Rob K Posted May 2, 2010 Share Posted May 2, 2010 Here's one for you; Bought a MkIV Spitfire which was sold to me as a 1300. I wanted to convert it to unleaded, so I bought a 1300 unleaded head. When I took the old one off it looked the same at first glance, but then I noticed that the new one was lower by about 3-4mm. When I checked the engine number, it turns out that the engine is actually a 1500. I called the engineering company who I bought the head off to ask whether it would be ok to fit. They assured me it would be fine, and would actually give me greater compression. I have now rebuilt the engine, and find that I cannot get any clearance between pushrod and rocker. Not surprising really if you think about it! My question is this; are you able to get shorter pushrods? i.e are 1300 pushrods shorter than 1500? Also, has anybody else got experience with swapping 1500 and 1300 heads?Any advice greatly appreciated! Thanks, Rob Link to comment Share on other sites More sharing options...
Gt6s Posted May 2, 2010 Share Posted May 2, 2010 Yes 1300 pushrods are shorter.Take the head off. The resulting compression of using a 1300 head on a 1500 will be far too high. You need a 1500 head. Link to comment Share on other sites More sharing options...
Rob K Posted May 2, 2010 Author Share Posted May 2, 2010 Thanks for the advice! What will happen if the compression is too high? Link to comment Share on other sites More sharing options...
Gt6s Posted May 2, 2010 Share Posted May 2, 2010 It will pink like a bastard and you will knock the bottom end out very quickley. Link to comment Share on other sites More sharing options...
Rob K Posted May 2, 2010 Author Share Posted May 2, 2010 Not good. Time to swap the head! Thanks for saving me from a disaster! Link to comment Share on other sites More sharing options...
rhodes Posted May 4, 2010 Share Posted May 4, 2010 Back in about 1982 I had misfiring on my 1500 and by the time I got someone to look at it, the head was kaput and was replaced by the local dealer with a second hand head. I took the car off the road in 1983 at 35000 miles and got it back on the road in 2003. However, during the refurb I took the head off and could not understand why the valves were bigger than for a 1500 until I realised that I had a 1300 head. The compression ratio is about 10.2:1 and it does pink slightly, but then it did so before the head change. It has now done 49000 miles and runs perfectly well.So, warnings of doom and gloom are quite wrong. Link to comment Share on other sites More sharing options...
Clive Posted May 4, 2010 Share Posted May 4, 2010 I am happy to be corrected here.....but here is my understandingI believe that a low compression 1300 head may be OK, especially if combined with a fast road camshaft.A high compression 1300 will probably give nearer 11:1, which will be destructive, especially with a std cam. Of course if the head has been skimmed that will increase CR even more...... Link to comment Share on other sites More sharing options...
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