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bimp
New Member

Canada
2 Posts

Posted - 05/21/2006 :  04:19:37 AM  Show Profile  Visit bimp's Homepage  Reply with Quote
i was wondering if you guys could help me with a little info on these two engines(304 and 404). like Hp rating, torque, reliability, specs ect... i want to put one in my blazer which will be doing a lot of hauling ( my race/show truck) but i want it to perform as well.
thanks in advance

ModMech
Top Member

USA
948 Posts

Posted - 05/21/2006 :  10:16:16 AM  Show Profile  Visit ModMech's Homepage  Reply with Quote
The 304/345/392 engines are all basically made of the same block (like the 283,305,350 GM engines; and 289,302,351 Fords). That is to say that most parts are interchangeable, but NOT ALL. Of those, the 392 is the most "durable" and powerful, but the 345 is the least trouble from my experiences (we had as many as 25 304/345/392s at one time, most gasoline, a few LP).

The MV404/445? are COMPLETELY different, and they are HUGE gas guzzlers. In fact, the 6.9L/7.3L diesels are based on this engine design. They are VERY robust, but heavy as well. I would not suggest these as a good swap candidate due to weight, economy, and parts availability.

If you want customer service, you NEED an International!
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Wolf0r
Top Member

USA
2181 Posts

Posted - 05/25/2006 :  2:34:32 PM  Show Profile  Reply with Quote
We have the old 304 we pulled from a 69 IH farm truck. It has a broken camshaft. The boss would probably sell it cheap.

“The good thing about science is that it's true whether or not you believe in it.”
Neil deGrasse Tyson
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IBTMech
Top Member

USA
973 Posts

Posted - 06/16/2006 :  4:23:42 PM  Show Profile  Visit IBTMech's Homepage  Reply with Quote
I wouldn't give you a plugged nickle for a 392 with a Holley 4BBL. Severe heat issues and a serious gas guzzler.

The 345s were far more dependable and economical with the Holley 2BBL. They had some camshaft problems but that usually was a high mileage issue.

If it doesn't fit, FORCE it.
If it breaks, well, it needed replacing anyway.
Pullin' wrenches for 45 years.
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ModMech
Top Member

USA
948 Posts

Posted - 06/16/2006 :  5:10:52 PM  Show Profile  Visit ModMech's Homepage  Reply with Quote
Oh, I don't know, 5.5-6 MPG for a gas 392 4V is not too bad at all, considering the 6.9L/7.3Ls got 6.5-7.5 MPG.

If you want customer service, you NEED an International!
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IBTMech
Top Member

USA
973 Posts

Posted - 06/16/2006 :  5:35:05 PM  Show Profile  Visit IBTMech's Homepage  Reply with Quote
Actually, I felt that the 345 was a real sweetheart after dealing with the V549s and V537s. The V537s were a real failure in my book. Talk about heat issues.

If it doesn't fit, FORCE it.
If it breaks, well, it needed replacing anyway.
Pullin' wrenches for 45 years.
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dozer
New Member

USA
5 Posts

Posted - 07/23/2006 :  12:49:12 AM  Show Profile  Visit dozer's Homepage  Reply with Quote
quote:
Originally posted by ModMech

The 304/345/392 engines are all basically made of the same block......Of those, the 392 is the most "durable" and powerful...

The MV404/445? are COMPLETELY different, and they are HUGE gas guzzlers.



hmmm....have to disagree here. The 392 is the MOST trouble-prone of the three SV engines. 392's are highly prone to cracking the heads. They really are a little beyond where the design should have been taken. They're a -quarter inch- overbore of a 345!

And to give some idea how far IH pushed that design...there's another in that series which wasn't mentioned...the original actually....a 266. So that series was taken all the way from 266 cu-in to 392 cu-in! ouch...

304's are great, but you're carrying the weight of a 345, without getting the torque and power. Great pickup engine; but kinda light on power for a medium-duty truck. The 345 is all-around best of that series, and a pretty darn good motor overall.

As far as the 404; it hasn't been my experience that they're "HUGE" gas-guzzlers. In a -working- situation, they generally get the same mpg as a 345/392. The 404's came out in 1975 I think, and have electronic-ignition; whereas all the older 345's (pre-78 maybe?) don't. That makes a difference in mpg, at higher power/rpm.

In situations where you're spending most of your time idling or at low-power, then ANY larger displacement engine will be less efficient than a smaller one. Perhaps that kind of idling/creeping usage is normal for a lot of buses.

In ALL engines, there is a molecular-thin layer of fuel-air along the walls of the cylinder which never burns. The larger the cylinders, the larger the amount of fuel-air which never burns.

In the situation where the engine is working at 50% or more of its rating, that 'dead layer' is a very small portion of the -total- fuel-air going through the engine. But at idle and low-power, the dead mixture is a much larger percentage of total.

So, when you're idling, or toodling along at 30mph on the flat using only 30-50 hp, a 304 will burn less fuel than a 392 or 404 etc..

But where you're climbing a 7% grade with a full load, using near the full 180hp, then a 404 will get just as good MPG as a 345/392, and is far more likely to handle the strain without overheating, cracking heads, throwing rods, etc..

As far as the weight goes....a couple hundred pounds difference just isn't going to be noticeable in a 12,000-30,000 lb bus/truck.

ps: that's an "MV446", and is indeed where the 6.9 IDI diesel came from. It's a stroked version of the 404. Same design.

Actually, I'm looking for some SAE housings for the 6.9/446, if anyone has them gathering dust...

pps: to answer Bimp's original question... ...here are some example numbers...

1973 304, 147hp/3900rpm, 240ftlbs/2400rpm 2bbl
1972 345, 197hp/4000rpm, 309ftlbs/2200rpm 2bbl
1972 392, 236hp/4000rpm, 357ftlbs/2800rpm 4bbl

Probably, if have a 2bbl 392, it would only be making 10hp more than the 345 (at same rpm). I'd really stay away from the 392; unless you're getting one free.

btw, the 404 (which is actually a 399 ) has these specs:

1975, 404, 210hp/3600rpm, 336ftlbs/2800rpm, 4bbl

hope this helps...
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ModMech
Top Member

USA
948 Posts

Posted - 07/23/2006 :  8:55:06 PM  Show Profile  Visit ModMech's Homepage  Reply with Quote
I don't doubt your experiences with the 392s, but our mid '80s versions, and we had almost 20 of them at one time, were completely reliable except for re-setting the points every other month, and losing a cam or two (#7 exhaust lobe on both). We put over 100,000 trouble free city bus miles on them all, except for the issues listed.

If you want customer service, you NEED an International!
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dozer
New Member

USA
5 Posts

Posted - 07/24/2006 :  01:17:16 AM  Show Profile  Visit dozer's Homepage  Reply with Quote
That wouldn't surprise me in that city-bus application, Mod-tech.

However, the engines in that application very likely spent little time producing high HP; which means they saw very little sustained high-rate heat flow in their lives.

Put them in an application that really works them, and it's a different story. As an example, a haytruck loaded to 25-30k lbs, climbing 5% multi-mile-long grades. That's the kind of app. where an engine is truly tested for being robust...or not.

In any case, it certainly is the -least- durable of the 3, not the most; simply because a huge amount more metal has been removed from what is essentially the same block as a 304. And the same bearing surface-area is handling more pressure, etc., etc.. With all other conditions equal, it's almost guaranteed to be less robust than the same parts handling the lower loadings of a 345.

But the real root-cause of the higher 'catastrophic failure' rate is that a 392 working hard is trying to shed a fair bit more heat from what is essentially the same internal surface-area as a 345; and doing it via the same cooling channel capacity as a 345.

Couple that with the reduction in internal strength (from the much thinner walls resulting from the bore-out), and it's only to be expected that it would be more prone to warping and cracking; which is exactly what they are prone to.

One other matter affecting things is that most 345's shipped as 2-bbls, whereas most 392's shipped as 4-bbls. That too stacked the deck against the 392 a bit more.

It isn't so much "my" experience I reported; but rather, the result of 20 years of seeing engines come into the shop from all sorts of IHC's in both truck and industrial power-unit apps.

Almost invariably, a 392 will come in with a cracked head; or at the least, a blown head-gasket and warped head. Whereas, 345's almost always come in with a "normal" mix of mundane problems like worn rings, spun bearings, whatever.

ps; You mentioned that yours were mid-80's. I believe IH finally did do some mod to the head design near the end of production-life, to improve cooling. My partner has mentioned something like that to me. But numerically speaking, the majority of 392's made were before this; and had the same heads (cooling-wise) as the 345.

Still a good motor....just not what I'd choose when I had a choice. I'd take a 345 any day; then add elec. ignition and a GM TBI setup.

Besides being a more robust motor, it'd save me about a grand over buying a running 392 (lots blown up = much more expensive on used-market).

Edited by - dozer on 07/24/2006 01:22:16 AM
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