dave123456789 Posted June 5, 2012 Share Posted June 5, 2012 How do i fix this? its crap. im guessing flatspot is the carb needing a tune, have that sorted as putting a weber on but how to i stop the valves floating around at piss all rpm? on the cheap would be good. Quote Link to comment Share on other sites More sharing options...
johnnyfive Posted June 5, 2012 Share Posted June 5, 2012 Whats the car/motor? Quote Link to comment Share on other sites More sharing options...
durty Posted June 5, 2012 Share Posted June 5, 2012 sounds like a good condition small ford motor Quote Link to comment Share on other sites More sharing options...
Yowzer Posted June 5, 2012 Share Posted June 5, 2012 If your valves are bouncing that low in the rev range it probably means something is fucked. Are you sure it's valve bounce? Quote Link to comment Share on other sites More sharing options...
dave123456789 Posted June 5, 2012 Author Share Posted June 5, 2012 65 super minx. yea man sure its valve bounce use shift at it when i was a teenager. Quote Link to comment Share on other sites More sharing options...
Vintage Grumble Posted June 5, 2012 Share Posted June 5, 2012 How do you get valve bounce that low in the rpm's? Valve springs must be fucked? Quote Link to comment Share on other sites More sharing options...
Bombsquad Posted June 5, 2012 Share Posted June 5, 2012 would a 65 minx actually rev any higher than 4500?? i would have thought those symptoms would be about normal for a near 50 year old motor Quote Link to comment Share on other sites More sharing options...
dave123456789 Posted June 5, 2012 Author Share Posted June 5, 2012 would a 65 minx actually rev any higher than 4500?? i would have thought those symptoms would be about normal for a near 50 year old motor I would have thought so. Engine in car appears to be the original one as I have about 30+ years of receipts and none stat any engine works except a valve clean up that i can find.. I always suspected it was happening at low rpm so i put a old tacho on it to check. Will try a second tacho to double check accuracy. Quote Link to comment Share on other sites More sharing options...
Borgweiser Posted June 6, 2012 Share Posted June 6, 2012 definitely a case of soft valve spring/s. Check vacuum advance, most likely cause of flatspot, also if it's 1725 the Zenith 34IV is a shit of a carb and needs accurate float adjustment. Bin it, find a suitable weber Quote Link to comment Share on other sites More sharing options...
Bazz1600 Posted June 7, 2012 Share Posted June 7, 2012 do these run balance shafts? Quote Link to comment Share on other sites More sharing options...
Seedy Al Posted June 7, 2012 Share Posted June 7, 2012 Not a chance in hell Quote Link to comment Share on other sites More sharing options...
SP450andLE Posted June 7, 2012 Share Posted June 7, 2012 Also valve recession could be causing you some troubles, restricted gas flow from recessed valves could possibly cause a flat spot. When's the last time you tuned it? Quote Link to comment Share on other sites More sharing options...
KKtrips Posted June 7, 2012 Share Posted June 7, 2012 Valve float will be your issue - valve springs will have done the hard yards and have reached retirement age - get them retensioned or snaffle a set of newbies if you can.. Don't expect to get much change out of $2-300 either way - labour to change them not included.. Quote Link to comment Share on other sites More sharing options...
dave123456789 Posted June 9, 2012 Author Share Posted June 9, 2012 definitely a case of soft valve spring/s.Check vacuum advance, most likely cause of flatspot, also if it's 1725 the Zenith 34IV is a shit of a carb and needs accurate float adjustment. Bin it, find a suitable weber Sundays my only day off so am heading out to check vacuum advance right now. Its the 1600cc version using some a solex 33sei or something along those lines, have a weber on the way which should fix that up. Also valve recession could be causing you some troubles, restricted gas flow from recessed valves could possibly cause a flat spot.When's the last time you tuned it? Will have to dig out the receipts but im pretty sure the only valve work I found was them giving them a clean up, cant remember when tho will have a look. Tuning wise theres not much to do, set the timing, adjust valves and play with a screw to get it to idle nicer. All these I have done. Have never had engine apart and would rather not at this point. Valve float will be your issue - valve springs will have done the hard yards and have reached retirement age - get them retensioned or snaffle a set of newbies if you can..Don't expect to get much change out of $2-300 either way - labour to change them not included.. Time to keep my eyes open for a set of new valve springs, not in a major rush. Car is still very driveable Quote Link to comment Share on other sites More sharing options...
dave123456789 Posted June 10, 2012 Author Share Posted June 10, 2012 Vacuum advance is sweet can move it by sucking through the hose and it doesnt slowly spring back with the end blocked so I assume that means its all gravy? Oiled what needs to be oiled. The rotor was mega dirty on the contact part so gave that a clean up but that didnt do anything except let me idle a little lower without the car shaking to pieces. Quote Link to comment Share on other sites More sharing options...
Frosty Posted June 15, 2012 Share Posted June 15, 2012 Before you go spending mega bucks on a rebuilt head/ valve springs. Check, Compression, dry wet method, will tell you if the valves and rings are OK. Fuel pressure at load, may be the fuel pump not keeping up. Dwell angle, will give you a much clearer picture of the condition of the points and condenser. Main shaft wear in dissy and mechanical advance. Float level, I think others have talked about this. Coil and leads, Nice blue spark (yellow = poor spark) and leads should test at near 0 ohms for solid core and under 17,000 ohms for resistive core, don't mix the two. Air jets in carb, minor blockage can create a major issue as the revs go up. Valve clearance, must check as seat erosion can make this zero or less. In the OHC Ford engines this alone stops them from revving. If you have a poor idle with no other obvious problems this is the most likely suspect, Then run fuel additive or Kero (20mL per 20lt approx) in the fuel to slow the erosion. All these can effect mid and high end performance such as it is in a Minx. I say this because I owned a 1965 Minx that had over 300,000 miles on the original engine and it still went to 80+ mph without a splutter, read here valve springs unlikely to be the problem unless it has had a major overheat in it's history. Like most pre crossflow English engines of this era redline is around 5500rpm so don't expect to much more. Even the Rapier versions with the twin valve springs, dual carbs and a cam only had a 6200rpm redline. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.