Ben Wight, me again.

[rob_w]

hi ben,
hotmail aint working on my browser, so i gotta do it the old way.

after a long and painful consultation with my finance minister [read chick], it has been determined that the g200 not be rebuilt.

however, this means i can use the head on the turbo 1600 that is under construction.

my question to you is, would a this setup run long enough for me to get it onto a dyno?

stock bottom end, freshend up with new bearings, good rings, perfect bore, 8psi boost blowing thru a 34adm [4lt jets], no intercooler, virgin but ported g200 head, stock cam, mech fuel pump,and locked dizzy advance at around 12-15deg btdc? i ask, cos thats the setup so far, and when it goes together, i want to be able to drive it to the dyno testers.

i know i need a better fuel pump system, but i feel that at lower rpm, ie less than 6500, [my redline is at 5000 tops], it should flow enough to not burn the pistons.

the weber is sitting on a majorly ported manifold, and the idea was to get a turbo setup from the head up working, and transplant to a g161 bottom end, till i get a real turbo motor built.

do you think that this would even work? let alone survive the trip to the dyno?

i remember hearing about a similar setup, but i wasnt sure.

cheers mate,
rob.

[Ben Wight]

I get the feeling you may be confused about the fuel setup. With a blow through carb system, obvisouly the flow is important, but the critical property is the fuel pressure.

The stock pump would be lucky to pump about 4psi of fuel pressure. which means whenever you boost past that, the boost pressure will force the fuel from the carb back into the fuel line, past the pump and back into the fuel tank.

Obvisouly, if you dont boost it at all, it will run fine, but you wont really be able to run the engine in, and there wont be much point going to the dyno, as you wont be able to make any boost past your fuel pressure.

What you need is a high pressure fuel pump, or at least one that will deliver a higher pressure than your maximum boost limit. No doubt you will want to boost it to say 15psi in the future, so you need a fuel pump that delivers at least 19 or so psi, with enough flow as well. A holley fuel blue fuel pump, or high pressure carther pumps will do the job, but you need a rising rate fuel pressure regulator to control the fuel pressure. A malpassi regulator is about $200. Keep in mind that you could go with a malpassi and an efi pump, and get all the pressure you will ever need, just in case you want to run 30psi of boost one day.

The standard cam will do, and you should have pretty low compression, which, coupled with the low boost, you should revise your ignition timing. You should be able to run about 28 degrees timing at full boost and high rpm, but you will be limiting yourself to 12-15. ALthough this is very safe, it is over the top and you will simply be loosing power. If 8psi is all the boost you want, then you should modify the slot in the advance mechanism to only allow say 13 degrees of mechanical advance, instead of the 24 which is standard. And then set the static advance at 15 degrees, giving a total of 28 degrees. The next preferred option, but definitely the easiest is to just run about 4 degrees of static advance, coupled with the 24 of stock mechanical advance, you will get your 28 total. It will be quite gutless at low revs though. Locking at 15 will be great at low revs, but at medium to high revs, your timing will be retarded and you will simply be losing power.

You may want to get your bore measure, make sure it doesn't need a rebore. I would also advise you to use new pistons, as I have built many motors with old pistons in moderately worn bores, but with new rings. THe results just weren't there, they didn't hold the compression they should have due to the large piston to bore clearance.

Incidently, if you feel you should buy new pistons, keep in mind they are only about $200 with rings, and that includes fitting them to your rods. Also keep in mind that 1800 pistons are the same price, and you will only need to pay another $100 or so to get the block bored to fit them.

So in summary, dont play with the engine too much untill you have your fuel system sorted.

[rob_w]

hey ben,
thanks for sorting that out for me, i didnt know shit all bout the fuel pressure thing, i thought all it was is the ability to keep the bowl full. i guess that it may have worked for a draw thru, but as you had previously noted, my tbo3 dont have carbon seals.

the cheapest prices i had been quoted for pistons was $290 with rings, for the g200.

i may just end up building another copy of andrews motor, with rb30et pistons and rings in it. it needs a 30 thou overbore and modded rods, [full floating rods], but his is bullet proof.

apart from the obvious shortcomings in my brief flash of misguided inspiration, the plan was to have interchangability with the two motors i have here. run one to death in the car, whilst sorting out the turbo, and build the other bottom end and pistons, to take 15psi. then when the time comes, all i need do is change the bottom end.

also it would have been handy if i got defected, as i could replace the turbo head with a stockie, and have all the pollution gear working for the tests.......

that is, till jeff sorts out the efi computer.

ok, ill get myself a malpassi then, and get a bigger fuel pump. by then maybe ill be a little wiser and more informed.

thanks a heap mate.

rob.