451 went boom

[flyinbrick68]

Jer those TRW/Sealed Power forged pistons are heavier than a dead priest, I'd look at something from Diamond, Wiseco etc.

The early blocks aren't actually any thicker than the late ones are. That is a myth. The iron they are made from tho is a little harder but the main webs are thinner so it boils down to the best block has the distributor in the front.

That RV block is as good a core as any to build and if I was going to the trouble of machining a block properly for a rebuild I'd pony up the price of a 4.25" stroker kit. When you do the math it maybe adds $1000 to the build and you won't get better bang for the buck than that.

Kevin

Icon makes two forged slugs for a 451 a flat top and dish...might check em out!

 

[volksworld]

twostick this was over 40 years ago and the details a little fuzzy...the pistons came from ed hamburger who was the local direct connection dealer...thought they were a DC part but maybe not ...idk when hypereutectics came out...2 different guys i knew had the same issues with them and machine shops/engine builders involved never mentioned ring gap...they said detonation/overheating...but i'll also say a good portion of what i know today is based on the disasterous results of the half assed things these guys tried back then and believe me if there was a way to screw things up they found it

 

[NewportRbod]

Well my much troubled 451 ended its career two weeks ago. Got on the freeway, and she began misfiring. Looked in the mirror and I couldn't see behind me the coolant was going out the exhaust so bad. Wrecker ride to the garage where I get it worked on. After sitting a day, the oil became overfull. Pulled the heads and found what you see in the pics:

View attachment 381021 View attachment 381022 View attachment 381023

From what we can tell so far, I broke a piston and in turn broke the block. Consulted a good machine shop, and will have the heads inspected for reuse. Owner looked at pics and knew right away what happened. The ring gap on the top rings was insufficient for a Keith Black piston, and it expanded and broke out the ring land you see in the pic. A year ago, when I broke one of my built iron heads we'd found that one of the rods hadn't been resized and the bearing was getting ready to spin. We rectified that With new bearings and resizing of the rod, but even then on start up I had to crank for a few seconds before I activated the choke so that you wouldn't hear rod slap on start up. In addition, the engine always made a "wah wah wah wah" sound until it was completely warmed up. In short, my machinist was a crook stealing from his business, his customers, and doing shoddy work. I got screwed. So now here I am with really bad choices. I can sleeve the bad bore, and have a new shop check all the clearances and fix whatever is still screwed. Or, I can put a low mile RV 440 in, utilize the 440 Source heads, my oil pump, water pump, and XE268H Comp cam and runs that. That's probably my best choice as I don't trust that 400 block anymore, but compared to the 451 this 440 will be a slug. Last option, walk away from the car and sell it for whatever I can get for it. I can't afford to rebuild engines once a year. This sucks.

Sleeving depends on the machinist. The good guys won't be cheap but the work is solid. My thoughts, use your 440 in the down time. Figure all options for the 451. The 440 with typical rv usage and lower compression should live a long life of cruising...at a little slower pace.

 

[carrman]

The 440 will receive the 440 source heads so compression will rise some, it will get disassembled and tanked, all measurements checked, new bearings and rings, the Comp XE268H cam shaft, the high volume oil and water pumps. Should get me going for a few years. I'll miss the 450 horses of the 451.

 

[NewportRbod]

Heavy? Yes, But I had that engine built by Muscle Motors in Lansing, Mi. over the winter of 2007+2008, and they'd been in the Business for 30 yearz at that time and are still doing it today. 2017 was my last trip to Carlisle and az far az I know they're still on Manufacturers row for Chryslers at Carlisle Show. I started with a '67 Imperial block, crank, and the 906 heads it was born with and using those pistons in a .40 over bore, It leaves you with a 9 to 1 squeeze when they fourge the pistons to set deeper in the bores when there manufactured. Had the biggest valves you can put in those 906 heads(188s + 214s and all stainless seats on both sides) One of Mothers Purple shaft just under 500 lift and it went merrily down the road burning 87 octane and it would light 'um up almost just by looking at my right foot. Every time I even think of the Batwagon I still get that warm 'n fuzzy feeling and it's been out of my life for 6 yearz now and I still think I made "0" mistakes in that build and it weighed 5800 with a full tank and me sittin' in it, and got 8 MPG with either a 323 or a 276 installed lol. Jer

Muscle Motors closed the shop down in Lansing, Mi.. I'm not sure if they retired or what, but they left a gap for mid-michigan mopar fans.

 

[Mike66Chryslers]

The 440 will receive the 440 source heads so compression will rise some, it will get disassembled and tanked, all measurements checked, new bearings and rings, the Comp XE268H cam shaft, the high volume oil and water pumps. Should get me going for a few years. I'll miss the 450 horses of the 451.

If you're throwing that much time/money into the shortblock now, why not find another 400 block and do that up instead? Buy one piston to replace the broken one and swap those over, but set the ring gaps properly.

 

[BIGBARNEYCARS]

Muscle Motors closed the shop down in Lansing, Mi.. I'm not sure if they retired or what, but they left a gap for mid-michigan mopar fans.

Hate to hear that. I became pretty good friends with Eric in that shop from the late '80s thru' about 2014. Great guy and very knowledgeable. I even cut cross country from Chelsea and met him at the Holt Fair Grounds just south of Lansing on a Saturday one time, Paid him in cash for a completely re-worked 906 head that I needed in a hurry lol. Dam, Nothin' stayz the same? Jer

 

[carrman]

If you're throwing that much time/money into the shortblock now, why not find another 400 block and do that up instead? Buy one piston to replace the broken one and swap those over, but set the ring gaps properly.

Time constraints, money constraints, finding another 400 block. Don't know if the cranks hurt or even was machined right from the beginning.

 

[carrman]

By the numbers, my replacement 440:

Jan 9th 1972 stamped as a 73 for installation. The 440 was built in Trenton plant. 8:2:1 compression 4.32 bore 3.75 stroke 275 hp with original heads. I wonder what my compression ratio will be going to the 82cc closed chamber heads.

 

[Davea Lux]

By the numbers, my replacement 440:

Jan 9th 1972 stamped as a 73 for installation. The 440 was built in Trenton plant. 8:2:1 compression 4.32 bore 3.75 stroke 275 hp with original heads. I wonder what my compression ratio will be going to the 82cc closed chamber heads.

The '73 346 head was rated at a design volume 81.5 cc, so there would not be much difference in compression. There are some variables in how much the block was decked from the factory to square it up and how much the heads were planed to square them up which would effect the actual volume of the heads as installed.

Dave

 

[carrman]

The '73 346 head was rated at a design volume 81.5 cc, so there would not be much difference in compression. There are some variables in how much the block was decked from the factory to square it up and how much the heads were planed to square them up which would effect the actual volume of the heads as installed.

Dave

Since mine was in an RV, shouldnt it have had 213 heads?

 

[Davea Lux]

Since mine was in an RV, shouldnt it have had 213 heads?

It probably would if it came out of a large RV. The 213 and 346 heads, if my memory is correct both have the same chamber volume but the 213 head had an improved water passage that was designed to improve cooling around the spark plugs for HD applications. Mopar was having financial problems in this era and the designed chamber volumes on all their heads suffered because of it with the volumes sometimes going out to as far as 88cc or more. If you were going to build the stock heads, that would be this first thing you would want to check. If you are going to pull the heads anyway, the head number is usually on the lower side of the intake runner for verification as to which heads you have. The final compression numbers will also depend on how far down the hole the piston resides at TDC as the deck heights on mid 70's Mopar blocks also varied a quite a bit.

Dave

 

[flyinbrick68]

My 73 had 213 heads on it unfortunately one was cracked so might wanna check em. Only had 56000 miles and never ran hot or used coolant was weird

 

[carrman]

My 440 Source heads are going onto this 440. They are down having valve guides being done as the machinist felt they were a little too loose.

 

[twostick]

Since mine was in an RV, shouldnt it have had 213 heads?

Chamber CC's should be about the same. They all measure at around 88cc's.

Any of those 8:1 motors when accurately measured come in at about 7.8:1.

Kevin

 

[carrman]

Chamber CC's should be about the same. They all measure at around 88cc's.

Any of those 8:1 motors when accurately measured come in at about 7.8:1.

Kevin

440 Source says their heads come out at 80cc. Sounds like I'm going to hate this 440.

 

[twostick]

440 Source says their heads come out at 80cc. Sounds like I'm going to hate this 440.

You'll get it up over 8:1 with those heads. Don't get crazy with the cam. If you are going to stick with iron exhaust manifolds, I'd keep the lobe separation angle wide, at least 112 deg and probably look at an advanced centerline install especially if your duration at .050 gets much into the 230's. It will help bottom end torque.

While your cylinder head guy is in there, maybe have him clean up the bowls a little and check to see if the seat inserts need to be blended into the bowls. I've heard the transition was a little abrupt there.

Kevin

 

[twostick]

The above is assuming you're sticking with the stock shortblock.

Kevin

 

[carrman]

268/280 Advertised Duration, 224/230 Duration .050", .477"/.480" Lift, 110 Lobe Separation; are the cam specs for my XE268H.

 

[70bigblockdodge]

268/280 Advertised Duration, 224/230 Duration .050", .477"/.480" Lift, 110 Lobe Separation; are the cam specs for my XE268H.

You will be okay with that cam. I would advance it, but your call. You will have a ton of valve to piston clearance due to piston down in the hole .120+
Did a quick Summit CR calculator and you will end up at 8.94 with 75cc heads, .040 gasket, and the aformention .120 in the hole. Gotta love those 3.75 stroke motors. I have 73 cc heads on a 400 and only manage 8.43, guess that helps explain part of the reason to put a 3.75" crank in a low deck, well that and getting rid of the 1000 gram pistons.

One other thing that comes to mind is, that era of RV 440 can either have a cast crank or six pack rods, both of which requires weights at the T.C. and a particular dampener. You need to match the factory imbalance or it will eat through the main bearings.