pickme
672 posts
Joined: 08/09/2004 23:10:14
Location: Chippenham United Kingdom (Excluding channel Islands)
LCB Manifold - Valve springs
its nothing to do with RPM and preventing valve bounce, but preventing spring crush. Youve just paid £250+ for nice alloy rockers, so why risk busting them for the sake of valve springs that dont bind. The springs also get worked harder than with the standard rockers and the fun usually doesnt stop at rockers, so while the head is off its worth it ready for a hotter cam later.
Posted: Feb 01, 2005 06:50 PM
John
1948 posts
Joined: 28/05/2006 16:49:46
Location: cambridge United Kingdom (Excluding channel Islands)
what valve lift can std A+ springs take
what valve lift can std A+ springs take before coil binding occurs? any one used them on a particular aftermarket cam and had no problems?
Posted: Mar 04, 2007 02:27 PM
Riise
14 posts
Joined: 07/11/2013 19:50:40
Location: Aalborg Denmark
Valve spring / seat load ?
Hi and merry Christmas to you guys
I need some help from you again. Thinks are that I’m working on my engine head 1275 / 1310’er Mini
It is already fitted with 36 inlet 31 outlet valves. A high lift forged rocker set 1.5 ratio. Kent cams MD276 fast road/rally, and my valve spring AEA 526 is mounted with a fitted length 1,35” That will give me the seat load 98.23 PSI, and at the valve tip when it is open 0.400” a load approx 210 PSI
So my question is,- do I need more load Thanks in advance
René Riise
Posted: Dec 27, 2014 08:08 PM
should my rev counter be reading 8k at optimum gear change on a 998 stage 1
998's can run at 8000rpm ok the pistons are stroung enouth and con rods stroung enouth and crank stroung enouth asumming its an A+ or cooper 998 but if there single valve springs ur gotta be careful cud drop and valve into the pistons, if it has standard cam ur be lucky to get it to reve that high in gear as power will drop off massivly at that sort of speed. 998's can reve up to 8000rpm tho so its not imposible urs is however at high engine speeds the points can bounce espeashally if uv got a simetic distributor cam lobe, this bounce can cause the revecounter to become very inacrurate, cud try fitting 32lb coopers S points might reqire some modification to distributor depending on age of car but that i would expect to give u acurate readings, anouther trick to to bend spring of points slightly to increase pressure. hope iv been of use
Posted: Jun 29, 2006 11:03 PM
barnesly
46 posts
Joined: 28/07/2008 22:46:10
Location: wareham United Kingdom (Excluding channel Islands)
RE
cool thanks. would i have to change anything i.e valve springs, rockers, cams in order to make this successful.??
Posted: Dec 17, 2008 07:34 PM
SimonJ
49 posts
Joined: 31/01/2006 11:40:27
Location: South Glam United Kingdom (Excluding channel Islands)
Valve Seals
Depending on your mechanical abiltiy and equipment it is possible to change the valve seals on an A series without taking the head off as i have done it myself. By placing the cylinder at top dead centre (the very top of its stroke) you can use compressed air (from a compressor) to keep the valves up. It is then a case of removing the valve springs and changing the seal. Double valve springs is good fun! Bear in mind if the valve drops or you cant get the collets back in you will have to take the head off! Bit of a gamble but it has worked a few times for moi...
Posted: Feb 13, 2006 10:46 PM
Alex
129 posts
Joined: 20/10/2004 23:06:00
Location: York United Kingdom (Excluding channel Islands)
Engine Numbers & valves
I am part way threw re-building my 1991 copper engine with loads of performance mods. I have just upgraded all the valves and valve springs to compertion standard one. I have 2 questions to ask: 1. Alot of folk say that the heads tend to snap of compertion valves it the springs are too agressive. Any truth in the matter? 2. I was preparing the faces ready to put the head back onto the block and notice were the engine number is is blank. This may be because its a recon engine. Is this a problem? Do i need to get one stamps? WHat do i have stamped? Baring in mind that the pistons are marked as +0.03 so this would suggest a re-con. Would i just transpose the engine number off the V5?
Posted: Mar 06, 2005 08:58 PM
Info stage 1
1.5:1 can work ok if a std cam which is low lift is kept, but its better to get a new cam and stick to std rockers or 1.3:1 rockers. with the small valves in the 998 there is no gain in having them open a long way as makes no differnce to the resistance around the valves. Even if larger valves are fitted because of the small bore dont like too much lift still as the bore shrouds them. small bore engines dont like any more valve lift than around .375 of an inch and best stick to cams under 270 duration. with the std 998 cam 230 int 240 exhaust you will get lifts at the valves with 1.5:1 of .375/.360. so the 1.5:1 rockers should work fine, but if you ever change the cam to a longer duration one the lift will be too much. also rember 1.5:1 rockers may cause coil binding of springs so best use uprated onces not too stroung tho or u will loose power around 140- 160lb would be good enouth but not factory springs as these arnt designed for high lift. also u will get increased cam wear and stress on your pushrods. So you can fit the 1.5:1 rockers and they will work ok maybe give anouther 5bhp(not alot for money spent), but a better bet is to stick to std rockers and fit a new cam of around 260-270 duration but the engine will need to come out for this.
Posted: Feb 04, 2007 12:15 PM
Leaded
well u could get it modifyied with oversize valves ect, if u deside to replace valves might be a good option, if ur taking engine out yeah new cam sw5 swiftune cam is good torque cam will give good power increase and will prob pull better than the standard cam thoughout the rev range. if ur looking for something a little more hot then a kent 266, mg metro cam, piper bp255, morspeed phase 2, will all idle ok and have even more power but wont pull quite as well at low revs, might not like top gear at 30mph say. if u want even more power, piper 270, kent 276, morspeed phase 3, these will idle ruff in a 998 and wont pull so well so will need reving more ect when u pull away and ul have to change down more, but ur engine will rev higher and have even more power, id say these are max for road use on a 998. dont fit too stroung springs morspeed do 160lb ones these will be best, the lower the lb springs u use the more power, but will bounce at very high revs but if they bounce at 8000rpm and u never go past 6000rpm they are waisting power. rocker wise i think it will have pressed steel ones these are better than the later ones, u dont want 1.5:1 rocker on a 998 as these dont work well on them. 1.3:1 are expensive and wont do alot compared to standard ones. just buy a new rocker shaft, standard one will be fine not harded tho as these wear rocker bushes out. also rember ul need new cam followers and it will needed timming correctly with offset keys to get the best power. id also recomend fitting a cheap duplex gear set cost around £20 off here this will lower timming scatter so improve power and reduce chain noice.
Posted: Mar 13, 2007 11:46 PM
LewisCr125
136 posts
Joined: 13/04/2006 17:03:39
Location: Old Knebworth United Kingdom (Excluding channel Islands)
Stage 3 Head (998)
Problem with the 12g295 head is first finding one. Then the price for one is silly. By the time you've had unleaded seats put in, ported, new valves, valve guides, springs it probably wouldn't be much less then buying the stage 3 head.
Posted: Jan 31, 2007 08:30 PM
non cooper 1275 90's intake valve size?
yeah il still get inserts as will do high mileage eventually dont wanna have to strip it down in 5 years and have valves recessed into the head espeshally after thinning the seats slight while porting it. yeah i think il use cast iron valves guides with caps on intakes. you dont know if mg metro uses uprated springs do u?
Posted: Feb 12, 2007 04:15 PM
1.7:1 rockers vs 1.5:1
iv bourt a piper bp255 now with 264/264 duration power band 1000-6000 rpm got if for £30, just have to get 1.5:1 rockers now and some spings that wont bind with 420 valve lift. hopefully mini spares 200lb ones will work although it says 400 lift max hopefully it will have enouth leway if not i can get valve spring seats skimmed slightly yea?
Posted: Feb 15, 2007 08:07 PM
Tapping
hmm this is prob unlikly, but could the valve be hitting the piston slightly. think the cam would need to be timed wroung for this, but as its high lift. normally when building an engine u can put plasterseen on top of piston, turn ova engine gently by hand then take it to bits to see the valves arent tuching the pistons. also did u leave ur standard springs in as these maybe coil binding. hopefully someone else will have some ideas
Posted: Jan 26, 2007 09:18 AM
Vegard
Joined: 13/09/2004 15:06:34
Location: Skatval Norway
rockers
Why fit better springs if putting 1,5 rockers on? As long as they dont bind there will be no need. Id say that the standard spings will be sufficient with the standard cam. A spi wont rev more than 6500 anyway, and the increased ratio of the rockers will make the valve springs harder.
Posted: Jan 31, 2005 10:28 AM
manicminiman
3 posts
Joined: 20/09/2004 22:34:54
Location: winchester United Kingdom (Excluding channel Islands)
how would i know
this could be a silly question ?we bought a 1293 engine not to long ago .have taken to bits now to rebuild..how would we know if it is what they said it was ..is it bore that has been changed or is it the stroke...also what pistons would you put in to improve torque.at the mo we are lookikng for good stage three head.or should i just start with replacing valves and springs.i have a 1.5 rocker set and a 1275 fast road cam.also iam hoping to get a ultralight fly wheel..and then follow with a aldon dizzy...but its more what should i chang the pistons and crank with any ideas would be nice ?
Posted: Jul 25, 2005 08:32 AM
RPM
U dont want to be sutaining a constant RPM over 5000 for any length amount of time really. which means u can cruise alone @ 80/90 mph ok. Max RPM is a grey area because new valve springs etc etc make alot of difference but as standard i expect it to be somewere near 7000- But i have heard of 8 port twin carbs that have had alot of work reving to 12000
Posted: Apr 01, 2006 03:35 PM
abs
98 posts
Joined: 08/11/2007 20:20:11
Location: cornwall United Kingdom (Excluding channel Islands)
re
Maybe an airlock in the gauge head as I remember one of mine playing up for a while before settling down again. Also did the ball bearing roll smoothly in and out of the valve bore, how about putting a washer behind the spring to see if you get an increase in pressure and go from there.
Posted: Aug 29, 2010 09:12 AM
Tim
1849 posts
Joined: 18/10/2004 09:40:59
Location: Bournemouth United Kingdom (Excluding channel Islands)
OIL PRESSURE DROP
Oh dear, that's way too low. Has it just started doing this or is it a gradual thing that's come on over time? Have you changed the oil and filter recently? Are you using the right oil - it must be 20w50 mineral oil, nothing else. It won't hurt to change the ball and spring pressure relief valve but if that doesn't do the trick you could be looking at new bearings and/or oil pressure pump
Posted: Aug 22, 2011 09:07 AM
Roller tipped rockers
they wont knakker ur engine. u will need to rearange them on the shaft to line up with the valves in a 998 head as they are in differnt positions compared to pushrods. if u have a uprated cam dont use they it will just cause bad running (too much lift). but with a standard cam the lifts will be just about OK. modern cams for minis are going short on duration and high in lift, with a 1.5:1 rockers it will be like this. u will get more cam wear if u overspring it but standard A+ springs (138lb) should be ok as long as ur not planning to take it over 6000rpm, if they bind then use minispares 180lb springs. if u go strounger ul find cam wear will increase. the roller tip shud reduce valve guide wear.
ud be better fitting a perormance cam tho than using the high lift rockers. but the rockers are easyier to fit. for a 998 a mild road cam will work best something like swifttune sw5, piper bp255, kent md 266, morspeed phase 2, mg metro cam (avalible from kent under 450/500
Posted: Apr 22, 2007 11:06 PM
1.5 high lift rockers with 310 cams, okay???
u do know u wont be able to drive it on the road yeah? its not going to have any power till its over 4000rpm. i think ud be far better with a milder cam even for race use. ur head isnt anything speshal either so ud need a race spec head to match if ur using a cam like that. ud be alot better going for a md286sp, wont be great on road but is usuable and should be good on the track. with the 310 cam with high lift rockers u need larger valves than that. ur standard rockers wont be up to the kinda of pressure of race springs and will break. use a 286sp cam and the 1.5:1 rockers. the valve lifts will be around 480 thousands like that. ul need the right springs too, if u use too stroung onces ul kill the power too weak and they will bounce and u wont be able to rev as high.
what is engine for?
Posted: May 17, 2007 12:50 PM