Thanks for the response guys, I don’t really know what to do. I bought an 86 firebird with 200,000 miles, stock engine (lg4) and tranny (700r4). From march to now I’ve taken the heads off, lapped valves, new valve seals, put in a new summit cam and lifters, new Holley intake, new gaskets, new Edelbrock carb, new hei vac dizzy, new radiator, thermostat, analog oil pressure sensor, timing set, new cooling fan (wiring needs to be reverted to original) and all new front suspension, new fuel and brake lines, all new brakes, and more. I’m pretty sure the engine and tranny had also recently been gone through (within a few miles of being put away for a few years before I bought it). Ever since I got the car running again, it acts weird. When running the engine reaches operating temp, immediately gets super hot afterwards, then after 5 seconds drops back down to ~ 215. It leaks a little oil from the oil pan gasket, and is sluggish (almost wanting to die) up to 2500 then it rips. Tranny shifts nice, but lockup was never reinsralled. Currently I don’t trust the car enough to drive more than a couple miles to local car shows. I’m pretty sure it’s running lean (in tank fuel pump is long dead). I don’t need a lot of power and am more than happy with the 305, but I’m debating whether I should seriously rip it out and rebuild it from the bottom up, or just look into a new block. I’m very tight on cash, I’m only a freshman in college. Any insight you guys have would be great, I’m only planning to drive the car reliably a couple miles per year in the summer and treat it nice. Thanks again.

 

Good looking machine. Sounds like a bad/sticking thermostat. Not unusual these days with all the crap parts available. With your upgrades you are not far from having a real great machine. (I'm liking that garage too)

 

Maybe not.

Is there a bolt in this hole?



"New block" won't fix this. Sounds more like an inappropriate cam choice; specifically, too much. What cam did you put in it?

"New block" won't fix this either. Sounds more like something about the cooling system isn't set up right. What fan clutch is on it?

So I assume (yeah I know) that you're running a mech one on the side of the block. If so, why the hell is the broken one still in the tank? "New block" won't fix that either. Neither will "rip it out and rebuild it from the bottom up". If you don't fix what's wrong with it, the same things will STILL be wrong with it, no matter what castings you put under the hood.

Fix the car. It's not that hard. Especially when you ALREADY KNOW what's wrong with it, like the fuel pump.

 

Thanks for the help sofa. Pretty sure I have a bolt there because I heard the horror stories from other members of the forum. The oil leaks from underneath the timing cover where the po messed up the rubber oil pan gasket. I’m gonna try a new thermostat like Tom recommended. Part of why I want to get the block out is because my oil pressure acts funny; when starting I sit around 35 ish but during driving it will progressively drop, and at some points has reached zero. Upon restarting it oil goes back up to 35. Oil level hasn’t dropped like I have a crack or missing plug anywhere. I’ve heard rumors the old nylon cam gears would break down and get sucked up by the pump, which already seemed a little tired when I was priming the lifters before first start. I currently have the summit 1065 flat tappet cam and lifter kit (see specs in pic below). As for temp, I was nervous that the bearings may be going because it’s such a high mileage engine and I have no idea what was done to it before me, I’m the 5th owner lol. Stock water pump, basic aftermarket fan (needs to be rewired per your recommendation in the other thread I posted, will probably get to that in December over break). As for the fuel pump, it’s the stock mechanical on the block that I cleaned out thoroughly before starting it. The one in the tank poses a problem because I don’t have access to any kind of lift to drop necessary stuff, and would have to do it in a small garage the old fashioned way on my back, or cut a whole in my trunk. No problem with that, but all of my experience comes from working on this car, some help from my old hs shop teacher and YouTube so I’m still really amateur. Id hate to start going at stuff without really knowing what I’m getting into 🤦‍♂️. The car has also sat inside and out for unknown periods of time, and I’ve heard that weather can compromise block integrity. I’ve also hear if it’s not compromised already then it’s not going to be. Thanks again for the response

 

Not sure but I don't think your later year motor would have the plastic timing gear. Used to be a big problem back the 70s.

 

Mine did. Thought that was the stupidest thing when I saw it lol. Why quieter idle on a “performance car”? I replaced it with a good set of rock auto.

 

Wow. In '86, didn't know that. Don't know about quieter but I'm sure it was also cheaper to build.

 

Not really.

Rubber parts, fuel in the tank, yeah; achunka cast iron, not hardly. Assuming of course that it's either drained dry, or has antifreeze in it.

Yeah the chinesium timing sprocket with the phenolic teeth used to come in pretty much EVERYTHING. Of course, back then, motors - CARS - hardly ever went much over 100k miles, so the teeth fatiguing and breaking off wasn't as big of a deal. Started to be a REAL problem in the 70s when gaskets and whatnot took a quantum leap forward from the 50s stuff, like cork and Indian Head shellac and rope seals, that had been used previously. I can't tell you how many people I knew in the 60s that literally threw their cars in the trash for oil, coolant, brake fluid, and other leeeeeeks. It cost more in those days to tear a car down and fix all that, with all the attendant risk of not getting it perfect, than to just buy a new one. With the introduction of better materials elsewhere though, and with many cars reaching well over 200k, those crappy timing sprockets became the weeeeeeeek link in the system. 2 times, in 2 different cars (a 74 and a 78), I've been driving down the road and had those POSs fail on me.

Note also, that the chain in that photo, is "stretched" (really, severely worn at the pins holding it together), meaning, it doesn't line up with the teeth on the gear anymore. One link of the chain is FAR longer than the distance between teeth. Needless to say, that stresses the plastic teeth MASSIVELY. Just another brick in the wall.

 

That’s great news. To get the oil pan low enough to clean it out I have to undo the motor mounts anyways, so I’ll probably pull the block and check the bearings and seal just for peace of mind. Probably a new oil pump as well. Maybe a little clean and paint? 😉. Pulling the parasitic fuel pump out of the tank, should I replace the pump or only keep the pickup? Probably Clean up the engine bay and redo the fan wiring. Below I attached a picture of the cylinders from when I rebuilt the upper end, should I run a drill hone through or let it fly 🪽? I’ve heard mixed opinions on those. Thanks again all for the help, I’m trying as much as possible to keep history screaming on the street.