HUNTD Posted January 4, 2009 Share Posted January 4, 2009 Is your iron head or steel???? Don't you mean........ Is your head cast iron or aluminium? You are correct Quote Link to comment Share on other sites More sharing options...
HUNTD Posted January 4, 2009 Share Posted January 4, 2009 and forced were talking about hilman hunter 1725 engines that have been around for many years there cast, alley wasnt even a thought on these engines hillman imps yes hunters no Sorry love he is correct. Either cast iron or aluminium head. If hes got the iron head its probably worth getting the carbs just for the manifold. they seem pretty uncommon. And skimming is worthwhile if using the aluminium head because they are so prone to heat/warpage. franklin cams have a good cam regrind available, cant remember specs of top of my head. kelford didnt really have an idea of what to do with hunter cam last time i contacted them You should do your exhaust first tho. makes heap of difference Quote Link to comment Share on other sites More sharing options...
forced Posted January 4, 2009 Share Posted January 4, 2009 Note ....... I said ......."skimming the head for more compression". There's nothing wrong with skimming a head to make it flat. To make any extra compression that's worthwhile, say bringing it up from maybe 8.5 to 9, or 9 to 9.5 involves taking a LOT off the head. Personally I've had 80 thou taken off iron heads and had ongoing problems which took me a while to figure out. All the strength in the head is in the deck, that's what supports the roof of the combustion chamber....... there's only a water jacket above it When the deck gets too thin the roof lifts slightly when the plug fires, unsealing the gasket. The gasket then reseals. Then lifts again next time the plug fires. But only under full load It's not very obvious on a N/A motor but the same thing will happen to ANY turbo motor when you use too much boost. Or on a N/A motor that was never intended for a turbo and had one added afterwards. The symptoms are blown (popped) radiator and heater hoses cracked top radiator tank leaking heater Leaking waterpump General overheating In a worst case situation you'll blow a hose clean off the motor........ that's after you've fixed all of the above. Modern Japper heads are better as the plug is in the centre and gives support but they will still fail too...... even stock. You must have seen cars at the drags getting 3/4 down the track then pop.... big cloud of steam.... hose blew off...... why?? The Hunter was one of the first to have an alloy head... they had both. The alloy heads were terrible for blowing gaskets.... I've had mates who've owned them. Even after skimming, the alloy heads would still blow gaskets....... of course each time they were skimmed the next gasket would blow a bit easier than the last one....... they got worse and worse. Not many left any more...... I wonder why? Steve Quote Link to comment Share on other sites More sharing options...
HUNTD Posted January 4, 2009 Share Posted January 4, 2009 Note ....... I said ......."skimming the head for more compression".There's nothing wrong with skimming a head to make it flat. To make any extra compression that's worthwhile, say bringing it up from maybe 8.5 to 9, or 9 to 9.5 involves taking a LOT off the head. Personally I've had 80 thou taken off iron heads and had ongoing problems which took me a while to figure out. Why suggest it then... why give advise that you know is going to fail and cause problems? What the hell does your speel have to do with "is it worth putting twin webbers on a hillman hunter?" Quote Link to comment Share on other sites More sharing options...
FLAWLES Posted January 4, 2009 Share Posted January 4, 2009 apologies steve lol had to be wrong sometime..............lol i can never prove huntd wrong no matter how hard i try hahahah you do bring some valid points tho Quote Link to comment Share on other sites More sharing options...
forced Posted January 4, 2009 Share Posted January 4, 2009 Once you open up the intake you can then, down the track, do a bit of port work, skim the head, do the cam and get some extractors and that should really get some nice gains for you. By then it might be worth looking towards those 45's but I'm sure the 40's won't be a huge restriction. I didn't suggest it, You just misunderstood.That's just the common "old school" way of making it go better. The "old school" skim the head part involves upping the CR....... not just making it flat. Very common 25 or so years ago. Steve Quote Link to comment Share on other sites More sharing options...
mikuni Posted January 5, 2009 Share Posted January 5, 2009 Cool, cheers for explaining the reasoning behind your statement so well. And makes sense too, several people I have talked to about skimming the head couldn't really explain the link between taking out 20 thou and the increase in CR. I'm sure there are certain heads that may allow a decent amount to be taken off but obviously not some. Quote Link to comment Share on other sites More sharing options...
Beaver Posted January 5, 2009 Author Share Posted January 5, 2009 i love it when threads explode like this haha whoe knew a hunter would be such a good discusion topic. nah but seriuosly thanks for all the advice. i think if he drops the price a bit ill go for it, and do the exhaust as well, although i think id have to get custom extracters because as HUNTD said, go fast bits for cast iron heads are bloody hard to find. and the exhaust man told me that its getting prety weak at one point where it used to swing around a bit, so ive got an excuse to replace it haha. keen for in front of rear wheel exit....... Quote Link to comment Share on other sites More sharing options...
RT Posted January 5, 2009 Share Posted January 5, 2009 twin side suckers always sound awesome even if they don't make you much more power.. but yeah, as others have said, if your engine isn't sucking any extra air over stock then it doesn't need any extra fuel. So without other mods the sidies won't do much. 40's should be fine for a 1725 the other thing I'd mention is the horrible tunability of twin side-draughts. My mates who used to have them always complained that they would go out of tune.. a lot.. hopeless for a daily driver. A friend who had twins on his fully worked 4K used to have to get them tuned every 3-4 months. So you'd be best to befriend some old mechanic who can tune twin carbs so learn to do it yourself but it's a bit of a black art as to getting twin carbs perfect. Quote Link to comment Share on other sites More sharing options...
FLAWLES Posted January 5, 2009 Share Posted January 5, 2009 shit yea agreed old work mate of mine use to be able to tune them with one of those doctor listing thingys and a lenght of string and a needle seen him do it on a eskie that one of the boys had how he done it only jebus knows but pple tend to command huge $$$ for tunning twin carbs, kind stupid really Quote Link to comment Share on other sites More sharing options...
forced Posted January 5, 2009 Share Posted January 5, 2009 There used to be a book availalable...... How to tune and modify weber carbys. Probably still is if you look hard enough. Got it sitting somewhere in my shed....... needed it when I had the 45DCOE on the turbo haha.but they're easy to tune so long as you can get the parts......even easier now with modern technology..... oxy sensors. Here you go Weber carburettors by John Passini published by speedsport motobooks 1973. It's a pommy book so must be good. No you can't have mine. The string and needle is used for setting up the linkage connecting the 2 together.... so they both start to open together. Steve Quote Link to comment Share on other sites More sharing options...
FLAWLES Posted January 5, 2009 Share Posted January 5, 2009 The string and needle is used for setting up the linkage connecting the 2 together.... so they both start to open together. Steve thats right i do remember him saying that. Quote Link to comment Share on other sites More sharing options...
Beaver Posted January 5, 2009 Author Share Posted January 5, 2009 ah well im always up for a challenge haha Quote Link to comment Share on other sites More sharing options...
RT Posted January 5, 2009 Share Posted January 5, 2009 ^ well then no probs. We don't want to bash twin carbs since this is oldschool afterall! (as long as when its coughing and farting on the way to work you can just simile and tell people that you have twin carbs then spend nights shaking forked sticks and peices of string to appease Venturii the Goddess of carburetors) Quote Link to comment Share on other sites More sharing options...
Beaver Posted January 5, 2009 Author Share Posted January 5, 2009 ^ well then no probs. We don't want to bash twin carbs since this is oldschool afterall!(as long as when its coughing and farting on the way to work you can just simile and tell people that you have twin carbs then spend nights shaking forked sticks and peices of string to appease Venturii the Goddess of carburetors) haha i love that statement Quote Link to comment Share on other sites More sharing options...
Jase Posted January 5, 2009 Share Posted January 5, 2009 you can also use clear tube a jam jar lid and some water to balance them, i had dellorto downdraughts but they were simple enough to balance off, once you know exactly which screw does what etc, i think they fell out of tune once for me and just a lil tweak and read the spark plug on the side of the road and they were fine Quote Link to comment Share on other sites More sharing options...
Beaver Posted January 5, 2009 Author Share Posted January 5, 2009 well my mountain bikes up for sale so if that sells ill buy them haha. what should i expect to be paying for a pair of good condition, correctly jetted, complete with all linkages 40 DCOE webers? they guy wants 550 including the manifold for the cast iron head (which is dam hard to find). is that a fair price? or should i just grab the manifold while i can and then keep an eye out for a cheaper pair (he wants 100 for the manifold)? its that fact that they are actulay set up for the hunter engine which attracts me to it, so they are prety much bolt on. Quote Link to comment Share on other sites More sharing options...
Dell'orto Posted January 5, 2009 Share Posted January 5, 2009 $550 is pretty damn sweet man, I'd go for it. Quote Link to comment Share on other sites More sharing options...
xsspeed Posted January 5, 2009 Share Posted January 5, 2009 550 incl manifold sounds like a deal to me Quote Link to comment Share on other sites More sharing options...
Beaver Posted January 5, 2009 Author Share Posted January 5, 2009 anyone want to buy a bike then? lol Quote Link to comment Share on other sites More sharing options...
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