67 fan shroud/fan question

[chewychevy67]

OK. So when I got my truck I'm building the motor and transmission, 327 th400, were in the box and not assembled so now I am mocking everything up before paint and everything is going well but I have now put the fan and shroud on and my fan sits pretty much flush with the back of the shroud. I have read it should be half in and half out. I have confirmed that my shroud is the shorter snout ac unit and my clutch fan is nos 3883158 which is correct for the cast water pump pulley. I'm wondering if there was a shorter shroud for 67 or was this how they made it that year? Anyone got any info? This is the shroud that was in the cab when i got the truck so i assume its original.

[oneshotkyle]

Only 2 shroud's available for a v8 in 3 row radiator. With and without A/C and there is only 5/8” difference. Ive never heard anywhere about having the fan half in or out of shroud. Where did you read that

[chewychevy67]

I should state my truck Is a 4 row hd rad as well. I would have to take approx 3/4inch off to make the fan centered in the shroud opening. Most of what I have read online indicates that it should be 50/50 . If the fan is all the way in the shroud it creates a pocket that the air just swirls in the shroud instead of pulling it thru. Mine only sticks out the back of it 1/4inch.

[HO455]

Well it hard to tell from the photos if you have the short water pump or not. If you've have the short water pump then that cast 3 groove pulley with the built in spacer would need to be swapped for a stamped steel version with no spacer.

What transmission is hooked to your SBC? Is it the stock engine/transmission combination? If not it is possible that they need to slide back.

Your new engine is looking good.

Here is a reference to fan spacing from Flex-a-Lite.

If you have a fan shroud, the position of the fan blades in the shroud is very important to maximize airflow. Looking from the side of the engine, the fan blades should be half in and half out of the shroud. If the fan is too far inside of the shroud, it won’t pull as much air through the shroud as it could. Instead it will create turbulence inside the shroud, spinning the air, but not efficiently pulling it through. If the blades are not far enough inside the shroud, the fan will pull air from around the shroud rather than through it.

https://flex-a-lite.com/blog/the-per...20engine%20rpm.

[chewychevy67]

Short pump, motor is in the v8 location.. it's all the original pieces that were in the truck (truck was a v8 th400 and i checked and the ones in the box are believed to be the original ones)except the nos clutch which matches the old one (and was very hard to find). That's why I thought maby for some stupid oddball reason 67 maby had a different shroud.

[chewychevy67]

I wonder if I trim the shroud would that cause any problems? It would be easier. All my pulleys line up and changing pulleys is asking for problems.

[Richard]

That shroud looks to need a larger diameter fan. The tips of the blades were maybe only 1/2"-3/4" from the shroud on my truck.

[oneshotkyle]

Originally Posted by chewychevy67

I wonder if I trim the shroud would that cause any problems? It would be easier. All my pulleys line up and changing pulleys is asking for problems.

Well now, you made me go do some reading and research. Best i can understand is the blades hanging out the back of shroud flung the air out away from engine and had less drag not being enclosed in the whole shroud. There is alot of science in the equation. I prefer in shroud for the safety and inderstand it may not be the correct fashion. By the looks of your pics you could only cut 1” or so and that may or may not put fan where you want but be closer to the oem quality and finish you desire.

[RichardJ]

>>All my pulleys line up and changing pulleys is asking for problems.<<

Asking or not, you already have problems and the pulleys seem to be the reason.
Why do you need four belts on the crank pulley and three on the pump? Is the crank pulley a solid pulley?

[chewychevy67]

These are all factory pulleys from a 67 327 with a/c and air injection. I've checked the part numbers. Every groove has a belt on it. So my thinking is this is how gm did it in 67 or there was another shroud . This is a picture of the only other 67 I know of that had air injection on a 327 and it does not have a shroud on it and I can't tell if it has aclutch fan ot not.

[chewychevy67]

Originally Posted by Richard

That shroud looks to need a larger diameter fan. The tips of the blades were maybe only 1/2"-3/4" from the shroud on my truck.

The fan is 18 inches and the hole is 19 inches so it is closer than the picture makes it look I guess.

[HO455]

From looking at the Time Capsule thread and this thread below. It would appear that your water pump pulley may be from an earlier year truck.


http://67-72chevytrucks.com/vboard/s...d.php?t=632007

http://67-72chevytrucks.com/vboard/s...d.php?t=188887

http://67-72chevytrucks.com/vboard/s...d.php?t=474244

[chewychevy67]

I guess it could be possible but it was with the truck when I purchased it and it's a really uncommon pulley to have laying in the truck I would think being that it lines up and there was no other. This truck was pretty complete but just the engine and brand were out and there was no shroud in the cab. This has me baffled.

[chewychevy67]

If you look closely at the one picture I have of the other 67 I think I can see the cast pulley there as well. Maby they just never had a shroud on air injection trucks in 67. I think I'll measure mine up and trim it.

[chewychevy67]

Originally Posted by HO455

From looking at the Time Capsule thread and this thread below. It would appear that your water pump pulley may be from an earlier year truck.


http://67-72chevytrucks.com/vboard/s...d.php?t=632007

http://67-72chevytrucks.com/vboard/s...d.php?t=188887

http://67-72chevytrucks.com/vboard/s...d.php?t=474244

Thank ho455. I looked at these threads and here's a 68 3/4 ton.with ac in one of them with that cast pulley and it looks like the fan may be further in the shroud like min is.

[HO455]

It just maybe that GM decided a poor fitting shroud was better than no shroud. And since only California trucks got a smog pump they may have decided that was good enough.

And of course there's the whole GM not being happy about having to make additions to vehicles just to appease California.

Are you having cooling issues? If not maybe wait before modifying anything. If the truck made it this long it maybe fine.

[chewychevy67]

I'm just mocking the truck up right now to make sure everything fits so im not having any issues right now. I actually have 2 shrouds , one for ac and one without, and I may cut the one without just so I have 1 of each. My thinking is if I get some of these things figured out now the less paint I will scratch taking things apart and modifying multiple times when my paint is fresh.

[RichardJ]

Weren't those pulleys used on the C40 and larger trucks. They used extra groves on the air compressors (2 belts) for air/hydraulic brakes and the alternators had double belts as well.

I looked back through your build thread and I don't know what to say. You added a bunch of stuff that was never on a '67 C10, but it is ALL GM and close to the same years. Some things are very innovative and unique, but some left me scratching my head.

[chewychevy67]

Thank you. Yeah it's a unique build. I just wanted to build something different. I wouldn't build it this way for a every day driver. I just wanted to build a truck like cadillac could have built it back then had there been a truck market for them like today and have it feel "old times" wheni do cruise around in it.

[chewychevy67]

Here is some more good info for anyone else in the future reading this later on with the same pulleys and needing info. https://67-72chevytrucks.com/vboard/...d.php?t=508169


Looks like I do not have the correct fan blade. Should be part number 3883159 and 5 blade. I have a 7 blade that looks identical except the blade count. I wonder if the pitch of the blades could be different and the original and would stick out the back?


Edit.....But then I look and my power steering pulley nut is only 1.5 inches fromm fan so it probably shouldn't come back too much more.

[NGN]

I was also thinking the fan five blades might make the difference. I don't know, do the pitch on the blades change when spinning, get that closer to the nut on the power steering. Not sure the difference usages with five blade and seven. Love looking at your project.

[HO455]

I removed a 5 blade non clutch fan and replaced it with a 7 blade clutch fan and I didn't notice any difference in the fan's position relative to the shroud.

On the factory fans for our trucks the pitch is fixed and should not change.

Personally I would source a different water pump pulley before I ever modified a shroud. Especially since the truck is not a factory correct restoration. For me the work involved to make a perfect cut of the shroud would be far more than finding and installing a new pulley.

There is an additional consideration about triming the shroud. That is it would reduce the area of the band around the fan blades. (Indicated by green on photo #1) The engineering of effective air flow through the radiator involves the fan blades rotating inside of a tube. Reduce the length of the tube and reduce the efficiency. How much I don't know but, it must have be a consideration as GM would have reduced or eliminated the band area of every shroud to save pennies per vehicle.

A stamped steel pulley would remove the space indicated in red on photo #2. It looks like that would move the fan back about 3/4" (At least thats what if looks like from my house. )

Good luck and keep us posted.

[chewychevy67]

I've decided to get a factory 5 blade fan before i go any further. It looks like it has more pitch than my 7 blade fan so well see. I'll post the results here when I get it.

I took my fan off tonight and it really does not have much pitch. I'm not sure where I got it from. Like only 1.75 inch. I remember selling my 5 blade so I could have a seven blade. Wishing hadn't now.

[chewychevy67]

Turns out the original style fan fits properly with the cast iron pulley perfect with the a/c shroud.

[Bob B.]

That truck has some interesting options. I see the heavy duty alternator along with the air cleaner pre-cleaner. I believe that alternator requires that cast 3 groove water pump pulley. Similar to what was normally used on a C-60.