McBreadhead

Does anyone have an internal micrometer capable of measuring 85mm cylinder bores? I need it quite urgently to order correct piston ring set. Thanks in advance.

This is to measure bores for the purpose of sizing correct replacement piston rings. I have unusual forged Arias pistons with no markings so they need accurate bore measure.

Hmmm internal micrometer, of course. But 200 notes?! Does anyone have one I could borrow?

Engine in car - what is most accurate method of measuring bores? Vernier calipers say 84.5mm but engine size and stroke suggest 85mm.

About to replace piston rings but in spite of calling manufacturers (Arias) they cannot identify (forged) piston and hence ring set. They have suggested measuring the bore of each cylinder which I have across two opposing diagonals for all 4 cylinders and come up with a consistent 84.5mm. I have also measured each piston around the skirt (not the tops as these have reduced dia) at 90 deg to the gudgeon pin as Burtons advise and come out with 84.5mm. Will these measurements (using vernier calipers) suffice? Aside from ring thicknesses what other information would be important? Also, has anyone had experience of Arias before?

I am not altering the carb set up or timing thus assuming I can just plonk the head back on and get running without a RR session then? However I am fitting a fuel pressure regulator (FilterKing) but assuming I set the correct pressure with a guage this should have no effect on carb set up/tuning or am I wrong? I've already paid for 2 RR sessions so want to avoid another if possible but if I read the advice correct I need to do some low rev road miles before I head to the RR? However 3,000 miles is a year's running - surely this is overkill!? I was thinking 500 road miles then RR.

About to finish the cylinder head rebuild on my Stage 4 xflow engine and need to know the running in procedure. I will be running same forged pistons with new rings, big end bearings, oil pump, valves and guides. Car runs on twin 40DCOE carbs. I will be taking car to rolling road but wonder if after only 20 miles running taking car up to max revs (7250rpm) will be too much too soon. What is the precived wisdom of blatchat on this? 😶‍🌫️ Do I need more road miles first and at what revs?

Try the Auto factors in Epsom on the A24 as you go towards M25 sorry can't recall name of shop but I picked up a Banner for £57 in April

I hardly think Nick Chan can be described as an 'old lady' 😬 but interesting theory nonetheless.

Is it fatigue, oil starvation, wear and tear, or what?

Need to remove pistons to renew rings and hone the cylinder bores but wondered whether the big end bolts need replacing? Engine designed to rev to 7,500 (limited to 7,250) and currently using (from what I can see) are std 1600 xflow bolts. These appear undamaged but is it a must to replace - what's the wisdom please? Also, I have flat top forged pistons stamped "Arias" - anyone know what these are?

Brian, One of my exhaust valves was about to let go when I caught it just in time. I am no expert so others may disagree but this is what the man at Burtons and I discussed: The inner pair of cylinders run a bit hotter than those on either side so the valves tend to go first, but exhaust before inlet. It could be that the exhaust valve has let go and taken the inlet with it. Mine run 2 piece friction welded valves and they have failed thru fatigue we believe all around the weld. It would be worth trying to establish if there is a regular circular crack on the exhaust valve, roughly 1cm dia which is where mine failed. Is it possible the cylinder was overfuelled thus making it run hotter? Depending on what state of tune your engine is I have been advised up to Stage 2 then 2 piece valves are OK; beyond you should go to single piece items. Having said that another source said some F1 teams use 2 piece valves but I cannot honestly believe that given the revs and fatigue they would be subjected too. Burtons do both Accralite and Cosworth pistons from circa £150 ea - you will need to think about balancing the new one into the fold however. Nick

Brian, Just been to Burtons today and they are refurbishing my xflow head for approx £325 leaded or £425 unleaded and for that are replacing all new valves, new (duplex) springs, new bronze valve guides and valve stem oil seals. Incl is warp test, crack test, pressure test new valve seats. Admittedly it's a Stage 4 so not sure if they charge differently for (I assume) standard xflows. However you may want your rocker gear checked if any strain has resulted from the valve incident. Speak to Guy who's the crossflow expert and has a 195bhp 10,000rpm screamer. Good luck

Ta

Just swopped hands - a mate's mate has just bought one and been blown away. Astonishing value too for an immaculate HPC for 93 vintage. Does the owner know what fun he's getting into?

Burton's offer Cometic (wow what a price) head gaskets in bore sizes of 84mm and 86mm . My cylinder bores are 84.9mm so do I go large or small? Reasons please (.............to be cheerful ) Cheers!

Smoke? Me? Setting fire to hedgerows and lighting up verges at night? I should say so......

Peter thanks. If that's the case then I'll spec it without seals; however if it means oil consumption is considerable and I propose using sthg good like Mobil 1 what kind of oil loss could I expect? Difficult I know to be precise but if I'm going for new valves and guides anyway would any loss be minimal?

Samsocks blimey with readings like those I'd have the head off for an inspection immediately. I did and found a valve that was seconds from letting go and lunching my engine.

Alloy head not an option due to cost so will stick current one as can't afford cracking if unleaded inserts used; I'm also used to using additive as it reminds me of them good old days. May mean I can't use super unleaded but quite frankly the car goes like stink on std leaded set up (well it did before I had the head off) Thanks for advice.

What is the opinion on running race (Stage 4) race big valve heads with valve stem oil seals? The man from Burton today said it "depends on whether you mind smoke coming from your exhaust or not". I suspect it's a bit more complex than that. Current head has none but Burtons are advising I have the option as part of the refurb.

I'm booking my 7 with Tom Airey later this month as I've heard good reports. He's booking approx one week ahead at the moment. Let me know how you get on if you go there.

Come back RK all is forgiven..........

Could it have dropped a valve or part thereof? (Sorry this is valve week for me as I've had a rather sobering experience) I'm taking it that the car is a xflow from its age? The oily bits near the carbs are: filter and pump, crank breather, rocker cover, dip stick. Did the car run a breather return into the rocker cover that could have worked loose in vicinity of carbs?

Running a xflow with Stage 4 race head (with A6 cam) which is due for refurbishment new valves and all and wondered if I should convert to unleaded? Or will this give rise to problems given its high state of tune as per Ian Hoper's experience? What's the wisdom?