Exhaust stud snapped, tried all the usual heat plus gas penetrating lube mole grips didn’t work, welded a nut more heat and plus gas sheared off tried again sheared the remaining bit of stud off flat with the head. Plug welded a washer and nut also no movement So brought expensive Bosch stud bolt remover drilled the stud taped in the remover it bit well and screwed in fully to the stud I applied pressure to my socket it didn’t move the stud so more heat and penetrating spray applied more pressure and the head cracked below the stud and at the side. Have I messed up is the head ruined?
I'd try building up that bit of weld on the stud with more weld, highest power you dare, smallish bursts so it doesn't just destroy the weld build up, then try it with molegrips to and fro while it's still hot. Hopefully that application of heat might loosen it.
Not the best shot but you can see the crack at 6 o’clock below the drilled stud it’s also showing fine crack at 9 o’clock And part of Theseus still in I’m thinking drill it to 6.7mm and run a m8 1.25 tap down it What do you think? Im thinking how strong does it need to be to hold the heat riser Btw it’s a vintage speed exhaust
Hi Zed I did that first time round actually 3 times the stud just kept shearing you’d think with all that heat it would have shifted
Cracked I'd give up on it to be honest though I'd still persevere and try to get the stud out just for the experience and you never know, maybe you'd find someone who would weld it for you, but you'd need to take it off for that. There isn't so much meat around the studs as it looks like from end on. It's already M8 BTW.
Because the metal may actually be a fairly thin flange and what is locking the stud may actually be a fuzz of rust where the stud appears the other side of the flange, it may never come out until you deal with that orange blob. Take a look. True animals drill and tap another hole beside the knackered one. .enough room for another M8 maybe with a small nut...
I reckon you might be ok with that, depending on how deep the crack is. Only way of getting the stud out is to drill it, then retap or helicoil it. Don't be tempted to use a screw extractor...
All gone horribly wrong drilled it and tapped it and the corner of the head by the crack fell off leaving not much for the new stud to grip onto I’ve opened it up to 10mm and put in a helicoil is tentatively holding I’ve attached the exhaust riser top bolt tight and bottom stud lightly nipped up I’m hoping as it’s not near the exhaust port in the head the gasket might seal and I can get away with it. Other wise I can see mo option but new heads Might be a good excuse for bigger heads!
Engine is a 1776 full flow balanced etc, twin 40 dels, mild cam Engel 100, standard rockers,040 heads 54cc, deck is 0063, CR 7.9 I was thinking CB 044 just cut to 90.5 no other modifications but it would be bigger valves than the 040, the CR would drop slightly as 044 are 55cc . I can’t see a reason to fly cut and I don’t want the bus to run hot What are your thoughts
I would stick with stock valves. You might gain a few HP if you're a high rev racer but at the expense of slower port speed at lower rpm = less power at lower revs. I'm not a genius of engine building but I'd guess it would be a bit of a dog below 2,000rpm and not really come on song until about 3,000rpm. The stock valve sizes are not holding it back but they are good for lower rev torque which is a bit essential in a bus. CR and heat - low CR is not good in that respect, I'd aim for the higher side. I note air-cooled.net recommend 7.5-8.25:1 so you're good there, though IMO he errs on the low side so I'd be heading for the 8.25 end personally and wouldn't want it lower than you have. You could try some big valve heads and see for yourself of course but mind out for that conformation bias! If you wanted to make an improvement with the heads, the best bang for buck across the rev range is a 3 angle intake valve job and some unshrouding of the intake valve. That would be a better way to go than bigger valves. The exhaust best to just leave it alone, it's already too flowy and the bigger contact area is better for transferring heat from the valve to the head. 1:1.25 ratio rockers are supposed to be good for that cam too. Depends how you feel about that and what springs you have, you could be getting into that "spend a lot for a small improvement that wears the engine faster" territory.
Thanks Zed Dan always used to say to me I should get bigger heads if I want more HP Alternatively I could see if I can get my stud mount repaired and stay with what I have certainly cheaper either way I have to drop the engine and take off at least one head
And yes he's right for certain circumstances. So much advice doesn't take into account that you actually might be driving the thing around and not looking at a graph from a rolling road. So much advice on upping the peak power which is always going to be at maximum revs and though I can't speak for you, I spent zero time at max revs! Actually that's not true but only because my present engine only really revs to 4,000rpm (see below). Whenever you push that, you loose at the other end. Try a google for a/c power graphs and you'll see most of the "powerful" engines the graph doesn't even start before 3,000 rpm because the various mods to increase peak HP do it by pushing the peak torque higher up the rev range.. HP is approx torque x revs. Torque is roughly a result of capacity. The further up the revs your engine design produces peak torque, the higher your peak power will be. But then look back down the rev range to where you have reduced the toque in the pursuit of peak power and you find not much torque x not many revs = not much power. That's why VW designed them with the max torque at lower rpm, it gives a better overall balance for driving about on the road as opposed to a race track. Like this... The torque drops off, but the revs are increasing so the HP is "smoothed out" across the rev range you actually use. So, yes you can do mods to increase the peak power but in reality will you ever use it? If say it was at 5,000 rpm, perhaps you might hit that for a second while accelerating through the gears. The way I look at it that seems a bit silly, when you could design your engine more like VW did and benefit from increased HP at revs you use a LOT. That gives you an engine that keeps going up hills better without having to go down through the gears, or just accelerates generally whatever revs you are at. My last two engines were one of each type - A big valve 2L type-1 with a racy cam and counterweighted crank that could rev to over 6,000rpm - 135HP. It was a dog below 3,000rpm. It wanted to be in 3rd gear at 50-60mph so it was a bit rubbish for motorway driving but went hell for leather through the gears at 3,500-6,500 rpm. Type-1 cooling and that design meant it got too hot cruising, just like a 1600 does. I wish I had a graph for it. So I possibly over-reacted and got a 2.4L type-4 built with a stock cam and worked 1700 heads. It just has big pistons really. The torque peaks even lower than the above 1600 graph, but the result is lots of HP at lower revs - it's as many HP at 1500rpm than a 1600 has going full chat. For it's size the peak power is nothing to write home about but again - it's at useable rpm - motorway cruising speed to be exact so it doesn't slow down, it will accelerate up any motorway hill in the UK. In reality it's ot aa bit more than the graph below where it was jetted too rich and had a stock exhaust and a blocked idle jet but you get the idea - a shallow HP curve that starts with quite a fair amount of HP at low revs ad "enough" at high. So, having had the extremes, while I can see the fun in faster smaller one (which was a fair bit bigger than yours) in reality unless I was racing between roundabouts past Milton Keynes it wasn't much practical use. The big lazy one however is a joy to drive, it's quiet, it overtakes stuff, accelerates up hills, runs cool because it's not stressed etc. In a way I'd like to see how powerful it "could" be - maybe 150+ peak HP but I'm almost certain if I did so I'd regret it and fiddling with Type-4 engines costs a bomb. It comes down to what you want - High peak HP bragging rights or a driveable bus or a bit of both. I expect a mild cam in mind would have paid off but only because of it's large capacity low end covering nature. I might then have had 120 peak HP and decent power from more like 2000pm.
If it was mine I’d weld it but then I would have tried to carefully drill it out in the first place .. There is a bit of a knack involved in the weld nut to extract broken stuff , TIG seems to work better
Worth a try with the welded nut, but I agree just drilling it out wouldn've been better. Should be TIG-able.
