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850 / S70 & V70 '96-'99 / C70 '97-'05 General Forum for the 850 and P80-platform 70-series models |
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850 R engine rebuild time - what to be careful about?Views : 2489 Replies : 19Users Viewing This Thread : |
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Jul 28th, 2021, 19:38 | #11 |
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One more question...
Should I decide to go down the B5234T4 rebuild road, how much overbore can these blocks take? Piston diameter (availability) will dictate the size of the hole needed. As always, thank you! Best. |
Aug 1st, 2021, 08:20 | #12 |
The Brit Brick
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Just a thought...Daughters feller has an older Focus ST with the 5 banger engine. If you come up short trying to find a Volvo man suitably qualified to do the work then a search for Focus ST/RS specialists may find you one.
Best of luck. It's going to be an expensive pain, but sounds like a great car so worth making the investment.
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2005 C70 2.4T Collection convertible. 40,000 mile sunny day toy. |
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Aug 3rd, 2021, 23:53 | #13 | |
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get a 2002 or later 2.3 (02/03/04) the 01 rods and pistons are still 139.5mm with an ME7 version of the N motor piston, unless youre buying rods AND pistons, in which case it has the lighter crank then thats a good candidate. i actually have 5x 147mm rods here i removed and replaced with H beams if theyre of any use if youre considering new pistons (not the worst idea tbh) yes, custom pistons if you want over 420bhp safely (so the ringlands dont crack off) but stock pistons come in +0.2 and 0.4mm oversizes at about 90 pounds a piston. yes, keep 850 oil pump if you keep your 850 head yes the ignition bits wont need modifying i just used an RNC prepped 2004 2.3 (rarest of rare - only occur within a 6 month range from what i can find) for my latest build, had it rebored to 82mm, had DP Engine Parts design me bespoke pistons, skimmed head, MLS S60R head gasket, kept the crank that came with the block as its substantially lighter than the N crank, new mains on the crank using block and crank code, and ACL race bearings for the big ends. few pictures of the custom pistons attached
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https://www.facebook.com/VolvoComposites/ Horsepower is how fast you hit the wall Torque is how far you take the wall with you Last edited by DunkinBiskits; Aug 3rd, 2021 at 23:58. |
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Aug 4th, 2021, 00:02 | #14 | |
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if you want OE pistons you need to have good straight bores within 81-81.4mm, but if you buy pistons stay sub 82mm. Wiseco do 81.5mm and 81.75mm i think. once you go over that there isnt much liner left and its a MUST you shim the expansion gap between the liners to avoid cracking due to flex. Basically what kills the 83mm bore engines, which people end up having to drop Dartons into when they crack (not cheap) i shim anything i take the top off these days just because.
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Aug 5th, 2021, 09:00 | #15 | |||
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- Keep stock head (rebuilt, of course) - Go for overbore and use stock / Mahle, 2nd oversize pistons (+0,4mm) - Go for H-beam forged connecting rods (set is around 300-ish EUR) For the sake of not making this more expensive as it needs to be, I'm probably going to use the same (stock) crankshaft, with new bearings, of course. Anyways, that's the idea - we'll see how things stand once the engine is taken apart and how much work is needed. I'm also going to want the engine balanced well as a whole. I'd also like to figure out what exhaust & intake manifold to use. Should I keep them stock and port them or just go for another model ones that fit bolt-on. Thank you again! |
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Aug 5th, 2021, 12:40 | #16 |
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i wouldnt bother rebuilding if thats all your goal is. id find a used lump and drop it in if thats an acceptable power level. a stock 850 engine can do more than 300 in stock form and thats the one with the weak rods. Im currently doing 360bhp on a stock 850 bottom end in a track car. its all about boost entry.
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Aug 5th, 2021, 20:44 | #17 | |
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This way, at least I know what I'm getting. The rest of the car is in excellent rust-free condition and I like to do the same with engine. Power-wise, 300-ish hp is plenty for me, especially since I'm using an M56 box and the car is FWD. And intend to use the car - it's not going to be a garage queen / weekend warrior / track rocket Thank you! |
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Aug 6th, 2021, 18:36 | #18 | |
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buy a complete car WITH said engine already fitted. This way its proven before you even buy the thing, as you can see it running and can perform a multitude of tests prior to handing so much as a cent over.( leak down, crankcase pressure logging with a boost gauge connected to the block, inspect oil compression test, sniff test etc etc) Break the car, sell all the bits surplus to your requirements, negating the original outlay and possibly even returning a healthy profit. thats how people acquire 2.4 T5 engines for little to no money, because it comes with a tad of work with it. If you chose a 2005+ p2 T5 youll get not only a 2.4 T5, youll get a P2R ex manifold, Twin VVT head and camshafts, blue T5 injectors, a k24 turbo, an ME7 sump with onboard oil cooler, rear water manifold, a later M66 with a clutch and flywheel assembly that is compatible with your setup all bar making a rear gearbox bracket, let alone the odds and sods you would sell off the car itself. The M66 box completely changes how the car drives, far more torque/mechanical advantage in 1st thru to 4th, negating the need to work the engine as hard for the same speed sensation. that way you arent already out of pocket if you go ahead and rebuild the bottom end and head. it also means you wont need rods either as a 2.4T5 bottom end can do 450bhp no problem stock. maybe just a rebore and new pistons
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https://www.facebook.com/VolvoComposites/ Horsepower is how fast you hit the wall Torque is how far you take the wall with you Last edited by DunkinBiskits; Aug 6th, 2021 at 18:43. |
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Aug 13th, 2021, 14:20 | #19 | |
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Unfortunately, I'm (currently at least) in no position to invest so much time and effort into this. Very sound advice though - if i choose to go down this road in the future - so, thank you! |
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Dec 20th, 2022, 11:22 | #20 |
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It's finally happening - more questions
So, after numerous people-related issues and let-downs, Volvo finally went to a specialist for an engine rebuild. After engine tear-down, he'll check and measure everything to evaluate what needs to be done. I decided for complete rebuild using original parts with the exception of using forged rods.
Now, I have also been thinking of doing some other upgrades, as the engine will be out: - NA intake intake manifold - 2.5T exhaust manifold (S60R, XC90 2.5T ...) - Maybe NA cams Car already uses a larger turbo and a Ferrita 3 inch downpipe so these mods probably make sense, especially since they're relatively cheap. My goal is an optimised setup capable of cca. 350 HP using the least amount of boost possible in order not to stress the engine too much. I do have some questions regarding the possible bottlenecks: 1. Air Intake I will remove the BMC Carbon intake and use the stock airbox (MOT is a bitch where I live). I intend to use performance filter panels (such as K&N, BMC or similar) in order to allow the engine to breathe better. Any ideas what figures are possible with a setup like this at best? 2. Injectors Same question here - what are the R fuel injectors limits? 3. Fuel / oil pump Again, same as above - can I keep my fuel and oil pump and reach wanted numbers without any issues? 4.Any other possible limiting factors? Clutch? I realise tuning the car up to 350 HP is far from big but I still wanna be safe. Thank you for helping me! Best |
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