Frankenstein 454 swap. Overheating at idle.

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Bextreme04

Full Access Member
Joined
May 13, 2019
Posts
4,439
Reaction score
5,581
Location
Oregon
First Name
Eric
Truck Year
1980
Truck Model
K25
Engine Size
350-4bbl
Nice! Glad to see it work out. I'll be putting my big block radiator and fans in soon as well.
 

83Burban

Full Access Member
Joined
Apr 10, 2021
Posts
207
Reaction score
268
Location
Kansas CIty, MO
First Name
Matthew
Truck Year
1983
Truck Model
Suburban K10
Engine Size
454
@Bextreme04

When fans kick on, I lose between 150 and 200rpm at idol. Drops down to about 600ish. Is this pretty normal? All seems to be functioning properly otherwise. Maybe set idle a little higher than recomended 800rpm?

One time while crusing around today it stumbled a bit at take off....almost killed it. Think fans kicked on just as I started to give it throttle.

Everything else was flawless.
 

Bextreme04

Full Access Member
Joined
May 13, 2019
Posts
4,439
Reaction score
5,581
Location
Oregon
First Name
Eric
Truck Year
1980
Truck Model
K25
Engine Size
350-4bbl
The fans are a big power draw... but you have dual batteries and a decent sized alternator, right? It shouldn't be drawing more than 30-40amps total as they run. The GMT400 serpentine alternator I have for my 454 is a 110amp, the stock 80's one is like 40amp or something silly. How do you have the second battery connected?

Is it on an ignition activated relay with a large 4-8ga wire? How are you feeding power to the fans?

There is a solenoid that mounted on the front of quadrajets to kick up the idle when the AC was activated, that might be an option.
 

Matt69olds

Full Access Member
Joined
Jan 8, 2018
Posts
2,451
Reaction score
3,819
Location
Central Indiana
First Name
Matt
Truck Year
81
Truck Model
GMC 1/2 ton
Engine Size
455 Olds
The fans might draw 60-70 amps at startup, then settle down to a much lower draw. Mount the relays as close to the battery as possible, go overkill on the wiring.
 

83Burban

Full Access Member
Joined
Apr 10, 2021
Posts
207
Reaction score
268
Location
Kansas CIty, MO
First Name
Matthew
Truck Year
1983
Truck Model
Suburban K10
Engine Size
454
Hmm...never got alerts for last two posts? My bad guys.

I'll post pics of my "Painless" fan relay wiring set up. Its not actually been "mounted". The previous owner installed it directly between the fan shroud and the motor. Had been spliced SO MANY times and with the toaster oven conditions in the engine compartment it was cooking off the relays. One of the longer wires was made with 3 colors of wire...all different guages.

Lol ive got it mostly sorted now....its just not been "installed".

If weather holds up today....ill make a video detailing the lay out and see what you all think.
 

83Burban

Full Access Member
Joined
Apr 10, 2021
Posts
207
Reaction score
268
Location
Kansas CIty, MO
First Name
Matthew
Truck Year
1983
Truck Model
Suburban K10
Engine Size
454
The painless wiring harness has three (3) 40a relays and a 70a fusible link. Forgive the mess. I'm still sorting it out. It will all be put in a propper wire loom once I know whats what.

xc_hide_links_from_guests_guests_error_hide_media
 

Rusty Nail

Full Access Member
Joined
Jan 29, 2015
Posts
10,041
Reaction score
10,133
Location
the other side of the internet
First Name
Rusty
Truck Year
1977
Truck Model
C20
Engine Size
350sbc
Looking at your picture again, the serpentine belt drive is not factory. Homemade, not working with that water pump. Also does not have a very good rap around the power steering pump pulley either.

I believe you need to address the belt drive system.

X2
There us an ASSLOAD of deflection in that belt scheme.
 

Latest posts

Forum statistics

Threads
44,163
Posts
950,654
Members
36,276
Latest member
2manysquares2care
Top