4.1 Blocks: ending with 291

D

DarkForce

New Member
Joined
May 26, 2001
Does anyone have any information on the quality of one of these blocks. Pulled one yesterday only to find a destroyed rolled fillet crank, several shattered rod caps, and what resembled very stressed bearings in the pan. The block itself may be all right but before I salvage it, I wanted to know if it would be worth it. I won't be on the net much over once a day.
 
Almost forgot, the phone number of anyone who knows these blocks would also be a great help.
 
There's some photos on the other site of the 291's. The info that I've seen on the net, is that the 291 is the best one out of the production 4.1's. Appears they have a little more meat in the deck area than some of the others.
 
Originally posted by DarkForce
Does anyone have any information on the quality of one of these blocks. Pulled one yesterday only to find a destroyed rolled fillet crank, several shattered rod caps, and what resembled very stressed bearings in the pan. The block itself may be all right but before I salvage it, I wanted to know if it would be worth it. I won't be on the net much over once a day.
Click to expand...

Don't worry, your 180hp will never stress the limits of the block.
 
Thanks getchasum. I was going to leave that block for the crusher but I'll make a trip to the bone yard tomorrow morning to see if it has any cylinder damage. The mains appeared good. I bent the flywheel like a pretzel attempting to break the crankpully bolt free with a 3/4" breaking bar and it still never let loose. A machine shop will be able to remove the bolt.

cool84, hope you are right. 180 hp per cylinder should within safe limits.

I'll let you guys know what happens tomorrow.

Thanks again.
 
I debated with Mike over that one. I don't think it has any more meat than the next 4.1... be it a 484 casting, etc... Check the deck! Have it magnafluxed and sonic checked. If all looks good build it.
 
The 484 block had no problem putting down 500hp at the rear tires for me at only 20# and ran 125 mph all day long at the 1/4 track.I don't think there is much difference.

The 84-85 blocks are best from my research,only because of better oil passages.
 
Pulled everything out of the block this morning and it went like this:
Two rod caps broke off, #4 & #5
Rod bearings #4 & #5 thin as paper and very burnished
Main cap bearing basically gone, #3
Oiling hole for #3 main cap plugged, see three items above
Rolled fillet crank destroyed
One piston had a broken pin retainer and no skirt up to the oil rings
One rod broken in half
Enough RTV to build 10 engines
Two cylinders took hits and lost material at the very bottom
(going to check these out tomorrow)
One hit in part of the web next to the #3 main lost some material
(getting that checked also - girdle should do the trick)
Broke the crank pulley bolt free with an air gun - after 8 tries
Oh, did mention a double handful of free parts in the pan

Guess it could have been worse. The last 4.1 block had the typical head bolt cracks and was tossed. This block is pretty dirty and I was not able to see any cracks so it may still be a good one. Cylinders look good and are standard. Going to drop it off tomorrow for tanking, sonic checking and magnafluxing.

One question about oil passages. Are you referring to the passage from the pickup tube to the pump (which is a minor issue to me) or those used for the mains, rod, and cam?

Let me know of any special problems you've encountered with your blocks. I really appreciate your replies, even cool84.
 
If you are looking for a good 4.1 core to build I would suggest getting in touch with Chris McDade.He sold me one that was in perfect shape for $150.
 
Originally posted by Intercooler
I debated with Mike over that one. I don't think it has any more meat than the next 4.1... be it a 484 casting, etc... Check the deck! Have it magnafluxed and sonic checked. If all looks good build it.
Click to expand...

I went back and re-read that post. It seems to me that you agreed that there was more meat in the deck area, in that post. There's some pretty good pitures of a 291 & a 484 (I know the 484 was yours) deck area in the post. I wish I could post the link but the filters here block it out. Just do a advance search on "4.1 deck" by Orlando_87 over there.
I do agree w/ you that they should be checked, magna, etc. which ever one is used, AND I'm not stating one is strong than the other, just what I've read, the pics I looked at and from what I can see from the 2- 4.1's I have sitting side by side (a 291 & a 484).

;)
 
Mike and I could only compare pictures since neither of us had both side by side. If you have them both there mic them out and see what if anything is different. Maybe the bridging on the steam holes? I don't think that would matter much. The big kicker is the meat on the deck surface and cylinder walls. You have .125" thinner deck to start with. I wouldn't machine it at all unless it is totally needed and don't bore it more than .020". Some books have that as a spec too.
 
As for a street application, the 4.1 appears to be an excellent choice. Your posts and the additional research I've looked at are consistent. Personally, I becoming convinced that the 4.1 blocks have been seriously unestimated.

The block has been dropped off for cleaning and inspection. They know to pay particular attention to the deck and cylinders in regard to cracking and thickness. Hopefully some useful data will come back that can be passed on.
 
Originally posted by Intercooler
Mike and I could only compare pictures since neither of us had both side by side. If you have them both there mic them out and see what if anything is different. Maybe the bridging on the steam holes? I don't think that would matter much. The big kicker is the meat on the deck surface and cylinder walls. You have .125" thinner deck to start with. I wouldn't machine it at all unless it is totally needed and don't bore it more than .020". Some books have that as a spec too.
Click to expand...

Jesse mine was bored .055 over and never even ran hot.The machinist that sonic checked it said .060 should be fine.No problems as of yet.
 
The block was junk. The #3 main was cracked at the webbing and had cracks at three head bolt holes. I'm donating it to cool 84 due to his support. A little JB weld in the cracks and it'll be good as new.

May have a line on another block. Maybe it doesn't make much difference between the 291s and 484s. Which cams have given you the best results with the 4.1s?
 
Originally posted by sixgun86gn
Jesse mine was bored .055 over and never even ran hot.The machinist that sonic checked it said .060 should be fine.No problems as of yet.
Click to expand...
Did he sonic test it to give you this info or just THOUGHT it should be okay? Published info says no more than .030" on a production 4.1. If you are getting away with it then keep trucking. I personally wouldn't though.
 
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