1979 401 cooling issue

[wiley-moeracing]

You should have a shroud that goes all around the fan so it creates maximum pull through the radiator itself.

[rapom]

I think your high speed temp. problem will be fixed with this mod. I found that you can do to your thermo clutch. I did it and while I really wasn't overheating at highway speed. It still made a big difference and at 65mph I'm at only the halfway point on the temp gage where I was at the 3/4 point before the mod.

http://www.stl-vettes.com/65vette/corvette_misc/images/fan_clutch_adjust.pdf

I found this link looking for a heavier duty thermo clutch that would come on earlier or at lower rpm's.

For cooling a stock 401 a 18" 7 blade high pitch 3-1/4" pitch like out of a 1977 caddy el dorado with a 472 v8 seems to be adequate matched to the stock shroud especially with a 180 mr gasket or robert shaw high flow thermostat. (stock fan is 16-7/8" or 17" 7 blade with a hair under 2-1/2" of pitch, another fan is from a 1981-1986 Cadillac with the 4.1L v8 it is 7 blade an 18 inches also with similar pitch right at 3" and moves a lot of air) i moved the MORE motor mounts up almost an inch since i have a 1" body lift to clear the 18" fan in stock shroud. Since i was going for a flat belly pan with my clocked dana 300 things needed to be shifted little any ways i re=drilled the more mounts 7/8" up and 3/8" for ward sliding the motor slightly ahead helped with valve cover clearance at the fire wall, moving it up allows you to continue using the stock radiator shroud.

I used a Hayden Severe duty fan clutch #2797 (buick with the diesel in the early 80's on some models like napa i had to notch the holes just a smidge to clear the bolts into the water pump but on a summit model i didn't, it was slotted deeper with universal slots). Also these fan clutches need some adjustment they like to engage at 210-220. Read this article about thermostatic fan clutch adjustment

I run 30% dextron synthetic coolant and 70% Distilled water with a 180* mr gasket high flow thermostat. Iw as running a 4 core brass radiator but recently on ebay there were some aluminium radiators for $139 + shipping another $30 called champion aluminium radiators, 3 row (3- 5/8" tubes) that are down flow and bolt in. for the price a good deal and seem to be providing good results for me.

I also changed to a synthetic motor oil 20/50 found i shed another 5 degrees across the board in engine temps.

Consider Evans NPG if you are having major cooling issues, check into it if you are really diggin for a different option to cooling. heard alot of good results i pondered looking at it in my jeep but so far the caddy fan with the ultra cheap aluminum down flow radiator seems to be sufficient

[AZChief]

Thanks for all the input. Ive got a lot to cover as soon as a day off from work shows up, but Im really anxious to dive into this some more. As soon as I get more info on whats going on, or if something works, Ill be back on here right away!

[AZChief]

Compression check turned out fine, lowest number was 134 and the highest number was 145. So no indication of combustion gasses blowing into the coolant somewhere. Checking the timing and carb tomorrow.

[AZChief]

So here's the latest update for those who haven't gotten bored and moved on to other posts.
I checked the timing yesterday, and low and behold, found the timing at what I can best estimate at about 6 degrees retarded. The timing marks on this new timing cover I put on do not show any marks for retarded timing, The first arrow starts with TDC. So by looking at the spacing of the advanced timing marks, 6 degrees retarded is where it was at. Im not going to waste my time wondering why the previous owner had it set there. I went ahead and set the timing to 5 degrees advanced(yes, vacuum advance disconnected). So, Im not saying that is the be-all cure for my problem, but that sure does explain what was happening!
I checked the idle fuel settings and they were set in too lean, so I adjusted that in conjunction with the idle speed. The vacuum is strong and steady now as well.
I didnt get to test drive it yet, as I was pulling apart the exhaust to make sure the heat riser valve wasnt blocking the flow, and one of the studs sheared off. I am going to leave out the heat riser valve, replace all four studs, button it back up with some new seals, and give it a run. That wont happen until next week due to my schedule, but I will post the results. Later.

[rang-a-stang]

My 79 Chief with a 401 really liked 10 degrees static timing at idle....

[AZChief]

Did you encounter any detonation with ten degrees advance, or was it good? What other mods do you have, parts and/or tuning?

[rang-a-stang]

None. Stock except for headers, no cat, and single 3" exhaust.

[AZChief]

How does that 3" exhaust work for you, did you get a little more power out of it? The stock exhaust, especially the 'Y' pipe up front, doesnt look great at all, the flow cant be very good. I've already thought to myself that I'd be improving that in the future. Maybe 2 1/2" head pipes with a nice transition 'Y' into a 3" feeder into the muffler, good flowing muffler, and then maybe a 3" tailpipe. I bet that would wake up this engine.
I'll test drive it first to see if the adjustment in timing solved the hot condition, and if it runs well, maybe I'll bump the timing up a little more to see what I can get away with. Thanks.

[rang-a-stang]

Love it.

When I bought my rig, it had stock 360 exhaust with a plethora of exhaust leaks. I had the cat back made first becuase I have to pass CA smog. As soon as the cat back was done, I took it home, removed the manifolds, stock y-pipe, and cat and put the headers on, drove it back to the shop (open headers ) and had the new Y-pipe made.

I have Hedman headers for 79 and down, they flow into a 3" Y-pipe, down the passenger side of the truck into a Borla single 3" inlet, single 3" outlet, up over the axle and dumps out the stock location. The whole exhaust fits up in the chassis (my factory muffler hung below the chassis, as does the cat) so I gain a slight amount of ground clearance with it.

When it is running stock manifolds, cat, and 3" back it sounds totally mellow, and there was almost no noticeable difference in power. When it is running headers, no cat, and 3" exhaust there is a HUGE power difference, it sounds a bit raspy, and throttle response is noticeably better. In my opinion, exhaust should be the first upgrade to one of these. I would like to run a 3" high flow cat but CA says that is not legal.

Here are 2 threads I started regarding my exhuast:

http://www.ifsja.org/forums/vb/showthread.php?t=182656

http://www.ifsja.org/forums/vb/showthread.php?t=184867&highlight=exhaust

[Don S]

..

401's seem to run a little hotter. Mine was punched out .030. It Ran cool enough when every thing was up to snuff.
One time I bought a new water pump. The 401 ran hotter. Apparently it was a pump for a 360. It did check out like my 81 360 pump.
I still had the old pump. the shaft was an 1/8th inch bigger and the old worn down impeller looked like it was more heavy duty in it's younger day.
Some cars rely on full time hot water through the heater core to help cool one of the banks of the V-8s.
Age has allowed me to forget who's V-8s You can mount a tranny cooler between the rocker and the frame on Passenger side to help with the cooling.

BTW I timed at 8*

Good Luck.. Don S..

[fulsizjeep]

It's probably lean and/or timed poorly.

It's also a 401 in Arizona. One of the many reasons I like 360's.

My .030" bored 401 runs 195-200 all day long in Arizona, New Mexico, Utah and Colorado.