galant_gto Posted June 30, 2010 Share Posted June 30, 2010 I have a fairly good condition 4G52 in my 73 Galant GTO which i am looking at doing some work on. As far as I am aware it is the original engine which was the one before the Astron 80. The previous owner had done some work to the engine such as oversized pistons, lightened flywheel, balanced crank, ground cams, and extractors. I am looking at keeping this car fairly original so do not want to put a later model engine in (even though it would be the smartest idea) but want to get some reasonable power from this engine. Just wondering if anyone has any ideas where i can begin on an engine like this. I have been considering replacing the twin down draft carbs with a pair of side drafts... good start? Only thing is i know roughly how much parts will cost it is just the tuning of the carbs i have no idea about. So any information on increasing performance or the process of slamin twin side drafts on this engine would be much appreciated. Also if anyone knows anywhere i can source new/used/performance parts for this engine could you please let me know. After hours of web searching very little turns up. Quote Link to comment Share on other sites More sharing options...
fuel Posted June 30, 2010 Share Posted June 30, 2010 Unfortunately the Astron series isn't the best base to work with. But you can get them singing with a bit of work. Best thing to do is open up the breathing with some twin sidedrafts and a decent set of exhaust headers. Then perhaps a good port job finished off with some port matching. The cam profiles in them from factory are quite sedate so with a good aftermarket cam it would really open it up. The bottom ends are very heavy, almost agricultural. Getting the crank and flywheel lightened and balanced up would do wonders too. That's basically all you can really do before going really crazy with it. Quote Link to comment Share on other sites More sharing options...
Unclejake Posted June 30, 2010 Share Posted June 30, 2010 You should do all the things that have already been done Theoretically done of course Quote Link to comment Share on other sites More sharing options...
Spencer Posted June 30, 2010 Share Posted June 30, 2010 I would say raising the compression wouldn't hurt, I would say its asthmatic from factory and cant hurt with a cam. Coincidently a work mate has just bought a GTO with one of these engines, I've been meaning to point him here for advice Quote Link to comment Share on other sites More sharing options...
fuel Posted June 30, 2010 Share Posted June 30, 2010 You should do all the things that have already been done Theoretically done of course haha my bad, I thought it was another one of those posts from someone who had a bone stock one. Well in that case other than twin sidedrafts and some work to the head like oversized valves and port work there's not much else to be done. It would be sweet to know what pistons the previous owner rebuilt the engine with, whether they were just standard compression or higher compression. Quote Link to comment Share on other sites More sharing options...
Ogre Posted June 30, 2010 Share Posted June 30, 2010 Higher comp is always good on those engines.The 4g52 is better than the 4g54 IMO, rev alittle better but damn they are getting big and heavy compared to newer stuff. The engine seems to have the basic shit done.Any idea of the comp?I think they are 9.5:1 standard, so maybe alittle higher would be good.Get a long duration cam in there, like 290 degree or somthing.High lift dosnt seem to do as much in those engines.You can get sidedraft manifolds for them easy, and alot of guys run the factory sidedraft makunis (sp) or some 45 weber/dellortos are mean. Only guys that seem to work with them much anymore is ozz and a few in the US.Could run the blowthrough turbo that they ran in the sigmas in OZZ, they get ok power outa them. More info here: http://www.sigma-galant.com http://homepages.paradise.net.nz/mitsubishigto/ http://www.network54.com/Forum/133789 http://www.aussiemagna.com/ Handy link also: http://www.kempys.co.nz/mitslinks.htm Thats all i can think of right now.Have you cheaked out the build threads on here?Should chuck some pics and alittle info in there with your car so we can have a look Good luck and keep us posted man!! Quote Link to comment Share on other sites More sharing options...
galant_gto Posted June 30, 2010 Author Share Posted June 30, 2010 I will have a look this weekend at what has been done and the tests on the engine which have been carried out and see what has been done. Cheers for your posts so far everyone. Good to confirm how much of a tractor engine these things are and the rarity of parts haha. Quote Link to comment Share on other sites More sharing options...
dwlee Posted July 1, 2010 Share Posted July 1, 2010 The original pre-balanceshaft 4g52 i.e. dizzy driven off the crank, are quite a bit better than the later balanceshaft motors. However, they do take a bit of work to get the best out of them. To add to the list that Fuel has already given you is to install electronic ignition (either aftermarket or from a late 74 early 75 GTO) and possibly swapping in a 4g53 crank from a canter truck to get a longer stroke. One thing to note is that you can't use a later 4g54 crank due to different diameter main bearings (pre1978 4g5X 66mm versus later 4g5X 60mm). Quote Link to comment Share on other sites More sharing options...
Jif Posted July 5, 2010 Share Posted July 5, 2010 I got a celeste with this engine in it and I just stuck some twin carbs on it and now it missfires quite bad. What have I done wrong. Also how much can be taken off the fly wheel? Quote Link to comment Share on other sites More sharing options...
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