mk1-forum.net

Has anyone direct experience of swapping a 649 for an SW23, I'm told that they are a bit torquier and have a wider power band. Please note this is for a different engine than my other questions about cams. For a 1380 with a very good cylinder head st cut box etc. Possible sprint / hill climb/ Blyton use.

God why is burning petrol such an expensive habit lol!

my race car pulls far further with the sw23 than with the 649, that's certain

Thanks Rich. Does it waken up any sooner? To throw another spanner in the works an STR930 is supposed to be better as well.

A long duration cam will always be a "dog" until the air/fuel mixture gets moving ... at higher rpm. If you want something that "wakes up sooner" a long duration cam is not what you want. I would say about the longest duration for poking around town is about 270.

Yes Larry I totally understand, I want the power I have now, It's maybe what you could call "modern equivalent" syndrome. Why and how is it better?

saw reputed (not reported .. as i cannot confirm this) that the sw23 is the same profile as 649 but LSA different... i think closer, 100 instead of 103 so the mid range torque is more...

i thought STR930 was a clone of 648/649 so again a good cam
if the 649 was a good cam ( and all reports it is) then slightly wider torque band offered by a newer version would be a good thing....

thinking about it some more.... when did 1.5 or 1.6 rockers make their way onto racecars? .. i am wondering of the development timeline of this and the cam designs

... again from hearsay .... from a racer in the states who has run both the SW23 and the 649... both good , couldn't really say if one was better ... but runs high CR ( near 14)

Good point about the silly rockers.

I have a 1430 with 37/31 head with MASSIVE PORTS. Sleeved pushrods...it is extreme. It does run normal rockers though. Old race engine. The cam is totally unknown and is stamped "319". I assume it's something to do with a 319 duration somewhere....perhaps 319/319....

I was wondering if it was going to be a dog and wondered about fitting something a bit more tame. I have decided that I am going to stick with it and see how it goes.

If I change the cam/rockers, it's going to be a totally different engine.

I don't think anyone has answered the question re:- rocker ratios.

I suppose you could look at it differently and consider "curtain area" of a valve, this would give you a A/t graph which would then exclude rocker ratios. After all, ignoring the size of the ports and how good your head is, the A/t graph is the crux of the matter.