I recently replaced my old 305 and put a 383 stroker in my 86 berlinetta. I am having problems with it overheating and bubbling out of the resoviour tank. The first time it did this was when I was running the break in of the engine it bubbled over I quickley shut it off and removed the thermastat thinking that was the problem . THen for a couple of days it was fine. I just put in a 180 degree thermastat and also had to replace the alternator. I was driving to the shop to have a freind help me adjust the rocker arms and out of no where it started overheating and bubbling over I have an aftermarket gauges and when it overheats it reads 230 degrees. The waterpump is from the 305 and stock radiator with the electric fan need some suggestions before I tear all the brackets down and replace the waterpump lol??

 

Water pumps are not the usual cause of overheating. Your 383 generates a lot more heat than the 305 and the radiator may not be large enough. One stock electric fan is not enough to keep the larger engine cool. Also if spark timing and/or fuel mixture are off it can cause the engine to run hot.

 

I know the timing is off for sure and possibly the carb I have a 670 holley street avenger and had it tuned for the 305 but it seems like its getting good fuel. What kind of timing tab do i need for the 383? What should I do with the carb to see if it not tuned right? Also ithe motor kept wanting to stay running after i cut it off and I need to adjust the rocker arms could this have somthiung to do with it?

 

1) Find TDC on #1 and then get the timing marks set up. May want to invest on a $15 TDC tool.
2) Adjust spark timing
3) Get the rocker arms adjusted properly

The after running could be due to hot spots in combustion chamber, spark plug heat range too high, throttle not closing fully (idle speed too high), compression ratio too high for fuel used, excessive spark advance, etc..

If the carb was working OK with the 305 it should be fairly close with the 383, but may not be big enough, depending on heads, cam & compression.

 

I did a similar swap two years ago and used a very well built stroker with all the goodies, and felt my stock radiator was good enough....wrong. I used a be cool custom fit one and stuck with my stock fan....wrong again. It took a long time for the motor to get hot but when it did, i could not cool it down that told me I was good on the radiator, but wrong on the fan. Finally I gave up and bought a much better fan. I'm in Tucson AZ where summer daytime temps are well over 100 and as long as I keep moving it stays 180. I will admit I typically park it in may and pull it out right around this time of year.

I had an afterrun issue as well and felt for sure it was timing as I run 18* advance at idle and 30* at full advance (3K RPM using an MSD stand alone distributor and box). It ended up being fuel. I can only buy 91 octane out here and all the drag guys said anything over 10.5:1 needs somewhere north of 95 octane...at least here.

I suggest getting a new radiator, checking to see if your bottom hose collapses (should have a spring) and getting a higher CFM fan. First check your timing, carb adjustments, float level and fuel pressure. I do not know your specs, but be careful with it and you'll get it dialed in. It took me a full year to finally get it correct.

 

Is the electric fan hooked up to turn on the way it originally was? If you "hot wired" the fan directly with a switch, your run on issue is because the fan is acting as a generator while it's still spinning when you shut down, and it's back-feeding power to the ignition. If that's how you have things hooked up, switch the fan off a couple of seconds before turning the engine off, and the engine won't run on. Hooking up the fan with a relay will take care of that problem.

 

That could be another issue unto itself. If he does have all the original electronics hooked up, then the fan may not be coming on until its pretty hot. The 305 was fine all day long at 220....I wouldn't want a high performance aluminum head 383 running at 220....but I don't know his setup.

 

djs, where does your 383 run, temperature wise?
I'm also wondering if he somehow got his hands on a reverse rotation water pump.
Wasn't 87 the transition year going to serpentine/reverse rotation pump?

 

I believe all carb'd motors ran Vbelts and TPI ran serpentine for 87. After I got everything dialed in I'm at 180-190. Only if I sit in traffic do I come close to 200. I'm very sensitive on temperature since I'm aluminum in Tucson running high compression. I had it out saturday night and I watched the temp gauge like a hawk. I still use the sending unit gauge in the head, but have a backup mechanical in the manifold. So even when the sending unit gauge has 200, I'm more like 190 on the mechanical gauge. I struggled for almost a year in tuning before I was comfortable though. There are so many variables....