FJ 40 SB Chevy conversion running hot? (1 Viewer)

[Trippster]

Those with SB Chevy conversion, what’s your temps running at?

I have SB conversion with Vintage Air AC system and two speed electric fan. My temp is reaching 215 degrees. Is this normal, all good or start over?????

Thank you all,

Ben

 

[peesalot]

What temp thermostat is in it ? FWIW I have run an old school sbc & an LS both on the stock radiator, & mech clutch fan. 20+ years good temps 190 ish usually, will get to 210 when crawling all day in the sun but rpm pulls it down. IMO PS, trans coolers should be separate fan but thats just my tastes. Have you checked fan to see when it kicks on and which speed it runs ? I would wire a temp hot to run fan on high, run it full time and see if the temp stays down that way you will know if the system in general will cool it. If that works I would look at the temp the fan goes on at and what speed. Is it pushing out fluid when 215 * ? What psi is the cap ?

 

[Trippster]

Good point, I currently have my low speed set to 160 and high set at 190. I think thermostat is around 100 not sure exactly? I’ll switch my high speed to a lower tempt to run continuously on high and see if that fixes things.

Thank you, Sir

Ben

 

[67azcruizr]

what peesalot said

I ran Flex-a-lite fans in a few 4X series with SBC's in them. the fans had 3 settings, OFF (for river crossing etc.), ON (manual for crawling etc.) and Auto (thermostat driven probe inserted into the radiator) for normal driving conditions. I found myself using the switch more frequently than I had guessed I would.

180* thermostat is recognized as most used with carbed/non-emissioned SBC engines. there is always the 165*, and with driving in San Antonio may be your ticket

everything looks very clean, and your shroud looks like it fits nicely. just curious, they appear to be stock height valve covers but is this engine "stroked"?

the headers wrapped also look very clean, side note: if you have them started eating up gaskets per thermal expansion/contraction like mine did, my fix were Ram's Horns. they also gave the engine a quieter/deeper sound

 

[Trippster]

Thanks for all the info. Good stuff! No Sir, just crate engine from Jeggs. Normal cam, all stock.

 

[JohnnyFish]

I drove mine today in Austin the furthest I’ve ever driven it, which was about an hour and a half total. Most of the time it ran 185-ish but occasionally it would spike to 220. I realized that the front disc brake conversion on this 72 SBC FJ40 needs some maintenance because the brakes were staying engaged. The engine is getting hot because it’s pushing through the brakes on the highway. I pulled off the highway this morning coming home from the land cruiser meet and the front brakes were smoking. I manually knocked the pads off of the disks and was able to make it home with no further incident. I guess I’ll take the calipers off and inspect them to make sure they’re operating right. I recently switched from an electric fan to a non clutch mechanical. I prefer it so far.

 

[Trippster]

Glad you made it home

 

[69FJ40NJ]

in NJ, runs 190 to 210 with electric fan constantly running. May switch to a flex fan, shroud, ditch the electric fan, and a new 180 thermostat.

 

[69FJ40NJ]

Another question, with the SBC motor and carb, are you running a electric or manual fuel pump? Thanks

 

[JohnnyFish]

Another question, with the SBC motor and carb, are you running a electric or manual fuel pump? Thanks

Stock mechanical fuel pump on mine. It’s reliable and stops running when the engine does if I crash. : /

 

[Trippster]

Electric fuel pump. I’m running the MSD EFI with ready to run distributor. I should have held off for the Holly Sniper system.

 

[texcwa]

Just installed the Holley Sniper EFI and Hyperspark Ignition on my sbc 355, made a world of difference, although may not add much HP it sure unleashes the HP you have. Throttle response is unbelievable, have to take caution when pulling out of a stop sign for a turn since I can spin my 34's at half throttle. Have timing set at Idle 25 adv. Cruise 40 adv, WOT 35 adv. Any advice on timing settings would be greatly appreciated.

 

[B y r o n]

I drove mine today in Austin the furthest I’ve ever driven it, which was about an hour and a half total. Most of the time it ran 185-ish but occasionally it would spike to 220. I realized that the front disc brake conversion on this 72 SBC FJ40 needs some maintenance because the brakes were staying engaged. The engine is getting hot because it’s pushing through the brakes on the highway. I pulled off the highway this morning coming home from the land cruiser meet and the front brakes were smoking. I manually knocked the pads off of the disks and was able to make it home with no further incident. I guess I’ll take the calipers off and inspect them to make sure they’re operating right. I recently switched from an electric fan to a non clutch mechanical. I prefer it so far.

If you added front disc and kept the '72 master and didn't pull the front residual valve that is why the disc stayed against the rotor. Drum residual valve is 10 psi and disc only needs 2 psi or none at all.

 

[Trippster]

That looks really nice, sounds like it’s running great. Sorry, I’m not the one to ask about timing setting. There’s a shop down the road from me that has a Dino setup that’s going to set me up. I’m currently running 10 degrees….sounds like I need to go more????

 

[texcwa]

I drove it for the first drive today (about 100 miles) after installing EFI, the temp was at 175 cruising on flat at 60 mph, 196 on 3 -5 mile uphill grade (2000 ft alt change). I may reduce my Idle to 23 deg and cruise to 38 deg to see if it makes any difference in temp.

The motor does have a moderate cam, Comp Extreme 262H thus why I am running more advanced, plus the motor seems to like it.

 

[JohnnyFish]

If you added front disc and kept the '72 master and didn't pull the front residual valve that is why the disc stayed against the rotor. Drum residual valve is 10 psi and disc only needs 2 psi or none at all.

That is EXACTLY the kind of insight I come to mud for. Thank you!

I know nothing about the conversion as the whole truck was built by a PO. There is a valve on the front brake line, which I imagine they put on to address this problem. Didn’t get it fully sorted before selling.

 

[texcwa]

When I did the front disc conversion (about 15 years ago) I used the FJ60 Berts (Chevy Rotors and Calipers bolted right on), had the Brake Booster rebuilt and used an FJ80 Master cylinder (single reservoir) that was a direct bolt on to the booster. Never have had any issues running the discs on front with OEM drums on rear. The attached pic is not best quality, but you can see the master brake cylinder in the upper right.

 

[bikersmurf]

That is EXACTLY the kind of insight I come to mud for. Thank you!

I know nothing about the conversion as the whole truck was built by a PO. There is a valve on the front brake line, which I imagine they put on to address this problem. Didn’t get it fully sorted before selling.
View attachment 3357308

The valve on the front cylinder looks like an adjustable proportioning valve. I have never seen one installed in the front circuit before. Usually they are added to limit rear wheel lockup after converting to disc brakes. Usually they are needed for both 2 wheel disc conversions and 4 wheel disc conversions. I've needed them for both my front disc conversion and my 4 wheel disc conversion.

 

[bikersmurf]

Those with SB Chevy conversion, what’s your temps running at?

I have SB conversion with Vintage Air AC system and two speed electric fan. My temp is reaching 215 degrees. Is this normal, all good or start over?????

Thank you all,

Ben

View attachment 3356969

How close to the fire wall are the valve covers?

Often electric fans are inadequate for keeping a V8 cool.

 

[WILLD420]

You have to separate the front of the radiator from the back. Heat builds up in the engine bay and the hot air coming off the fan tends to work back in front of the radiator and cycle back through. That is why you see all the seals around the front end of newer cars. Don't forget the bottom as well. It will come out, and get sucked forward and back up into the radiator. If your timing is off a little, that will make it run hotter. If you didn't verify the TDC mark on the damper, you could be adding or subtracting more than you believe.