AFR Heads
Thread Starter
Instructor
Joined: Apr 2009
Posts: 175
Likes: 12
From: Jacksonville NC
AFR Heads
Ive built a new dart SHP engine with AFR heads and temperature switch hole in AFRs ar 3/8 and wanted to know what sender will work for factory gauge. Looking at Holley 534-2 switch but can't find anything. Thanks
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
You could always have a machine shop drill & tap for the correct size. I believe its a 5/8 NPT? Don't remember. Anyway a local shop charged me $30 to do that. That's a $500 piece of aluminum, so I figure let the pro's do it. Then you can use the stock sending unit.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
I have AFR 210 heads and I originally installed the sender on the side of the heads. It always read artificially too high because of the proximity to the exhaust ports. so I moved it to the intake before the thermostat.
It is on the other side from the brass plug.
It is on the other side from the brass plug.
Le Mans Master
Joined: Oct 2007
Posts: 7,451
Likes: 974
From: RI, Now Franklin/Nashville TN
What I did with my AFR's and the stock sending unit^^^^^^^^^^^^^^^^^^^^^^^^^
Safety Car
Joined: Oct 2004
Posts: 3,926
Likes: 739
From: Youngstown Ohio
I just moved mine to the intake manifold. But I believe Willcox has one that fits aftermarket heads..........https://willcoxcorvette.com/corvette...79-3-8-npt-new
Le Mans Master
Joined: Oct 2007
Posts: 7,451
Likes: 974
From: RI, Now Franklin/Nashville TN
Problem is most of the aftermarket units that fit aftermarket heads are not 100% accurate like the OEM one and the reason I opted to have my AFR's tapped by my builder for the OEM sending unit. I was aware of the Willcox and other units but passed on feedback I read.....about them be inaccurate
Last edited by jb78L-82; Jan 14, 2019 at 06:28 PM.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
Just move the stock one to the intake manifold or to the water pump. Where you see the blue plug in gkull’s picture.
you can also get thermostat housings that will accommodate the stock sender.
then put a pipe plug in the hole in the heads.
you can also get thermostat housings that will accommodate the stock sender.
then put a pipe plug in the hole in the heads.
Last edited by REELAV8R; Jan 14, 2019 at 10:22 PM.
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Race Director
Joined: Jan 2000
Posts: 12,399
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From: San Jose CA
Problem is most of the aftermarket units that fit aftermarket heads are not 100% accurate like the OEM one and the reason I opted to have my AFR's tapped by my builder for the OEM sending unit. I was aware of the Willcox and other units but passed on feedback I read.....about them be inaccurate
The bigger reason I'd recommend going 1/2NPT is that you just don't have to deal with it after the fact, if/when the machined sending unit goes bad.
Last edited by Shark Racer; Jan 16, 2019 at 09:58 PM.
Melting Slicks
Joined: Oct 2002
Posts: 2,317
Likes: 111
From: St Louis MO
I had this problem with AFR 210s. Upon examination, it appeared that resizing the hole in the heads to 1/2" NPT would cause the bottom of the temp sensor to hit the runner internally. Like others have done, put it in the intake manifold instead.
Last edited by larrywalk; Jan 16, 2019 at 10:15 PM.
Le Mans Master
Joined: Oct 2007
Posts: 7,451
Likes: 974
From: RI, Now Franklin/Nashville TN
The Willcox unit is correct temp sender, but milled down to fit the head. As long as everything is reasonably on-center, this can be done. If there's any shift in the casting or previous machining caused the temp sender to be offset, you can end up ruining the sending unit when milling down to 3/8. I don't think this is a significant cause of concern, but is possible.
The bigger reason I'd recommend going 1/2NPT is that you just don't have to deal with it after the fact, if/when the machined sending unit goes bad.
The bigger reason I'd recommend going 1/2NPT is that you just don't have to deal with it after the fact, if/when the machined sending unit goes bad.
Yes, I do remember Willcox explaining this process^^^^^^^. Again, this is not Willcox's fault by any means and I could be wrong but I read at the time of my decision that most of the aftermarket 1/2 inch GM type sending units often have/had accuracy issues (AKA-the OEM ones are superior to what you can buy today). So, Milling down an aftermarket 1/2 inch sending unit still leaves you with an aftermarket unit that MAY not be accurate. If the 3/8 inch aftermarket units are accurate, I am good to go....don't tap the heads for the OEM unit....
Last edited by jb78L-82; Jan 17, 2019 at 06:25 AM.
Race Director
Joined: Jan 2000
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From: San Jose CA
Yes, I do remember Willcox explaining this process^^^^^^^. Again, this is not Willcox's fault by any means and I could be wrong but I read at the time of my decision that most of the aftermarket 1/2 inch GM type sending units often have/had accuracy issues (AKA-the OEM ones are superior to what you can buy today). So, Milling down an aftermarket 1/2 inch sending unit still leaves you with an aftermarket unit that MAY not be accurate. If the 3/8 inch aftermarket units are accurate, I am good to go....don't tap the heads for the OEM unit....
I agree 100% that the aftermarket offerings for temp senders requires a lot of buyer precaution.