72 chevota wiring help please (2 Viewers)

[Mopdog]

I was dealing with a similar but worse wiring nightmare on a Chevy V8 swap. With it being so far from stock already and having all kinds of other ground issues and gremlins I just went to an American Autowire harness, Chevy column, and Chevy ignition. I know this makes a lot of purists eyes roll and It’s not done yet but I can’t see regretting it once it’s complete. 50 year old abused wiring just won’t be reliable.

 

[Vandal FJ]

I was dealing with a similar but worse wiring nightmare on a Chevy V8 swap. With it being so far from stock already and having all kinds of other ground issues and gremlins I just went to an American Autowire harness, Chevy column, and Chevy ignition. I know this makes a lot of purists eyes roll and It’s not done yet but I can’t see regretting it once it’s complete. 50 year old abused wiring just won’t be reliable.

I should REALLY come over and help/observe this project. Haven't done mine yet, but it's due!

 

[Mopdog]

I should REALLY come over and help/observe this project. Haven't done mine yet, but it's due!

My son and I will be working on it this Saturday if yup want to swing by.

 

[franklin40]

that’s a deeper rabbit hole that i’m willing to go at this point. i have another 40 that need to take my real time and money. i just want to get this mine running. for now i just need to get this temp sender adapter so i can install the toyota sender. anyone know if the thread size of the temp sender changed from pre 72 to post 72?

 

[pb4ugo]

According to Rockauto looking up temp senders for 72 and 77 the temp senders threads are the same(M16-1.50). I looked at standard motor products reference sheets. I think I purchased my adaptor from the local Toyota dealer. It fit my cylder head. I believe the differences between 72 and 77 senders is the length and ohms. The Toyota threads for the oil sender are different than the SBC's, but really close. You should be able to thread it into the sbc next to the dist. If you search this site all the info is here.

 

[pb4ugo]

I edited and corrected the temp sensor thread to M16-1.50. In the above post.

 

[franklin40]

thanks. i have an adapter for the oil pressure sender. it won’t thread in directly because it’s so big it interferes with the intake manifold. i needed the adapter to get it up above the height of the manifold. i know the early 72 temp senders talk to the gauges cluster of the same years hence needing the right sender. just don’t want to wait to order it to find out what size adapter i need then wait again for the adapter. i want to get this running!! thanks guys

 

[archie73]

I can’t tell you the year break down on matching senders to cluster, but I can tell you that I did fight this on my 350. Best set is to match the luster to the temp sender. I believe I got mine from Cool Ctuisers- Toyota OEM packaging. I had reliable readings once I got the right sender.

 

[franklin40]

yep just ordered one from cityracer (@Racer65) to make sure it matches my year. found an adapter to to go with it and ordered that too. i have been reading and searching through many threads and the common theme is use the sender that matches the year of the cluster or it won’t work!

 

[pbgbottle]

instead of a diode you can use a dummy light also.
I wired up my oem brake dash light as the dummy light now I’ll know when my alt ever stops charging or I left the ignition turned on big red light glowing on the dash. Lol. I bypassed the amp meter in the dash also after one of mine got cooked. I only run the stock gauges with my 350. I can look up what I did I got some info from here somewhere that walks you through the three wire install of chev alternator if I can find it. charge wire ,sensing wire ,diode or dummy light. It was pretty simple hook up if your harness wasn't all hacked up

 

[pb4ugo]

instead of a diode you can use a dummy light also.
I wired up my oem brake dash light as the dummy light now I’ll know when my alt ever stops charging or I left the ignition turned on big red light glowing on the dash. Lol. I bypassed the amp meter in the dash also after one of mine got cooked. I only run the stock gauges with my 350. I can look up what I did I got some info from here somewhere that walks you through the three wire install of chev alternator if I can find it. charge wire ,sensing wire ,diode or dummy light. It was pretty simple hook up if your harness wasn't all hacked up

I did the same. I think eliminating the ammeter and running the alt charge wire to the batt is a much safer setup.

 

[archie73]

I did the same. I think eliminating the ammeter and running the alt charge wire to the batt is a much safer setup.

Yep

 

[archie73]

yep just ordered one from cityracer (@Racer65) to make sure it matches my year. found an adapter to to go with it and ordered that too. i have been reading and searching through many threads and the common theme is use the sender that matches the year of the cluster or it won’t work!

I’m curious about the adapter. I made one from hardware store parts. It works, but takes a while heat up.

 

[franklin40]

i talked to my hot rod/drag race buddy and he recommended using the intake manifold right near the thermostat for the temp sender. said it more accurate so you don’t get combustion temps. i’ve heard it argued both ways but took his advice. i found an adapter that’ll go from the 3/8 npt on the manifold to a m16 thread.

 

[pb4ugo]

i talked to my hot rod/drag race buddy and he recommended using the intake manifold right near the thermostat for the temp sender. said it more accurate so you don’t get combustion temps. i’ve heard it argued both ways but took his advice. i found an adapter that’ll go from the 3/8 npt on the manifold to a m16 thread. View attachment 3293599

Accuracy? The stock gauge doesn't have any numbers on it.

I used Toyota # 90404-16160 to adapt the stock temp sender to my sbc. I used the drivers side cyldr head which is typically GM's stock location for the sender. I try to avoid a bunch of wires running on top of my engine. I think I only added 2 non stk
wires on my sbc conversion. 1 alt charge wire to the batt and 1 for my alt idiot light. I didnt use the stk white/blue wire. All the rest is stk color coded fj40 wiring. I added length to the temp sender wire(yg) so I could run it along the drivers fender to sender. Coolerman sells stk color wire, terminals and plugs.

 

[franklin40]

i don’t think he meant accuracy in terms of a number on the gauge but more along the line of normal operating temp vs over heat temp. normal operating temp is better judged at the thermostat for operating temp. the sender in the head will read hotter because of proximity to combustion chamber. apparently the thermostat reading is a better judge of over all cooling system. i don’t know i’m not a race car builder. i’ve read and understand the validity of both arguments. i want something that gives me a notification that something has changed so i can stop before i actually over heat and set off a dummy light. by then it’s often too late. i do
like actually temps on my performance engine but this is a pretty mild 350 so i don’t think actual numbers are quite as necessary as it m not pushing this one quite the same. it’s a happy medium between actual coolant temp and dummy light.

 

[franklin40]

instead of a diode you can use a dummy light also.
I wired up my oem brake dash light as the dummy light now I’ll know when my alt ever stops charging or I left the ignition turned on big red light glowing on the dash. Lol. I bypassed the amp meter in the dash also after one of mine got cooked. I only run the stock gauges with my 350. I can look up what I did I got some info from here somewhere that walks you through the three wire install of chev alternator if I can find it. charge wire ,sensing wire ,diode or dummy light. It was pretty simple hook up if your harness wasn't all hacked up

what circuit did you wire the brake light into? the charging system ( ie the white blue wires that come off the back of the amp meter?

 

[franklin40]

View attachment 3230000
Figure 2A

View attachment 3230001

From one of my painless wire directions when re-wired the vehicle a few years ago

k trying to get my head wrapped around this. i’m not good with wiring!!

i’ve bypassed the amp meter and reconnected the white blue stripe wire cutting out the extra that was built into the accessory amp meter. so it’s now gone.

according to the above diagram this white blue strip should now go to the charging post on the alternator?

then the red wire here should be the jumper to the white blue stripe?

lastly the #1 post should then come from where?


i did build a new fuseable link into the white wire coming off the pos battery post

 

[pb4ugo]

If you use the diagram # 2a, you won't be using the white/Blue wire, which imo, is a good thing. You should run a new large wire from the alt large post to the batt. Your red wire #2 from the small plug loops to the large post on the alt also. The #1 terminal on the small plug would be the sensing wire, it would typically go to an idiot light. All this has been covered previously in this thread.

 

[franklin40]

that last post has been the most clear answer i’ve had. thank you. i’m sorry if you feel you’ve answered it a few times but the answers aren’t that clear to be honest. for instant yes i get that the red wire needs to go to at idiot light. that’s been mentioned a few times but no one has mentioned in what circuit. is it connected to the ignition? or simply to an idiot light and then grounded. when you used your brake dummy light what did you do with those wire?. just connect them and bypass that light?these are the small seemingly unimportant details i need. i’m really not experienced with this kind of wiring and though i’m trying to learn there are gaps in the previous explanations. also while the diagrams seem very simple they don’t match the wiring colours i have plus none of them have the mess my PO left me. believe me i’m as frustrated figuring this out as you feel explaining it.

also if i’m not using the blue while wire anymore what does bypassing it at the amp meter do then? i’m sorry but it just doesn’t all make sense to me. i’m the kind of guy who likes to know why i’m doing something so i understand better. not just because i’m told “that’s the way it works”.