Post #73
If I were you, I'd do what I did and buy and read a few books on engine building, if that sounds like too much trouble pick up a copy of the Burton Power catogue, its got lots of useful engine builder info and calcs for working out compression ratios. Before you make another expensive mistake with your engine, familiarise yourself with a few of the basic principles behind how naturally aspirated and forced induction lumps work and that will help you understand what is being suggested to you.
You need to decide which route to go down, sounds to me like your cheapest route is naturally aspirated. For this to work you will want the high comp pistons and some hotter cams, check the cam manufacturers lift figures carefully, you will need to make sure that your cams will be compatible with your intended piston. (The only way to know this is with a dummy build, the details of which will be covered in even the most basic engine builders manual) go for something high lift and long duration, forget cams designed for standard pistons (PT81's etc) you are buying race pistons so fit rally cams, these will give you some driveability whilst making the most of your new, higher CR (compression ratio) You should consider a look at the induction, throttle bodies are a popular choice. If the budget will stretch to it think about upgrading the ECU to something mappable, this will save you money in the long run if you intend to upgrade the engine over time as tweaks can be made without requiring a total remap.
If you can do the swap then the pistons will cost you nothing HOWEVER, check the wrist pin is the same size, as far as I know low comp Wössners use a 22mm pin the high comps use a 20mm one.
The cams will set you back 2-400 depending on what/where you buy. You will need an updated head gasket and a skim if you haven't had one, budget 200 for that. Mapping is going to be 2-400 depending on wether you have a mappable ECU or standard, standard means a trip to Chip Wizzards and £400. I don't recall you mentioning rods, but if you stay with standard ones you will handicap the rest if the build as you will have to restrict yourself to 7,500 rpm, this could rob you of potentially 10-15 extra horses if you can take it to 8,000 rpm on some forged rods then you really should do it. Budget £500ish for PEC Nd £900 for Saenz.
If this is starting to sound a little expensive, tough, building a reliable and powerful engine requires all of the main components to work as a whole, you can't just insert one extreme race part and expect it to coexist with standard bits and still work. I would guess you are a third of the way there with your bearings, sundries, pistons (if they are compatible) and your machining. If you need a car on the road fast, chuck in a used engine to get you going, then save for the other bits needed to do a proper job of it.
Stick with it and you will have a stonking engine, rush into a half arsed job though and at best you will has an expensive engine that struggles to exceed standard power or at worst completely destroys itself within a few hundred miles.
The choice is yours.
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R H Davey Welding Supplies. I sell new and used welding equipment in the Hampshire area. I take on welding jobs in the evenings, ally casting repairs are one of my specialities but I can weld pretty much anything. PM me with your requirements.
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Engine mount/chassis repair
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stan_306gti6
Posted 16th Mar 2012 at 07:25
