wanted 505 extractors
need a set to suit 505 sli can any one help or do you know whre i can get them
thanks
john
need a set to suit 505 sli can any one help or do you know whre i can get them
thanks
john
<font face="Verdana, Arial" size="2">Originally posted by John black:
need a set to suit 505 sli can any one help or do you know whre i can get them
thanks
john
<font face="Verdana, Arial" size="2">Originally posted by Chipper:
I have heard that a set of extractors would be no better than the original manifold.
I was told that you continue the twin pipes from the manifold down 750 mm to a collector and this gives the same extraction effect.
Seems to be a pattern with the Pugs, as thats the same thing I was told about the 205 exhaust manifold, after I put on the extractors
Seemed to make my engine feel happier to spin out to the higher revs, but didnt give any real increase in "power" as such...
Sounds good tho...
Chipper
<font face="Verdana, Arial" size="2">Originally posted by davemcbean:
Generally, the longer the cam timing, or the larger the cylinder capacity, the longer the pipes have to be before meeting at the collector.
The standard 504 manifold and system can be a little restrictive when larger duration cams, etc are used. When I modified my 504 engine with 266 degree cam, slightly modified head and Weber carb, I found that the engine felt smoother than before up until 6800rpm when it felt like you were hitting a rev limiter, whereas in standard form 504s (the early ones with oil bath aircleaner) have no trouble reving up to 7000rpm and even beyond. Admittedly there is no gain in reving a 504 past 6000rpm, but it is an indication of breathing ability. Being very rigid motors with a good steel crank, they seem to be unbreakable unless they're low on oil or pinging.
I replaced the exhaust manifold with a non-tuned length, but free flowing 4 into 1 manifold joining into a 2.25" mandrel bent system with a tri-flow front muffler and log-leg rear resonator. After this the mid range and peak power and torque felt exactly the same as before, however the engine felt much more tractable below 2000rpm (it was already excellent in this respect) and it reved out to 7000rpm quite easily (athough with pushrod engines those revs are always noisy).
It sounds funny that the engine improved at both low and high rpm, but when you think about it it is not quite a silly as it sounds. When the manifold is tuned length, it is designed to give an advantages extraction effect (negative backpressure) at a certain rpm, but can have unfortunate shockwave effects at other rpm (increasing back pressure). When a manifold is just designed to be very free flowing but with no extraction effect at any rpm (like the old pre-WW2 racing cars) it tends not to have and negative effects at any rpm, but you don't have the advantage of an extraction effect at a particular rpm and so peak power and torque are not as high as a tuned manifold joined to the same exhaust system. The disadvantage of a system which just works on the free flow principal to reduce backpressure is that they can be very noisy.
If I had my time again, I would probably just use an early 505 manifold (possibly with a longer down pipe and large collector), a good quality large diameter tri-flow front muffler, and I would leave the rest of the system as per standard. I think this would give the best compromise between free flow, quietness and cost.
Dave