matt_lamb_160

Re-ran some numbers and you are close to wanting 1 3/4" primarys. Two options both are 6-2-1 configuration, the other configuration doesn't change much (not sure what the support for the 6-3-1 is based on really). For both options the tail pipe can split into a twin system after the collector. As Ando said push the mufflers back as far as possible. Both are for peak HP at 6,500 rpm. If you think it is higher you can shorten the primary and secondary lengths a bit. With your big cam it is boarder line whether you should use baffle or merge type collectors (I would go for merge purely based on what I have read) for between your primaries and secondaries. If you use merge type aim for a 10deg tapper. Don't stress about the lengths too much for the primaries and secondaries but they should be a pretty good target. Option 1 Peak Torque Under 4,500rpm: Primary Pipes: 1 5/8", 25" long Secondary Pipes: 2 1/4", 12" long Collector: Type Venturi merge, Min Diameter 2 3/4", Nozzle length (tapper from secondaries) 5" (or ~10deg taper), Diffuser (Min Diameter to Tail Pipe) length 2.7" (or ~8deg taper) Tail Pipe/Collector Outlet Dia: 3.5" (could get away with 3 1/4" but going bigger with the correct collector costs nothing, if you choose to not use 3.5" it changes your collector diffuser length only) Option 2: Peak Torque at or over 4,500rpm: Primary Pipes: 1 3/4", 25" long Secondary Pipes: 2 3/8", 12.5" long Collector: Type Venturi merge, Min Diameter 2 7/8", Nozzle length (tapper from secondaries) 5.3" (or ~10deg taper), Diffuser (Min Diameter to Tail Pipe) length 2.25" (or ~8deg taper) Tail Pipe/Collector Outlet Dia: 3.5" This is my own approach based mainly on my understanding of acoustic tuning, what I have read and dyno. comparisons of others (I have not tested it myself as it cost $$$). I have PipeMax, but I do not use it. Interestingly Clevo’s primary diameter (most important in my opinion) and total extractor length are about the same as mine (it is the combined length that you tune for). PipeMax seems to use a 50-50 split whereas I split my primary and secondary lengths to target two octaves, I doubt you would notice the difference but I think the 50-50 split is odd.

Fair enough, not super sensitive anyway.

Need cam timing if you want length estimates (for what they are worth, diameters are more important).

Among others. What's your duration at 50thou?

What is your best guess (or target) of your peak HP, peak HP rpm, peak torque rpm? When does your exhaust valve open (deg BBDC)? Just guessing some numbers I think you need 1 5/8" primaries, 2 1/4" secondaries and 3.5" exhaust (after around 350HP a 3" exhaust is going to start to cost you). I will try (time permitting) to come up with more info later.

Vents sound good. They XE will attract more attention though.

I get your frustrations mate. Nothing worse than no it alls that really no nothing and not being able to get work done. Possibly the two things I hate the most. Plus, people need to pay. What is $50 really? I hope things pick up (they will, it is just a matter of time). People are always afraid to try new people. Perhaps you could get some of your final work flow tested independently? Might give people more confidence? Before and after engine dyno results? Build an 11sec Cortina with you business name on the side, haha. I am not sure, all the quick ways to build a reputation seem to cost $$$.

Low mount log manifold, haha.

Hmm. He said "my head". And I think "free flow" means a free look at Glen's work (R and D) which everyone else needs to pay for (buy a head). You did say you were keen to have a look and take some measurements (sounds kind of like a privilege). It is also a great chance for you to compare your head with what many people once thought to be the best. I am certainly interested in the comparison once you finish your head. Xrglen's name seems to blow innocent statements out of proportion, he must have really burnt some people.

The M112 will be great. Keep us in the loop.

Thom's advice is pretty good I think. Our OHS guys tell you no gloves for angle grinders but I just read SafeWork's (SA) guide for angle grinders and it says "Well-fitted gloves that allow a good grip of the tool". Gloves are a definite no no for bench grinders.

No worries Ando, Just chasing alternatives incase yours are a different dish,

Hi all, I have been trying to buy 20-22cc pistons in std. bore to suit crossflow but cannot get any. Have tried Precision International but they say they are not in stock anymore. Seems to be the same for 22cc ACL pistons Any ideas? Regards, Matthew

Yep, no worries.

Yep, no worries.

Wow, makes the old manfold expensive. Would like to see flow figures for the new manifold.

Exhaust to inlet ratios should never go below 60%, high ratios (above 80%) are not a concern so long as you are not giving up inlet flow to improve the exhaust. There is a heap of stuff in technical papers/books that came mostly out of MIT back in the day (Charles Taylor mostly) and have since been supported by people like Vizard and Bell. I would not be worried about low lift ratios of 85% (not that this will be an issue in your case) and would be trying to make sure I had at least 70% most of the time. I would consider the ideal 75% as an average value over the whole lift cycle which can be altered by the cam and/or the head. In your application you need to analyse the ratio with the inlet manifold on and you will need to make the assumption that, on the exhaust side, the head is the most restrictive item. Then make sure you don't get less than 70%. Chances are the stock exhaust valve size will be ok. Also the point you make about the higher lift lobe and fat part of the cam is exactly what I was trying to say and is why I recommended up to 0.55" lift.

I like that you have to work with a restriction, means you need to do it right. Your head achieves the manifold flow at less than 0.35" lift. In lift versus flow terms you don't really need more than 0.45"-0.5" lift. But then how do you get the duration you need and a fast ramp rate if you have such low lift? I would be aiming for 0.5"-0.55" lift with as flat a nose as possible (but this would require a helpful cam grinder). Running more lift will give the same flow but will require the engine to do more work (as Ando said). I would also be running wide-ish lobe separation (110 or so deg.) to help with the restrictive intake. The head's ports are better than they need to be, but because the cross-section has been maintained there will be no negative effects. The low lift mods are all that was really required, but this head is a great all rounder and will work with much better intakes as mentioned above. We need square cam lobes and some magic way of keeping the lifters on them, haha.

Internal seal is the worst part. They can be hard to get out of the timing case even once it is off as well,

No way it can groove the crank, the balancer maybe but not the crank. They are trying to rip you. Not that hard to do, but takes a while. If you do it buy a puller to get the harmonic balancer off before you start. Talk to your neighbour and see what he says, if he's not keen you have to take it somewhere or put up with the drip. If it is not using a noticeable amount of oil I wouldn't be too worried about it.

Nice work mate. Thanks for the pics.

Thanks mate, agreed extra flanges are asking for leaks. Looking at making a manifold (low mount high gate) now or getting a good cast log one. KLR250's old low mount mani had the wastegate between number 5 and 6. Mine will be in the centre but it just shows what can 'work' (on logs at least).

Ok, fair enough. Sheet metal is nasty.

I wouldn't be wearing gloves when grinding, or cutting if it is an angle grider. Can be nasty. I am new fan of saftey goggles, even just working under my dirt riden Falcon they are good.

That's what I thought, but could not prove. Basically the extra port work is only required if you have over 0.55" lift. Agree on the chamber work, it has made an even bigger difference than I thought it would and is important for any engine.