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73-87 Chevy _ GMC Trucks => 73-87 Chevy & GMC Trucks => Topic started by: 77c15 on January 23, 2008, 07:14:51 pm
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I have recently upgraded my 74 c10 with a 69 vette 355 small block and HEI distributor from a 79 c10. I had my neighbor (retired ASE city of New York tech) rebuild the distributor (new magnetic pickup coil, coil, and ground strap). I have had some issues with getting something hooked up to the BAT terminal on the coil. I ran direct 12v from the firewall junction block and fried the coil (reason for the rebuild). I have found several 12v sources on the fuse block, but tested them just a few minutes ago and found that they go to 0 on the voltmeter when attempting to crank. I know this is normal because all acc are off during cranking to ensure fire. Well, that's my problem. Where should I tap into so I get constant 12v with the key on and cranking? The fuse block, other than constant 12v BAT terminal is out of the question, and I really don't feel like frying another coil. Any help would be appreciated. Thanks, guys!
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When I swapped my 74 C10 to HEI all I did is cut the eye connector off the battery post wire on the old points coil and put a spade connector on then plugged it into the battery post on the HEI coil.
My truck is stripped to the frame right now for a full restoration and my harness is boxed up somewhere. So, I can't look at it to tell you which wire on the fire wall block will work.
You should be able to find the right one with a test light/volt meter while someone operates the switch.
Good Luck
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All you need is a Key on B+ Fused wire to the coil. You do not want hot at all times or you will overheat the coil. Don't just randomly tap into other circuits. Your fuse box has ckt protected hot in run tap sources and you can run a new wire to the coil.
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There should be a slot labeled ING on the fuse panel you can tap into. That is what I did on my 73.
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I tried the IGN labeled circuit and the ACC circuit and they both went to 0v while attempting to crank. I thought this was weird also, but that's what happened. Any other ideas?
Also, I have a new harness that I got for christmas from American Autowire and it has the old coil wire for the points system, but the other end of it is supposed to go to the starter terminal and when I hooked all that up the engine was attempting to crank without the key in the switch.
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You will need to use the Ign circuit with a ballast resistor for running after start. To get the truck running, use the starter circuit as well. This will be a full 12v and used during cranking.
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If the ING slot is not hot switched, and the starter is engaging without the key, my first thought is there is something wired wrong in the new harness, or you hooked up something wrong.
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You will need to use the Ign circuit with a ballast resistor for running after start. To get the truck running, use the starter circuit as well. This will be a full 12v and used during cranking.
He's done an HEI conversion. No ballast resistor or resistance wire should be used unless he wants low coil output.
The R terminal on the starter solenoid is energized only during cranking. You should not be losing B+ during cranking. Is your ignition switch properly adjusted/ wired?
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Quote from: ccz145a on Today at 11:28:14 AM
You will need to use the Ign circuit with a ballast resistor for running after start. To get the truck running, use the starter circuit as well. This will be a full 12v and used during cranking.
He's done an HEI conversion. No ballast resistor or resistance wire should be used unless he wants low coil output.
man, I completely misread the post. my bad. :-[
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I double checked the harness...the cranking without the key was because I had the yellow wire to coil hooked up to the wrong starter terminal. I ran it to BAT (fused) on the block and it started fine, but now i've got more lovely FelPro gasket issues...the intake manifold gaskets are yet again leaking coolant into the engine, so I got the Mr. Gasket ones that Edelbrock recommends with the intake. Still:
Can I run that yellow wire to the R terminal on the starter?
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OK wait ??? You have the coil wired to the starter?
You will NOT use the R terminal on the solenoid. Nothing should be hooked up there.
As far as Fel=Pro gaskets being the cause of a failure I've never had a problem with Fel-Pro gaskets. Where do you see coolant? In the oil in the crankcase?
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The coolant was shooting out from around the oil filter and did come out when I drained the oil. I took the Edelbrock Performer intake manifold off and can see, just like with a head gasket, where the coolant escaped from around the gasket and got down in the valley and through the oil passages.
I really need to know where to tie in the BAT wire for the distributor. From the factory, the coil wire for the points system did hook up to the R terminal to give it 12v at cranking and a constant 9v while driving. I'm not concerned about that, I just need to know where to hook it up to HEI BAT terminal so it will get 12v at cranking. With it hooked into IGN at the fuseblock, I had a spare plug in the #1 wire and wasnt getting any fire/shock while cranking.
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The R terminal only gets 12 V during cranking. After that it is zero volts not 9 volts. The 9v came from the resistance wire. If you have where the factory harness connected to the points coil there just cut out the resistance wire and run a regular wire from there to the coil. You should still not lose B+ during cranking. If worse comes to worse run a wire from the R terminal and connect it to the wire you have going to the coil now. That will energize your coil during cranking if you can't figure it out.
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The switch, not the lock cylinder, is bad...it is being replaced today. I am going through the brakes and the engine overall today to get her in road worthy condition before having her towed to the exhaust shop tomorrow. I can't wait to drive it home from the exhaust shop. I have been waiting 3 years for this.
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""If worse comes to worse run a wire from the R terminal and connect it to the wire you have going to the coil now. That will energize your coil during cranking if you can't figure it out.""
Vile, if he runs a wire from the switched start circuit on the starter, to the same ignition wire from th switch to the coil, then won't his starter stay engauged when he turns on the key. May need to install a heavy duty diode. In short, there has to be something wrong with the ignition switch. If he has power, then it goes away when cranking, the switch seems to be the most likely culprit, right??
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""If worse comes to worse run a wire from the R terminal and connect it to the wire you have going to the coil now. That will energize your coil during cranking if you can't figure it out.""
Vile, if he runs a wire from the switched start circuit on the starter, to the same ignition wire from th switch to the coil, then won't his starter stay engauged when he turns on the key. May need to install a heavy duty diode. In short, there has to be something wrong with the ignition switch. If he has power, then it goes away when cranking, the switch seems to be the most likely culprit, right??
It seems he figured out it was a bad ignition switch. The R terminal on the starter is only energized during cranking. It was originally used for this purpose to deliver full 12volts to the coil during cranking. It gets energized by the solenoid from the B+ terminal on the starter. It will not keep the starter energized, that's what the S terminal does.
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Hijacking my own thread...but first: I did conclude that the switch was bad, because there shouldn't be a 12v drop to 0v at the IGN source on the fuseblock.
Okay: Anyone have Flowmaster single chambers on their truck with true dual exhaust? I'm taking my truck to the exhaust shop tomorrow and i'm going to have them put between 2 and 3 feet of pipe between the headers and mufflers, then the flowmasters with turndowns on them (right under the seat!). Are they annoyingly loud and obnoxious? I had a shop put them on my brothers IROC, but they were the only thing that would fit under his F-body with true duals from the headers to the side exit exhaust (almost like side pipes). His car is loud, but not obnoxious. It's a pleasant tone. I'd rather hear the music of the motor than the junk on the local radio stations anyway!
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Your truck is going to be obnoxious and you are going to drone yourself out of the cab. BTW you don't need an exhaust shop to do that, it's not even an exhaust sytem :D My advice is install a 2 or 3 chamber flowmaster b4 the axle, bring the pipes up toward the bed and turn out behind the rear axle. Sounds awesome inside and outside plus it looks the best that way.
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Also, an H pipe is easy enough to do too without any obstruction
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The H pipe is highly advised. It helps performance and in my own 2 cent opinion it gives a better,more mellow tone that these trucks are noted for. I've got 2 chambers onmy wifes 3/4 ton with a bigblock and it sounds great. I've run other mufflers in the past, but they don't have the same sound. I have flows on everything. I am putting singles on my choptop, but it won't be daily driven, no stereo, and I want obnoxious.
By the way Vile, Thanks for the info on the s and r terminals, it has been a while since I have messed with the points stlye trucks and forgot.
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You will hate the exhaust within a week if you dump it under the cab...
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The exhaust is dumped under my extended cab, and you are RIGHT, i DO HATE IT. Next stop, exhaust all the way out the end.
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Single chambers (i assume you're talking about the race 10 series) are no louder than blown out glasspacks, and thats the most common sound I hear on these trucks..dumped before the rear axle. I kinda like it, but I don't like the extra attention you get from being THAT loud..especially with certain neighborhoods having noise restrictions.
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I am looking at the single chamber Flowmaster for my choptop because it is so small. I willl be running a 496, routing the exhaust through the frame, and the muffler will be under the cab where the fuel tanks were, the the exhaust will exit under the step on the bed. I have alot of mos to do it I think it will work. This truck will lay on the ground when done, so I need all the clearance I can get
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Just had the exhaust done today...it exits right in front of the rear axle with turndowns right after the mufflers (flowmaster 40 series) and at idle the cab vibrates! Here are some pix of the job:
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That last picture is the entire reason I trust this guy working on my truck...he even talked me into dumping the mufflers and turn downs right in front of the axle...his truck was sweet! He sold that bad boy for 10 grand without the blown 427!!!