Jump to content

matt_lamb_160

Members
 View Profile  See their activity

  • Content Count

    483

  • Joined

  • Last visited

Posts posted by matt_lamb_160

  2. Posted

    Yep. I have used that cam (208 deg one). Perfect FWY cam with 2.77 gears. I have used it with 3.27 gears as well and it works well. Goes to 4000rpm easily enough. You will have way more grunt below 2,200rpm with the EFI mani over the 4brl setup. 4brl is slightly better above 3000rpm. I have used both with this cam. You can go higher than 10:1 if you modify your ignition advance curve.

     

    The 225 Impco is a perfect match for the cam and either a B2 or a model L Impco will work.

    slydog reacted to this

  7. Posted

    For a cam I would go Camtech CT142-509 (especially if it is auto and 2.77). You CAN run std valve springs with this cam. You can dial it it but I'll bet you won't gain anything over just lining it up dot to dot (if the dots are out it won't be by much)

     

    I doubt it needs new cam bearings, I have seen way more engines fail with new cam bearings than old ones, so I say if it doesn't need them don't change them. But check them.

     

    Definitely want new rings and big end and main bearings though.

     

    Pity you can't use an EFI manifold, I have tried a bunch of different ones with LPG and the std banana EFI manifold beats them all for low end grunt. I would just look for a second hand Redline off eBay for what yoy are doing.

  9. Posted

    Those numbers are pretty good up until 0.5" lift and with a basic tidy up will be even better (compare the 0.35" lift with some others here). Value for money may be questionable, but don't be too disappointed Chris.

     

    Also remember that the cam should lift beyond the peak head flow figures (because you are not at max lift for long) otherwise your cam is too small.

     

    The step at the bottom may be fixed by making sure the manifold is all the way up when you bolt it on. I wouldn't be taking too much material from that area, you'll end up with massive ports for little gain.

     

    I am sure it will come out great.

     

    If you guys get 212@0.5" without a big cross-section and can maintain it to 0.6" it'll be a weapon.

  18. Posted

    And it is not because they have tried a 6-2-1 setup and it didn't work. My bet is if you added up all the fast 6s all over the world there would be more 6-2-1 setups. Both of the mentioned 6-3-1 setups were made by the same person.

     

    No bets for me on the test as I recon not everything else will be equal about the two sets. Still be good to see though.

  19. Posted

    PRO, in my opinion Pacemaker know very little about pipe sizing. The 1 5/8" primaries yet small exhaust outlet on their crossy extractors are a perfect example of what they know. Also for most road cars/cars revving less than 5,000 short primaries long secondaries are the go, but Sly's beast is a different animal.

     

    Sly, the ones I was going to get were HU252a, but yeah the number you gave look good if you want to go that way.

  20. Posted

    Pacemaker's R&D? They make pipes. They are great at what they do (fabricating extractors), but I wouldn't give them too much credit.

     

    "See how the secondaries stop short on the 4.0l set. I reckon that has more to do with ease of fitment up to the Cat convertor than actual exhaust design". This quote from Ando is spot on I recon.

     

    He is also correct about this "One area where pacemaker are well ahead of the others is the pipe over cone design". The cone over setup is about the extent of their "R&D" in my opinion.

     

    The ratio between primary and secondary pipe length is reasonably arbitrary as it will not change the "tuned" rpm of the extractors (neither will the total length), it will just "rock" the output about the tuned rpm created by the pipe sizes (I am not going to go into how, because it doesn't matter). Long primaries and short secondaries support the upper rpm for the tuned region (5,000+rpm in this instance). The 50-50 idea is ok as it is taking a middle of the road approach. But, I think people designing extractors for maximum effort engines that use primaries that are on the short side when compared to the secondaries do it for one of four reasons:

     

    1) They think the pipe diameters may be slightly to large (some could say this if Sly was to use 1 3/4" primaries as it is hard to pick between it and 1 5/8")

    2) It is easier to bend two pipes around things than six

    3) They are guessing because they saw someone else do it

    4) They don't care

     

    Stepped extractors would work for you Sly especially because you are right on the boundary between two pipe sizes. But, you need to make sure you do not bring the step in to early (based purely on what I have read/heard from professional engine builders, not my understanding).

     

    I think the best bet is to tell us what you have got to modify and make the best possible setup out of them. If you keep similar lengths you should be able to cut them up and get the bends copied in a more suitable pipe size (if need be).

     

    Or you could get these guys, http://www.hurricaneheaders.com.au/hurricane/index.htm, to bend you up some in one of their stock configurations but with your pipe sizes and you make/add your own final collector. I asked them about doing a set for me a few years ago (I ended up using a set of stock Perry extractors instead) and they were happy to do it for a reasonable cheap price ~$500 at the time I think.

  22. Posted

    The valve is not actually open longer in total, it just opens and closes at a faster rate. The cam type will not have much influence on the required primary pipe diameter which is set by the average mass flow rate/air velocity entering the exhaust. The same air is still pumped out, the better cam just makes it easier for the engine (lower average pressure drop across the head).

     

    The main effect the cam type will have is on the tunned length as the effective valve opening will occur sooner.

     

    Realistically speaking, because Sly will not use the power band below 4,000rpm and he will spend most of the time above 4,500rpm, the 1 3/4" pipe is probably pretty safe.

     

    Hopr that all worked, all typed on my phone.

  23. Posted

    Ok, wagoon that's fair.

     

    Clevo, if you are looking for pulse tunning you use a baffle collector between the primarys and secondaries which in effect creates a big step anyway as a result of the collector volume. Without the step up you do not have two seperate volumes to tune (also why I do not like the 50-50 split) and you could use a 6 into one setup instead. The step up is a part of how tri y setups work. The 6-3-1 setup could be better (I have not put too much thought into it), but the 6-2-1 is a long standing arrangement.

     

    Sly, if you do go 6-3-1 just watch your firing order and make sure the exhaust pulses entering each collector are evenly spaced.

    Clevo120Y reacted to this

  24. Posted

    The collector allows you to run larger diameter exhausts and is used for tunning purposes (which requires at least two pipes). Without the collector it is like having massively long secondaries, including the taper just makes them stepped secondaries.

     

    What are your 1 3/4" primaries based on??

  25. Posted

    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.

    slydog reacted to this
×