Exhaust manifold

[jonlabree]

Does anyone know if the 90 and 91 Exhaust minifolds are the same or different?

Jon..

[dship]

I looked it up in the 1988-1993 Parts & Illustration Catalog for Riviera/Reatta:

Left hand exhaust manifold part# 24501727 good for 1988-1992 LN3 & L27 3.8L engines

Right hand exhaust manifold part# 25537100 good for 1991-1992 L27 3.8L engine only

Right hand exhaust manifold part# 25531722 good for 1988-1990 LN3 3.8L engine only

[2seater]

I seem to remember the front manifold went to a cast manifold on the later model to help with converter light off due to greater heat retention. Hopefully someone with a '91 can confirm.

I just looked at those part numbers and the right manifold is the one on the rear? I would have thought that would be listed as the left, as in the engine positioned front to rear like in a rwd? In any case, the '91 rear manifold looks exactly the same as the LN3 except it has no provision for an EGR tube. I did see a reference to two different designs for the front, one with a seperate crossover and a second design with a crossover integrated with the front manifold.

For reference purposes, bone stock, the individual ports flow 151-202 cfm @ 28"w.c (or approx. 1 psi of pressure). This is tested as assembled on the engine pulling a vacuum through the rear outlet with an O2 sensor installed. A ported and ceramic coated set I have flowed 196-249 cfm under the same test conditions. Removing that rear restriction really does help potential flow. Modified further as below helps even more.

[jonlabree]

Anyone have one that is pipe not cast for sale?

Rear only.

Jon..

[dship]

Reading from the pages of the Parts & Illustration Catalog....Left hand is front, right hand is rear. Cast manifold was on 2nd design of the 1992 Riviera model L27 engine.

[2seater]

Now that you mention front/rear vs left/right, I realize I was imagining the engine rotated the wrong way. Now it makes perfect sense. Sheeesh.

[padgett]

I prefer front/rear or drivers/passenger side. In this country that is unambiguous. Most V engines I have known the odd cyl were on the driver's side but Chrysler is different.

[D-a-n-i-e-l]

2SEATER,

You are runnign your turbo off one side. correct?

How is it holding up?

[2seater]

Yes, it is still connected to the front manifold only, hence the reason for the odd modification to the rear manifold. Boost is a little lower than I would like at about 4 psi max, but it works seamlessly. No real tuning done, just the stock chip and about 30% larger injectors. Looking for a used Ford pattern .36 A/R turbine housing for a Garrett T3 to spin it harder. It will just max-out the MAF reading at 172 gr/sec