david auster

iTrader: (10)

I was wondering if the y pipe from a 3.1 would directly bolt up to 2.8 without any modifications.

Do they use the same thermostats?

Can an auto trans from a 91 3.1 bolt up directly to the 2.8 without modification?

I have a 91 RS and a 87 camaro both V6s just one is the 2.8 and the other is the 3.1, and I am curious as to what parts are the same just in case I have to swap stuff.

Thanks

kretos

everything is completly and utterly the same

david auster

iTrader: (10)

Oh thats great to hear.

So I guess the only differences are the displacement and that the 2.8 is a MAF setup where the 3.1 is speed density?

kretos

yeah and a couple of sensors are in different spots. but nothing worth mentioning

Dale

iTrader: (12)

Wrong

Intake is different
Some of the pullys may be different (depending on year)
EGR is different
Vac routing is different
Elec system is different
fuel injectors different
Flywheel/flexplate different
Trans is partly different (can be made to swap)
valve springs are different (I think)

Alot will swap, but some wont. Exhaust should be ok to swap.

Alot of the sensors are in the same spot. Only major one on that is the Fan switch which on 2.8 is in the head, where the 3.1 uses the ECT and the ECM turns the fan on.

ljnowell

I've got a 3.1 mpfi and a 2.8 mpfi intake side by side, and there are no differences that can be seen, you can bolt one to the other, and vice versa. What gives? Most all fo the accessory brackets look the same, I cant tell much of a difference. What makes the difference in the trans? They are both 60*?

THEGENERAL

only reason i can see the transmission wouldnt work would be speedo issues but thats easily fixed by swapping tailshafts from one to the other......

ljnowell

thats just a year to year thing.

david auster

iTrader: (10)

I am very interested to know the difference in the transmissions and what would need to be done to put the 91 trans onto the 2.8 motor.

As far as the speedo goes on the V8 cars the only difference is one uses the cable drive speedo and the other uses the electric, but to change them over is very simple. You defenitly don't have to swap tail shafts.

Thanks for the input

ljnowell

The speedo is the same, v6 or v8. You just have to have the right one for the car. Changing the tailshaft takes about 5 minutes, it is one method of fixing the mismatched speedo problem. But the real question is, what exactly are these "huge" differences between the 2.8 and 3.1 that were mentioned??

Doward

There aren't any.

The 'huge' difference in the intake, is the CSI (cold start injector) in the base of the 2.8 intake, and the '2.8' proudly displayed on the top. Look at the 3.1 base intake - you'll see a plug where the CSI once was. That's the difference - costmetic. Volume, runner length, bolt patterns, etc (aka, all the IMPORTANT stuff) is the same.

3.1 has bigger injectors (15pph vs 2.8's 13pph)

That's about it, as far as the motors go.

Dale

iTrader: (12)

2.8 intake doesnt have a vac port for the map sensor . Also where the TB bolts on is slightly different.

middle intake is same

lower is the CSI.

Trans is different due to speedo cables. Also, the older versions are said to be weaker. As I said, they CAN be made to interchange.

Also fuel rail is different.

ljnowell

pretty well the same then.........

Dale

iTrader: (12)

for me its a huge difference.

THEGENERAL

the transmission is a huge difference???

or the intakes and injectors ??

ljnowell

Yep totally different animal.

Bout like a 305 to 350

FbodTrek

Trans EXACTLY the same. As for the rest of the motor, the 3.1 is a MAP air metering system, 2.8 is a MAF air metering system. Also, the 3.1 EGR is electronically controlled, the 2.8 has the 'flying saucer' EGR valve setup. All of the HARD parts are the same however. Same manifolds, heads and TB. And the cute little 2.8 MPFI badge on the intake

Dale

iTrader: (12)

intake

ljnowell

yeah, and as long as you put the right one on, its the same.

TomP

I'm sure a hole could be tapped to get the MAP vac signal from a 2.8 intake. Injectors are, of course, larger on the 3.1, but you'll still pass emissions with 3.1 injectors in a 2.8 motor (I did that earlier this year, passed on NJ's dyno emissions test.)

kretos

ok maybe not completly and utterly the same, but the differences aren't really that big