T4 question

[lilbill]

Would a stock 2 liter T4 motor live on the street with a turbo and NOS ? I'm mainly concerned with the lower end holding up.
Are there any "recipes' around here for building a killer street motor? My 2180 just doesn't fill my need for speed

[Tony Z]

I think the standard advise is always applicatble, strip down the engine. Get the crank counterweighted and all your rotating parts balanced. That should give you a few more revs with less engine damage. While the engine is apart, change the cam for a slightly hotter one. Also, smooth out the inlet and exhaust ports. Put all together and get a decent exhaust.

If you dont want to open the engine, get a decent exhaust.

As for a turbo on a stock engine, well to start, it will work, but... any higher revs will do damage unless you counterweight the crank. If you use the same revs, it will work to a certain extent, also remeber, you will have a cam that is not designed for a turbo, so will loose out on power there too.

[Oliver Knuf]

Tony you're right. I would change at least the pistons to units, that dissipate more heat and transfer the heat faster, so I would change to forged units. A c/r of 7.5:1 is enough when driven with turbo! No ideas else, as I never tried it!

[lilbill]

Thanks guys. I wasn't sure how well the t4 lower end would take higher revs in stock form. I guess I better start looking for a crank, cam and pistons. Is there a certain year or version of the t4 motor that would make a better basis for a turbo app? I know the 914 2litre has the best heads but what about blocks? What oversize bore will give good longevity? If I have to buy PCs anyway I might as well pump it up a little.

[Tony Z]

As far as heads go, Oliver will help you the best. From what I have heard, there are a new set that are soon to be released. For a turbo application however, the stock heads, with a little work should be more than good enough. If you are keeping the stock 94mm pistons, you shouldnt need to go bigger than 42x37 on valve size, then clean up the ports. If you got 103mm pistons, you might want to go up to 46x40 valves. Remember that a turbo forces the air into the chamber, as well as makes more power than a normally aspirated engine, so the head work does not need to be as radical, which allows you to keep some more strength in the heads wich will be needed for the extra power.

[BOBTAIL]

Unless you expect to run more than 300 bhp,there is no need for a counterweighted crank or for that matter special rods.

You wont have to rev it more than 6.5k if the turbo is sized correctly,I personally wouldn't use NOS for the fact of it not being available all the time.
But I would use thermo coating on the pistons and given a choice an aftermarket engine managment,so you can control the spark and fuel better.

Heads do restrict the performance as do carbs, I seem to recall we couldn't get more than 200bhp with ported but unwelded heads(we got some from Eurorace which were welded and ported to take it up to 265bhp)


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