My 4D55 gets a new 4D56 head. PICS OF SHINY THINGS!

[maxslack]

I just got a few hours sleep and am heading back to my shop (at midnight!) for the undisturbed final assembly...

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[randy12v]

Nice.
curious, did you get the new head from ebay? or some other source?

[dancinggecko]

I know the 4d56 has a slightly longer stroke than the 4d55, did you have to do anything to make up for that? And did you have to make any modifications to the block to get the new head on there?

[huff]

I know the 4d56 has a slightly longer stroke than the 4d55, did you have to do anything to make up for that? And did you have to make any modifications to the block to get the new head on there?

There aren't any modifications needed - you only need to take the old head off and put the new one on. The difference between the heads is the 4d56 has roller rockers.

[dancinggecko]

Okay, one more question, how much of a difference is there in power, fuel economy and things like that with the 4d56 head over the 4d55?

[huff]

I'd be surprised if there was a significant difference, apart from how much wear there is on a multiple-100k-mile engine. I have a 4d56 head, but I didn't have enough experience with the engine beforehand to tell you if it was different.

I only got one because I was redoing the engine (again) anyway. My old head had some ugly pre-combustion chambers, and had been resurfaced at least once maybe twice before. Otherwise it would have been a case of "if it ain't broke, don't fix it". If you are looking to improve performance, I think the first thing to do is to make sure the IP and the injectors are in good shape, and focus on getting the IP tuned for how you drive. Next, get an intercooler. After that, you can play with the turbo adjustments. And so you don't damage anything, you should probably have a pyrometer.

[dancinggecko]

Some of that is a must, like the pyrometer, and we do plan on doing a little fiddling with it to get it where we want it as is. We do have another truck with a 4d55 in it though and it has a hard time getting out of its own way.

[maxslack]

The truck runs great with the new head and the IP timing advanced 4 degrees BTDC. I just did a drive on rt 40 of about 400 miles averaging 70mph and got over 30mpg. Nice! It'll pull easily past 80mph and even did Old Fort mountain in 4th at 60+mph with no problem. Hell yes!