mpT70 .96 spool vs .81

[68TurboFastback]

Presently have a .96 mpT70 on my 306 sbf, seems to start making boost around 3000 and full @ 3500, what kind of spool rpm would i be looking at if i changes to a .81 exhaust housing? Presently can make 3lb on the 2 step, could i make more boost with the .81 housing. looking for more help getting the car out of the hole, poor 60 foots.
Thanks

[95turbomustang]

what rpm is your 2 step at?

[68TurboFastback]

I have tried 2500 2lbs, 3000 3 lbs, 3500 3lbs, 4000 3lbs. Did some data logging today and the boost starts at 3300 in first and second  full around 4200 ish, maybe i just need to get a better cam and some straight thru muffler to help free up the exhaust. The cam i have right now is a comp 280H (230@50/.512 lift 110 lsa). I have a older syle block so i'm looking for another hydraulic cam, any suggestions?
Thanks for your help.

[enigami]

stock block? A f cam would be good or even a stock grind on a stock block. What gears are you running?

[jaredsamurai]

stock block? A f cam would be good or even a stock grind on a stock block. What gears are you running?

I believe by older style block he means non roller. F cam won't work for that.

That 110 lsa may be hurting you. Not that 230 duration is huge but opening up the lsa will probably help. The F cam would probably help if you dropped the coin for the link bar lifters and swapped some plug wires. Its only 226@.050" with a .512 lift. I don't remember the lsa but I believe its a decent bit wider than yours. I don't know anything about the 289-302 non roller cams so I couldn't recomend anything for ya. Some one else will prob chime in and give a good rec. Good luck.

EDIT: I read around and it seems f cam is 114 lsa

[68TurboFastback]

. What gears are you running?

3.50 with a spool

[slowboat]

What is your exhaust made up of now ?

[68TurboFastback]

What is your exhaust made up of now ?

Presently the exhaust is a 3 inch down pipe, that "Y" under the trans to 2.5 inch full lenght to the rear valance, with dynomax muffler. Also the crossover for the turbo is2.5 inches with a flex joint. If you look at the link to my build on my sig, i think there are pics.

Thanks for all the reply's on getting this figured out.

[slowboat]

Have you, or can you try disconnecting the exhaust and doing a "test" to see if you can build more boost on the 2 step. Might help steer you in the right direction before you spend money on parts. Also are you doing anything with your ignition timing on launch ?

[jaredsamurai]

Presently the exhaust is a 3 inch down pipe, that "Y" under the trans to 2.5 inch full lenght to the rear valance, with dynomax muffler. Also the crossover for the turbo is2.5 inches with a flex joint. If you look at the link to my build on my sig, i think there are pics.

Thanks for all the reply's on getting this figured out.

are those dynomax's strait thru?

[68TurboFastback]

are those dynomax's strait thru?

No, there chambered. offset in and center out.

[68TurboFastback]

Also are you doing anything with your ignition timing on launch ?

No, but thinking of getting a mallory 685, does this ignition have a feature to retart timing off the line?
Thanks for your replies.

[slowboat]

No, but thinking of getting a mallory 685, does this ignition have a feature to retart timing off the line?
Thanks for your replies.

Looks like it's got 1 retard stage so I'd say yes.

[68TurboFastback]

Thanks

[jaredsamurai]

First thing I would do is run it open down pipe at the track and see how that does

[brianj5600]

Your WG may be cracking at 3psi.  Mine does.  With a MBC putting pressure on top of the gate, mine would make more.

[slo5o]

I believe the msd 6530 also has the ability to retard the timing on the two step. That would help you out alot.