Hi all, I've been a forum lurker for a few years now, but this is actually my first post Currently have an OEM Mk2 16v with a KR, but the rings are on there way out, so as per title: I'm planning to make a start on a fast road 16v using a 9a bottom end and a KR head, just looking for some advice on a few areas! Goals: I'm hoping to hit the 175ish mark in terms of power (more would be a bonus!), I want to keep it driveable for road use with a sensible amount of low down torque. I'd like to build the engine up to be a strong unit, as the car is a life-long keeper for me, so wanting to do it right! Plans so far: 9a bottom end bored out, need to assess block bore condition before deciding final size. KR head ported and polished, considering putting cams in if budget allows. Will be running an 020 box, recently sourced a quaife to accompany the power increase! Will be running K-Jet with WUR mod Will be running Milltek 4 branch to a full stainless system Questions: Bottom end - Should I consider going forged for longevity, even though I'm not chasing huge power? If I do, who does forged pistons with a sensible CR? Presuming going high comp pistons would be a bit much for a road car and would need more than just pump fuel? If I do go forged, should I go steel rods too? ARP hardware? Cams - I've been looking at offerings from Newman, Piper, Schrick and CatCams around the 260-264 degree mark, any recommendations? Really don't to go too lumpy Head - Presuming I won't need to uprate valve springs? What's the crack with 3 angle valve seats? Worth planning for an oil cooler & catch can, or not required for this spec? Apologies for the long post, and thanks in advance for anyone taking the time to reply
From what you have said, bottom end I would recommend keeping the std rods and pistons, unless your going to use 7K plus revs. More compression always good. Not had a lot of experience of K Jet with modified engines, so can't comment. Jon
I've no need to push any harder than the standard 7200 red line, so winner if I can get away with standard bottom end bits, frees up some budget!
Bottom covered as above by Jon. Only additions are: Rod bolts: hard to get aftermarket replacements now. They're a stretch bolt so must be replaced once stripped. ARP bolts are available for similar cost to O.E (not always available either) so makes sense to go that route. Must be fitted by a competent machine shop that have experience of what's needed. Pistons: Last time I checked O.E spec aftermarket replacements no longer available (same situation as ABF). Rings available in some makes/sizes until stocks gone. Forged pistons are available though overkill for what you need but will be your only option if a re bore is needed. Cost wise very little in it over O.E spec replacements anyway. No need to go bigger than 0.5mm oversize (83mm) which can then be used with the 83.5mm bore O.E type MLS gasket (Multi Layer Steel). Use a direct copy flat top type piston...not an intruder type, you'll get all the C.R you need with them. Wossner ok for your needs but won't tolerate a bad set up/lean mixture under load. JE miles better for little more cost. Head: O.E springs more than fine for what you need, as is O.E/good aftermarket hydro lifters. Any head will do the same basic job....early KR 027 casting or late KR/9A/ABF 051 casting. Once modified along the lines you'll need they'll end up the same in terms of flow/power potential. 3 angle seats: They give a better flow particularly when the valve initially opens/closes over old style single contact angle seat. Nothing special in them as manufacturers have used them for many years now. The head should be ported only...i.e removal and re shaping of material, no polishing whatsoever other than the fine finish left by the porting process. Cams. 16v's are more sensative to overlap than 8v's due to the flow/time area so don't go overboard on a road car. You're thinking spot on the right lines with the 260-264 range. Schrick great but overpriced, all the others similar (2 you mention use the same manufacturers blanks). Custom cams are also possible to maximise what you want to achieve. BHP: Your in the right ballpark again. Don't worry too much about numbers....174hp won't be any slower than 176hp...don't chase numbers too much for a road engine, concentrate on the package as a whole to make it drivable, but you'll be in that area in terms of real world power. Hope that's a help to start with.
Thanks for the detailed response! That really sheds some light in a few areas Fingers crossed the bottom end I have is in good condition then! I'll get the head off tomorrow and have an inspection. I didn't realise that rod bolts had to be installed by a machine shop, why is that? Was planning to do most of the bottom end work myself, but don't want to cock anything up due to lack of experience! Have you much experience of 264deg cams compared to O.E? Much of a difference at idle & low rpm driving?
No problem at all. Std ones don't as they're a direct swap. They can be fitted with the rod supported correctly and a good tap with a large hammer, but ideally a press...which not many will have in thier home tool collection. The ARP type REALLY need pressing in...the large hammer method is a no no, so again need a machine shop to help. Also, and the main reason, the underhead profile has a bigger radius than O.E, so a countersunk taper in the rod is needed. Again, not many will have the right kit to do the job...you really don't want to assemble an engine with rod bolts not fully seated. Not used 264s personally, they're a bit tame for most of what I build, but the numbers suggest they should work fine. I've set up 260 Schrick's for a customer but no feedback as yet...I'll ask if it's running. ABF cams could be worth considering, they're pretty good and the best of the O.E profiles, but I can't see 264s being an issue. Or I can get a custom pair done to a profile I have in mind.
Thanks again for the info, didn't realise the ARP rod bolts took that much to fit! Would be really interested to hear about the 260 Schrick's if it's running. What sort of profile would you have in mind on a custom pair? Sounds interesting Stripped down the block yesterday, will get the bores properly measured soon, honing visible everywhere except a couple spots in cylinder #2, doesn't look great! Matching piston skirt marks too.. EDIT: Popped into a local place for a chat and they said it's definitely a rebore job, I'm inclined to agree
