Folks, I've been trawling through old threads, and can't find a definative answer (I doubt there is one) but I'm after some advice on a high-compression bottom end for an ABF. Basically, it needs to be a straifgt swap with my current ABF bottom end, so needs to use the crank trigger, and match my ABF head. Looking for ideas on CR around using 268s or 276 Schrick cams (11.5mm lift), fully worked head with 1/2mm bigger seats etc. It'll be on Jenvey ITBs too. Not bothered about gaining capacity...don't feel the need to go 2.1, but happy to go up if need be. Just looking for options on the best/easiest way of getting something that'll better work with bigger cams and ITBs. I'm not aiming for a 9000RPM VTEC killer...as I don't really want to mess with my top end (still hydraulic) so probably looking at 7500ish as a maximum usable rev limit - unless the lifters are known to be good for a bit more? I've not tried much over 7300 RPM. I'm just looking for suggestions as to what CR would be in the right ballpark...and with what mix of components... Or I could just throw money at Mart and getting him to do it! Any thoughts?
Brookster is around 11:1 on his? Wossner? Quick look here: http://www.eurospecsport.com/products/components/pistons.htm Nothing between 10.1:1 and 13.1:1 !! 236mm 4-valve, past half way down.
Hell! 13:1...a tad high for a road car perhaps? I was guessing at 12.x:1 may be in the right sort of ballpark?
You could get the head skimmed or block decked and raise the compression that way. Obviously the block decking option means an engine strip down but for what you are aiming to do that would be sensible anyway. You really need to cc check the clearance volume with a burette to get an accurate figure to work from. Especially as the head has been modded. It does not take alot of material removal from the head or block to alter the cr a significant amount. I have found that some of vws stated compression ratios to be far from accurate so basing machining dimensions on these figures is not the best practice. I suppose 11 / 11.5 : 1 with the cams you suggest would be somewhere to aim for. With management you should be able to map it to behave itself. Is the head no. 051 103 373D? The D on the end makes it the later casting and has slightly different combustion chamber shape amongst a few other differences from the 051 103 373 version.
Looks like the head will have to come off to verify the CC sizes. Sadly, Bill Blydenstein has passed away...and he'd probably have had that information to hand. I don't recall being told significant material had been being taken off the head...only enough to tidy up the surface. How much that was, I don't know. OK, cheers. It'll be on Emerald management, so should map up OK. Not sure...it's a 1995 ABF head.
...and also ruin the squish. essthree.... on the cams you want to run 11.5 as a max. What many forget is the cast pistons... to much c.r and they'll fail. 11.5:1 with either cam (268 or 276) will be fine. You could run a tad less on the 268 but it wont be an issue. As for rpm, it's not just the lifters you have to consider, the valve springs will be a weak link if the rpm is pushed too high. Even on tame cams they like to rev on, so limit rpm to a hard cut at 7,500, and all should stay together if it's in good fettle.... dont try running springs that have already done 100k at those revs for long!
Hi guys, sorry to butt in but my chip from stealth has hard cut at 7500rpm, is this just asking for trouble with standard abf bottom end, its running the same roughish specs as essthrees on the top end bar the blydenstein head, am i looking at an expensive bill if pushing this far occasionally through the first 3 gears. sorry again but this has worried me a bit as it can be easily missed when bagging it.
Standard bottom ends are very strong. I know and engine builder who has a customer that used to come back regularly with LOTS more rpm on the ecu's tell-tale due to over-reving on the down change with no broken rods or cranks. The big ends would go out of shape in the rods and result in a spun bearing, but nothing broken. At 7,500 rpm, yr not not even close to that problem. The first thing that will give up will be valve springs & lifters if pushed too hard, but 7 1/2k is ok.
Mine is 11.5 compression with 10.5 : 1 JE Pistons KR 051 Head and ABF Bottom End, Lehmann Cams are 11.5mm lift, Duration (Top Secret) i used to have Wossner and had issues, so did Paul Bargate with his 2.1L 16V Now he has Weitec Pistons. if you have wossners have 1.2mm machined off them to reduce the compression, which people have done and which is a better option than 2 gaskets.
Because Wossner High compression pistons have a deck Height higher than standard. check my build thread there are photo's on there of standard, wossner, & JE Pistons I have some pix of VW standard piston ABF, Wossner high comp, JE Standard Comp on there way to compare. Standard VW Pistion - pin to deck 21.46mm Wossner High comp - pin to deck 25.46mm JE Forged 10.5 : 1 comp - pin to deck 21.46mm
Yes i saw that on your thread but you said to take off 1.2mm. the difference is 4mm.That's why i'm asking.And what wossner are those? 12.7:1 ?
no they are not 12.7 : 1 comp, they are 12.5 : 1 ABF 82.5mm its all down to your specific engine spec ! head type and skimming etc. My friend had 1.2mm off his to get down to 12.5 : 1
Can't remember its that long ago since i did it. someone explain compression to our friend , i've had a long day at work and don't have the energy left to go through it all ABF Pistons Standard Wossner 82.5mm high compression piston JE 83.5mm forged piston 10.5:1 Comp (The best engineered ones i think) ABF Standard Gudgen pin Wossner Gudgen Pin JE Gudgen pin ( The best one too i think)
I am looking for a suitable CR and piston spec so that I can go with forged pistons as part of the upgrade. Perfect! Thanks for the guidance. I am hoping that new VW springs, titanium retainers and lightweght lifters will allow 7500 all day long? Currently run that set up with a 7300ish rev-cut and have no issues. Superb, thanks again.
What Piston's are you going to go for then ? http://www.intengineering.com/Shop/.../seo/1/menu_num/2/sfv/32093/page/10/SFV/32093
