426 Crate Engine Experience

Discussion of Hemi crate engines.

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t machine

426 Crate Engine Experience

Post by t machine » Thu Feb 23, 2006 10:48 am

To add some further input on crate motor problems, this is what I ran into with my crate 426 Hemi, purchased in early 2000. The engine is mounted in a t bucket street rod.

Problem: When the engine was first fired, one lifter was knocking loudly.
Solution: Pulled the valve cover and readjusted a loosely set pushrod by Cummins.

Problem: One exhaust pushrod approx 1/8” longer than the other exhaust pushrods. It was visibly obvious because the adjuster screw for that rod sat higher than the other exhaust screws.
Solution: Cummins said they see this occasionally during assembly, but had no explanation and hadn’t had any complaints from the field about it. They sent me another pushrod. There’s more to this story but I won’t go into it now, other than to say that they had originally put in a mechanical lifter pushrod. The longer rod had no noticeable effect on performance and there was clearance with the rocker arm. But it just bothered me.

Problem: Dull knocking sound from the valve cover area. Rocker arm adjuster screws were lightly hitting the valve cover baffles under the breather tubes. Inspection showed two slight marks on each baffle.
Solution: Cummins admitted to the problem; had no explanation. They indent the affected areas with a punch, which is what I did.

Problem: Headgaskets weeping oil from both heads.
Solution: Cummins admitted that defective (?) shim gaskets were used in early production runs. They sent a replacement set of composite style gaskets. I haven’t installed these yet, though I did double check the head bolt torques – they were right on the money. The oil leaks have noticeably slowed with engine use (there’s now about 900 miles on the car.)

Problem: Coolant slowly disappearing from radiator. No visible external leaks anywhere. And it doesn’t seem to be winding up in the oil pan.
Solution: Haven’t found the problem yet. But it might be related to the head gaskets.

Problem: Some spark plug tubes had holes that were slightly too small for the plug to slip through, causing the plug compression ring to get chewed up during plug tightening.
Solution: Didn’t bother with Cummins this time. Just bought a new set of tubes that fortunately had the right size hole.

Problem: Oil fouling spark plugs.
Solution: Installed the aluminum Milodon cups. This eliminated the exhaust smoke, but some oil still manages to leak around the plugs. When the plugs are pulled for inspection, at least two look oil fouled, but it’s never the same two plugs.

Problem (?): As someone mentioned earlier, I, too, have 85-90 psi oil pressure. But so far haven’t noticed any ill affects. (I had a 454 Chevy motor that had the same pressure and it ran fine.)

The guys at Cummins are nice enough to talk with and they try to cooperate, but I think the expertise just isn’t there. At least not when I bought my engine. Knowing what I do now, I would have taken the Hemi to a reputable shop and paid the money to have it completely dissembled and reassembled. And maybe even had it broken in on a dyno before installing it in my car.

I love the Hemi engine and have no regrets about buying a crate motor. But it is sad that it’s ‘buyer beware’ when purchasing an expensive factory designed and built assembly.

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Joined: Fri May 26, 2006 5:57 pm
Location: Plum Pa, outside of Pittsburgh

Post by HemiMark » Fri Jun 23, 2006 6:58 pm

Problem: Coolant slowly disappearing from radiator. No visible external leaks anywhere. And it doesn?t seem to be winding up in the oil pan.

If you look hard enough you will see the coolent ozzing from the heads.

Try this.....Replace your radiator cap with a 7 lb cap. That will fix the problem. It worked for me.

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Joined: Sat Dec 01, 2001 6:00 pm
Location: Maryland

Post by Bailiesdad » Mon Jun 26, 2006 6:50 am

All the problems could be eliminated if they sold these engines as "kits" that need extensive testing, measuring, balancing, machining, and custom fitting. The way DC does it now is to throw them together with shelf parts.

If anyone buys a crate hemi the very best thing they could do is tear it down and start as if you were doing the build from scratch.

This way you have everything to start with and just have to modify or replace suspect components prior to them failing and causing extensive damage.

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Joined: Mon Dec 04, 2006 2:58 pm
Location: Manteca Ca.

Post by hobbeekid » Mon Dec 04, 2006 7:04 pm

I would have to agree with Bailiesdad on the fact that these HEMI crate engines should be sold instead as complete part assemblies that should be torn down & inspected then reassembled before firing. That would weed out any possible mechanical or assembly screwups.Kinda like the old ls6/ ls7 bigblock crate assembly's that gm used to sell during the 70's & 80's.If you don't have the skills to do it yourself, sublet the work to a competent machinist engine builder.It may cost you a few more $$$$ but considering what you've spent on your investment, It'll eliminate any headaches or heartaches in the future........... :wink:

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