I have 91 heads with ported 90 housings
11-17-2018, 01:54 PM
#1
Racer
Thread Starter
I have 91 heads with ported 90 housings
What do I have to do to the pcv system on the injector housings to make the pcv system work correctly .i looked at a couple of threads but really can't make heads or tails out of it sorry for the dumb ? Could someone share what I have to do to make this work . Thankyou
11-18-2018, 05:49 PM
#3
Drifting
I see you got your answer. I have the same set up. Conventional wisdom is that this combination will work without modifications since both the heads and the IH’s have the same restriction. I am not having any issues. Recently I have noticed that Marc Haibeck is recommending that the IH restrictions be opened up somewhat to at least 3/4 in. Makes me wonder what he has noticed or experienced to make that recommendation.
H
H
11-19-2018, 07:07 AM
#5
Drifting
1990 model heads were machined to 3/4" diameter for the PCV vents, but too much oil was being passed through the PCV system. The fix was to install a baffle/washer with abut a 5/16" hole in the center, into the injector housings. For 1991 & later models, they reduced the 3/4" holes in the heads to 5/16" and eliminated the machine work & labor to make & install the baffle/washers in the injector housings.
If you have 1990 injector housings on a 1991-2, you can just remove the 2 baffle washers from the injector housing. No drilling or other modifications required.
There is a free, detailed tech data sheet with photos available on Jerrys Gaskets web site that explains all the differences between injector housings.
If you have 1990 injector housings on a 1991-2, you can just remove the 2 baffle washers from the injector housing. No drilling or other modifications required.
There is a free, detailed tech data sheet with photos available on Jerrys Gaskets web site that explains all the differences between injector housings.
11-19-2018, 09:58 AM
#7
Drifting
Dom,
Marc states this in the following thread, post number 5.
http://www.zr1.net/forum/showthread....jector+housing
Jerry,
To be clear, many past posts, even your spec sheet, which detailed the IH variations and possible combinations a few years ago, stated that a 90‘ injector housing on a 91‘-92’ head does not require modifications.
H
Marc states this in the following thread, post number 5.
http://www.zr1.net/forum/showthread....jector+housing
Jerry,
To be clear, many past posts, even your spec sheet, which detailed the IH variations and possible combinations a few years ago, stated that a 90‘ injector housing on a 91‘-92’ head does not require modifications.
H
Last edited by ccmano; 11-19-2018 at 10:07 AM.
11-20-2018, 02:01 AM
#8
Drifting
I don't know what Marc is thinking. I would imagine he is not a fan of two, in-line restrictors and is simply opening up the baffle/washer in the 1990 heads to make the flow path more like the 1991-95 design and nothing magic about the 3/4" sizing. The modification made for 1991-95 models all had the restrictor hole drilled in the head and a cast-in PCV port (about 1") in the injector housing.
11-20-2018, 02:17 AM
#9
Drifting
Dom,
Marc states this in the following thread, post number 5.
http://www.zr1.net/forum/showthread.php?t=28608&highlight=Injecto r+housing
Jerry,
To be clear, many past posts, even your spec sheet, which detailed the IH variations and possible combinations a few years ago, stated that a 90‘ injector housing on a 91‘-92’ head does not require modifications.
H
Marc states this in the following thread, post number 5.
http://www.zr1.net/forum/showthread.php?t=28608&highlight=Injecto r+housing
Jerry,
To be clear, many past posts, even your spec sheet, which detailed the IH variations and possible combinations a few years ago, stated that a 90‘ injector housing on a 91‘-92’ head does not require modifications.
H
You are correct, I don't think it's necessary to modify or remove the PCV baffle in the injector housing when used on a 91~92 cylinder head.
We're not talking about high pressure or high flow rates that would be cause for concern about a back-pressure increase of any detrimental effect. The entire purpose of the small hole is to keep oil in the cylinder head while providing a path for the fresh air inlet flow to each cam cover. It does not double the restriction.
Regardless of what my personal opinion is, removing the baffle/washer in the 1990 injector housing or drilling a 3/4" hole certainly isn't going to be detrimental.
Last edited by A26B; 11-20-2018 at 02:20 AM.
11-20-2018, 08:38 AM
#10
Le Mans Master
I don't know what Marc is thinking. I would imagine he is not a fan of two, in-line restrictors and is simply opening up the baffle/washer in the 1990 heads to make the flow path more like the 1991-95 design and nothing magic about the 3/4" sizing. The modification made for 1991-95 models all had the restrictor hole drilled in the head and a cast-in PCV port (about 1") in the injector housing.
Also, I’ve always had what appears to be “grit” coming from the plenum.
Last edited by Dominic Sorresso; 11-20-2018 at 08:40 AM.