Re: [Amc-list] Concord Engine Question - 4.0 EFi Six

[Frank Swygert <farna@xxxxxxx>]

My first point: There is no "prone to" anything here! The fact that a couple people have managed to split open a couple blocks does NOT mean the 91-95 4.0L is prone to cracking. It's not. ANY engine when thoroughly abused can be split open. I've seen a few Ford 5.0L and Chevy 350 blocks split open, but I would never say they are prone to do so. The 91-95 4.0L block is nevertheless a little weaker than earlier and later models. All that really means is if you want to build an all-out race engine or high psi turbo motor (such as Brien has been contemplating) one of those isn't a good choice. For anything less it's fine. Only the first year or two had some noise issues, and those were due to excess piston to cylinder wall clearance. 50-60K engines started sounding like they had 100K added to them all due to about 0.001" of extra clearance (I got that from a machinist who took care of a few engines for the local dealer). The AMC six has a short piston with rather tight clearance,
  and Chrysler loosened it up just a tad, which turned out to be a tad too much. 

Material was added to the block along with the stud girdle mainly due to complaints from yuppy drivers who wanted a nice quiet road car, not a tough Jeep, but I guess they liked the looks and room of the Jeep anyway. I recall reading a Motor Trend report saying something about the "thrashy six". Later in the article there were hints as to how they were driving it -- like it was a high revving V-6, I-4, or short stroke German six. Keep it in the high rev range (over 3K) and it is a bit "thrashy". But there's no reason to do that on a regular basis -- the long stroke six has enough torque to leisurely motor along without running over 3K. But you gotta please the masses! I don't mind that they strengthened the block to reduce a bit of engine noise, mind you, but there was never any danger of the engines coming apart or lasting a substantially shorter time. 200K is still common on any year 4.0L that's been half-way taken care of, any year. 250K isn't uncommon either. There is pot
 ential for the stiffer block to last longer, but in reality everything else starts to wear out at 200K+. But a little more material in something like a block is always better, especially if you want to abuse it later! 

Secondly: Mark sent me an e-mail and apologized for getting a bit carried away on the list. He only did that because his post came AFTER my "we won't get carried away" post, but before he'd seen that post. There will be no fight. People get carried away at times, realize it, and back off. That's what we hope for, so that Tom or myself don't feel a need to get involved and moderate. Which will happen if necessary in private if a public mention isn't enough. I understand that it may be a few hours before a message is read, and that a reply might be typed and sent just moments before -- especially if reading the digest. I often reply to Digest msg #4 just to see it was already answered by the time I get through to msg #10. So I give a bit of leeway (a day or two) before "saying" anything to anyone. That's time to either reel yourself in or let out some rope... 

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Date: Tue, 10 Mar 2009 21:56:05 -0700 (PDT)
From: d stohler <das24rules@xxxxxxxxx>

ok gentlmen, i love to hear all the advice from the list. but sometimes this bickering gets just irritating. 

the guy didnt ask what block is the strongest for an all out race motor. 

so i have now learned what blocks are prone to what. ok, lets get over it

can we please end this bickering i guess is my point? the guy, the way i understood it, just wanted to know what it would take to install a 4.0. and you 2 went overboard i think. 

just my thoughts. FIGHT NICE!!!!


-- 
Frank Swygert
Publisher, "American Motors Cars" 
Magazine (AMC)
For all AMC enthusiasts
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