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Thread: Glowing Exhaust Manifolds 1992 454 TBI 7.4L P30 Motorhome

  1. #31
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    Quote Originally Posted by Kaweh View Post
    Thanks for your thoughts! I put brand new exhaust manifolds on as part of my rebuild!!
    I am confused at how the exhaust manifolds have anything to do with the intake manifold.

    What I was saying is the 455 Oldsmobile manifolds were known to crack under the carburetor in the exhaust crossover passageway and when the engine was working hard and hot the crack would expand and dump exhaust gasses right back into the intake charge.

  2. #32
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    Did you confirm that the TDC mark on the balancer is actually TDC?

    If you look-up the ultimate TBI mods you can find info on how to make the stock regulator adjustable. It's not as easy to adjust, but there is a screw you can release so you can make small adjustments without buying any parts.

  3. #33
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    The timing is correct and I tried it at 4 degrees TDC, 6 and 12. We also did it by ear once. When it started to knock we backed off a bit. And that's where it's at right
    now, 12 degrees. Great power. just the harder I push it to go up a hill, the hotter they get. Supper bright! Some folks think this is normal and that chevys were prone to cracks and glowing exhausts because of the restrictive nature of the exhaust. They say maybe I didn't notice it. But this is scary red past the Y pipe. The GM foreman agreed to go on a test drive with me with his scanner next week so we'll go and see what he says. I say it's time for headers and dual 3" exhausts. Let's face it everyone I have been in touch says the design is poor and should have never been made like that and that is why in 96 GM changed it.

  4. #34
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    You're going to swap manifolds for headers so then you'll have glowing red headers.
    On my '92 454 I have headers to dual 3" exhaust all the way back to the bumpers. What I said before about GM changing to a steel "shorty" header type manifold, the point is steel is less prone to crack. IMO headers are more likely to glow red because they're thinner than cast iron manifolds.
    Heres a video I made several years ago, this is whats going on inside your exhaust. https://youtu.be/CLYi4JDnTSQ
    And BTW, haven't changed anything on that engine since, except oil and filters, and it's been run several times for 24 hours straight fully loaded in the bed while towing a car on a trailer. Do I care if my headers are red? No I don't.

  5. #35
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    Jay, i use 91 octane at the moment. I ordered a BAMS chip from Harris Performance. I just received it today and haven't put it in yet. I had the injectors tested and they were too low for this motor according to many sources. now I have 90 lb/hr injector in there and a EP381 AC delco fuel pump which is overkill but Harris recommended the upgrade as well. The backfire happened because of a ground short from the injectors. i bout this rv used and someone had messed with the injectors. and no matter what, it had great power and up the hill to burnin man six years in a row yielded no problems. anyway, the backfire is gone. engine runs great just up the hill the manifolds start to glow in a matter of seconds and it's scary. I am going to make a video of this before i put in the prom just to show the level of the severity.

  6. #36
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    by the way thanks for sharing this video Jay. I wonder what might happen if i take the manifolds off and run it. But on my rv there are a lot of power, oil and what not lines running right next to the driver side manifold. Do you have a link to the right steel manifolds that you are referring to?

  7. #37
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    Quote Originally Posted by Kaweh View Post
    Jay, i use 91 octane at the moment. I ordered a BAMS chip from Harris Performance. I just received it today and haven't put it in yet. I had the injectors tested and they were too low for this motor according to many sources. now I have 90 lb/hr injector in there and a EP381 AC delco fuel pump which is overkill but Harris recommended the upgrade as well. The backfire happened because of a ground short from the injectors. i bout this rv used and someone had messed with the injectors. and no matter what, it had great power and up the hill to burnin man six years in a row yielded no problems. anyway, the backfire is gone. engine runs great just up the hill the manifolds start to glow in a matter of seconds and it's scary. I am going to make a video of this before i put in the prom just to show the level of the severity.
    You don't know what injectors you have unless they have been flow tested @ a specific PSI , I have asked multiple times for you to provide where these new injectors came from but never received an answer , there were never any 90#/hr injectors EVER released from GM so I know for a fact you do not have those . I still contend the engine is running out of fuel or has a vaccum leak as it gets hotter and works harder. Again I will say , Unless you get hard data out of either a datalogging software program or a scan tool , you are pissing in a fan throwing parts at this thing . You need data to support weather a change you make is doing any good or not , simply using the manifolds as a tuning tool is a poor way to diagnose. You are already pissing in a fan ordering anything from TBI Chips , you can do your own research on that on this very site. You can have all the fuel pump in the world and as big of injectors as you can find , if the calibration and the input from the related sensors is incorrect , it will still perform like a$$ ........

    FWIW , my '94 3500 with the 502 (509) regularly sees 14K# of 5th wheel camper , add that to the 6440# the truck weighs and its over 21K# with my not so small a$$ in the seat and full fuel tanks , EGT stays right around 1300 at the collector merge , never do the headers glow under load . I run Edelbrock coated TES headers to Dual 2-1/2" exhaust with an X pipe . This isn't my first rodeo here .......


    Diagnose first , then change parts as necessary .

    TOM
    1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
    1992 S-10 434 SBC/Tremec - '7427
    1986 Monte Carlo SS
    1984 S-10 , SAS, 496/700R4/205 , D44/14BFF -'7427
    1980 Z-28 496/700R4
    1979 Corvette 496/700R4
    1977 Olds 98 Regency 403/700R4

  8. #38
    billygraves
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    .............
    Last edited by billygraves; 06-30-2019 at 06:45 PM.

  9. #39
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    The injectors are from RockAuto:
    STANDARD MOTOR PRODUCTS Part # TJ11 {Click Info Link for Alternate/OEM Part Numbers} Throttle Body Injector; 90.77 lbs/hr

    https://www.rockauto.com/catalog/moreinfo.php?pk=47657

  10. #40
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    Quote Originally Posted by Nasty-Z View Post
    You don't know what injectors you have unless they have been flow tested @ a specific PSI ,
    STANDARD MOTOR PRODUCTS Part # TJ11 {Click Info Link for Alternate/OEM Part Numbers} Throttle Body Injector; 90.77 lbs/hr

    LINK: https://www.rockauto.com/catalog/moreinfo.php?pk=47657


    I just got off the phone with Rock Auto and I was transferred to technical. The gentleman said that they were test at 14.75psi.
    For me to test them means taking the whole tbi out and dropping it off at the shop here in San Jose, Ca. Rockauto said they'd take
    them back if I find anything different than 90lb/hr provided i include the data sheet. That'll work I say.
    Last edited by Kaweh; 05-05-2015 at 09:54 PM.

  11. #41
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    I like RockAuto for most things, but sometimes their parts don't actually work in the application they have them listed for. I don't know why they'd test them at 14.75 psi as I don't believe any TBI system operated at that pressure. In their listing, they show these as being used in everything from '87-95 (and all the way up to 2007 for Volvo). The injector flow ratings weren't the same through all of those years on the 454 (especially '94-95), so I don't think that the data they're giving you is reliable. If I were you, I would get them tested at 13psi and see how they flow there. You may need to find another source for injectors if they don't flow enough.
    1973 K-5 Blazer, TBI 350, TH400, 1 ton axles & 38" SSRs'
    1975 280Z, TBI 350, 700R4
    1953 M-38A1, TBI Buick 231
    1951 Ford Panel, 5.3 with 4L80E

  12. #42
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    http://www.cfm-tech.com/ USED TO have a lot of good information. It seems, as of two or so weeks ago, the site has been down.
    I know the '92 uses different injectors than '94-'95, and that a 94-95 fuel pump and adjustable regulator can provide more performance when used on a '92. Thats what I've been running. All info I followed was from that site.
    Last edited by jay72; 05-06-2015 at 01:30 AM.

  13. #43
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    94-95 uses a lower flow rate injector @ a higher pressure . Spec for the 94-95 GM 454 TBI system was 28-32 psi . The fuel pump was different as well as the spring in the factory regulator to produce the required pressure to the injectors. Spec on the 87-93 454 TBI system was 9-13 psi .

    As I have said many times in this thread , the replacement injectors have no flow data , and were parts store specials , they may or may not be of the correct flow rate for the system , the pump , lines , filter , regulator may or may not be working properly. No one knows , and no one will ever know without DATA !!!!!

    As I said in post #37 this morning , using glowing manifolds as a tuning tool is a poor way to diagnose.

    Ignition timing , fuel pressure and volume , and cooling system are the key areas the OP needs to address. I would use a piston stop to find true TDC , verify the balancer mark is actually # 1 TDC , that would rule out timing , pull the D/S rocker cover and use a dial indicator to check cam timing , that will rule out an incorrectly installed timing chain , use a scan tool and go for a drive , watch the O2 and fuel trim parameters , this will rule out a lean condition , check the cooling system to see if its running too cool OR to warm , both will affect EGT's in a negative way. Etc , etc, etc ................

    TOM
    1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
    1992 S-10 434 SBC/Tremec - '7427
    1986 Monte Carlo SS
    1984 S-10 , SAS, 496/700R4/205 , D44/14BFF -'7427
    1980 Z-28 496/700R4
    1979 Corvette 496/700R4
    1977 Olds 98 Regency 403/700R4

  14. #44
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    Finally, my youtube video uploaded. It took all night long. it's a little bit shaky but I did collect some data.


    https://www.youtube.com/watch?v=JIxM...ature=youtu.be


    I hope this helps. The snap on versus was attached today and I did another vacuum leak test all round the TBI and nothing showed up. The short term fuel trim and the RPMs did not change. by the way the MAP sensor is fine. No fuel present in line.

  15. #45
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    I'm not an expert at this stuff yet, but I did watch the video. It was very difficult to get a good idea of what was happening due to the shakiness and focus problems. I'm sure most of the guys that could help you best here would much prefer a datalog that they could play back on TunerPro. I think I saw some high BLMs at one point which could point to a fueling problem, but it was just hard to tell and it was very hard to focus on more than one reading at a time.
    1973 K-5 Blazer, TBI 350, TH400, 1 ton axles & 38" SSRs'
    1975 280Z, TBI 350, 700R4
    1953 M-38A1, TBI Buick 231
    1951 Ford Panel, 5.3 with 4L80E

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