ozconnection

Hypothetical: You need to cross a river to get to the other side. Would you cross at the widest part of that river or cross the river at the rapids where there is a comparatively little ground to travel? Same volume of water, yet vastly different effects. Do you see where I'm coming from? Is the effect of reducing the port size the same as the river scenario above? Can we tune the ports to match the power band? I think I know what to do, at least go so far as 'giving it a try' and see what happens. I will dyno the before and after and I'll try and post the results on here. Cheers.

Daeron, if the ports on an L20 engine aren't any larger than 30 mm's, its doubtful the manifold runners would be larger than the head ports! Remember, Tony said that there was a large step difference between the N42 head and the P65 manifold. My measurements of my unported N42 measure 34.7mm's. So putting that all together, I'd say the runner size of the P65 manifold would be no larger than 32mm's and probably closer to 30mm's. Did you ever measure the port runner size Tony? I have L20AET injectors here, but haven't ever bothered to have them flow tested to see how they compare to other injectors in the 6 cylinder family. But power figures for that engine were fairly close to an L28E so one could almost say they were the same items. Dunno for sure though. Tony?

Oh yes, the chamber is detonation resistant alright, it's from an ET engine! I should pop into the shed after dinner and take a few snaps of the chamber so you can see what I've got to deal with. Just the valves now, might be a bit small like you said, but a larger cam could fix that, couldn't it?

I remember reading an article years ago written by this one guy who did some investigation into the inner workings of such a setup. Shame I don't have that article to re-read. In a nutshell, it was a setup that was prone to problems based on the firing order and carb groupings. Su's apparently run the best when the pulses through the manifold are at even intervals. A manifold such as this doesn't allow for this beneficial effect to occur. And if I remember correctly it could work if the cylinders were grouped differently. Again, something to do with the number of degrees of crank rotation/firing order sequence.

I'd like to know how many N42/N42 L28's can break traction @2.5 K in second gear! Yes, yes, that's what I want as well. Imagine the response at 60mph in top. Just floor it! Wrooooah. And how long will the engine live for at those rpm's? A day or two past forever is my guess. I have seen those P65 intakes too Tony, again often snubbed because of their small runners and poor top end power potential. Shame really. In the right hands they are gold, as you will testify. (I know where I can get them...lardy da da! ) But more specifically, what about the L20 heads? Have you seen one of those on an L28 bottom end? And think about the compression hike, surely that's got to help with torque? I like what you said about the anti reversion step (big port/small runner scenario) but if one were to continue the runner diameter all the way to just behind the valve itself, would that be icing on the cake? A workshop near me has been working on headers. They want me to experiment with a 6 into 3 into 1 setup with 'tuned' pipes, the primaries are 1.375 inches in diameter or 35mm's. So in keeping with high velocity intakes, would there be a benefit in running with something like this?

510six, what's going on with that manifold? Cheers.

Thanks for that Mack. The site is a bit...well...OTT, but the info IS interesting and is in similar vein to what I'm proposing. I guess that the limiter with this one is finding small port heads for our engines in any volumes that would make experimentation feasable. In that sense, I guess I'm lucky! What about all the engine builders out there who have played with L series engines/heads for years......what say you??? Worth it or not? Don't be shy.

I want to know what you guys think of this idea. Firstly, whenever I read peoples comments on head port development, it's often suggested that making the ports a 'little larger' will help with power output. That's fine. I can understand the idea that larger ports have the potential to flow greater volumes of mixture into and out of the engine to produce more power. The idea I have, specifically for my application is to use an L28 shortblock and use a head with smaller than stock ports! If bigger ports make more power at the top end, then does it follow that smaller ports promote low engine speed torque? The standard intake port on my N42 head is 34.7mm's. The intake port on my 'other' head is 30.0mm's. That's quite a reduction in cross sectional area and port volume, but surely the airspeed would be great between 2000-4000 rpm's with a big fat torque curve between these rpm's. The valves are also smaller with the inlet being 38mm's and the exhaust being 33mm's! The inlet and exhaust valve would be completely unshrouded compared to larger valved unmodified heads. An option would be to run a bigger cam than stock....much bigger. The smaller ports could help with minimizing reversion at low rpm's, perhaps even to the point where the idle could be somewhat smoother than expected. Would this boost low speed manifold vacuum for better carb signal strength and better functionality for the power brake booster? And would the bigger cam help to restore the top end power shortage experienced by the smaller ports and valves? The power may not be spectacular but sufficient since it's low speed torque I'm after, not top end performance! The final aspect that would benefit this combination is a hike in compression, from 8.3 to a calculated 10.2 to 1. So, what do you all think? Are there any traps/pifalls/shortcomings that you can see? Please let me know you're thoughts. Cheers!

I wouldn't make the ports any larger. Good gas velocity through the ports is very important for a streeter. Sure, do the usual cleanup around the bowls etc but don't hog out the holes! Good luck.

Thank you.....

I have made several comments about this manifold, both here and on ClassicZcar. I like the Clifford manifold for the top end performance it can provide. There's a great big open plenum under the carb mounting area which is a good and bad thing. A good thing because it creates an air/fuel volume reservoir which reduces charge robbing to some degree. A bad thing because gas velocity falls flat on its face when it enteres the plenum and this corrupts the lovely air/fuel mix that has just found its way into the manifold. End result, low speed torque is down, top end is up, compared to the Arizona 4bbl manifold, for example. Depends on which carb you use too, but that's another story!

I posted in that thread. One of my N42's doesn't have injector ports either. See my pics! The only difference is my head came with the self oiler cam.

Your response off the line with the carb is governed by your accelerator pump and its calibration. Once you're over the initial hump of takeoff, your torque is clearly superior to FI because of your comment on how much power is made at 2K rpm!. Some tune time will improve your 'off the mark' acceleration. The Arizona manifold is designed as a 'dual plane' manifold and is responsible for your low down grunt. The stock EFI manifold isn't a dual plane, it acts like a single plane, which is why it doesn't have the low end of the Arizona. The interesting point is that even as a single plane manifold arrangement, it produces only a fraction more power than the Arizona combo. It would suggest to me that the EFI manifold is a compromise manifold, built to be reliable but not particularly spectacular in any one area except for providing the engine with a stable A/F mix and that is the responsibility of the ECU, not the manifold! The Arizona was built primarily with torque at low rpm's in mind and to nearly match the EFI at the top end is clear evidence of the ordinary nature of the EFI casting. I feel its those long and skinny runners on the EFI that hurt the top end IMO. Unfortunately, the Z chassis doesn't easily allow for goodies that I have added to my car. A 1 inch phenolic 4 hole spacer keeps the carb cooler and allows the mixture to mix better before the turn into the manifold. It's also a progressive diameter/volume change from venturi to spacer to manifold, hence not upsetting the air velocity greatly and keep the fuel in suspension better. The other point of interest is the height above the carb choke horn the top of the air filter top sits. I run a K&N 3 inch 14 inch diameter filter on top of my Holley. There is reasonable height above the horn as to not upset the flow of air into the carb mouth. If you don't need/want to rev your engine too high, keep the revs below 5.5K and enjoy the torque of the Arizona/carb combo. That's what I have on my engine because, like you, I enjoy the simplicity and responsiveness of that combination. BTW, that #34 secondary plate reads the same as a 52/53 Holley main jet.

Saw this cam and I thought I would post it. Reminded me of Babalouie's cam. I don't know what the letter 'F' means. I haven't seen that before.

When I mentioned 'specification', I was referring to the list of features offered by the manufacturer. It would include the processor and its speed of calculation, its inputs/outputs which effects its engine control capability, its interface type and installation process. Yes, there may be some overkill with the range of features supplied by some of the more expensive units out there but isn't it also true that those units offer a higher degree of tuneability and accuracy than some of the less expensive units? Ultimately, isn't that the feature you'd be buying the ECU for? I can't imagine running a highly stressed engine powerfully and reliably with a cheap, low resolution computer for too long. I agree with Tony that the money spent on such a unit should reflect its use. But if I'd spent tens of thousands on a stout engine, I would want, at least, the insurance offered to me by an advanced aftermarket ECU and its potential to tune the engine correctly without catastrophic (and expensive) failure. Just maybe I have it all wrong in my head (as usual...its a southern hemisphere thing!).

Yes, that makes sense. So it's the wide range of driving conditions encountered on the street that warrants the top end of ECU's, a race car runs at WOT most of the time and doesn't see stop/start city driving with the A/C on etc. Ok, fair enough. So would a Taurus have a higher specification ECU than a Formula One car because it encounters a greater diversity of driving conditions? Could you compete at that level with a MS, for example? Just curious?

Tony, when would suggest a top line Motec ECU is appropriate? Reading what you've said, one could get away with a fairly basic ECU for a race car because of the risk of crashing and the availability of spares? I would have thought that a highly specified track machine would warrant the finest components available, including ECU's and that it was important to carry some spares if the chance of breaking something was high. On the other hand, would you run a top of the line Motec on your daily driver? Does that kind of vehicle deserve that kind of ECU? What do you think?

I'm happy for you that you found increases in midrange torque. That really makes the car 'fun to drive' and really responsive to your right foot. Well done on your upgrade. Those torque curves look a little erratic IMO. I had graphs that looked like that when there was wheelspin on the chassis dyno. It's just so difficult to interpret curves that look like that and what to tune/correct with engine calibration to 'smooth' things out a little. Post some sounds from your tailpipe here so we can have a listen please. Better still, strap a small one to the arse of the car and take it for a spin so we can listen to it properly 'winding up under load' Cheers mate.

Oh, this one is for me. Nothing will give you better low down grunt than your stock cam. Perhaps the only exception is putting in a stock factory turbo grind because of the minimal overlap these thing have. One trick is to 'advance' your stock camshaft. I have done this and it will make an appreciable difference to the responsiveness of the engine. I know this is not 'precise' but I moved the cam to position 3 on the camshaft sprocket from an original position of one. This advances the cam about 8 crankshaft degrees, position 2, 4 degrees (depends on how old your timing chain is). I have an old L28 engine in my car and it has probably travelled over 200K kilometres. The compression test I did on it the other day showed an average figure of 174 PSI. I attribute some of this to the 'small' cam that I'm using in it....a stock L28S camshaft. (12,48,54,14 are the timing figures and about 0.43 valve lift. 8.3 comp ratio N42 head and bottom end). What else can I say. You don't have to do/spend virtually anything to get what you're looking for. Cheers.

I have found that a few times with reground cams. They're noisy!! As your youtube video is testament. Doughey throttle response too if you don't mind me saying. For that combo, theoretically, it should be very 'snappy' but sadly it isn't. But it soon will be, hey! I suspect it something to do with the ramps being poorly designed or the recommended lash being all wrong. JM might be able to do something with it...he loves 'em big and lumpy

Try putting the trans in 5th and chock the wheels with the hand brake on. Or you can use a long braker bar, lean it against a solid part of the car with a rag in between or on the road and bump your starter motor. I've tried both methods and they work as I didn't have an impact wrench at home at the time. Judging by that last lot of photos, that was a built engine alright! Yeah, so long as the compression figures are all about the same, I wouldnt worry too much about the bores. Good luck mate.

I use the L4n71b hydraulic trans behind my L28. It might be an old box but its pure and simple, with predictable gearchanges that can be firmed up with some simple tweaks. I have a high stall converter and an adjustable vacuum modulator valve too. There are parts around for these guys aplenty...you just have to ask the right people. Oh, these boxes were also put behind Mazda 626's and others if you need one. I like the hydraulic version as opposed to the computer controlled version because it's a simpler proposition all round IMO. (L4n71b Vs E4n71b)

I don't think it really matters Daeron. I had a factory L20AET that ran the 'Y70' head. That head had round export ports with liners AND it had a turbo manifold that was exactly like the one I had on my other L20 turbo engine which had a square exhaust port 'O5L' head. I don't see how it would matter much on their bigger brothers?

Chances are they're not stock retainers. I'd say that because your thicker lash pads needed taller shoulders on the retainer to stop the pads from being 'spat out' like 1fastz said earlier. Rip the head off and start fresh. You'll be able to finally see what that head is. We're all curious too. A P90...with N42 valves, that's a possibility! I wonder why the engine wasn't performing. Do you think it was the old cam?

Have you tried any thinner lash pads in your engine yet? And have you tried the rest of the valve train to see if the problem is with all the rockers? It goes back to an earlier question I asked, were all the old pads the same thickness for that old cam? It may have been a case that the valve seats were machined too deep by the machinist but a mock up with the old cam, rockers, valves and lash pads worked out ok with a suitable rocker arm wipe pattern and it was left at that, deemed acceptable. This, rather than valve seat recession is what I'm thinking. Trying to put in a new cam with less material ground off it manifests itself with the problems your having. Bite the bullet and take the head off OR put the old cam back in, build a new head on the bench and swap them in one go. Is it a stock head on there ie no porting etc as far as you know? That would make it a much easier (and less expensive) decision IMO. Good luck mate.