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MG Midget and Sprite General - another stupid dumb donky head question
| I just had an intresting converstation with cometic HG company.... So riddle me this... How the hell do you remove .035 off the head and loose metal off the head for the firing ring...after confusing the poor tech guy.... Im now more confused then ever, it you take more layers of metal off a domed shaped combustion chamber... Wouldnt you have more metal for the head gasket to ride on... Yeah, thats what the cometic tech guy thought also...makes scence to me... So so how in raindeer farts did my combustion chamber pockets get bigger and not smaller And here i was yesterday feeling good... Now im pissed as hell again Im guessing he shaved the pockets is all i can figure Gez Prop |
| Prop and the Blackhole Midget |
| Btw.... Exactly one year left till the end of humanity....i seriously cant wait... bring on the damnation Dec 21 2012 Prop |
| Prop and the Blackhole Midget |
| Oh.... It will cost about $150 to have a custom head gasket made What are your thoughts Prop |
| Prop and the Blackhole Midget |
| So If I get it correctly (you where rambling a bit) -the guy shaved off a lot -he changed the chamber shape -a special HG will cost less than half of a cylinder head |
| Onno K |
| If it was me and I wanted to keep the existing head, I would get someone trustworthy to look at it and give me an opinion before shelling out 150 bucks for a custom gasket. Your head shop wouldn't give me a terribly warm cozy feeling, and I guess it's a 150 bucks every time... |
| OrangeSpyderMan |
| How much bigger are the chambers? enough to have a reasonable CR even with the skim? There's such things as decompression plates (available for lowering the CR for supercharging) if you really wanted that head on, 2 x the gasket fun though. |
| Rob Armstrong |
| I thought that the problem with the fire rings was that they wouldn't locate onto the oversized bores, rather than the head chambers being too wide. Or was it both? Did the same machine shop that has messed up your head do your re-bores as well? Did you check the bore diameters - a number of people here thought they looked too large. At the moment you seem to have too many uncertain variables to make any sensible decisions. You need to do some accurate measuring and establish some facts to be able to plan your way out of the mess. |
| Guy |
| Never mind... Sorry guys, im stil the idiot It was the area for the intake valve...that little over hang is where the spill over takes place...when your that pissed off its amazing how you remember stuff Im thinking for The price tag of $150...im seriously thinking about having a custom made head gasket made and giving it a try Cometic.com Prop |
| Prop and the Blackhole Midget |
| If you buy a custom made gasket you will need to buy more than one anyway for when you take the head off next time. For that sort of money you can get a good new head off ebay: 160697868879 |
| Guy |
| Prop I'm struggling to work out what you are saying (although Onno has done his best to interpret) Can you post some pictures please...? JB |
| James B |
| Hey james, I wish i knew what i was talking about also....hahaha Which is actually a Fairly true statement, i got my head back from the shop today ....( finally ). And everything is so close, im not sure which direction to go As guy says... Its $150 each time the head comes off .... So im still leaning heavily towards building another head.....ill try to post some pics tomarrow evening of what i got Also .... I came up with the coolest way to locate the head gasket today...pure simple genius...it came to me while picking up the head, i cant belive i never saw the cooliness of it before, so ill post a pic of it...im sure you guys will be shocked by the concept. Needless to say the gasket dosnt move at all. Thanks guys Prop |
| Prop and the Blackhole Midget |
| Cool new way or not, I would certainly go with Guys' suggestion - that head that he has flagged up looks very fine, and certainly, the bloke has put some comments up on his description that he is going to have to stand by, so you'd know it's coming good and ready to use. Kinda sounds like he'd also do whatever work you need doing on it as well, so, I think it's worth having a chat with him about it. $150 each time sounds sooooooo much money, especially as you don't know the quality and lastability of it until AFTER you've paid for it ........ |
| rachmacb |
| I can guess Prop. You are going to drill and tap the head or the block, and screw the HG to the head or block, so that hg can move. Correct? :) |
| Lawrence Slater |
| There are actually lots of heads on ebay, USA, some more than that and quite a few cheaper ones. I just quickly picked out what looked to be a good one at about the same sort of price that Prop is considering spending on just a gasket! But Prop you really need to do some measurements on this engine, both on the cylinders and on the head. You cannot guess at the eventual compression ratio just by looking at the head! Unless he is only giving us part of the story I don't see how he can decide whether the head is usable with the cam and octane value of the fuel available. And then there may yet be other solutions if the CR does turn out to be too high. What about a bit of reshaping of the chambers to increase their volume? |
| Guy |
| Prop, I think we're all somewhat confused as to what issues you are trying to deal with here. I suspect it would be helpful if you could go back to basics and identify what you think the problems are and then those that know about these things may be able to give you some constructive advice. As I understand it, you finally got your rebuilt engine running but after a spirited drive your head gasket blew per the pictures a couple of weeks ago. After taking the head off it would appear that either the gasket itself failed or something was striking the fire ring. Since then you have taken the cylinder head back to the machine shop. Yes or no? If yes then why? If yes, did they then skim it too much or was that done prior to the engine rebuild and the gasket going? Is your theory that the overskim on the head was responsible for the blown gasket? If not, why have we moved on from the gasket failure to your cylinder head? I can't help thinking that you may be looking for too many problems here. Instead of rushing out to buy a custom made gasket why not buy a cheapy one (maybe not even a Payen) of the correct overbore size (check your bore sizes first per Guy)bolt on the cylinder head and give it another go. What is the worst that could happen? The gasket fails again but no significant money spent. |
| Matt1275Bucks |
| Sorry to correct you Matt but I want to make one thing clear. Head gaskets are not sold in overbore sizes!!!! You have one for the smallbore engines (948 1098) And one for the big bore engines (1275 1380) Anything else is very special and not needed on prop's engine |
| Onno K |
| Thanks Onno. Now I know! I wonder if Prop will listen? |
| Matt1275Bucks |
| That hope should been long gone. Prop goes through all the effort to make clear that he does not care how we respond |
| Onno K |
| Sorry guys I dont mean to be so obsitnate....its just ive repeated myself blue inthe face... There is nothing wrong with the bottom end, all to spec, compression ratio BEFORE THE IDOIT TRASHED the head is 9.3 Yes im ball parking the new compression ratio...using a cr calulator and taking the thickiness out of the head gasket...its not cosier, but gives me a rough idea as to what the new CR will be Hey recessed screws thur the head gasket...haha, not bad, but now way easier and simpler Btw....Happy Birthday to me !!!! Yep im now 47...but i feel 67 |
| Prop and the Blackhole Midget |
| "47...but i feel 67" lol. And we all feel 87, trying to keep up with the twists and turns in your never ending story Prop.:) |
| Lawrence Slater |
| Prop, Why did you get the head skimmed? I thought it was just going in to have the valves checked. How much did they take off? Have you been able to check the combustion chamber volume since it was skimmed? |
| Guy |
| A very Happy Birthday Prop! Measure your head - ball park doesn't get you anywhere - up to you whether you take advice, but you already know that assumptions can be the mother of all f**k ups... You could be scrapping a usable head... There are a number of people on this site who have built championship winning A series race engines (I'm one of them). You could take advantage of that experience or you can ignore it... Happy Christmas James |
| James Bilsland |
Props head - 3 pictures - to follow:
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| rachmacb |
2
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| rachmacb |
and 3
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| rachmacb |
| I should say that when I was building race engines a lot I have spent all day just measuring, calculating the CR and machining, for the very reason of not scrapping a very expensive race head by taking too much off it... |
| James Bilsland |
| Have the edges of those combustion chambers been chamfered to remove the sharp edge left from surfacing the head? |
| David Billington |
| I suspect the reason for the gasket going last time had something to do with the aluminium tape, which I can see no reason why you would need... I would run it like that (albeit I agree its close) so long as the CR is manageable... You can always sort out another head for next summer if it makes you nervous... |
| James Bilsland |
| Thanks rach for posting my pics Thats a new gasket...not compressed yet so you can see my issue...my new idea for locating the HG is roll pins placed in the intake valve water passageways... Is that an awsome idea or what...absolutly no movement in the gasket during instalation... I figure ill ream out the roll pins for extra water flow, but there split..so probably not nessary Anyway... I just got the head back last night, so now i can actually measure the cc volume on the cly head... As you can see the HG is new and not compressed yet, and its already spilling into the combustion chamber...and will only be worse when its compressed down If you remember the head suffered a blown HG due to Detonation... I had converted.back to points from a failing pertronix chip and didnt readjust the timing which was 26 degrees tbc So i took the head in as a percaustion and we discovered the valvea where leaking... The head was only supposed to be resurfaced .005 But i got into a pissing match with the machinest...paid the price wit alot of head surface removed....appeartly deep low spots... I and no one else saw them... So oh well Still the idea of roll pins in the water holes for the intake valves is a great idea to completely line up the head to the block and lock down the HG from ever moving...i dont know why i never saw it before...way better then wrapping aluminume tape around 2 cyl studs to keep the head and HG from moving around So now im down to figuring if i want to build another head or going the custom made HG direction....at least i got the holiday to give it more thought I figure while im in st louis, ill have a couple other mg guys look at it for there oppinion Thanks guys Prop |
| Prop and the Blackhole Midget |
| Prop. In all the years the A series engine has existed, don't you think it likely that somebody would have used spring pins on the head gasket location by now if it was needed? I think even if you ream them out they might resrict water flow. And worse, what if they drop through? Not convinced that is a really good idea. I'd be inclined to prove the amount of suspected movement in the hg, before I used an idea like that. |
| Lawrence Slater |
| What Lawrence said. Have you measured the studs and determined they are all the right diameter? I'd spend more time trying to figure out why the HG moves so much and fixing that rather than inventing new ways to hold it in place. Especially if at some point you spend 150 bucks on a HG. |
| OrangeSpyderMan |
| Prop, You have missed the point that we have been telling you - there are two stud holes in the gasket that are Smaller than the rest - why ? THEY line the gasket up to the block - not using water ways or what ever ! Have a good Xmas. R. |
| richard boobier |
| You guys are killing me... who remembers the amount of play i posted (many many many times ) between the stud and the hole in the Head gasket for the line up....seriously how long do we need to keep revisting this conversation...ive even posted photos of the gap ....i have no clue how to convey there is a gap on the center 2 studs between studs and the head gasket hole Yes... Its a 1/16 th of an inch.... Now go back ... Look at the photo above...look at the new head gasket laying over the pocket...and pleas tell me how you come up with 1/16th of an inch play thats acceptable....cause i dont see it... Im seeing .003 of an inch i can play with... Not 1/16Th....its not there, i wish to god it was, but its not And no there is mothing wrong with the head gasket,...ive measured 3, there is nothing wrong with the studs... There 3/8 inch diameter... Both arp and oem Bolt it down and go is not an option....this is why im struggling to find a way to locatethe head so there is no movememnt while installing and while its running I simple cant make it any more easy to understand, im clueless to help you understand the issue at hand...im so done repeating myself over and over ... Seriously what thread count are we at now..600, 700, 800....its a head gasket gentleman, not thermodynamics, and not even camshaft design Seriously.... Dont worry about it, ive got this figured out...im now able to manage fine on my own with this issue Thanks to all that have played This is now offically a dead issue.... Id say dead horse, but even that has been reincarnated to a huge hemroid fashioned squarly on my left cheek Prop |
| Prop and the Blackhole Midget |
| Which brings us back to the other option - get a new head. If all the tolerances aren't tight enough for the head you're using, use another one. I don't quite understand how your amazing new idea will locate it any better as any pins you'll be putting in will be smaller OD that the holes they go in, and therefore smaller OD than the corresponding gasket holes, ergo, there will be play. I'm sure you'll work it out, though. |
| OrangeSpyderMan |
| I'm not sure you are addressing the right problem Prop. Yep it would be better if there was more metal between the the bores. But you can see from one of your original pics, that the hg didn't really fail between the bores. It failed to the water jacket, and I don't think exactly why that happened has been established. You might just have been unlucky, it might have been over torqued, or it might have been a damaged hg. As for hg movement. Just to please everybody here, and set minds at rest. See it as educational, for those who doubt you. :). Could you please install all your studs, and place the hg in position on the block. Then take a series of pics showing the gaps around ALL the studs. Especially the ones that are designed to hold the hg in the correct location. They are as follows-----. From Guy in an earlier post. "The smaller diameter holes are one next to #1, on the pushrod side of the engine, and one between #3 and #4 on the spark plug side." Death by a thousand cuts Prop. lol.:) 
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| Lawrence Slater |
| Lawrence, do your two pics suggest these are different makes of gasket? eg water passage hole has no reinforcing ring in the top shot and black material continues to a rounded finish approaching the section between the two bores in the bottom shot. That is if I am reading these correctly. If so, is the failed gasket spec for this head or, if not, could that be where Prop's issues of movement originate? I know the B configuration by sight but over to you Midget experienced guys on this one. |
| Roger T |
| Roger, Just about all that can be said about this gasket problem has been said. Prop is insistent that we aren't reading his words and he definitely isn't seeing the advice offered. And besides, he has made it very clear that he doesn't want it discussed any further. He will sort out his own solution in his own style, as he usually does. That is what makes Prop so unique! |
| Guy |
| Roger, I'm not sure. But note, the gasket is viewed from the top, in the upper segment of the composite picture, and the bottom, in the lower segment. I think the fire rings are different from above and below. I don't have one handy to compare. Guy, I don't think Prop will mind. :) And besides it's interesting to discuss possibilities. I don't mind if Prop ignores advice. I ignore plenty myself. lol |
| Lawrence Slater |
| Looks to me like the morons used a much too large stone on regrinding the valve seat, and took out the side of the chamber. Should be easy to see in person. I have done that on purpose as a start in chamber mods, but you have to know how far to take it and dress the stone accordingly. They owe Prop a head and prep. FRM |
| FR Millmore |
| Guys FRM is on the money I reckon, but do you think that with a little, carefull relocation of the gasket slightly away from the pencil in the pic. towards the next cylinder and pinning the gasket in place he might just get away with it. I have had B series heads with tighter headgasket tolerances than that and have given excellent troublefree service---------- Cheers Willy |
| William Revit |
| The problem is that as the engine has been bored oversize, AND the head has also been excessively relieved around the large intake valve. It is difficult to tell if the head and block now still align accurately enough. Even if the gasket can be positioned precisely enough to suit either one or the other, all 3 components may well not match, and there is apparently little or no tolerance. I think Prop's best bet really is going to be to get a new, unmolested head and start again. |
| Guy |
| Assuming the CR calculation is favourable I'd be inclined to put it back together and see what happens - no tape, no roll pins (can you be sure that the water jacket holes are accurately aligned...?) and no specially made gasket. Head gaskets tend to blow next to the exhaust valves (that's where the heat is) not next to the inlet (lots of cool inlet mixture for every other revolution). maybe I'm wrong (difficult to be conclusive when you're only looking at pictures) but it would be the cheapest and quickest solution if it works - if not you're down the price of a head gasket... the key question (which, as often with Prop, gets lost somewhere) is what is the static CR on the engine? Only accurate measurement will tell.... Happy New Year all James |
| James Bilsland |
| Guys.... Thank you so much... You are getting it exactly, this has been the core of my dilima...just trying to figure out what to do next Guy said it best....linning up the 3 componets.... The head, the gasket, and the deck.....with those 3 componets at such tight clearance....how the heck do you get everything to line up for what has to the absolute match up...with no room for error. So the solution ive come up with out of several workable options is to START WITH A NEW HEAD and use a machinist that has exoeriance with MG heads.... Which i have found in st louis....i figure going with specialised experiance is going to be worth while in the long run over the hassle of what im sure will be several round trips of 400 miles AND... I lucked out the other day and found what appears to be a good buildable head that that we have barrtered on... The head for a wooden steering wheel that i have in reserve...and the head is close by... So no shipping fees on a heavey block of cast iron So im very happy with my decision...ill be able to get the new head rebuilt to the same spec as before...as all the parts will transfer over on to a meater head...so ill only have to source the hardened seats , brass bullet valve guilds, and an intake gasket... ...so hopefully by mid febuary... This eisode will be just a interesting memory Thanks guys Prop |
| Prop and the Blackhole Midget |
| Sorry james I just havent had time to remeasure the pocket with a burnette and do the calulations for a new current static CR...i simple used a on line CR cal and reduced the HG thickness by the amount the machinist removed to get a rough idea of the new current CR which was just over 11... Which lead to the option of a custom made Head gasket ....which was a great option i gave a long and serious tgought to But in the end, a new head just seemed to be the correct course of action for me... Im sure to someone else, salvaging the current head and forcing it to work would have been a good choice.... I guess thats why we have republicans and democrates...its the ch oices we make based on the known facts at the moment. Btw... I want to appologize for any arrogent behavoir on my part...i know you guys just where trying to help.... this issue really got my skin worn down to rather thin and just completely activate my fight vs flieght response... Which unfortantly most often is to fight Prop |
| Prop and the Blackhole Midget |
| Hey Prop, we all understand your frustration. BTW what was the make of the wooden steering wheel? |
| Dave O'Neill2 |
| Dave ... Thats one way of being diplomatic...im sure everyone was feeling the frustration...hahaha Tourist trophy ...moss Prop |
| Prop and the Blackhole Midget |
This thread was discussed between 21/12/2011 and 29/12/2011
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