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Engine Combo Thoughts?

Discussion in 'The Garage' started by Russell, May 24, 2006.

  1. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Hey guys!

    While the Tuned Port Injected engine in my truck does run now, the engine is far from optimum for making good power, esspecially with EFI.

    Right now, I have the stock rotating assembly with a stock set of heads, an XE262-H comp cam, and the TPI intake slapped on top. It runs very rich at an idle due to the cam's overlap, and due to the low compression, it just doesn't run as good as it could.

    So, I just tore the 355 from my 89 apart to see if the damage in it is major, or something easy to fix. I found 1 worn out conn rod bearing (down to the bronze), 1 cracked piston skirt, 3 gouged conn rod bearings, and 1 gouged main bearing.

    The cylinder walls are glazed over, and need to be honed (same problem as my GMC, TBI was thrown off by cam overlap, and ran rich enough to wash the cylinder walls, glazing them, causing nasty blowby, and gas fouled oil), but will not need an overbore.

    The gouged bearings were damaged due to dirt in them when the engine was first rebuilt, cause it was a deep gouge, and I can't think of any way I could possibly have gotten crap that big into the bearings. The knocking bearing would have been the worn out one, which was caused by running the engine low on oil due to a nasty rear main leak, and the other knock must have been the cracked piston.

    The cam bearings look great [​IMG]

    So, since the engine block doesn't need anything more than a hot tanking and a honing, I am going to build it up for my GMC with EFI in mind [​IMG]

    So, here is my plan:

    - 86-89 Corvette Aluminum L98 heads (58cc combustion chambers, 163cc intake runners, 1.94" intake and 1.50" exhaust valves. Possibly a mild port job)
    - Cam with specs similar to 212 in. / 218 exh. Duration @ .050, .449 in. / .456 lift, and an LSA of 112 degrees
    - Dished pistons to bring my compression ratio to approx 9.5 - 9.8:1 compression, highest I can go without requring higher than 87 octane fuel
    - Clevite 77 bearings
    - Felpro gaskets
    - Stock crank and connecting rods
    - LT1 intake converted for use on a SBC

    I am aiming for strong torque, moreso than horsepower. The truck is used for daily driving, and towing on a regular basis (13 000 lb bobcat). The cam should give me a very strong vaccum signal for the MAP sensor, and have very little overlap, so the 02 sensor should not have any issues at an idle. The high compression should give me lots of engine braking with the standard transmission, and give me lots of snot off the line to show up a ricer if needed [​IMG]

    The LT1 intake may not come until later, as it a bit pricy, and I'll be short on cash having built the engine in the first place. The LT1 intake uses all the same electronics to run as the TPI intake does, however, it flows way better, and will accomodate the engine through it's full powerband, while the TPI will be totally out of breath by 4800 RPM tops.

    Anyone have any thoughts? Any predictions on horsepower / torque curves? What is the maximum compression I can run with the aluminum heads and not require better than 87 octane?
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    I'd say if you don't have the AL vette heads lying around, spend money on better ones. Aftermarkets or Vortecs (although LT1 intake+Vortecs =?) would be a better bet.

    10:1 is probably doable on AL heads and 87 octane, but 9.2:1 or so with a (good) 64CC chamber is right up there. The additional compression "gained" with AL heads is offset by the head material, so comparable heads in iron, with lower compression, will make the same power.

    Of course, I like aluminum parts (shave weight any way you can) so if you can afford some AL aftermarket heads, I'd go that direction.

    I think pro-topline is now "RHS" (racing head service) not sure what their catalog looks like now, but they might be something to check out. They are quite cheap comparatively.
     
  3. tiger9297

    tiger9297 1/2 ton status

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    I am planning my first engine build, and every time I read a post like the one above I realize how much I DON'T know. :confused:
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    I would be a lot happier had I know half of what I know now, back when I built mine!

    An engine build should involve a WHOLE bunch of research and questions. In the end it's just like building a computer, you have to decide between a lot of options, but in the end you should have what works for *you*.

    Rushing to buy parts right off the bat only results in finding better choices after you buy. :)
     
  5. resurrected_jimmy

    resurrected_jimmy 1/2 ton status

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    minor hijack: but do any of you guys involve an engine builder in your projects or do you just stumble through it and hope for the best? I have been planning an engine for a while now and will build it when I get back to the states but haven't started ordering parts yet becuase I think I might be in over my head
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    Most machine shops are very experienced in building engines, and their advice (in my experience) is usually well founded.

    Not to mention that sometimes the place that hot tanks and bores your block can sell parts for cheaper than you can get elsewhere.

    I don't think anyone would say they stumble through a build. A "basic" rebuild (take an entire engine apart, have everything freshened up, re-assemble) is a pretty simple process, it's when you start talking about different heads, valve springs, pistons, rods, bore diameter, compression ratio, and so on that it gets a bit more complex. The basics are the same, you are just adding more to that.

    But the machine shop owner I dealt with was more than happy to sit down with me for a few minutes and discuss things like cam choices, head rebuilding, parts needed, etc.
     
  7. resurrected_jimmy

    resurrected_jimmy 1/2 ton status

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    All I have ever done is basic rebuilds, that part I understand. I always put my money in drivetrain parts and just rebuilt the engine to run and not leak or smoke, for once I can afford to build a hi-performance motor.

    The engine I want to build is totally custom starting with a world products 4.00" bore standard deck small block. I got the idea from a dyno test in engine masters. This is why I think I may be in over my head without the help of an expert.:crazy:
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    Haha enginemasters...only magazine I try to get my hands on anymore, amazing I can find it over here. :)

    I'll pm you to keep out of Sierra's thread.

    Sorry for the highjack(s) Sierra :)
     
  9. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Hmm, sounds familiar, and prehaps why I am building another engine now :rolleyes: :haha:

    No worries about the hijack!

    I can get these vette heads for under 300 bucks for the pair, ready to bolt on, so I'm fairly sure I'll go for them.

    The LT1 intake is not a 100% done deal yet, as I know I will loose a fair bit of torque capability by switching to it. I could port the snot out of the TPI intake and get it to flow throughout the powerband, but I am not sure the costs involved would be worth the torque lost to upgrade to an LT1 intake...

    And to add to my own hijack (I didn't think there could possibly be that many opinions on an EFI engine here LOL) rebuilding an engine just involves a lot of patience, and a lot of attention to detail. You need to check every clearance, angle, and torque to make sure that everything is setup correctly.

    You can slap an engine together, and have it run. But chances are it will not run to it's best potential. A guy needs to do stuff like degreeing the cam to make sure it is timed properly, checking the valve geometrey to make sure that your spring pressures and such are proper so you don't wipe a cam lobe, or bend a valve spring, checking your quench, and milling the head as required to get it to where it should be etc.

    I didn't do any of this stuff on my TPI engine, and I am sure that I will have problems down the road. It'll run for now, but sooner than later, that rich idle is going to wash cylinder walls, letting fuel into the oil which will wear bearings out, probally bust a valve spring, or wipe a cam lobe out.

    I'd rather have a new engine ready to go when that happens, then ignore the potential problem, and just run it till it blows up, then frantically search for money and parts for a new engine.

    Besides, my neighbour gave me an interesting prospect. He wants a tuned port engine built for his car as well, and likes the sounds of the engine combo I am building for my truck, and will pay for all the parts, and my labour to built it for him. Probally help pay for many of the parts for my own engine as well...

    We'll see how things go :)
     
  10. tiger9297

    tiger9297 1/2 ton status

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    :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow: Wish I knew all of that. I am struggling with this. I do plan to take my time so hopefully I'll end up with a quality engine. We should have an "Engine101" forum for people like me. Or maybe "The complete idiot's guide to building an engine"??? I'm sure yours will do very well.
     
  11. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    I'm actually surprised that there isn't a forum dedicated to gas engine building. I learned all I know about it from an old timer on another forum, and while I do know enough to be able to kinda figure things out, there is still a whole lot I don't know about building an engine...
     
  12. tiger9297

    tiger9297 1/2 ton status

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    I know most around here know engines backwards and forwards (at least that's how it seems). I know the basics and terms, but there are many things that I run into that I simply do not understand. Cam specs would be one of the first that comes to mind. Anyway, the garage seems a little "advanced" for some of the questions that I would have. I usually just don't ask. Surely there are a few others here that are in the "beginner" stage too.
     

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