Starter Question

I am dealing with a starter issue I do not understand. I have a SBF 302 '81 model in my 40 hot rod truck. I can go out and turn the key and the motor turns over strong and it starts right up. After I drive the truck around and the motor gets warm it is a different story. When I turn the key then the motor seems to struggle to turn over. If I let it sit for a while to ambient temp it turns over strong again.

My battery is mounted in the back of the truck, and the solenoid is about 3ft back of the starter

 

You are losing amperage through the long cables. When the starter gets hot it will draw more power. Check the size of your cables and all connections. 0 or 00 Welding cable works the best. Be sure to check the ground cables as well.

 

How close does the exhaust run to the starter? Hot starters tend to drag. If heat is the problem, then a simple heat shield between the starter and exhaust will solve the problem. An easy way to check for heat is to pour cool water on the starter and then try to start the engine while it is hot.

 

Try making a shield to keep the heat off the starter . They are also made and I think can be found in Summit , Jegs or a place like that . You can also use some header wrap on the exhaust near the starter . That is some of the first easy things to do to keep that extra heat off the starter .
Also how far away is the batter from the starter ? Just remember the longs the cable ,the bigger it should be . If in the trunk then you need bigger wire to carry the current from the battery . Like someone else said , welding cables work great for that job . Sometimes you can buy some good used cables on C/L . I got mine that way and you only need enough for the positive cable . Neg goes straight to the frame .
You can also have a battery warehouse or a battery shop test the drag on the starter for free . If you have a load tester , that will tell you the problem .

Retro Jim

 

I ended up putting a high torque starter on my 302---hot start condition due to the proximity of the header. Cured the problem---already had the welder cable to the trunk.

 

I would also recommend that the ground cable from the battery should go directly to the engine.