70mm throttle body on stock intake?

tsiemens

my welding skills arent really skills
Jul 14, 2018
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Picked up a 70mm BBK throttle body and I had intended to put it on my stock upper intake but the gasket will plug up the lower hole in the intake. Is there a solution to this or did I simply buy an incompatible egr spacer/throttle body? Yes I'm aware the bottle neck is still the smaller upper intake. Do I need to buy a different gasket?
 

tsiemens

my welding skills arent really skills
Jul 14, 2018
136
27
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ontario
You can see how both gaskets cover the bottom hole. Is either one ok? Its an 86gt
 

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7991LXnSHO

wanna catch the space herp
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That bottom, oval hole Is for the EGR. You do not want that to leak air either way there. You also have to be sure your EGR/tb spacer seals with the right gaskets. Having coolant sucked into the intake will act like much like a head gasket leak.
I would not be comfortable with either gasket. Is the 70mm TB that much of a misfit? That looks like a huge step for air disruption, more than you can port and blend in.
 
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OldManRiver

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Nothing will be gained using a 70mm TB with the small opening in the stock intake,but even so you can still use stock gaskets for the Explorer since the gasket ID is 72mm.Installing an Explorer intake would be the next move,and a worthwhile one.
Felpro gaskets part #61081 and #61082.
 

tsiemens

my welding skills arent really skills
Jul 14, 2018
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Sorry I see the 1 reply said neither gasket is appropriate and yes Ive been down the dump coolant out the back wrong gasket before. I don't know why they sell these as a stock upgrade if the gaskets aren't right. Frustrating to no end. I wanted a new TB just to replace the old crusty one.
 

7991LXnSHO

wanna catch the space herp
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If you have the parts, line them up and see how they fit without the gaskets. If the gap shows without the gaskets, you need a smaller TB. (It looks like your coolant plate is still on.)
I cannot remember the max size that can fit explorer and stock intakes. I’ve ported the throats on both but what sizes is missing info. Sorry. A search or a someone with a better memory will answer it.
 

KRUISR

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If putting on an Explorer intake, grab the Explorer 65mm TB while you are at it.

Or sell/trade the 70mm for a 65mm. It will probably fit the stock intake better. A 65mm TB will not be a bottleneck on the stock intake.
 
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Mustang5L5

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A 70MM on an ‘86 HO upper is going to cause more trouble that it’s worth, especially seeing how the gaskets line up.

It’s the ultimate hotdog down a hallway.

Squirrel the 70mm away and as long as you have that 86 HO upper, you really don’t need to go much bigger than the stock TB or even the 87-93 stock TB.

And ‘87+ HO intake would be an upgrade for you.

Honestly, I’d just squirrel it away and combine it with a better intake.
 
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7991LXnSHO

wanna catch the space herp
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A 70MM on an ‘86 HO upper is going to cause more trouble that it’s worth, especially seeing how the gaskets line up.

It’s the ultimate hotdog down a hallway.

Squirrel the 70mm away and as long as you have that 86 HO upper, you really don’t need to go much bigger than the stock TB or even the 87-93 stock TB.

And ‘87+ HO intake would be an upgrade for you.

Honestly, I’d just squirrel it away and combine it with a better intake.
I am glad you can tell from that angle it is an 86. That makes more sense. I skipped that year.
 

Mustang5L5

Put lubricant all over the balls
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I am glad you can tell from that angle it is an 86. That makes more sense. I skipped that year.

Those 86 EGR spacers are rediculously tiny in terms of bore diameter. Smaller than the 87+ cars.

Lowers were the same E6SE lower so back in the late 90s it was common to hear of 86GT guys getting 87+ HO uppers, EGR spacers and TBs and swapping them on.

All forgotten now because HO intakes are doorstops when exploder intakes are plentiful (for now). There was an E6, E7, E8 and F0 upper and I remember folks debating on which was the “best”. How far we have come
 
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jrichker

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The stock heads are the bottleneck - they limit the flow so badly that any change in throttle body size is a waste of time and money.

See https://www.stangnet.com/mustang-forums/threads/flow-rate-for-5-0-cylinder-heads.713161/post-7027297 for the flow numbers.

OR
Head Flow Data In CFM-Source: http://users.erols.com/srweiss/tablehdc.htm#Ford

Head......................................Head CC..........Valve sizing (Int/Exh)...Flow at .500” lift

E7 Irons............................................. ......................1.78/1.45........... 159/109

If you put high flow cylinder heads on, you will need to update the Speed Density computer system to Mass Air computer.

Computer system differences in 86-95 Mustangs.

Revised 15-Jan-2018 to add requirements for larger fuel system components to support large changes in airflow through the engine.

All 5.0 foxbody engines from 86-95 are OBDi
OBD1 comes in Speed Density and Mass Air Flow versions. It differs from OBDII in that diagnostic data cannot be streamed through the diagnostic port in a real time mode. The diagnostic data is stored in volatile memory and dumped on command by an external jumper or code reader connected to the computer’s diagnostic port. Watching the Check Engine Light, an external test light or voltmeter are all that is need to dump the codes on an OBDI system. An OBDI code reader can be used, but it isn’t an absolute necessity.

ODBII is capable of streaming data through the diagnostic port in real time mode. It requires a code reader that handles the OBDII data format. No code reader, no way of knowing what the codes are. The plus is you can watch changes in sensor data as they happen, and use the information to plan changes in the computer's program. OBDI requires a laptop & some specialized hardware to do the same thing.

Both OBDI & OBDII have adaptive learning to accommodate changes in sensor output, so as the sensors and airflow values change, the computer adjusts for them. Mass Air systems have a greater range of adaptive learning than Speed Density.

Speed Density uses Manifold vacuum (MAP), Throttle position (TPS) and RPM, & Air Temperature (ACT) to guess how much air the engine is pulling in. Then it uses all of them plus the O2 and ECT sensors to calculate the air/fuel mixture. It is dependent on steady manifold vacuum and minimal changes in airflow from the stock engine configuration to maintain the proper air/fuel ratio. Change the airflow or vacuum too much and the computer can't compensate for the changes, and does not run well. Forget about putting a supercharger, turbocharger or monster stroker crank in a Speed Density engine, because the stock computer tune won’t handle it. Every time you seriously change the airflow through the engine, you need a new custom burned chip to make the engine run at peak performance. Most aftermarket cams will not work well with Speed Density, and that includes the Ford letter cams.

Mass Air uses a Mass Air Flow meter (MAF) to actually measure how much air is being pulled into the engine. The computer uses this information and inputs from the O2, TPS, ACT, ECT, RPM and Barometric Pressure (Baro) sensors to calculate the proper air/fuel ratio. It is very tolerant of changes in airflow and vacuum and tolerates wild cams, high flowing heads, and changes in displacement with minimal difficulties. Just remember that large changes in airflow require more fuel than the stock fuel system can deliver. At that point, you will need larger injectors and a larger fuel pump to make the engine run like it is supposed to. Larger injectors can be used with either an aftermarket calibrated MAF or a custom dyno tune. This makes it possible to use the stock computer with engine displacements from 302-408 cu in, and make many modifications without a custom dyno tune chip. Put a new intake manifold on your 331 stroker and the computer figures out how much more fuel to deliver without having to have a new chip burned to accommodate the extra airflow.
 
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