Leadership Team SLR No.77 Posted January 27, 2005 Leadership Team Share Posted January 27, 2005 Does the workplace temperture make any difference to the values I should be looking for when shimming a vhpd head I'm aware that everything will expand with temperture and hence the need for the tappets to be shimmed correctly for the running temperature of the engine and the differing temperatures across the inlet & exhaust areas of the head. But should the cold values differ if being shimmed in a cold garage (mine 🙆🏻) as opposed to a nice warm garage (like DVA's 😬) Just a thought whilst I'm aiming for a sewing-machine-like setup rather than a rattly monster Stu. Link to comment Share on other sites More sharing options...
V7 SLR Posted January 27, 2005 Share Posted January 27, 2005 They get bloody hot when you grind them anyway Stu. Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted January 27, 2005 Author Leadership Team Share Posted January 27, 2005 Very technical Nig Link to comment Share on other sites More sharing options...
Mr Locust Posted January 27, 2005 Share Posted January 27, 2005 Stu, sounds like you need to negotiate some working space on the kitchen worktop if it's too cold in the garage 😬 Ian Green and Silver Roadsport 😬 Link to comment Share on other sites More sharing options...
Jason Plato Posted January 27, 2005 Share Posted January 27, 2005 There will be a difference obviously dependant on temperature variance , how much depends on the metal and the measurable clearances and the accuracy of your measuring kit . If you are looking at 8 - 12 thou clearance for your followers then 10C change in room temperature wont make that much difference in my opinion . If you want to be sure ( and comfortable ) take the clean head upto a spare bedroom or do it in the kitchen Nigel points out that the shims get red hot when ground away, on I assume a bench grinder ? , trouble is its likley that the face of the shim wont be flat and you will get different clearances depending on rotation of the shim and the loads on the follower will be inconsistant in use leading to failier. Much better to machine the shims in a lathe *thumbup*if you have access to one . It should also be noted that the clearance will alter when you torque the head bolts up , its not unusual to see clearances alter 2-3 thou across the head on a K . Dave C7 TOP Powered by Hellier Performance 😬 Now updated Link to comment Share on other sites More sharing options...
V7 SLR Posted January 27, 2005 Share Posted January 27, 2005 OK, a clearer explanation for those challenged by my original "ooh the phone's ringing so I must finish this quickly" post... The ambient tempt of your workplace will be insignificant compared with the temperature the shims get up to when grinding. If you'r worried about thermal expansion owing to a change of about 15 degrees, then what do you think will happen when the shim gets to 150 degrees? Sure makes the quenching water boil. Even after I've cooled them to "handling" temp, they are warm to touch. You can't cut them in a lathe. They're too hard. DVA grinds them. I sent my original lot off to a company in Coventry who also couldn't cut them on a lathe. DVA holds the shims in a special home-made tool then offers the shim up to the side of the grinder wheel. By rotating the tool, you prevent any chance of your grinding the shim into a wedge. You may get a conical shape but the last nth of a mm is best taken off by hand anyway with some wet n dry on a flat surface. You can get the shim to a very accurate size this way. Hurts the ends of your fingers though. Those shims needs holding tight and your fingers can only manage it once. 16 times and you're close to bleeding for your trouble. I don't have a tool like that DVA uses but found I got equally good results by sticking the shim in the chuck of my drill then spinning the drill up against the spinning grinding wheel. In the end I was defeated by my "measure and cut" technique (using a micrometer) against DVA's "measure against the ACTUAL cam resting in the head" technique. Needless to say, experience is everything here. That said, most of mine were pretty good. I tended to have only two or three out, so I am satisfied that my grinding technique was sound. It was just the measurement technique which was flawed. Then again, I wouldn't do it again. It's tedious work and bitterly disappointing when you fall short of perfection. I have not found there to be any difference in measured clearances after I had torqued up the head. The biggest "problem" comes from not acknowledging the fact that the cam doesn't actually run in the head. It runs in the cam carrier. When you measure the clearance by placing the cam on the head (with the other 7 followers on the bench, i.e. not exerting any upward force on the cam), you ought to allow for up to 2 thou increase in clearance when the cam carrier is bolted to the head because at that time ALL the followers will be in place, pushing the cam into the cam carrier. Most of all, good luck. There is an element of luck involved, although probably very small. Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted January 27, 2005 Author Leadership Team Share Posted January 27, 2005 Thanks guys Spare bedroom or kitchen - with a wife and 3 kids in the house there's not much chance of peace to do the job there There's only one room in the house that offers real solitude, and that's not big enough to take the head in (if you know what I mean ) I'll do my next round of measurements and then put it somewhere warm and measure again. Could be an interesting result 🤔 Stu. Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted January 27, 2005 Author Leadership Team Share Posted January 27, 2005 I see where you're coming from Nig. I have a hand grinding block like Dave's, so I'll have a play. I assume that when Dave (J) suggests putting them in a lathe he is refering to linishing them whilst spinning rather than using a cutting tool. I also understand that shims can be bought from PTP in 1 thou increments which is always the soft option. The biggest "problem" comes from not acknowledging the fact that the cam doesn't actually run in the head That explains why all my gaps are 3-4 thou bigger than I expected Got my head round that one now! Stu. Edited by - sforshaw on 27 Jan 2005 13:26:50 Link to comment Share on other sites More sharing options...
Paulo Posted January 27, 2005 Share Posted January 27, 2005 A one metre steel bar will change it's length by 0.012mm for every 1°C change in temperature. As you are working to relatively large tolerances 0.2 / 0.3 mm, I can't see that it will make that much difference. To be sure, leave all the parts, tools and inspection equipment in the garage for a few hours before starting work, at least you will eliminate some of the errors due to temperature fluctuations. If it's really cold in your garage the biggest danger might be FROSTBITE 😬 😬 😬 Another One Powered by Hellier Performance Link to comment Share on other sites More sharing options...
Jason Plato Posted January 27, 2005 Share Posted January 27, 2005 Nigel , your talking bollox "You can't cut them in a lathe" "I don't have a tool like that DVA uses but found I got equally good results by sticking the shim in the chuck of my drill then spinning the drill up against the spinning grinding wheel" "most of mine were pretty good. I tended to have only two or three out" "I have not found there to be any difference in measured clearances after I had torqued up the head" I'm not botherd what you choose to say , apart from when you clearly say I am telling porkies, but you have some serious flaws in your statements. no further comment . Dave Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted January 27, 2005 Author Leadership Team Share Posted January 27, 2005 What have I done .......................... *confused* Link to comment Share on other sites More sharing options...
Sheds Moderator Posted January 27, 2005 Share Posted January 27, 2005 Ooh, handbags! You've done it Stu, this one is going to be as good as the carbon threads! (Checks for teachers coming to break up fight) Link to comment Share on other sites More sharing options...
Jason Plato Posted January 27, 2005 Share Posted January 27, 2005 [chomps on curlyworly ] see you at the gates .......... 3.45 ! 😬 😬 😬 😬 😬 just dont mention the Germans ! Link to comment Share on other sites More sharing options...
Coose Posted January 27, 2005 Share Posted January 27, 2005 FIGHT! FIGHT! FIGHT! FIGHT! We will mend it We will fix it... Link to comment Share on other sites More sharing options...
Jason Plato Posted January 27, 2005 Share Posted January 27, 2005 😬 😬 😬 😬 😬 😬 😬 we are all daft as ****ing brushes 😬 😬 😬 Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted January 27, 2005 Author Leadership Team Share Posted January 27, 2005 no further comment . Dave Does that mean something different in Welsh 🤔 For a moment there I thought you were ducking the action 😬 Stu. Link to comment Share on other sites More sharing options...
V7 SLR Posted January 27, 2005 Share Posted January 27, 2005 What didn't you like Dave? Chessman Engineering, a company I was recommended to use in Coventry couldn't cut my shims in their lathe because, and I quote "they are too hard". In addition, the skirts of the shims I had off DVA were a tad too narrow to fit the finger of my follower so I put them in my friends lathe to see if I could loose a tiny amount of width off the skirts but I couldn't because they were too hard. The tool simple squealed as it and the shim got hot, but no metal was removed. In the end I had to grind the finger slightly thinner with a grind stone. In addition, I have now ground shims with the head off the car 3 times, and once with the head on the car. Discounting the latter because it doesn't matter here, there was NO measurable difference in the shimmed gap before I torqued up the head and after. I'm confident in this because the three shims that I wasn't satisfied with troubled me long after I'd put the head back on the car. I have a table on my PC showing the gaps and sizes of the shims and when I returned to my shims sometime later to rectify the gaps I was unhappy about, the measured gaps were the same as before I'd installed the head. Edited by - V7 SLR on 27 Jan 2005 19:04:32 Link to comment Share on other sites More sharing options...
Jason Plato Posted January 28, 2005 Share Posted January 28, 2005 Your assumptions are based upon using shims from DVA, other shims used in purpose designed mechanical lifters from Arrow, PTP or Piper can be machined . I guess you are using converted VVC followers ? Link to comment Share on other sites More sharing options...
Mike Bees Posted January 28, 2005 Share Posted January 28, 2005 "Your assumptions are based upon using shims from DVA" - do you know that or is it just an assumption 😬 Are the Arrow/PTP/Piper ones not as hard as they could be then? Does it matter (I guess not). Just stirring Mike Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted January 28, 2005 Author Leadership Team Share Posted January 28, 2005 My original Rover shims (ala vhpd but from a 1400 racer - I assume these are actually PTP ones)) show small "dents" where they sit on the tops of the valves - they would appear to be a softer material than both the valve stem and the follower bucket 🤔 The buckets and shims have both done around 12,000 miles - the buckets are immaculate, the shims are not. IIRC DVA's shims are a "special" with a ring on one side to locate on the follower peg in addition to sitting in the spring cap. I have no knowledge of whether they are harder or softer than the original item, but judging by the lateral movement available for a shim (in the spring cap) they're probably a good modification? Stu. Link to comment Share on other sites More sharing options...
V7 SLR Posted January 28, 2005 Share Posted January 28, 2005 The original ones I had were called a "biscuit" type. They are like a small coin. Mine were shiny where the valve stem and follower finger had hammered it but not indented "measurably". DVA's are Cosworth ones I think although I'm sure I have heard him say he's having more made up too. Can't recall accurately. Link to comment Share on other sites More sharing options...
Rob Walker Posted January 28, 2005 Share Posted January 28, 2005 I always final finish my shims on an oilstone rubbing the shim in a figure of 8 to take off the last two thou. It has been my experience that the head distorts when torqued down onto the block so I shim my heads after torquing. Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted January 28, 2005 Author Leadership Team Share Posted January 28, 2005 Rob - are you saying you fit the head and torque it down, without the cams and carrier 🤔 Stu. Link to comment Share on other sites More sharing options...
Mike Bees Posted January 28, 2005 Share Posted January 28, 2005 I remember that when Roger King built my engine he stressed how important it was to measure the clearances with the head torqued down and cams/cam carrier in situ, i.e. how it would be when you turn the key. I get mine close with the head torqued down and the cams laying in place (no cam carrier), then bolt the cam carrier down/remeasure/remove cam carrier/adjust shims/repeat etc. Mike Link to comment Share on other sites More sharing options...
Rob Walker Posted January 28, 2005 Share Posted January 28, 2005 Stu, I fit the head and torque it down. I do not fit the cams or carrier I drop one cam in at a time and measure the clearance on each two inlets or exhausts and allow upto .002" for the cam to run within the journal. So measure your clearance if its .005" on an inlet then add .002" giving you .007" you can then take the last .001" off on the oil stone giving you the recomended .008". It has been my experience that if you grind your shimms spot on with the cams resting within the journals of the head, when you fit the cam ladder all the clearances will be too large as the cams find their natural resting position within the oilfilm within the camm ladder/head journals. There are those out there that will not approve of my methods stating that the only proper way is to take the clearances with the cam ladder torqued then take it all apart again repeatedly make adjustments then reasemble. IMO this method is a sure way of ending up with a bent /distored cam ladder. Link to comment Share on other sites More sharing options...
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