Checking valve adjustment after racing

[AcecaRacer]

Hi,
   
   I am looking to get feedback on whether or not it should be standard practice to adjust the valves after every race on a D2 motor.
   
   For racing, I will regularly go to 6000 RPM.  Average race length is about 20 minutes.  When done, the car always idles nicely and is shut down after a cool down period.  Is there any reason to believe that the valves should get out of adjustment?
   
   Just curious as my mechanic wants to check them after each race which seems expensive and unnecessary.
   
   Thanks all -
   Rob

[Robin A Woolmer]

Might be best to Talk to In Racing in Nottingham who make new Bristol Blocks & heads  44 115 978 0663 ' info@inracing.co.uk '
   Robin

[AC Ace Bristol]

Rob.
   
   Have competed in a fair few events and never found that my valves need resetting after each event.
   
   Twice a year (4000/5500 Miles), I check valve clearance and find majority as originally set, three or four might open to 2.5/3 thou. Compression approx 10.2 / 10.3...  Sports Cam, lightened and balanced crank, rods,pistons, flywheel, rockers etc
   
   Always set mine at a tight 2 thou when engine is COLD. ( Factory setting )
   
   If you are driving hard and holding 5500 plus for long durations
   and heaven forbid exceed 6500RPM [B)], then it is worth checking  frequently.
   
   Keith..[]

[AcecaRacer]

Thanks for the feedback.  I do drive it hard as it is competitive track racing. It's rarely held steady at any revs! I do have a rev limiter put in for 6200 and rarely if ever hit it. I will check with the race guys referenced to get their take.
   
   Cheers and good racing!
   Rob

[AC Ace Bristol]

Rob
   
   Received the following email from Terry Richards :-
   
   
   Keith.
   
   Personally I do not post on the club website, quite possibly because I have never mastered the logging on process!  However, I  noticed your post and advice about resetting to 2 thou when cold and that was the  Factory setting as we all know.  But a word of caution, for quite a few racing engines that have been rebuilt in recent years may have incorporated a new camshaft with a different profile and higher lift, that may require a  tappet clearance of 5 thou.
   
   I have a Steve Stanton engine with one of his cams and the clearance is 5 thou and not one thou less!
   
   Regards
   
   Terry
   
   ACECA BRISTOL REGISTRAR
   Fulwell House
   Nunney
   Somerset BA11 4LG
   
   Terry
   
   Good Point,  Valve clearance would vary according to Cam Profile  and dwell angle etc. all is relative.
   
   Andy Shepherd ..  .. I believe also runs a Stanton engine for track events,  I will give him a bell and ask for his input.[].
   
   Cheers for Now
   
   Keith..[]

[3.8Jaguar]

It is good practice to check valve clearances before or after each race, rate of change differs from one engine to the next dependent on valve train combined weight and grind of cam.
   For example a comparison between two engines we ran last year both completing 6 races each:
   
   Engine 1  100A with standard push rods, 9.8:1 CR 100D cam giving a moderate 141 BHP, we found that after each 20 min race we were experiencing a 40% variation on some valve clearances after races on the faster circuits.
   
   Engine 2 100D2  With light weight valve gear, 270 (with not too harsh ramp) cam 11:1 CR 158 BHP with excellent torque curve, we were only experiencing a variation of 25% max from original settings.
   
   Both engines were on our standard valve springs and we do not suffer from any valve bounce, the 100A was red lining at 6300 RPM and the 100D2 at 6500 RPM.
   
   I suppose the moral of the story is keep those reciprocal weights down, don't go over board with valve spring periodicity.
   
   Interestingly If we did not re-set the valve clearances between races we got negligible extra variance! more research needed there.
   
   Interesting stuff
   
   Kind regards
   
   James
   
   www.bristolengineering.co.uk

[AC Ace Bristol]

Rob.
   
   Spoke to Tim Pearce this evening who is racing both his Ace Bristol's at Donington this Easter Sunday,  His highly tuned Green Ace Bristol runs a special sports
   cam and valve clearance of 5 thou. Yet to establish settings of his red Ace.
   
   Will speak to both Andy Shepherd and Paul Conway whilst at Donington to establish  settings they run their Ace Bristol's and intervals /  frequency of checking
   valve clearance..[]
   
   
   Keith..[]

[AcecaRacer]

Brilliant stuff gents!  Keep it coming!!!
   
   I too am running a Stanton race cam on a stroker engine.  Again, my engine seems to purr just fine after running 7-8 hard laps - 1-2 warm up and 1 cool down. However, my mechanic currently checks/adjusts after each race weekend. So, in total that is probably 40-50+ total laps in a weekend.  May run it up to 6200rpm as the dyno said I had torque right up to 6200 before dropping off. 148 HP.  Stock rods and crank. Stanton Cam and Pistons.  Triple Webers.
   
   Now, if I could just do something about the body roll!!!

[3.8Jaguar]

What Does your car Weigh in at?
   Can you fit ant roll bars under the regs for your races?
   
   
   
   www.bristolengineering.co.uk

[AcecaRacer]

She weighs about 1800lbs.  I run 15 inch tyres. I have a sway bar in the front, but not in the rear.  She rolls like a boat in hard turns.  Thought I might scrape my door handles!

[nikbj68]

Could you go down the single leaf route?

[AcecaRacer]

I suppose I could.  But I am unfamiliar with the procedure...

[shep]

Hi Guys, I have just noticed this thread. There are all kinds of personalities involved in car prep and racing. Personally the driving gives me the buzz, and whilst I understand how all the widgets work, it is a chore spending hours in the evenings preparing my Ace to go racing. The engines which Steve Stanton builds normally get a check halfway through the season (after about 6 x 40 min races) and then again at the end of the season. If anything sounds wrong, or the lap times deteriorate, then I will take the car round to his workshop for a twiddle. Unless anything goes wrong, they get rebuilt every 2 or maybe 3 seasons. I don't check the valve clearances, but they are 5 thou as far as I know. Other people love tinkering, and may check clearances after every outing, but I haven't found it necessary, and the results speak for themselves. Bigger problems are brakes, tyres, fuel supply, spark plugs and points (as we can't run electronic). As far as the rest of the engine goes, it's pretty much fit and forget. Anyone not busy this Easter Sunday, there are four of us in Aces, racing at Donington in the Fiscar race at the MGCC Meeting. I will be in David Emmans' Ace, up against Healeys, MGs, Astons, Jaguars, Lotus', a Sunbeam, a Fairthorpe and a Cunningham! Should be fun, so please come and say hello. Andy.

[3.8Jaguar]

Andy, You are absolutely correct, if some thing aint broke dont fix it. Though for the time it takes I still maintain that it is good practice as even though you may be comfortable with settled clearances it is still not uncommon due to racing pressures for components to fail in the valve gear. Checking clearances before a race could show up a variance from what you know it should be, that could indicate- a failing cam follower, inconsistent hardening in the manufacture of cam shaft, deflecting push rod, receding push rod end, valve stretch etc etc. All of which have been experienced by many of the best competition engine builders and manufactures. To have prior warning of a potential component failure, saves frustration for the owner/Driver and unnecessary major cost as well as loss of enjoyment and satisfaction for not completing a race with a broken engine that could have been prevented for the sake of a simple check.

[3.8Jaguar]

If you are a shooting man, do you not check your barrels are clean and free of obstruction before a days shooting or do you just presume as it is a well looked after gun all is ok and just pull the trigger??