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.

weakest part of motor

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by jplagg, Aug 6, 2001.

  1. jplagg

    jplagg Registered Member

    Joined:
    Jul 23, 2001
    Posts:
    38
    Likes Received:
    0
    Location:
    Holland, MI
    first off - i have a gmc truck, but i'm guessing that the 350's they used were all bascically the same...right?

    performance speaking, what engine parts really hold back the power- intake (i have TBI), heads, emissions stuff? or is it the stock exhaust? how bad (restrictive) is it? i dont plan on spending to much (need new rims/tires) yet... :) but was thinking of doing something to get some more power in the short term.
    thanks
    josh


    1987 GMC High Sierra 2500 4x4
     
  2. newyorkin

    newyorkin 1 ton status

    Joined:
    May 8, 2001
    Posts:
    16,555
    Likes Received:
    157
    Location:
    Los Estados Unitos
    Hmmm.. Low buck upgrades...

    K&N air filters are supposed to make the motor inhale a little easier for about $40 (I think) and actually add about 15 horses.
    Every time I buy a new vehicle, I replace the ignition system (cap, rotor, wires, plugs, possibly coil), and it runs 10 times better than before, like regaining some lost factory power. Run some injector cleaner through maybe.
    TBI spacer for more low-end push
    Not so cheap upgrades:
    High performance ignition system...
    Dual exhaust, headers, bigger pipes, high-perf cat, and a freer muffler would help.
    New Vortec heads with a new manifold, then a better cam would also give you a boost...
    There's a lot you can do for more money and time...

    Should be a lot more you can do on the low buck side too. More folks'll see this post and tell ya...



    Ratch
    <a target="_blank" href=http://k5.8m.com>k5.8m.com</a>
    **I need a house. Friggin realtor went and sold mine.**
     
  3. Twiz

    Twiz 1/2 ton status

    Joined:
    Mar 8, 2001
    Posts:
    3,729
    Likes Received:
    0
    Location:
    Clearfield Ut.
    "Weakest part of a motor?"

    My right foot!

    <font color=purple>Twiztid</font color=purple>
     
  4. jplagg

    jplagg Registered Member

    Joined:
    Jul 23, 2001
    Posts:
    38
    Likes Received:
    0
    Location:
    Holland, MI
    the igntion stuff is a great idea. i feel fine spending up to about $300 right now. I was just worried about how the dual exhaust would go over with my engine and having more computer stuff on there. has anyone had problems with that?

    1987 GMC High Sierra 2500 4x4
     
  5. 84_Chevy_K10

    84_Chevy_K10 Banned

    Joined:
    May 30, 2001
    Posts:
    17,669
    Likes Received:
    0
    Location:
    IL, USA
    Hmm, didn't I just answer this on another board posted by the same person?

    High performance ignition is a total waste of money on a stock motor. Anybody that tells you otherwise is a complete moron. I'm not the only person to feel this way either.

    A K&amp;N is a good investment. I've had them on two trucks, including this one. I need one that will fit in the current air cleaner that I have.

    Like I told you on CT, you need to match everything. Cam, intake, and exhaust will really help a LOT. Heads will double the effect if you've already got the cam, intake, and exhaust.

    If I had $300 to spend, I'd get Dynomax headers in the painted style, Dynomax header dual exhaust kit, two mufflers of my choice, and the K&amp;N. Depending on what mufflers you choose, you'll be set back $300 +/- for that. Since you have TBI, you're going to need to get a bung welded into one of the headers (driver's side????) for your O2 sensor.

    Next, I'd do the cam. The cam is REALLY going to help, but be careful, because if you get one that isn't going to work with the computer, it's going to be fighting itself and you'll lose all the effect that that cam could possibly provide and then some.

    If you're still not happy, which will take at least a year, then do Vortec heads. The reason I didn't mention the intake in the above paragraph is because you're going to end up replacing it when you go to Vortecs anyway.

    And if your short block is worn out you're going to have to minimum re-ring it so you might end up pulling the motor before you put the heads on anyway.

    Oh yeah, and the stock exhaust is about as terrible as it comes.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles<P ID="edit"><FONT class="small">Edited by 84_Chevy_K10 on 08/06/01 10:25 PM.</FONT></P>
     
  6. mpascino

    mpascino 1/2 ton status

    Joined:
    Jan 1, 2001
    Posts:
    557
    Likes Received:
    0
    Location:
    Connecticut
    HEHEH sorry just had to laugh, but Once again did you know adding a CK5 sticker adds 10 HP and takes 1 second off your quarter mile!?[​IMG]

    You call that dirty!?
     
  7. 84_Chevy_K10

    84_Chevy_K10 Banned

    Joined:
    May 30, 2001
    Posts:
    17,669
    Likes Received:
    0
    Location:
    IL, USA
    One last comment--if you can, ditch ALL your emissions stuff except the PCV valve. Some is bad for performance, and the rest just plain doesn' t need to be there.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  8. newyorkin

    newyorkin 1 ton status

    Joined:
    May 8, 2001
    Posts:
    16,555
    Likes Received:
    157
    Location:
    Los Estados Unitos
    Umm, what kind of emission stuff are you talking about ditching? The air pump? EGR? Those don't really drain any power... Maybe EGR, but only under certain conditions. I'm not sure, but I think just about all 50 states have at least a visual inspection of emissions stuff...

    And for low-buck, I think better ignition system's will help. If you use a crappy ignition system, you will have a slower spark, and slower combustion, resulting in a smaller (or slower) explosion, and probably less power.
    At 1000 RPM, your spark plugs are firing 4 times per second. When you're boiling things down to .25 seconds, don't you want to have a fast, complete, stroke? I'd rather have the faster spark that will likely ignite more fuel at once and cause a bigger, faster, more complete combustion.

    If high-perf ignition on a stock motor is only for complete morons, then what exactly makes a more built motor with expensive spark not for morons? They both need the spark to light the fire, and they both use the same ignition principles. How does a better spark make a difference on a higher comp/perf engine, but not on a stock motor? Clarify this for me please, because I truly do not believe a high-perf ignition system on a stock motor is for morons, and if I'm wrong, I'd like to know. I try to make it habit to NOT state my opinion as fact, because there is always the chance I could be wrong.

    I'm really not trying to flame or start a fight.
    And I kind of agree with the exhaust opinion.

    BTW, I noticed a significant performance gain with my CK5 sticker. Sadly, I'll never know how much MORE I could've gotten from it if I hadn't wrinkled some letters...

    Ratch
    &lt;a target="_blank" href=http://k5.8m.com&gt;k5.8m.com&lt;/a&gt;
    **I need a house. Friggin realtor went and sold mine.**<P ID="edit"><FONT class="small">Edited by newyorkin on 08/07/01 09:02 AM.</FONT></P>
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,979
    Likes Received:
    189
    Location:
    Roy WA
    Actually I wouldn't have used "moron" but I agree with him on the ignition. Just making a hotter spark isn't going to burn the mix better. (notice they say how many volts in the ads?) Who the hell cares? If you are "putting the spark out" (like some race motors can I've heard) then you'd need hotter spark, right? THAT makes sense.

    The ignition upgrade they are talking about comes from the coil saturation times. Stock coils take a long time, but that "long time" is relative, and you (or I) are not going to be turning our truck motors to 7000RPM, where the saturation times of the stock COIL is going to be a problem.

    Your combustion times are not going to "slow down" by a colder flame. Does a pail of gas take longer to burn if you start it with a match or an acetylene welder to ignite it? If its lit, its lit. Now, using two plugs in a cylinder, different combustion chamber, (IE Vortecs) that could make a difference.

    To cap all that off, if you think what I say is bunk, why is it that there have been, to my knowledge, absolutely 0 dyno tests back to back of HEI and an aftermarket ignition, with no other mods? If you increase the effiency of a motor, (no matter how it is attained, from less friction to free flowing exhaust) which is what the aftermarket claims with ignitions, its measurable power WILL go up. That is very simple, and a constant. if aftermarket ignitions made any difference, the ONLY way to measure it would be back to back dyno tests, where NOTHING (plugs, wires, exhaust, etc) was changed BUT the ignition components necessary to the unit. (like an MSD box)

    With that said, on emissions, you won't be losing any seat of the pants power by running it. Don't think you are going to get some extra power from removing it, all you are doing is hurting the environment and yourself if you have to get it inspected or sniffed later.

    The cat converter is the one emissions device that may hinder you, that is easily changeable. I say "may" because yet again, the aftermarket claims big gains from their products, yet uses 10 year old factory exhaust components to measure against. Try a NEW factory cat against your new aftermarket then I will believe them. However, a used cat is a used cat, and if it is breaking down, it will restrict flow.

    Personally, I'd have true duals put on from the manifolds back, and if enough money, and you want to be "eco friendly" you could have dual cats put on. Still won't be legal, but it will be more efficient than stock. Go figure, you do the factory one better for the environment and the government can still nail you. Headers if you want the extra power, and the potential hassle. The pwer gain IS there though.

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</a>
    No anti-theft measures on your truck? No pity when its stolen
     
  10. txbartman

    txbartman 1/2 ton status

    Joined:
    Jun 1, 2001
    Posts:
    1,975
    Likes Received:
    0
    Location:
    Plano, TX
    I don't know much about ignition systems (stock or aftermarket), but I would agree with newyorkin about replacing some of the components. But the ones I am talking about are the plugs, wires and cap. I know my truck was running kind of rough and had a lack of responsiveness. Once I replaced the wires and the plugs (my cap was fine), things really changed. Hot spark, cold spark, doesn't matter if your wires are in bad shape (causing sometimes no spark). In addition, if your plugs are all fouled, it doesn't matter what kind of plug you are running.

    I went with some good quality (not top dollar) plug wires that carried a 5 year warranty. They were a little heavier than the stock wires. I went with AC Delco Rapid Fire plugs. The wires and the plugs combined cost me around $60. It now idles smoother, runs better, has better repsonse, and is friendlier to our environment than it has in a long time. That is a low-cost, low-effort place you could start.

    Brian
    Click to see <a target="_blank" href=http://tx85gmcguy.alloffroad.com> My 85 Jimmy </a>
    PM me for a great deal on blinker fluid! Best price on the net!
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,979
    Likes Received:
    189
    Location:
    Roy WA
    Totally correct. Change your plugs and wires at least once in a decade, your performance is guranteed to go up lol! but its true, my '83 ran like crap until I replaced the plugs and wires, which probably had 10 years on them at least!

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</a>
    No anti-theft measures on your truck? No pity when its stolen
     
  12. 502Burban

    502Burban 1/2 ton status

    Joined:
    Jun 8, 2001
    Posts:
    379
    Likes Received:
    0
    Location:
    Southern California
    Dorian &amp; Tim,

    While I agree with you both regarding the limited benefit of a hotter spark in a lower rpm engine application, I think that the one benefit of an aftermarket ignition that you may be overlooking is the multi-spark feature.

    Quoting from MSD's literature, "Below 3,000 rpm the MSD produces multiple sparks rather than just a single spark. This spark series lasts for 20° of crankshaft rotation whether there is two or six sparks. This ensures complete combustion of the fuel mixture producing more power and quick throttle response. At speeds over 3,000 rpm, there is only a single spark, however that spark also lasts for the full 20° of crank rotation."

    I have found, on multiple vehicle applications ranging from off-road to drag and road race, that engines with an MSD ignition start easier and idle smoother due to the multiple spark feature.

    As always, just my 2 cents worth.[​IMG]


    Robb
    '73 GMC Suburban - 502DFI
    <a target="_blank" href=http://community.webshots.com/user/robbrj>community.webshots.com/user/robbrj</a>
     
  13. pjwalters

    pjwalters Registered Member

    Joined:
    Jul 30, 2001
    Posts:
    11
    Likes Received:
    0
    Location:
    kansas city ks.
    yeah i was having the same problem with my blazer too. except i was running a 305. well a new crate 350, performer intake, headers, dual straight pipes, no emmisions and new carb later i run like a champ. except you have efi so forget the carb. and it cost me around 1,200. not too bad.
     
  14. Leadfoot

    Leadfoot 1/2 ton status Premium Member

    Joined:
    Nov 28, 2000
    Posts:
    3,112
    Likes Received:
    1
    Location:
    Western Massachusetts
    502, you are correct about the multiple spark because of the duration. It doesn't increase the intensity of the spark, which is what most aftermarket coils do (by increased voltage and less saturation time). That being said, changing out old ignition components (cap, rotor, wires, plugs, [​IMG]points and condensor[​IMG]) with high quality stock (AC delco type) components will increase performance as much as most aftermarket items (without the high price tag). I think most people wait too long to upgrade their components (ignition components degrade in performance over time), like when it barely runs, and then go get aftermarket components and it runs like new. They attribute the great running to high dollar components, instead of the fact that they are just fresh/new components. Where the high dollar ignition have the advantage with higher voltage is race engines where the compression and RPM's can actually put out the flame so to speak. Stock motors aren't affected. The other high dollar ignition advantage is the kind that allow you to adjust/program ignition advance and retard from right in the cab. The ignition that 502 spoke of is great for stock or aftermarket motors because it does promote cleaner burning through spark duration rather than spark intensity, which can lead to better performance at low RPM's, but I still don't think it's enough to notice it in the "seat of your pants" so to speak.

    If you didn't build it yourself, how can you call it yours.......?
     
  15. 84_Chevy_K10

    84_Chevy_K10 Banned

    Joined:
    May 30, 2001
    Posts:
    17,669
    Likes Received:
    0
    Location:
    IL, USA
    I don't agree. It only takes one spark to light the fire. GM HEI is one of the best ignition systems ever. It has even been adapted to Ford, Jeep, IH, and other applications because it's so good.

    If you must have 5000+ RPM performance, buy the aftermerket module and seperate-from-cap coil. Since the new style HEI that this guy has already has a seperate coil, I can't really see myself upgrading it.

    The cat really is the only emissions device that hurts performance in my opinion. Depending on what kind you have, that is. The new ones that come on the Vortec motors are excellent (96-98 trucks).

    Newyorkin, HEI is FAR from a crappy ignition system. If you don't believe me pull one of your plug wires off the cap one day and grab the terminal. If you've ever done it you'll see just how hard it bites, and I have to say, it HURTS!!!

    For years automobiles used points ignition and it worked alright. HEI is so much more powerful, and just about the greatest distributor ignition to come in any vehicle. If you ask me it is the best I've dealt with. Others may disagree.

    You're also wrong about all states having visual inspection. Here, we don't have any emissions tests at all. In Illinois we do have some emissions areas, but their are no visual inspections in Illinois. If you can pass the sniffer test, you're good, and I'd be willing to bet some good money that my truck runs so good (brand new motor) that it'd pass with flying colors.

    Loosing your air pump and EGR might not free up any power but they definitely do clean up your engine compartment of a lot of crap and vacuum lines that simply don't need to be there.

    I guess it isn't saying much--but my 305 makes more horsepower and torque than all of your 350 TBIs that are stock did brand new. In fact, it makes about 20% more. I don't really have anything more than some basic upgrades either.

    Why do built motors need more spark? That's easy. They have more compression, (harder to make a spark under those conditions) possibly domed pistons, (hide the flame front) and generally just more fuel and air in the combustion chamber. Add supercharging, nitrous, and a couple other things to the mix and you'll quickly realize why aftermarket ignitions exist.

    But all of them are a complete waste of money on a stock motor. At the most it might be easier to start in the winter. And from what I hear--stay away from Jacobs. I only know one person that has had good results with them on his '93 K1500. Other than that I've heard and awful lot of bad.

    Yes, a basic tune up is a give. You're going to change air filter, spark plugs, wires, cap, rotor, ignition module, O2 sensor, and oil and filter (use a Napa Gold filter) as a bare minimum.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles<P ID="edit"><FONT class="small">Edited by 84_Chevy_K10 on 08/07/01 12:59 PM.</FONT></P>
     
  16. 502Burban

    502Burban 1/2 ton status

    Joined:
    Jun 8, 2001
    Posts:
    379
    Likes Received:
    0
    Location:
    Southern California
    I agree, Leadfoot. You should not expect to feel seat-of-the-pants improvements with an MSD ignition, except in higher rpm, higher compression, or higher cam duration applications. However, I have noticed better starting and driveability with 4x4 applications, especially at low-rpm rock-crawling speeds. I think that this is probably due to the multi-spark feature.

    Robb
    '73 GMC Suburban - 502DFI
    &lt;a target="_blank" href=http://community.webshots.com/user/robbrj&gt;community.webshots.com/user/robbrj&lt;/a&gt;<P ID="edit"><FONT class="small">Edited by 502Burban on 08/07/01 12:58 PM.</FONT></P>
     
  17. Thunder

    Thunder 3/4 ton status

    Joined:
    Jul 20, 2000
    Posts:
    8,946
    Likes Received:
    1
    Location:
    Northeast Nevada
    The mod that helped my stock 350 TBI the most was high performance Exhaust.Headers Flowmaster ect.
    It is the first mod you should do and will give you the most bang for your buck.Your engine needs to breathe. If your engine cant breathe any other mod you do to your engine is not as effective.
    After you do the exauhst then do the other mods.
    Beings you have a TBI dont mess with any emmision stuff. Your engine is computer controlled so if you start disconnecting emmission stuff you will screw everything up. The computer needs all this stuff to make the engine run right.
    The only thing you can safely take off without effecting the computer is the catalitic convertor. If it is legal where you live to do so.
     
  18. 88streetblaze

    88streetblaze 1/2 ton status

    Joined:
    Jun 27, 2001
    Posts:
    314
    Likes Received:
    0
    Location:
    middle of sticks, oklahoma
    the smog equipment is not computer controlled. unless you are talking about the egr valve then yes it is needed, but you can unhook the air pump(the main part of the cali. emmisions package without worrying about the computer causes the computer has nothing to do with it, but you will not notice any major improvements in proformance because of ten horses you might pick up because there is less drag on the crankshaft since it isn't turning the belt for the pump.
     
  19. newyorkin

    newyorkin 1 ton status

    Joined:
    May 8, 2001
    Posts:
    16,555
    Likes Received:
    157
    Location:
    Los Estados Unitos
    Lunch was good!

    OK, I will admit I was irritated at the moron comment when I wrote the above post. I will not edit or delete it now because people have responded and I just think that's wrong sometimes (to delete content after someone's commented on it). I'm a little less annoyed now, but still think the terminology used was immature and egotistical. I really wasn't trying to start an argument, either.

    Originally, I had included the high perf ignition in the better stuff list. But, not including multi spark (which I didn't know about), I still think a higher perf ignition system would contribute to a better running engine. I think I misworded a few things in my second reply. Apparently, I also didn't know enough about them.
    When I said stock over built, I meant motor as it comes from the factory as stock, and built as in a motor that you stuffed a cam in, upgraded heads/intake on, etc. not as in running special fuels.
    Ignite a bucket of gas with a torch, I believe you'll light more fuel at once, than you would by simply sparking it, no? Wouldn't more fuel igniting simultaneously create a stronger force than an equal amount of fuel igniting gradually? You may not see it in a big bucket, but at a minute level it would probably be apparent.
    Unburned fuel exits through exhaust. Why would a better spark not adjust this somewhat to reduce the unburned fuel?
    I did not call the HEI crappy. Had I meant to I would have said "Crappy stock system" instead of just "crappy", meaning cheesy replacement parts (although still hei, short lived improvement). I did also say that replacing the old stock components with new yeilds a significant improvement.
    Granted, tune-up should be a given, but it's not often thought of.
    Multi spark sounds pretty cool, but I hadn't known about it until these subsequent posts.
    Dang, a troll couldn't have done better to throw the topic around... What was the original question?

    Ratch
    &lt;a target="_blank" href=http://k5.8m.com&gt;k5.8m.com&lt;/a&gt;
    **I need a house. Friggin realtor went and sold mine.**&lt;P ID="edit"&gt;&lt;FONT class="small"&gt;&lt;EM&gt;Edited by newyorkin on 08/07/01 02:56 PM.&lt;/EM&gt;&lt;/FONT&gt;&lt;/P&gt;<P ID="edit"><FONT class="small">Edited by newyorkin on 08/07/01 03:01 PM.</FONT></P>
     
  20. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,979
    Likes Received:
    189
    Location:
    Roy WA
    And I would turn right around and say that if you try and fire the mixture in a cylinder when the piston is already halfway down on the power stroke, you are wasting your time, and gas/power.

    Granted, unburnt fuel DOES make it past the initial "spark" in some cases. However, even GM didn't see a need to fix this, since AIR is there SOLELY at the manifolds for complete combustion in the exhaust manifold during warmup. At operating temp, AIR is diverted to the cat, and has nothing to do with unburnt fuel right at the manifold any longer.

    I'm not arguing with you, I'm taking this up with the aftermarket claims. If your vehicle is running correctly, there should be NO advantage at any time except perhaps at startup, when the A/F mix exceeds the 14.7:1 ideal ratio due to choke. (granted, thats not what it is all the time, in all of our trucks, but it is the ideal)

    I can perhaps see it helping, but conversely, my trucks 350, with HEI of unknown vintage or application (could be a 267 dist for all I know) will run below 500RPM if it needs to, and gets at most probably two rotations when its bone cold, before it starts. And that could be attributed to carburetion.


    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</a>
    No anti-theft measures on your truck? No pity when its stolen
     

Share This Page