620 exhaust / downpipe / Y-pipe question

[carterb]

I am in the process of switching the intake and exhaust in my '78 620 from the stock downdraft carb with heavily integrated intake/exhaust manifold with single downpipe to a 510 dual SU set-up with the 510 4 into 2 exhaust manifold and 2 into 1 Y-pipe.

 

The problem is that the Y-pipe runs into the torsion bar. 

 

Did earlier 620 trucks come with the 4-2-1 type exhaust system?  Is the exhaust manifold the same as on the 510?  What does the Y-pipe look like?  Anyone have a spare I can purchase?

 

It looks like the 510 Y-pipe would work if I could twist it to fit between the torsion bar and frame rail, but as-is, there is no way it will fit.

[banzai510(hainz)]

Im thinking the early L16/18   yes then the late L20 had 2 types I know of.

 

HOWABOUT  a 521 y pipe.

The exhaust manifolds are pretty much the same on 510/521 that I seen of. beside air injection or not.

 

here is where I think people were using the Common sold Trimill short tube header  and making a way around the the torsion bar

Edited March 23, 2020 by banzai510(hainz)

[DanielC]

This is a thread on how I made the exhaust system on my 521 trucks.  They pretty much have the same exhaust pipe clearance issues.

https://ratsun.net/topic/61167-how-i-replaced-a-521-exhaust-system/

 

[Stoffregen Motorsports]

56 minutes ago, carterb said:

 

It looks like the 510 Y-pipe would work if I could twist it to fit between the torsion bar and frame rail, but as-is, there is no way it will fit.

Can you weld? Buy some mandrel bends and make it fit.

 

https://www.summitracing.com/search/part-type/exhaust-tubing/exhaust-tubing-type/bend/tubing-material/steel?N=tubing-material%3Asteel&SortBy=Default&SortOrder=Ascending&ibanner=SREPD4

[datzenmike]

Only the '75 through '77 had the integrated intake and exhaust on the U67 head. The '78-'80 with W58 were separate.

 

Maybe your engine was swapped.

 

The '73 and '74 has L16 and L18 engines with the 4 onto 2 exhaust.

All L20B were 4 into one manifolds.

 

[carterb]

Thanks.

 

I know the bolted together integrated intake/exhaust you are talking about.  The L20 stuff isn't quite that bad but it's still pretty much a unit with the metal connection tube and all the other associated garbage.

 

 

I found what must be a 521 collector?

 

 

But even that has some fitment issues.  It hits the transmission.  I think it may have a larger than stock exhaust pipe welded to it and that plus the weld is creating the interference.

 

More here:

 

 

 

[datzenmike]

I have the U67 head with the co joined manifolds. I took them off and put an earlier L16 4 into 2 manifold on.

 

 

I had an L16 exhaust flange and surprisingly a 240sx dual down pipe is pretty close and as the 71B and 71C are physically similar transmissions, it fits around it quite well.

 

I narrowed the 2 pipes to 1.5" so they would fit up into the L16 manifold and welded them in place

 

 

End result was almost the same as a long tube header...

 

 

The intake was useless with that big hole in it. So used a later '79 intake and drilled out the U67 head so it had coolant passages for the manifold. To make it look like an earlier intake I took the EGR manifold off and with some grinding an tapping and some JB weld...

 

This

 

to this.