Chasing weird temps on small block? - Team Camaro Tech
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post #1 of 4 (permalink) Old Aug 21st, 14, 06:17 AM Thread Starter
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Join Date: Apr 2001
Location: Newark, Ohio
Posts: 706
Chasing weird temps on small block?

So a little history first. I bought a 67 Camaro with the original block 327 with 462 or 291 heads on it ( I can check tonight if it make s a difference). I installed an Atomic Efi from MSD and it has been running great. This weekend I installed a PRC aluminum radiator and dual electric fans and having the ecu control the fans. I installed the temp switch for efi in the rear of the Edelbrock RPM Air Gap manifold and my normal Auto meter gauge is in the front of the manifold by the water neck.

My issue is that both my gauges (one in handheld for EFI and the other under the dash) are reading 70 degrees difference. The temp by water neck is the hotter of the two to the point that my fans wont kick on until the mechanical gauge is reading almost 240 degrees.

I understand that I can switch the sending unit locations and see what that does. Also, I have a thermostat housing spacer with a port for a sending unit I can install and try and get both up front.

My biggest question is: Is this normal to have such a difference between the front and back of a motor?

Thanks, Erik

67 Camaro Pro Street, 540 Bill Mitchell Merlin big block, Merlin Aluminum heads, Holley 870, hydraulic camshaft, 2" Hooker Super Comp headers, Mallory and Crane ignition system, TH400, 2600 stahl, Ford 9" w/ 4:10 gears and posi.
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post #2 of 4 (permalink) Old Aug 21st, 14, 06:43 AM
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Location: Lyman, SC
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Re: Chasing weird temps on small block?

I was told not to put my EFI ECT sensor in the rear of the manifold since circulation is so poor back there, it's kinda a dead end. My question would be is the probe for the mechanical gauge "bottoming out" in the front intake port...

Your heads might not have a coolant port on them but if so, I bought a cheapo gauge kit at the parts store and it had a full set of different sized reducer bushings in it so I was able to use one of them to put my Auto Meter mechanical gauge in the head.

To answer the temp spread question though, 20 degrees or so is more of the spread you should see.

And I know it sounds stupid to mention, but make sure the ECT sensor is not actually in the vacuum port on the back of the intake. I only mention it because I bought a Blazer a long time ago that someone had done that to.

'69 Camaro
Dart 400-AFR 195-224/224 HR-Powerjection III TB with F.A.S.T. Sportsman XFI
TKO 600-Moser 3.42-Detroit Truetrac

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'69 Camaro Beater-SFT 327-M20-Moser 4.10-sold
'02 Z/28 vert-stock-sold and totaled
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post #3 of 4 (permalink) Old Aug 21st, 14, 10:38 AM
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Location: virginia
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Re: Chasing weird temps on small block?

I have a mechanical gauge in each head and there is less than 5* difference. the passenger side head (gauge toward back)does read a couple degrees hotter
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post #4 of 4 (permalink) Old Aug 21st, 14, 09:04 PM
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Join Date: Jan 2005
Location: 2 Dog Town in West Texas
Posts: 11,154
Re: Chasing weird temps on small block?

Steiner is correct, the back ports on the Airgap are tapped but has no flow unless you got it going somewhere.
I plumbed these two holes to an adapter block just under my T-stat to eliminate that hot spot. No flow there also causes corrosion on some intakes.
If that fan switch is set for 240, might do what Kevin is saying, go to the head which would be the hottest spot.
Just wondering where that MSD EFI unit has the air temp sensor.
I have seen some guys add a adjustable capillary style temp sensor switch into the radiator hose inlet. Have more control with the off/on , you could stagger the second fan to come on later , main fan runs constant.

TC # 349
Zdld17:69 Z/RS,306, NOR141111, 9N554XXX, 12A, X3G, 59/59,723, AFR 195,CCC282/290HR, TKO 600, BU1122B1E Owner since Dec 1968

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