70mm tb or 75mm?

SlinginBeauty

Registered User
I am in the process of cleaning up my SC and making it go pretty quick. My next idea to look into is possibly the thrttle body. its pretty much between the 70mm tb or the 75mm tb. The 85 will be too much b/c i dont want my car for racing and the other 2 will suit me just fine(to blow away those ****** gt's). Im somewhat interested in the 75 but i heard something about you having to port your inlet pletnem or something to make it work on my car. I have a 90 auto and i have no idea. Any info and advise on how yours helps. Maybe even the 70mm can try and talk me into it if its nearly as good. Thanks for the advise.
Zach
 
On my 95 with a BBK 75mm, I did not need to port my stock inlet plenum. If you use a mustang t-body which some have done, you WILL need to modify the throttle stop slightly. And may or maynot need to port the plenum.

70-75mm might both be overkill, so take your pick. I went 75... The SC will wine more if nothing else.

-Julian
 
The inlet plenum should be port matched to the throttle body regardless of year or size if you are adding a 70mm or larger. Failure to do so will create turbulant air as it enters the inlet plenum and reduce flow and performance.

Paul
 
I haven't seen any dyno tests on 70mm vs. 75mm (with their own unique ported plenums) but I would guess that the 75 is way too much for a stock or lightly-modded motor. 85mm whatever.

I think if you made a double resonator from two stock ones that would be cool, kinda like those sweet double intercoolers that really work!
biglaugha.gif
 
ANYWAY....the 70 0r 75 mmTB will bolt up...Maybe even the 85mm..But why put 70-85mm tb to a hole that is probably the size of 60-65mm..Wouldnt do any good in my book..If you do the TB mod...get a dremel and portmatch it..70 or 75mm tb will be just fine..Make sure its for an SC and not a mustang or you will have to modify it..Easy enough answer..However Id go with a bigger mass air first:O)
 
Alrighty, Here is my first hand experience (check my member page to see mods),
bigger MAF = good
Raised top = surprisingly good
exhaust new resonator & mufflers = best $ so far
no cats = didn't notice anything
cold air intake = stick with panel filter
75t-body = didn't notice anything.

I'm not going to say it's a bod mod or anything because it will probably need to be done sooner or later and it is an easy bolt on. P&P heads and a cam would be the sh1t though. Someday ah.......

I'm changing SC pulleys tonight and hopefully my double IC comes in as well. :eek:
-Julian
 
SlinginBeauty,

I would get the 75mm....not because it's going to flow anymore than the 70mm using a stock or ported plenum. But because it's nearly the same cost, fits every CAI kit and best of all, when you decide to upgrade superchargers and more importantly the inlet plenum, your TB will bolt right on and provide enough airflow for 450 HP at the crank.

You may be able to bolt the TB to the plenum and it will function as in the throttle plate doesn't hit anything, but porting the first inch or so of the plenum will flow more air.

BTW, You'll save yourself tons of money by doing your mods once and making them large enough the first time.

David
 
Thanks for the info. I think 75 is they way to go. I do have cold air and maf and other **** done since i got it. Just ordered new headlights as a matter of fact. I need to update my parts list. Thanks for all your advise. especially David(i think thats your name(i got a short term mem)).
 
mines slightly moded

mine is slightly modified and the stock tb is doing alright but im at its max .

its good for a few mods . exh ported heads ported blower,and ported mass "removed the post and drilled out 15/32 sample tube, my next step is 36 lbs injectors, and a 75mm tb it goes step by step use every part until its out dated by other mods .
so far stock tb is working fine. but my car has stock cam still .trying to extract all I can from stock injecters,tb,mass
 

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Notice to all posters! Some of you have forgotten this is the technical board. So, I have taking the liberty of deleting all non-tech related portions of this thread.

I'll give a bit of advice to the two main protagonists in this Greek tragedy, you'll get a lot more respect on the boards by staying clear of train wrecks like this than you will by adding to it.
 
No fair...I want to see train wrecks.

And to keep this technical...TBird4VR...have you done any dyno testing or runs at the strip or are you just using the butt meter? I don't know why you are looking forward so much to just ported and polished heads....you probably won't feel a lot of difference from ported stock valve heads and cam other than slightly better pull on top end. If you want a killer mod, you should do a blower upgrade. Most have agreed that the S model (MP2) made the biggest improvement.

Micah
 
Not really. Several people have run S models @ 15 psi and been fine. But their exhaust systems were opened up first.

If your headgaskets are that touchy, then they will probably pop anyway as you climb up the HP ladder (or just continue to drive it hard).

Micah
 
Micahdogg said:
No fair...I want to see train wrecks.

And to keep this technical...TBird4VR...have you done any dyno testing or runs at the strip or are you just using the butt meter? I don't know why you are looking forward so much to just ported and polished heads....you probably won't feel a lot of difference from ported stock valve heads and cam other than slightly better pull on top end. If you want a killer mod, you should do a blower upgrade. Most have agreed that the S model (MP2) made the biggest improvement.

Micah

Really? I was under the impression that heads cam are the way to go. The blower is something I could bolt on myself, so maybe that will happen.

You really never know who or what you are talking to on these boards other than the big guys I guess.

And no I have never ran it or dynoed. supercharged95 and myself may go to an 1/8th track shortly (I hope). I thought someone said there was a dyno here in Ames, but I'm not sure how much it runs. All I can say is my car does feel significantly quicker than stock.

I do have a g-tech that I never got to work right:eek:

-Julian
 
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Heads are the key to making big power. If you get an aggressive head and cam package with oversized valves then you can turn your SC into a screamer. But you said, "port and polish" which is not a "big valve" head package. If you just tear your heads down and port/polish them then you won't notice as much of a difference as you would with a blower upgrade. Every little bit helps, and it depends on who is doing the porting/polishing, but I wouldn't bother doing anything to the stock heads and cam unless you are interested in making MAJOR HP.

It's already been shown that you can go with "bolt ons" only and achieve near 300RWHP and 400RWT.........which equates to anywhere from 375HP to 400HP and 500 to 530ft-lbs of torque at the engine. It would require all MP products along with a fresh air intake, MAF, injectors, fuel pump, underdrives, overdrive, ported manifolds, exhaust, whatever else and a good tune, but the results would be a relatively mild mannered SC with good idle. It would be relatively low revving which would make the power curves short and spikey, but the low revving nature would be better for longer engine life.

You could go with a head and cam package, but it would be $2500 to buy (the price of a MP2 blower and front mount.....which would be the same if not more power gain than the heads/cam) and you would have to put up with a lumpy idle which can be quite annoying if you have an automatic (occasionally stalling) and the increased power range would just put more stress on the bottom end. Not to mention the engine would probably be running a lot hotter.

That's just my opinion though.

Micah
 
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