/images/icons/grin.gif
     

Share This Page