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Fix old engine or build new one? Opinions please

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  • Engine: Fix old engine or build new one? Opinions please

    So my 1982 Avanti with factory 305 small block has unfortunately developed a very bad mechanical knock. My mechanic was unable to diagnose the root cause without tearing the top end of the engine apart. I have a newer 350 small block torn down in my garage awaiting a trip to the engine builders. The plan for that engine was to build it slowly as not to strain the wallet too much.

    So I am at a crossroads, do I get the current 305 engine fixed, which has an unknown cost associated with it depending on what the cause of the knock is. Or do I speed up the time table to build the 350, which involves not only building the new engine, but also removing the old one, installing the new engine, and based on my research the stock 2004r transmission would have to be rebuild to handle the added horsepower of the 350. If money were no object then the 350 would be the obvious route, but it is, so that means some of the things like installing the engine and transmission I may have to brave doing myself.

    What would you do and why?

  • #2
    I wouldn't give any thought to fixing the 305. I'd simply do what you planned with the 350 (albeit, a little ahead of your schedule) and enjoy the 350. I don't think you'll have any trouble using the 2004R.
    Howard - Los Angeles chapter SDC
    '53 Commander Starliner (Finally running and driving, but still in process)
    '56 Golden Hawk (3 speed/overdrive, Power steering - Running, but not yet driving)
    '62 GT Hawk (4 speed, A/C, Power steering - running and DRIVING!)


    • #3
      Agreed, build the 350 and as they say..."don't look back".

      On the trans., while I'd take a 200-4R over a 700-R4 any day, a "stock" 200 may not live up to too much abuse. Normal daily driving, no problem. Run it, and replace when required. Art Carr in So Cal. has three variations depending on your budget and power requirements.



      • #4
        Depends on what you mean by build a 350. If you really build one, have the 200R4 beefed up. If you are just headed for a 300 HP or so crate engine, just run it as is. If you break it, it'll still cost the same to rebuild/beef it up.

        I agree, ashcan the 305 and go directly to a 350. As an aside, a beefed up 200R4 will set you back about $13-1500 around here.

        If you decide to drop in the 350/tranny combo yourself, I'll post the forum writeup I did to drop in the 383/T56 combo I put in my 74. Pretty straight forward with an engine hoist which can be rented.

        Last edited by sweetolbob; 04-23-2014, 04:24 PM.


        • #5
          Another thought, we are talking about Avanti Motors here NOT GM.
          I don't know, but it seems very possible to me that they could have used a 700R4 behind that HO 305! Did you actually check, or just going by what General Muckup would do?
          Second Generation Stude Driver,
          Proud '54 Starliner Owner


          • #6
            To add to what StudeRich said above, try to stay with the same type trans you have. Changing a 700R4 to a 200R4 (2004R) or visa-versa will require a change or refabrication of the rear transmission mount and changing the length of the driveshaft.



            • #7
              No there is actually a 2004r tranny behind the 305. It was standard on all Avantis of that vintage. I had originally had aspirations for BUILDING the 350, but I think I will be plenty happy with a 300hp engine over the 150hp 305 any day.

              Sweetolbob that would be great it you could post that write up.

              One of my big concerns is the fact that this car has a computer and the difficulty of adapting some of those systems to the new engine. This is the early GM CCC that they added to handle the emissions things and the computer controlled quadrajet. Anyone have any experience with that?


              • #8
                This is the 383/T56 install http://forum.studebakerdriversclub.c...-SBC-T56-combo

                Thoughts on the ECM setup on your engine based on my 83 Avanti. I replaced the 305 in my 83 (bad engine) with a 355 making 350-400 HP. I was not about to use the OEM ECM/carb setup on the much bigger engine. I decided to go with a 650 Edelbrock carb for starters and began to track down the ECM wiring. It didn't take long to realize that the ECM setup was an entirely independent wiring harness from the cars wiring harness.

                I don't have emissions checking here so I just removed all of the harness, ECM, sensors etc and installed the Edelbrock carb and an MSD HEI big cap distributor. It ran fine but I eventually changed the carb/HEI to a Holley EFI setup.

                That carb and HEI now set on/in my 74 with the 383/T56 setup.

                It will be your choice but I just don't like an older economy/emissions setup from the dark past of computer control holding the reins of a larger, more modern engine built for performance.

                Avanti, Bob


                • #9
                  Go with the 350 for sure. Easy build of 350 hp or a little more on a low cost budget. A 383 should go 400 plus street able on a budget. I built a 383 for a local guy's model A that went 400 on stock parts. and built a 377 drag race motor with stock chev parts that went 450 hp and a ran 11.30s in a vega drag car.


                  • #10
                    That's awesome to hear about the wiring harness. I really was not prepared to go in there and start doing a bunch of electrical work. I just want a carburetor that works and an engine that runs right and gets decent mileage.

                    You make putting that engine and tranny in there so easy! I've never had a car project that went quite that smooth.


                    • #11
                      Get some bids on building what you want. I can ship you a moderately strong blueprinted 350" with a 4-bbl intake and HEI distributor for about $1850.

                      jack vines


                      • #12
                        An '82 was my daily driver for many, many years... but, NOT with the factory engine! At about 50K miles the cam finally went so flat it would hardly pull itself, even with the very best of maintenance. Only then did I do the research and found that many of this era had a number of well-known and documented problems. So, I sold the old engine to a high-school kid for $250 and bought a new GM 350 crate-engine and installed it. I should have done so years before. Everything simply bolted up and dropped in, no issues of any sort ever again.

                        With luck maybe you too can find someone who is actually willing to give you money for the old engine.


                        • #13
                          Anyone have any experience with one of these?



                          • #14
                            Originally posted by CaffeineRacer View Post
                            Anyone have any experience with one of these?

                            Crate engines are crate engines. They'll work just fine but why go there when PackardV8 (Jack V) will build you one for the same money or less and he has an excellent reputation of building just what the customer wants at a fair price.

                            Not only that but I'll bet he's pretty helpful at startup if you have a question.

                            Nothing against Summit as I buy a lot there but if I were to buy an engine I'd call/PM Jack.



                            • #15
                              @sweetolbob Most definitely. I didn't mean to offend Jack or imply that I didn't think he was a good engine builder, sorry about that. I will most definitely shoot him a PM and chat. I was just looking around. Having a big factory warranty was just something I thought might be good to have.

                              @PackardV8 PMing now.

                              Has anyone installed a vortec 350 engine into an Avanti II? One of the engine installers I talked to seemed to be concerned about the linkages for the TV and Throttle on the carb since with the vortec intake the carburetor might be in a different position. Is this a real concern?