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Recipe for 250+ hp with 3400/3500?

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  • Recipe for 250+ hp with 3400/3500?

    I have spent way too much time perusing this forum along with the car-specific (Monte Carlo, Camaro, S10, GrandAm, etc) pages the last week or so digesting information.
    Now that I'm a member here I'd like to ask for some guidance.

    I am looking at putting a 60V6 into an older RWD non-GM car. With me in it and a full tank of gas the car is under 3000 lbs.

    The original engine came in several varieties up to 250hp stock so I'd like to be able to get a 3400/3500 to at least that much output to make it worth doing.
    250 is a minimum, 275 would be great, more would be gravy. I am OK sacrificing some low-end for gains higher up since the car is light and I have ~3.38 rear gear. Stock base engine in my car made 140 lbft peak. I figure with 3.4+L of displacement it should still have 180+ lbft most of the rev range.

    From what I gather the 3500 heads/LIM/UIM are the best of the bunch in stock form.
    For ease of tunability etc it looks like I'd need a 3400 ECU/harness setup so it's possible I'd start with a 3400 block and do a 3500 top swap, if I can't get a full 3400 harness/ECU by itself.
    I would put a cable throttle on the 3500 UIM. For the most part I would like to keep the short block stock.

    This is not really a budget build so "while you're in there" part suggestions are appreciated.

    Question time, since intake and tune can be managed:

    1) I have plenty of room for long tube headers; has anybody tried the Pacesetter or ebay brand headers (that are marketed for a 2.8L) on a 3400/3500? The pipes are 1.5" OD which seems small for these engines. If nothing is available off the shelf I can make some myself.

    2) What camshaft/valvetrain setup will get me to 250hp+? I don't care for "lope" but will accept it if the cam specs otherwise require it. If I can get good lift/duration with a smooth exhaust sound that would be ideal.

    3) I have read that the stock valve springs are questionable in the 5000 rpm range; I have seen LS6 and Comp and other upgrade springs available, but is there anything in the engine design (oiling system is my primary concern) that would keep the engine from going to 6500-7000 rpm to take advantage of a bigger cam and the head flow?

    4) Emissions are not required (Tennessee Antique Plates) so EGR would be removed unless the ECU absolutely required it. Fuel efficiency is not a concern either so no need for an "MPG cam", this is not a daily driver.

    So, with this in mind, could someone recommend me a cam/springs/etc package? Will stock lifters handle some more lift/duration or can you suggest an upgrade? I am OK with custom pushrods if the stock ones won't cut it with the bigger cam.

    I realize my goals would be a ton easier to achieve by starting with an LZ9 but I would need to find the cam bearing spacers or have a suitable cam made to make that work at all, if there are leads on that I would appreciate it!
    Last edited by v2rocket; 05-25-2020, 10:04 PM.

  • #2
    so, a stock LZ9 without a cam is pretty much there already, couple that with longtube headers and a good tune and you're probably already past your current goals.

    you're going to need a pretty decent cam to meet those goals N/A, Superdave put down 260 WHP in a Camaro with an automatic, his build involved ported heads, LIM, a big cam and a custom ITB setup on top of a stock LIM. IIRC, the car actually went faster when he put a ported LX9 plenum back on it after dealing with tuning issues.

    As far as headers go, I wouldn't go any smaller then 1.625" (1-5/8") unless you do a stepped long tube setup. I drew up flanges a while ago, and I have intentions of editing the drawings for different primary tube diameters eventually, but probably not any time soon. if you want to check out the flanges, the drawing is available for download here:

    you can download the file and send it to a laser cutter and they will cut the flanges, I used OSHcut, and I think they ended up about $120 for a single set in 1/2" 304SS, IIRC, 3/8" ran about $100 a set.

    FWIW, the LX9 engine uses the same crank reluctor as a LS1 V8 and is supported by megasquirt. the later VVT engines like the LZ9 use a 60-2 wheel which is also compatible with MS. you can run an LZ9 as is on a MS3 with a DBWX2 controller to control the DBW throttle. Either way, using MS will give you the most flexible tuning solution.

    The big problem right now, is that there aren't any cams available new, I'm not sure if this is a temporary problem, or a long term thing yet. I hope it temporary because I'm not done with these little engines yet.
    Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us.

    I get bummed out every time I type "titties" in the search bar and nothing pops up....

    Built not bought, because bolt-ons don't...


    • #3
      Thanks for the reply.
      I see on the Wot-tech site that Comp is out of cores; do they start with new blanks or are they regrinding stock cams?
      Could an LNJ (Equinox/Torrent 3.4L) cam be reground to a hotter spec? Those have the same bearing size as the LZ4/9 engines and I saw at least one LNJ at my local pick and pull last week.
      Unrelated to cams and power, I'm trying to wrap my head around coolant flow in these engines. The LZ4/9 "u-flow" seems like most conventional engines; water pump pushes coolant through block to the back, then up to cylinder heads, and forwards to upper rad hose outlet. This matches how a 60V6 RWD or LIM-flipped FWD would flow.

      However, in a stock, FWD engine with the upper hose at the back, are both the block and heads flowing "front to back"? There are lots of little holes in the head gaskets to allow coolant to go up from the cylinders into the head, is that all the coolant flow the heads get? If it works it works, just curious if you could confirm.
      Last edited by v2rocket; 05-26-2020, 06:29 AM.


      • #4
        Comp gets the cams with a rough grind, so not a true custom blank (and also not the cost of a full roller blank either). You could grind a solid core 3400 cam but it costs more to do that rather than wait for Comp to get the core back in stock. They were on order since Feb and as of last week its Mid/Late June. Stock are all hollow cams with pressed on lobes. You can have those ground but only mild and it isn't something I would recommend. Can't help you with the coolant flow as I haven't given it any thought and 2:30 am isn't when I plan on starting


        • #5
          Got it.

          I've looked over your cam offerings and saw the Dynomation/Desktop Dyno simulation cam comparison on the 3400.
          Looking at the numbers and the simulated graphs I'm of course tempted to go all the way to the full Race cam as the graph doesn't suggest any real loss of power at the low end.

          Would any of your drop-in springs be compatible with that cam? Would standard pushrods suffice or does that cam require a different length?

          Secondary question, as I waffle back and forth between LX9 and LZ4/9 (the head design and displacement just keeps bringing me back)...will the late LA1/LX9 camshaft position sensor physically fit in an LZ4/LZ9 engine? Looking at photos they appear to be in nearly the same place, but most of the successful LZ4/9 swaps I come across on the web run the OBD1 ECU so they don't even need the cam sensor. I am thinking that an LZ4/9 might be able to run on an LA1 ECU when fitted with the LA1 24x crank balancer, a 7x crank trigger wheel, cam bearing spacers and an LA1 type cam, the LA1 cam sensor, and of course an appropriate tune - am I on the right track here?
          Last edited by v2rocket; 05-28-2020, 09:23 AM.


          • #6
            I typically cut the spring seats and increase the install height to use the 26918 springs, but customers have ran the 26986 spring that drops in and has plenty of clearance before coilbind. Longer pushrods will most likely be necessary unless you machine the block and heads enough to compensate. Wouldn't expect stock pushrods to work otherwise.


            • #7
              I mentioned this in the other thread, but what do you think of having cams for the LZ4/9 made by taking a 3x00 hot cam and welding up/grinding the journals to size? IIRC it's about a 4mm difference in OD which should be doable by anybody who does crankshaft grinding, as long as the cam material is easily weldable.

              That way they'd be the right size/clearance without needing a bearing spacer.


              • #8
                What would that cost?


                • #9
                  Probably depends how many cams can be done in a batch. Offset grinding a single 4 or 8-cyl crankshaft 1/4" is around $500 from most places I've checked with in the past.
                  More cams would mean less of a setup fee and cams just have to be "round" rather than turning one circle into a smaller offset circle.

                  Though it'd be even easier if the Comp (or others) rough blanks could be ordered with oversize journals.


                  • #10
                    In a batch? How many 3900s are you going to build?


                    • #11
                      zero to one, lol. Depends if a solution exists for a hot camshaft and a cam sensor to run on a tuned LA1 ECU.

                      I was asking more hypothetically in case there's other people who were on the fence about trying out an LZ4/9 but can't find the cam bearing spacers. Though I realize I'm a few years late to this party.
                      Last edited by v2rocket; 05-29-2020, 04:25 PM.


                      • #12
                        I am having them made once the specs are finalized. First set was a little too loose, so I am testing 2 more to verify the crush diameter once installed. This is a 3400/3500 discussion though so...not really important for a 250 hp 3400.


                        • #13
                          Let me start over...

                          I am looking at putting a 60V6 into my old car. As I see things the easiest/best ECU to use would be from a 3400 LA1, since it is widely available and easily tuned.

                          I want at least 250 hp so I am looking at putting a hot 3x00 cam in one of the following:

                          A) 3400 with 3500 top end
                          B) full 3500
                          C) LZ4/9 (with bearing spacers, and if the LA1 ECU/cam sensor could be made to work)


                          The LZ4/9 would be the most ideal because of the great head flow and potential added displacement.
                          But if it can't be made to work with the LA1 ECU, then one of the older designs will have to suffice.
                          However it sounds like 250hp isn't that hard to find in a 3500 with the right cam and exhaust, is that your experience?
                          Last edited by v2rocket; 05-29-2020, 05:56 PM.


                          • #14
                            As suggested above, going with an aftermarket ECU, like a Megasquirt opens up much more possibility for tuning and (later) upgrades.

                            The cam sensor would only be needed for SFI/sequential ignition, or if you run an OEM ECU that requires it. I'll hopefully be able to look at getting a cam sensor to work with a 3400 style cam in the stock location in an LZ9 soon. ARP fasteners are ordered, just waiting on them, so that I can start putting my bottom end together.

                            I think your goals are achievable, I just don't know anyone that's actually done it. Most end up putting turbos on these engines for the 350+ HP level. A good cam, good headers and exhaust and a good tune I'm sure will add the 50 or so HP that you're looking for. I would go with the full 3500 (LX9) at minimum. There's zero benefit to using the 3400 bottom end with the LX9 top end, when you can just use the LX9 bottom end.

                            Obviously starting with the LZ9 would be the easy way to get to your power goals, since it starts with 240 HP, and that's in restricted SAE trim, meaning that simply adding headers and a better way to get air to the throttle body will IMO easily add the 10 HP minimum you'd be after. I have toyed with the idea of using a stock LZ9, with a Megasquirt in one of my vehicles, which will be a daily driver again, but I have other plans there. I may still end up with a stock LZ9 running of a Megasquirt anyway, just because. The Megasquirt is capable of controlling the VVT function. It would be interesting to see what kind of power curve could be made utilizing the VVT with custom tuning, and maybe a turbo...

                            The cooling system works like any other engine, it just exits at the rear of the engine. The flow of coolant just flows from the front of the engine to rear, making one pass through the engine, not two. If you flip the intake so tha tthe thermostat housing is then at the front of the engine then you get the double pass through the engine (through the block, then turn and back through the heads). Both ways work.

                            What are you putting this in? I have an LX9 (with an LA1 UIM to make the swap simple when I did it, I had 28 days to get the swap done...) in my 1973 Datsun 240Z currently and will be replacing it with the LZ9 I'm building, the LX9 will then move to my 1985 GMC Jimmy (S15). I ran the LX9 off an OBD1 GM ECM and have since moved to a Megasquirt MS2 and then MS3X.

                            James: 1985 GMC Jimmy, 3.2L turbocharged, intercooled hybrid 13.873 @ 99.08 218HP & 270FT/lbs @ the wheels
                            The Daily: 2000 GMC Yukon
                            1973 Datsun 240Z: Turbo intercooled LX9, running on '7749 with $59 and DIS. 12.71 @ 115

                            "If you're not living on the edge, You're taking up too much space."

                            Still waiting for the 1st or second Ostrich I was promised, from Paul.


                            • #15
                              Thanks for the post.
                              Running coolant one-directional is alien to me - everything I've ever dealt with had the double-pass/U-flow; block first, then up to heads at rear, exit heads at front and back to radiator. But if it works it works.

                              I am looking at putting this into a Porsche 944 I've owned for 15 years; due to age and market attrition, parts are getting horrifically expensive, the supply of good used engines is running out and the blocks most often cannot be re-used unless you can find one of maybe 10 shops nationwide with the equipment and experience to properly refinish the Alusil bores (or just install sleeves). A set of rod+main bearings will cost you $250+ and there's only 1 manufacturer making them with not-great QC. A hot camshaft is $600 minimum and a set of 8 new lifters is $2400.

                              GM stuff is so unbelievably inexpensive by comparison that it's a really strong draw to swap and go. 250-300hp is plenty in this kind of car, your 240Z is similar design/weight so you know what I mean.

                              There are commercially-available (and expensive) kits to LS-swap these cars but they have a lot of fitment issues and "extra needed stuff" that the kits don't tell you about; and I just don't really dig the cross-plane V8 sound coming from that body shape.

                              I actually do have an aftermarket ECU (VEMS) on my 944's engine currently and I could probably adapt that to run a 60V6; but in general OEM stuff is higher quality, much easier to find spares of, and just better figured out than even a great standalone unless you have a ton of time to DIY tuning or pay someone to tune it for you. I figure with 15 years of the LX9 somebody has to have put headers and a hot cam into one of these and tuned it; that's why I started this post asking for a "recipe". Despite lots of reading the past 3 weeks on all the various forums there's little in the way of actual results (minus cars with turbos and sometimes 1/4 ET's).

                              Currently my 944 has a 2.9L stroker engine with 12.5 compression, E85 fueling, hot cam, and it's about 210hp. Getting more power from a cheaper, newer, mainstream engine on regular gasoline sounds pretty good to me.
                              Last edited by v2rocket; 05-30-2020, 10:44 AM.