Gday all,
Just building a bargain basement/backyarder blow thru carby v8 set up..
Its a 308, truck turbo (not sure what size,F'n big!) auto, big stall..blah blah blah..
Im typing this at work so i cant go into too much detail, no time...
quick question or two:
What are the limitations of a quadrajet carby flow wise, im hoping to use what ive already got in the shed and ive got one of these. obviously ill have to modify it to suit forced induction, but basically what i need to know is, is it worth it or are the limits of one of these little fellas just too low? Id only be looking at 6-8 Psi in the end but why start with something restrictive if i dont need to.. keep in mind im doing this for maximum enjoyment and minimum cash.
secondly, is there anyone in melbournes east that can do piston modification? i want to drop the comp a bit and rather than get new pistons or run a few head gaskets which puts the intake manifold out of line, id like to take a bit out of the ones ive got.. is this a good idea structurally? will it compromise the pistons strength? Is this common?
any experiences/suggestions/questions are welcome
thanks
Steve
What compression ratio do you currently have? If you're after low boost then the higher comp ratio will be much more fun and a heap snappier.
You could try your quaddy... it might be ok for low boost but ideally you would want a boost references carb thats new and ready to go but they cost money. Stick the one out of your shed on and see how it responds!
Also you might find that your combo is a bit mismatched by the time you get it into the car... too big of a turbo means it wont come on boost until really late in the rev range... and you dont need a massive stall convertor generally with turbos. But it sounds like a case of trial and error. Just make sure you take it to someone to get it tuned! Once thats sorted theres much less chance its going to lean out and go kaboom!
Quote:
Originally Posted by PROGMH
What compression ratio do you currently have? If you're after low boost then the higher comp ratio will be much more fun and a heap snappier.
You could try your quaddy... it might be ok for low boost but ideally you would want a boost references carb thats new and ready to go but they cost money. Stick the one out of your shed on and see how it responds!
Also you might find that your combo is a bit mismatched by the time you get it into the car... too big of a turbo means it wont come on boost until really late in the rev range... and you dont need a massive stall convertor generally with turbos. But it sounds like a case of trial and error. Just make sure you take it to someone to get it tuned! Once thats sorted theres much less chance its going to lean out and go kaboom!
At the moment its at between 10 and 11:1 i believe.. the short motor will be the only thing that we'd prefer doesnt get lunched by the end of this,hoping to use it for something else later on.
As we'll no doubt turn up the boost later on (or sooner), for safetys sake i thought we'd knock the comp back a touch.
The stall is at about 3000 so when i say big, maybe i meant moderate..The turbo should be ok, ive sourced a smaller rear housing which will help a bit, but more worried about getting fuel into it. It will never be registered and will mainly be used for "powerskids" etc. so low down torque and general drivability isnt really an issue, as long as it can actually get up on boost and stay there ill be happy. Cheers for the reply, ive got a few more things to go over now i reckon.
Maybe try a suck through setup with no cooler? easy to do and if your only running bugger all boost maybe worth a shot. Run it rich as and not alot of timing? you might get away with it. Might..
With forced induction there is usually no cheap option for longevity.
Ok... 3000 convertor isnt bad... but 11:1 comp is! If it were me I'd buy new pistons... otherwise its just going to lunch it up. Fly cutting pistons is a half arsed option.
Just looking into suck thru set ups now..interesting. a cheaper alternative in a few ways (expensive in others). but doesnt lend it self to future enhancements as much as the blow thru style set up. Still, worth looking in to.
I thought that new pistons would be the go, hoped there might be an alternative.. but thinking about it now, i cant really be bothered pulling the motor down twice. It will have forced induction (blown/turbo?) in the future so ill drop the comp and be done with it i think. As much as i want to spend as little as possible on this, i cant justify doing a half ased job.
It might look like an abortion at the end, but as long as it works, looks can be disguised with tyre smoke..
especially because you are prepared/ going to be pulling the motor down to machine the pistons in it, you would be way better off to get new ones, even some stock casties from vn or something, theyre like 8.4:1. also dont forget to weld in the oil return for the turbo while the sump is off.
by the time you pay for machining of the ones it it, it probably wouldnt cost to much more to get new ones.
as for draw thru dont waste your time, your better off getting the carby done now, that way you have it for future performance or the resale value will still be pretty good. also ive heard the seals in the turbo dont like draw thru to much either?
apparently its pretty straight forward to boost reference a holley so try do some research into it, could possibly be done at home. also you will need some form of rising rate regulator aswel.
if you spend the time to get the comp acceptable and get the fuel side worked out, you will be happy with the results. as for the cross over for the exhaust use a 2 inch pipe as it keeps the heat in and the velocity up, which will aid in spooling the turbo.
good luck with your project
draw through certainly can suck balls... It is cheaper sort of but not in the long run if that makes sense. everything has its ups and downs. A good blow through set-up with a decent cooler and the like will make better power and whats forgies worth for a 308? Maybe machine the rods to suit a .927" pin and use Chev pistons. I cant remember what you had to do to use chev pistons and the like anymore.
If you need your carby boost-referenced. Jakes Performance does it in Canberra. His torana and the summernats WB both use blow through setups. One makes a 1000hp and the other about 2500hp.
if its not going to be registered, then consider running methanol or another race fuel. That way you could keep the high comp pistons, would just need a fuel setup thats alky compatible. Would probably want to either keep boost levels low or make sure the heads are well sealed (stud kit, copper gasket, oring block etc) otherwise high comp & boost will prob blow them out - meth should keep it running cool & detenation free though.
