We've been busy with a number of projects of late but one in particular took the "late" bit to the limit!
Nick Penfold runs one of our engines in his MK1 Golf which was originally built to the old Slick 50 regs many moons ago. That meant the good old archaic K-jet injection system coupled to a lumpy cam...not the best recipy for a smooth idle but with some juggling it works to a point.
The first round of the VAG Trophy was cancelled due to snow earlier in the year and was re scheduled to join the British GT championship on the new Snetterton 300 track. After Nick's first outing of the year at Cadwell Park it was obvious the game had moved on a bit from last year. Nick had fitted new suspension for this season which had mostly transformed the previous "drunk camel on roller blades" handling (more on that later) but the hills of Cadwell highlighted the class B cars Nick runs with had a clear power advantage under the new power to weight regs.
With Snetterton only a month after Cadwell and Nick away on business and a holiday between the two rounds it didn't leave a great deal of time to execute a plan...some bright spark said "your not going to Snetterton to run at the back of the field...get the car down down here before your trip's, whip the K-crap off and we'll sort the power issue...oh and take the head off while yr at it!!...
Said clever cloggs went on the hunt for an ebay special manifold only to draw a blank...hmm...I dont give in that easy. A call to fellow MK1 racer Tony Barber (tonyb) to ask if he may have a DCOE type inlet manifold in his parts collection revealed an even better option..."may have!....in fact there's a pair of 45 Dellorto's here too!"...RESULT!!
I already had some Weber's lined up for a short term loan, but Tony's set up had a better starting point in terms of jets and chokes so that would help a treat, along with his "yeah no problem" reply to my next question...."do you mind if I make the holes in the manifold bigger!"
Not wanting to make life too easy for myself by just swapping the K jet for carbs, I wanted to go inside the head too whilst we were at it as I knew the power gain we needed wasn't going to come just from the carbs alone. Upon Nick removing the head we discovered a bit of a bonus...Nick's old Slick 50 head had 41mm inlet valves fitted when it was originally modified 15+ years ago, so I knew from previous versions of this head what the starting flow point would be (86-88cfm) and where I could take it. Sure enough the flowbench revieled the std flow for these heads in this form (87.3cfm in fact) which is a good bit below the potential on the valve size fitted.
As the inlet ports in the manifold needed opening to suit the required airflow and blending into the port, it was easy enough (relatively!) to continue the size increase into the ports so as to open them to my preferred size ratio to balance airflow with air speed...I wanted this engine to punch above it's weight in the mid range coming off corners as well as the long straights at Snetterton, so biggest wasn't going to be best here, plus there was a time element to consider...digging a valve seat at this stage wasn't an option! So the throats were left as they came for this phase with further improvements possible, all I needed this time was a flow increase to around 93-94cfm and we'd be on the money....so when the flowbench flashed up 96.7cfm I was a happy bunny indeed!
A thorough clean and assemble later revealed the first stumbling block...a broken inner valve spring! A quick rumage through the JMR spares boxes found the original valve springs that ran with the cam we use in this engine (Nick kept his original springs during last years re-build), so a quick clean up and in they went...but it wasn't going to be that easy! The previous head these springs were fitted to must have had the spring seats lowered...as I discovered when the cam locked up turning it over to check the valve clearances! Enter stage left the next hero of the hour...Tim Moll (mitlom)..."how you getting on with Nick's head...running yet"?...."not with a broken valve spring and another set that wont work"!!....."dont forget my two sets of springs sat on your bench"!
Oddly enough Tim's text came through just as I was eyeing up his Supertech boxes!.....cheers Tim! A quick measure up of both the free & fitted length reveled they would be perfect for the job! As it was rocking past midnight the sensible thing to do was call it a night...Nick had joined me in the workshop for a couple of days to get some small jobs done on the car and re-fit the head. With other pressing JMR duties looming and time not on our side I stripped the head again, fitted the Supertech's and re ground a couple of shims to get the valve clearances just right...after dropping spanners at 1.45am I figured trying to time the cam up was best done after some sleep!
By the time I returned in the morning Nick had the smaller (std) front roll bar fitted as suggested to improve the turn in, so it was straight on with torquing the head & putting a base cam timing setting in to kick us off later on the rollers. Whilst Nick fitted & wired up the fuel pump I gave the Dellorto's a clean up and base re-jet to save time later. A juggle with some linkage parts and we were all ready to make some DHLA type noise. After a bit of diesel battery boost from my trusty Passat and a bit of twiddling we had a race engine with an idle much better than it ever gave on K-jet with a 296 degree cam.
Nick had to get back home to Bristol for the next day but time was getting short to get on the rollers for the time I wanted to spend on the car...so Nick was dispatched homeward bound to let myself and my dyno wizard Alvin Powell at AP Motorsport drag the required power from the engine.
In K-jet form we extracted 124 at the wheels from it last year giving us 135hp per tonne, so with the power to weight target of 152hp per tonne at the wheels as the class maximum we needed to hit around 140hp at the wheels with the current 916KG weight. I was less worried about peak numbers on this as I wanted it to pull strong off the corners to get a head start on the turbo brigade as well as improve the top end breathing, so response was the key here...dyno numbers are useless without an engine that responds, which is something numbers don't tell the full story on.
After the best part of the day with my dyno man turning the wheels while I changed jets to get the fuel slope balance right, timing the cam for the best power spread and edging up the ignition until there was no more to give we hit our final power run....137hp at the wheels was resonable for the spec and only 3hp off the target, which I expected as the current exhaust manifold is too small now. The best bit though was the 10-12ibft torque increase in the mid range to make just on 140ibft total, which isn't at all bad for an 1800 8v, and not far off what I get from the full race/hillclimb engines making 30hp more at peak and a lot more revs. This engine is still on a largely std bottom end...std crank and rods, ARP rod bolts but with cast pistons, so we kept the revs down to a max of 7,500, where power was only dropping off 5hp from the 7000rpm peak.
Fast forward 3 days to Saturday morning practise...I awoke to Nicks first text of the day....brakes "awefull" (another story!)...engine AMAZING!
I had told Nick to expect much better performance than the numbers had shown, with strong punch off the corners and much better throttle response than the K-jet would ever give, but what I must admit I wasn't quite expecting was for him to be able to not only pull clear of the turbo cars off the turns, but also to hold them side by side in a straight drag under full power!
Whilst the turbo cars run to the same power to weight regs, they have a much better torque spread per tonne, so on paper their mid range grunt of almost a clear 30ibft per tonne advantage should give us a bit of a work out....but as is often the case, numbers dont tell the full story....turbo or not, our 1800 8v can more than hold its own right through the rev range now with a much better power spread than before...oh and there was another bonus...loosing the K-jet system has helped drop the weight by a few kilo's...we're now slap bang on the 152hp per tonne class limit!....every cloud....
After practice Nick worked his way up through the field in the dry start of race one, but with one eye on caution with an alarmingly long brake pedal and the other eye on the looming black cloud above, plus with another grid to line up for the next day he took the mid field finish in the eventual downpour with open arms.
The first race finish put Nick right in the middle of the pack for the second round on Sunday. I advised Nick to be careful not to accelerate into the back of slower starting cars off the line...something which he was a little doubting of until he lept off the line and started out dragging VW Cup cars who where invited to race with the VAG Trophy boys!
A race long battle with various VR6 and turbo powered cars is showing the MK1 is now on the pace...being able to run within the pack and hold off ex Leon cup cars on a fast track like Snetterton has shown what a great championship John Hillon and the team have put together to enable old & new tech to mix.
Take a look at the in-car action from Rob Allum's Ibiza...
...watching a brick shape MK1 Golf with carburettors and bob weights run up next to a turbo fed multi valve engine made me chuckle at the amount of times I've heard 8v's lack breathing.
Nick now has plenty of time to sort the lack of brakes before Brands Hatch at the end of August, along with some fine tuning of the suspension...replacing the front roll bar with a std GTi unit in-place of the previous bigger version has much improved turn-in as I expected, so if he can get the MK1 to stop as well as it now goes we can challenge for a solid class podium finish...Nick ran as high as 2nd in class at Snetterton but the long pedal didn't inspire the late braking lunges that the opposition were able to achieve, so the need to back off early saw him swamped too many times to be able to hold position....lets see how the next round goes...I'll be shouting from the Brands banking myself so hopefully my day pass from Devon will be worth the trip!
http://www.karlbowdreyphotography.co.uk/-/galleries/motorsport/2013/msvr-vag-trophy/cadwell-park
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