I don't know for sure, but I suspect the stock plenums / throttle bodies are choke points once you upgrade the internals – so something would need to be done. I thought about adding a spacer between the plenum halves to increase the volume, or maybe a custom lower plenum to fit a larger throttle body. So the top and runners would look stock, with the improvements hidden in the lower half. That said, the look and sound of ITBs is hard to resist. It's not entirely cosmetic though. Throttle response is improved from having the throttle bodies close to the cylinder, and torque / HP can be tuned by experimenting with different trumpet lengths / shapes. A low-profile manifold would give plenty of space to experiment with the trumpet heights. That's the thing, it seems it's all in the execution. Do it right, and the car becomes highly desirable for finally realizing its potential and fixing shortcomings. Do it wrong, and you killed the value until someone can come along who can afford to "fix it" back to stock. As far as the engine goes, to me (admittedly, this is a moving target), my "perfect" BBi would have cams somewhere between the BB and infamous "P6" grind (hints of LM, but still streetable), compression to match, lighter rotating parts, modern sodium valves, and a beefed up transmission. Probably need to do something about those exhaust headers too (to Paul's point about 6 and 7 getting pinched). Nothing crazy, but combined with EFI and ITBs (with exhibition covers, of course), I'd be happy. Somewhere between 400 and 500 HP, but in a very balanced package. I rather like being able to floor it everywhere.
Between a more aggressive cam and ITBs I'd bet the sound would be even better. 12 little air filters singing a new tune?
One of the theories for stack length is 12" from the very top to the valve on an archaic engine like these if you insist on the visual. The 355 is pretty close to this when you take the plenum off and look inside, the best of both worlds in length and plenum volume at the time. The placement of the throttle plate is also important, the 355 ITB's dont have the plate close to the head. I would say they were trying to increase port volume below the plate and then the 360 takes that even further. It's interesting to see the running changes through the years and you can get an idea of what they were trying to do, mistakes made / lessons learned etc.
That's interesting. Didn't know that. I actually just started mocking this up the other day to see how feasible it actually would be. It's super early, but since you brought it up, figured I'd share. This is showing 9.25" from the bottom of the manifold flange to the top of the stack; which is about the same total height as the existing runners / plenum. This is using a custom stubby manifold that I'd need to make, Jenvey 48mm throttle bodies, and Jenvey 120mm stacks. I'd retain the Denso coils and injectors (albeit shifted up a little bit from the current location). This is by no means a final design, just something I threw together to see if it was even doable (particularly in terms of interference). Image Unavailable, Please Login
This 308 was very successful, Tony Worswicks car. Image Unavailable, Please Login Image Unavailable, Please Login
Im going ITB's on my 308 project also with EFI and will most likely have stacks through the rear lid.
Will you being a doing a build thread? Really curious to see how others go about this. Think you'll run Haltech?
Yes and Yes. I have already started a thread titled 77 308 freestyle build. I haven't said much about the engine yet because Im at the mock up stage and working on a few hurdles at the moment before I show what I have up my sleeve.
I have an outstanding intake manifold guy in New Zealand who 3d prints anything you or he can dream up, and he's reasonable. Does lots of Datsun stuff but also did a Ferrari slide throttle system for a flat 12.
Love this thread. Those stacks look like the biz as they say in the Uk. Coil on plugs and efi? Only question I have is a BBI lid is different to a BB lid and the covers in the lid a little more inboard as the plenums curve in, doss this fit? Also if one went for the Koning style intakes of the roof then one gains a little height for stacks. Personally while 12 may be the ideal height, compromising to 9.25 to fit and look right seems well worth it, and there is going to be so much gain anyway between the ITbs efi coils pistons and cams. Question for the best and brightest here. What do we think the safe redline is on these motors, what's the weak link, valves? The redline on the 365 dropped to the 512, was there a tuning or mechanical reason. BBLM dis they run a stock crank rods and valves, oil pump etc. Seems like with right cams etc and keeping a decent bottom end its somewhere into low to mid 7s. Not that one is lookign for revs for revs sake, but if there is a great powerband why cut it off. For reference, Paul what was the redline on you Koning.
On my BB I would never exceed the factory redline. 512M redline is 7500RPM. Ideally you would run a 512M crank and 360 rods in a BB. For example the 360 crank is 9lbs lighter than a stock 308 crank and the combined weight of 8 rods is a 4lb weight reduction. So 13lbs less rotating / reciprocating mass combination on an 8 cylinder and they can rev to 10K, tested to 10K apparently but limited to less in production. I would be happy with 9K on my V8. On a BB I would run a 512M crank that I offset grind to increase stroke, 360 rods, cams I would chose my own grind, ITB's with stacks, porting, larger lighter valves and reworked exhaust manifolds. Redline 8K.
Hard to resist the look and sound of ITBs. End result would be EFI + COP + ITB, along with upgraded internals. I plan on rescanning the engine now that I've removed all the CIS. I'll then overlay the new CAD stacks with the existing plenums to see how they line up, but my guess is that vertical stacks will fit under the cover, but they won't be centered like they are with the BB. I'd have to angle the stacks inward (not my preference), alter the engine cover (really not my preference), purchase a BB engine rear lid, or simply nix the exhibition cover so you can't actually see that the stacks aren't centered. I'd really like to have the look of Paul's '79 though. Need to think through this a bit more. There are even more exotic solutions that I may need to consider. I figure it'll look somewhere between a BB and a BBLM. The carbs on the BB are taller than Jenvey throttle bodies, so I am able to use longer trumpets while having a similar overall height. The LM's have stubby manifolds as I have designed, and their throttle bodies are similarly short like the Jenvey. The LM trumpets are especially tall though since they don't have the same height restriction. So yeah, I figure mine would be somewhere in-between. That sounds awesome.
IF the stacks just clear then the only way to hide the fact the stacks are off to the sides a lot is to have the BBLM scoops without the windows. Koenig added the windows to the BBLM scoops. My carb'd wall art lid vs and injected lid. The carbs are dead center in the openings which is about 10" from the buttress. Image Unavailable, Please Login Image Unavailable, Please Login
Looks like the offset is not that big. A slight can’t woukd work and prob look a little more stylish than the rigidity of straight out vertical. I guess there is a slight drawback to the angle could also be maybe adjusted with the manifold ?
Another question Whether stacks centered or not, where can one get the koning off the roof intakes Woukd they work on a bbi lid I guess given the slight centering differences some small mods may be needed. I’m not that bothered by the glass view, imo lifting the rear lid to expose the stacks would be a real wow.
is the light rotating mass of the crank not more relevant to throttle reponse than strength. I guess lighter rods helps with durability at revs. it’s my understanding that these cars and tr’s had really heavy flywheels to help with pulling away from a stoplight. another solution to replicate lowered crank mass is to just go with a much lighter flywheel. did that on my car it definitely made It more reactive and not really that different pulling away. I always thought those big valves would be the crimp at revs and or the reliability weak link, assuming oiling good? In any event 7500 sounds more than plenty. the rods are an interesting idea. seems like that really light mass is way more important on an 9k rpm flat plane v8 than on a naturally balanced 7k 180 12, personally am not a fan of stroking motors but I do hear that the way a 512 m 12 revs up is the biggest change to the tr and that’s mostly rotational mass.
Status update. TPS I received my yellow zinc steel bracket from SendCutSend, installed it, recalibrated the 0-100% throttle position, and I'm good to go. The string pot is surprisingly accurate, so I can set the idle control to turn off when the throttle is 0.1%. Still would prefer a more conventional TPS, but I think this will do. Knock sensors I added the last two sensors, which were the knock sensors (one for each bank). I used the two unused threaded holes protruding from the block. Admittedly, I have no idea what they are intended for, but they're in a nearly perfect position as they are close to the top of the cylinder. The first is near cylinder 2, and the other is near cylinder 11. Anyone know what they're for? Better not be important, because those spots are too good! With the sensors in place, I am able to measure the noise / knock of all 12 cylinders. I am using 7k as the primary frequency, and this seems to be accurate. The ECU will retard timing and add fuel in individual cylinders if the cylinder noise crosses the "knock threshold", so I can start to play with timing without worrying about detonation (or at least, chronic / sustained detonation). Fuel Pressure Regulator brackets I received my SendCutSend brackets, and ultimately went with aluminum as they seem the most discreet. Not sure I need to draw attention to pressure regulators. I may tweak this design one more time to angle the regulators so the bracket isn't "flat". Probably way past the point of over-thinking this. Image Unavailable, Please Login Image Unavailable, Please Login ECU bracket I've not mentioned it before, as this might be a somewhat controversial decision. In-short, I chose to mount the ECU where the old LH exhaust "silencer" was. In a perfect world, I would have mounted in the cabin with the relays and run the wire harness through the firewall, etc.. Believe me, I considered this and a number of other locations, but all things considered (accessibility, size, aesthetics, heat / moisture, my modest garage, scope creep, my self-imposed "stay in the engine bay" rule, and other unknowns), I decided this was the best option. Anyway, I removed the charcoal canister and used the existing wheel well bolts to mount the PDM on a 3D printed bracket (PET-CF). I may cover this with a lid / box, and reuse the charcoal canister's bracket to make it look more discreet. The ECU and coil igniters are mounted to an aluminum bracket I had made. Typically, I would design this in Fusion 360, then 3D print a few iterations before sending to SendCutSend. This part was too big for that, so I had to just go for it. Luckily, the 3D scans I did really helped and the bracket shown is my first attempt. Again, I stuck to my "nothing destructive" rule, so I didn't drill holes, cut metal, etc.. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login IAT (intake air temp) I started experimenting with where to pull cooler air. Figured a good place to start would be the silencer corners, but I'll also try a straight shot to where the stock intake boxes were, as well as jerry-rig something to pull air from the roof (a la Competizione / Koenig). In my test using the silencer corners, the temps were about 45 deg C after fully warmed up compared to 65 deg C when pulling air from the engine bay. This did seem to make a noticeable improvement on how happy the engine was. In-fact, I came near to triggering a knock event when running on 65 C air, so I don't think this is an optional exercise if I want to push the performance of the engine. Image Unavailable, Please Login Misc Mostly cleanup. Finally removed the Dinoplex. Started to wire up the tach. Unfortunately, the signal coming from the ECU doesn't "just work" with the tach. Need to look into this more. I think the MSD has a similar issue solved with their "tach adapter". I have no intention of driving around with a laptop in the passenger seat, so I'll need to get this working before I can call this phase "done". I'm definitely on the home stretch of this project, and I can take the car out for spirited drives despite not having a proper dyno tune. I have the rev limiter set to 6500 (just shy of the Dinoplex 6600 rev limit). I'm not really sure there's much benefit to be had above 6k, but the car feels responsive all the way up to 6k. I'm looking around for a good dyno rental in Miami; which will allow me to fine-tune the VE%, A/F and timing. I expect the next few updates are mostly cleanup / refinement, and tuning / dyno. I'll start pulling together the costs for anyone interested. Took the car for spin and lunch at The Biltmore Hotel near my home. FYI, best brunch in Miami. Image Unavailable, Please Login
Pertaining ITB locations, I overlayed a 3D scan of the engine bay prior to the EFI conversion (but with the air filters removed). It seems there wouldn't be any collision if using the larger Jenvey SF throttle bodies / trumpets with 48mm inlets / outlets. However, it might make more sense to go down to the smaller ST throttle body, which is a little more narrow, and little shorter, but still supports up to 45mm inlet / outlet. Considering that the manifold gasket is showing it's largest width is only 35mm, that still leaves plenty of room for porting. You can see from the overlays that the stacks come up to roughly the same height as the plenums, but they're offset from the center (the runner / plenum gasket). Based on Paul's measurements (thanks for that), and looking at pictures of BBi restorations with the intake covers removed, I think the stacks would fit under the covers, but they'd be offset and wouldn't look as nice as the carbs which are centered (if using a Koenig style window). My preference is not to angle the manifolds as I think the straight stacks on a flat 12 just feels right, but maybe I'll get over that. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
Id get over worrying about the windows, Imo the non window effect of lifting the clam and seeing the stacks is more wow, and ultimately you're behind the wheel so its all about how the car drives.
This might be my favorite internet thread of all time. One secondary consideration on removing the charcoal canister to make room for other components - on my other project car I was considering this but decided not to because some folks on that forum had reported gas fumes and fuel being pushed out of the tank in some circumstances. I'm looking for that reference because I can't recall the mechanics of how that happens. But if you smell gas fumes sometime, you might not know if it's because the tank is venting "normally" or you have a small leak. My plan is if I smell gas sometime to find and fix it immediately, so I'd be annoyed by false alarms from lack of a charcoal canister.
I think this is a fair concern. Even if venting normally, it can really stink up a garage. My thought was that if I wanted to capture the gas vapor, I would just do it differently than the stock (large) canister. For example, using a "Vapor Trapper". I wouldn't bother will trying to recycle the vapor back into the intake. It's also smaller, making it easier to tuck in somewhere convenient. They have a video where they discuss mounting positions and the scenario that could lead to liquid gas finding its way into the canister.
That's great. I'm glad this being received as a positive thing (or at least those who grossly disapprove are remaining silent).
Tweaked the design to use the Jenvey 35-45mm ST throttle bodies and 100mm trumpets. For the moment, I think this is the front-runner solution. ITBs come with some quirks, so I'll need to do some more research before I really dig into this. Image Unavailable, Please Login
