Difference Between 84 and 85 720 Exhaust Manifold

[Stewart]

I’m trying to replace mine due to a crack and a huge leak where the pipe attaches.  I can’t seem to find one anywhere for an 1/1884 720 but there do seem to be some aftermarket for the 85-89 pickup 2WD.  The pics looks the same but it’s the internet and all.

 

Or should i just get an eBay header and call it good (the rest of my exhaust was replaced a year and a half ago so won’t get any power benefit and would prefer to not make things any louder)?

 

 

[datzenmike]

I'll look when I get home but are likely all the same for fit. The 4x4 tend to have two pipes for the air injection and 2wd have only one. Of course you could just cap an extra one. Some will have an O2 sensor but all Z24i 720 and D21 Hardbody will. Again if you don't have the O2 sensor, the hole can simply be plugged if not used. A header is a waste of money and you'd be cutting up a new down pipe.

[Madkaw]

9 hours ago, Stewart said:

I’m trying to replace mine due to a crack and a huge leak where the pipe attaches.  I can’t seem to find one anywhere for an 1/1884 720 but there do seem to be some aftermarket for the 85-89 pickup 2WD.  The pics looks the same but it’s the internet and all.

 

Or should i just get an eBay header and call it good (the rest of my exhaust was replaced a year and a half ago so won’t get any power benefit and would prefer to not make things any louder)?

 

 

I didn’t have much luck with aftermarket manifolds , some guys have. I’d try and find an OEM used one . Someone sent me one for the price of shipping .

[datzenmike]

All manifolds are the same after '82. There are some differences noted before, but should bolft together the same. Seriously why make a different manifold for different years or trucks using the same engine.?  

[Stewart]

2 hours ago, datzenmike said:

All manifolds are the same after '82. There are some differences noted before, but should bolft together the same. Seriously why make a different manifold for different years or trucks using the same engine.?  

Thanks!  It looks like ATP and Dorman both have different part numbers listed for 85-89.  The one for 81-89 or 81-85 is discontinued hence my question.  It doesn’t seem like it should be different.

[Stewart]

16 hours ago, Madkaw said:

I didn’t have much luck with aftermarket manifolds , some guys have. I’d try and find an OEM used one . Someone sent me one for the price of shipping .

What has the problem been?  It seems difficult to find a used one that isn’t cracked or warped nowadays.

[datzenmike]

I forgot to check the D21 Hardbody last night. It uses the same Z24 as some of the late 720s but it is in a different body and the outlet down pipe may be angled differently but I don't know. I'll try again tonight.

[Madkaw]

4 hours ago, Stewart said:

What has the problem been?  It seems difficult to find a used one that isn’t cracked or warped nowadays.

 
First one I got was cracked - sand castings are bad ? The second one I got fit like crap . I sent both back .

I did just take one off of a truck today - used OEM I’d sell. I need to check it over first . Truck had 108k miles 

[datzenmike]

I found a part number from '84 720 on and for '86-'89 D21 that were the same so I would say they are all the same shape just some may have O² sensor hole or extra air injection tube hole.

 

Best is a used one that isn't broken.

 

 

 

The left one is just run of the mill Z24 exhaust. The other is from a later 720 and has the O² sensor (green wire) and the snake tube isn't on the left one but you can see it has a boss that could be drilled and tapped for it.

[Charlie69]

The aftermarket manifolds have extra threaded holes so the work on all models of the Z24 and Z20 engines. Not sure on the Z22 as I have not ran one but the Exhaust manifold gasket to head are the same.

 

I have run the after market manifolds on 84, 85, and 86 720s with no problems.  Use the holes you need in the manifold and plug the rest.

Edited December 6, 2019 by Charlie69

[Madkaw]

Wouldn’t you know , I spent 30 minutes pulling one from the JY and found it was cracked afterwards - ARGH

[zrex]

 I never had good luck with the Dorman/Chinese exhaust manifolds. After pulling several manifolds that had the same cracking i found a 88 hardbody that wasn’t cracked. 
 

[Stewart]

Cool, thanks for that, you guys are awesome!  I'll see what I can find locally now that I can broaden the search.