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TPI convert for my sb 400 Help??

Discussion in 'The Garage' started by quicker, Jul 29, 2006.

  1. quicker

    quicker 1/2 ton status

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    I recently bought a 1975 blazer with a SB 400.

    In the first week I abused it and really the only problem that arose was the timing going out and a tick (sticky valves) in the heads. I planed on rebuilding or replacing the heads anyway so all is good.

    My problem is related to the conversion to a tpi fuel injection. Can I use a 1986 tpi system directly on top of SB heads or is there more to this swap?

    Any help or advice positive or negative is appreciated.

    I have a lumpy cam and I am also not sure of where to go or how to reprogram the computer for these tpi systems. I will probably end up with a westers garage chip.

    Thanks for any advise.
     
  2. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    My advice -- Don't buy anything yet, and do some serious reasearch first. There is a heck of a lot more involved with TPI than just slapping it onto the engine. Thats the quick and easy part!

    There is a crapload of wiring involved, and the tuning involved on a 400, esspecially one with a big lumpy cam would be very expensive if done professionally, and a big pain in the butt if you do it yourself. You'll be plauged with a rich idle, due to valve overlap, a surging idle due to the timing / IAC flying around wildly trying to steady the lope etc.

    TPI is great for a engine with a conservative cam ground on a 112 degree lobe seperation, or more, and that is built to be making all its power prior to 4500 rpm, even less on a 400. TPI makes huge torque, but really suffers in the top end due to the intake's restrictive throttle body, plenum, runners and intake.

    I made the big mistake of leaping onto the TPI bandwagon without understanding truely what I was getting into. When all was said and done, a year had passed, and I'd spent about 3 times what I was initially expecting to spend.

    In my honest opinion, your engine would probally run better with a carburator on it than a stock GM EFI system. I'd definitely be looking into aftermarket MPFI systems if you absolutely have your heart set on EFI, but either way, do some serious reasearch before you decide on anything.
     
  3. quicker

    quicker 1/2 ton status

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    Being in Alberta you probably already know of westers garage?

    I was going to talk to him about program options.

    A good tbi ready to go system will cost around 1500.00 not including final timing and other issues.

    I figure 500 for the whole tpi system with 1000 to spend on chip and related upgrades. I am expecting to spend "around" 2000 when it’s all said and done.

    I am willing to change the cam if needed and torque in the low range is what I am after. If needed I can make a sheet metal uim to suit my needs.
    If needed a new MAf and throttle body can be included with the custom uim and I can have my cake and eat it to. lol I hope.

    I am also doing alot of 9000 plus altitude wheeling so I figure all the torque I can get will be needed.

    Still if I am way off with my expectations I really do appreciate your input you obviously know from experience.

    What has worked for you? What was required to solve some of the problems you encountered? Did you get it to finally work reasonably?

    Thanks again for your input and help.
     
  4. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    I personally haven't dealt with Wester's, but know of a few guys who have, and they all have nothing but good to say about him :) I personally have been doing the tuning myself.

    I initially paid about 450 bucks for my TPI system, then put another 500 - 600 into new sensors, solenoids, injectors, missing bolts etc. Had I bought a complete donor car rather than parts off ebay, I would have wound up way ahead, as you can easily re-sell a thirdgen carbed for as much, if not more than you paid for it. That also gives you a complete running vehicle to get all yours parts from to swap over to the new engine.

    You'd want to convert your 400's camshaft over to a mild torque producing camshaft. It should idle totally smooth, and you don't want any valve overlap. If your idle is bumpy, the ECM detects that as issues with the timing, or idle speed, and fiddles with both in an attempt to make it idle glass smooth, but just makes the idle surge, and occasionally stall. You also don't want the valve overlap, as it allows fresh air directly into the exhaust, which causes the 02 sensor to send a super lean signal to the ECM, which will then pour craploads of fuel into the engine in a futile attempt to compensate.

    The decision of MAF vs speed density is a tough one. Both have their advantages and disadvantages.

    MAF is more willing to accept engine modifications without as major of chip changes, and is cheaper as well (less the MAF itself!). But, makes you run air ducting for the MAF, which forces you to run electric fans.

    Speed Density isn't quite as accepting to engine changes, and costs more, but allows you to run an engine driven fan by putting a filter right on the throttlebody.

    Either way you will be forced to convert to either the TPI style serpentine brackets, or an earlier style engine bracket that doesn't need the intake as a mounting bracket.

    Wiring was fairly easy.

    I used a stock 83-86ish speedometer head speed sensor adapted to my old 100 mph speedometer for my VSS, with a prom change to optical VSS. Optical is 2000 pulse per mile, which is stock for MAF, and requires a prom change to accept for the SD setups. They use a 40 pulse per driveshaft rotation sensor stock.

    Fuel tank came from an 89 Suburban, while the fuel lines are custom.

    I had to use a 4.3's water-neck and a rad hose from a mid 80's crossfire Trans Am so I wouldn't have to splice stuff.

    I'm sure there is a ton of stuff that I've forgotten, but this gives you a basic rundown of what all is involved.
     
  5. quicker

    quicker 1/2 ton status

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    After I find out what limits wester can reach I will base the rest of my shopping list on that.

    There are some options with the chip that can reduce some of the sensor dependence.. but again it all depends on what wester says he can do.

    I was not aware of the issue with the fan and would prefer to keep it attached to the motor being it’s a 400 and I am in California (hot).

    How far off is the ducting?? What was the limiting factor with regards to the ducting and the fan?? If you went up (higher) would it work…I know it will be a week before I can find out as I am waiting for the parts .

    Any pictures??

    What about going with the Accel super ram plenum?? Any information or do you know others who have used it?

    Thank you again for all the information you have provided, knowledgeable help is hard to come by.
     
  6. quicker

    quicker 1/2 ton status

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  7. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Also check out www.chevythunder.com

    The air intake ducting would be very tough to get around. The throttle body exits at the front of the engine with just enough space to put a throttle body filter on without fan clearance issues, but unless you got something specifically made, I can't think of any way you could get around the fan for the MAF ducting.

    There are electric fans available that will have no trouble keeping your truck cool. One such fan is the dual speed fans from the 3.8 V6 Ford Taurus. Not exactly sure on the year range, but those things move more than enough air to keep a big block cool. They are also low profile, and have a full shroud that is almost made for a Chevy rad.
     
  8. quicker

    quicker 1/2 ton status

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    Wow thanks again the fan option is one I would have never thought of. I am buying a painless wiring kit and a few other things you have suggested but right now I have to buy a few other items to keep the 400 going as is.

    It turns out it Sb 400 is a 10-1 compression and the headers are too small and I need a new distributor. Oh and the guy who sold it too me failed to mention that I needed high octane gas for this engine. Higher than 91 that’s for sure. I don’t care but I am not sure how this will play out in my end product with a milder cam.


    Right now I have a carb and will be switching to a tpi what msd unit would be best to buy?

    I just don’t want to have to buy a $300.00 distributor for the carb and then another msd unit 3 months later for the tpi.

    Thanks again for all your help.
     
  9. quicker

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  10. quicker

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  11. quicker

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  12. chevyryan

    chevyryan Registered Member

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    no it wont work. bolt angles are definately different. usually goin from an older sb to a newer, the bolt patterns are the same but angle are different. i ran into a similar problem when i tried to put a 79 400 in my 90 blazer. i put the stock 1990 throttle body injection on my 1979 400. the bolt angle when i tried to swap intakes were different. also u may need to do something with electrical side to get decent amount of fuel delivery from your tpi. that was another problem i had because i was using fuel injection from a 350 and putting it on a 400, but it can still be done you just need to do a little more work. just research AS MUCH AS POSSIBLE! call everyone who might know any little detail about it. i called around and everyone told me it would work, then later on i double checked and found more information i could have used weeks before, so learn as much as u can. Rely mostly on people who have dealt with this sort of thing befeore. i read in books certain things and later found out they werent trure, and they were supposed to be trusted and credited material. i had waisted so much time and money because i didnt know all the facts so i just put another 350 in my truck. however if i learned everything in the beginning i wouldnt have waisted time and money and could have put it torwards what i needed to make it work. so learn as much as possible first before you start dumping time and money into this
     
  13. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    It looks to me like he is doing the research now, and so long as he understands the dynamics of the install, and is willing to pay for everything, then the EFI should be nice when all is said and done. Like you mentioned, its not a good idea to just leap into a project like this without understanding it.

    However, the bolt angles are a relatively moot point. About 20 minutes with a die grinder and your problem is solved :D

    Besides, an 86 TPI intake will already have the old bolt angles for it's intake, it was in 87 when TBI was introduced in trucks that the engine changed to a new style of head, and single peice rear main seal.
     
  14. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    You have to be real carefull building a 400, especially here in california. 10.1:1 is WAY to high for an iron headed 400 with California grade gas, mine is 9.2:1 with iron heads and I have to add octane booster to 91 pump gas if I pull a trailer. I'd change the heads and try to go to a larger combustion chamber, maybe you will get lucky and the current heads are 72cc's, where a swap to a head with 76cc chambers will lower your compression enough.
     
  15. quicker

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    Yes California gas blows.

    I have access to true 100-104 and 107. It’s much more expensive but I also happen to work in the fuel truck industry and funny enough get free diesel all the time. Yes hundreds of gallons a month. Yes the diesel is already spoken for.

    Unfortunately I don’t come across much gas, especially 100 or 104 octane. High octane fuel is around 5 dollars a gallon.


    I can’t wait for e-85 to kick in then the octane won’t be an issue.
     

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