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.

(Pretty long)engine swap 305 to 350,no power,chip swap?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 87project, Jan 19, 2003.

  1. 87project

    87project Registered Member

    Joined:
    Jul 9, 2002
    Posts:
    98
    Likes Received:
    0
    Location:
    Alabama
    bought a 78 c-10 van w/a 350 4bolt main(rebuilt 20,000 miles) to put in my 87 jimmy which had a 305 tbi in it.I took them both to the mechanic to pull the 305 out and put the 350 in.He told me i needed to keep tbi off the 305 and put on the 350 because of the 700R4 tranny.In order to do this I found a Holley adapter http://www.holley.com/HiOctn/ProdLine/Products/FMS/FMSFIA/17-41.html The only problem with the adapter is it hit the egr valve,so he had a old cast iron intake without egr that he put on.So know (as of yesterday) I have a 350 tbi w/no egr,cats,A.I.R pump, and a 305 chip.It sounds great idling or revving it up in park,when you try to drive it,It has no power(runs worse than the 305)doesn't smoke,just sputters if you floor it and occasionally dies,(cranks right back up).All new gaskets,exhaust manifolds,distributor,Alt,TBI,off of the 305.What could the problem be?Chip?intake w/no egr?Fuel pump to little?The Jimmy sat for about 60 days before swap with a half a tank of gas so I put some stuff in the tank and changed fuel filter.That only made very minor differences.Any ideas would be greatly appreciated /forums/images/graemlins/confused.gif
     
  2. Thunder

    Thunder 3/4 ton status

    Joined:
    Jul 20, 2000
    Posts:
    8,946
    Likes Received:
    1
    Location:
    Northeast Nevada
    You need all the sensors and stuff (EGR, 02 sensor, knock sensor, colant sensor ECT ECT) for the TBI to work properly.
    When the computer reads no output from a needed sensor or A engine controll device like the EGR fails a working test. The computer usually goes into Bypass mode (limp home). When in this mode the vehicle will not run right (no power, stalling, hesitating, ect )
    You can get away without the cat ok. But you must have all the other sensors and controlls installed and operating. Or it will never run right.
     
  3. wayne

    wayne 3/4 ton status

    Joined:
    Feb 1, 2001
    Posts:
    6,178
    Likes Received:
    0
    Location:
    Carlisle, Pa
    Without the egr valve you will run into problems. I would start there.
     
  4. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    It would probably run also better if you put the TBI intake from the 305 onto the 350. All that's required to make it fit is a little bit of grinding on the manifold as 4 of the bolt holes have a different angle than the earlier design. Someone on here even found some tapered washers that made up for the difference in the angle.
     
  5. wrathORC

    wrathORC 1/2 ton status

    Joined:
    Apr 27, 2002
    Posts:
    908
    Likes Received:
    0
    Location:
    Hancock, MI
    You don't need no stinkin' EGR valve like others say. It doesn't need a catalytic converter or AIR either. Sure, it might not like not having them but you shouldn't get any trouble codes.

    You need a water temperature sensor, oxygen sensor, a computer-controlled distributor, et cetera. As long as you swapped every single thing over from the old 305 and plugged every single thing back in it should run. It won't run very well if at all though. The chip has a fuel curve for a 305, not a 350.

    If you pull your sparkplugs you'll probably find they're really white from running lean.

    Of course, if your fuel pump isn't putting out 9-13lbs of pressure then it'll complain. It will prefer 11-13lbs more than 9-10.

    You probably have bucketloads of trouble codes, what are they?
     
  6. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    The computer tests for EGR function and will set a code 32 if it detects that the EGR system isn't working. /forums/images/graemlins/frown.gif But I'm not sure if that failure is one that would set the computer into limp home mode. I don't see why it would as EGR isn't critical to the engine being able to run fairly well.
     
  7. wrathORC

    wrathORC 1/2 ton status

    Joined:
    Apr 27, 2002
    Posts:
    908
    Likes Received:
    0
    Location:
    Hancock, MI
    How does it know if the EGR valve is there? It's been a while since I've seen an older body styled TBI system (87 pickups, 87-91 K5/Surbuban/1 ton crewcab). I have an 87 pickup at my parents' with TBI and I thought for sure it had the no-brainer EGR system. I know the early OBDI 88-98s didn't know whether the EGR valve was there or not unless it was sticking open. Same went for the S-series. You could unplug the vacuum line going to the EGR valve and it didn't know any better. I've eliminated the EGR valve on an 89 S15, an 89 S10 Blazer, and an 89 K1500 pickup. None of them knew I did it.

    I doubt they would use the computer-activated EGR valve of the later part of the 88-98s on the 87-91s but who knows.
     
  8. mattyblazer

    mattyblazer 1/2 ton status

    Joined:
    Sep 22, 2002
    Posts:
    202
    Likes Received:
    0
    Location:
    Long Island, NY
    If its any conselation to you the chip is fine, infact I wouldnt consider messing with the computer until you have resolved your other issues. When I did the swap in my 87 we made sure that every wire and vacuum line got connected to the 350. The chip that was on the 305 ran fine for over a year.
    Good Luck!
     
  9. Thunder

    Thunder 3/4 ton status

    Joined:
    Jul 20, 2000
    Posts:
    8,946
    Likes Received:
    1
    Location:
    Northeast Nevada
    I disagree about not needing a EGR valve. Disconnecting it only hurts performance.
    One of the things the EGR does is cool combustion chamber temps under load.
    With cooler combustion chamber temps, better fuel economy is acheived by advancing the timing.Too much timing will cause "pinging". But when the combustion temps down, the timing can be advanced without the "pinging" effect. At highway speeds, the ECM commands EGR operation and will advance timing accordingly. With a blocked off EGR, the computer thinks it is flowing when it is not and will advance timing. Now that the combustion chamber temps are much hotter, the advanced timing is no longer a good idea and detonation
    occurs. Since detonation can severly damage an engine, knock sensors are used.
    When the knock sensor detects detonation, it will retard timing. It takes more to stop detonation that it does to cause it and this is where it hurts performance. For example, at highway speeds, your total advance may be, 30* BTDC. If the computer advances it one more degree to 31* and it detects detonation, it can't just go back to 30* to stop it, it must retard timing to like 25* to try and stop it, and if it
    still occurs it will further retard timing. If the EGR was working properly, the temps would have stayed cool enough to operate at 31* with no problem.

    Also I have an 89 TBI 350 and it throws a code 32 when I unplug the EGR.
    The computer tests EGR function when at steady speeds.
    When cruising down the road and the ECM sees that the temp, rpm and speed are right it grounds the EGR solonoid and allows the EGR valve to open fully. The ECM looks for a drop in manifold vacume via the MAP sensor. If it does not see that drop it sets a code 32.
    Seiitng a code 32 wont put the computer in linp home mode. But mulitple sensor failures can.
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,980
    Likes Received:
    189
    Location:
    Roy WA
    Right off the bat, I think your main problem is the knock sensor. Knock sensor and the module for it (ESC) are DIFFERENT for a 305 and 350. As I recall bore size is the reason there, but regardless, they are NOT the same part #'s, and I'd be willing to bet the 305 knock sensor on a 350 will "think" it's sensing knock, and retard timing as much as it can.

    As to EGR, if you can, run it. It does NOTHING to hurt power, and only increases mileage. Not a thing wrong with that.
     

Share This Page