does anyone have the 427 small block all aluminum engine from bill mitchell? whats it like for power? is it a well built motor?

 

I installed one last year but ran into delays with the exhaust system and put only about 40 mi on it driving to the exhaust shop before taking it off the road for the winter. Appearance-wise, it's great. I took the intake & oil pan off for some work & to inspect the innards & the workmanship looked great. I was not impressed with the intake manifold and head port location. Bill Mitchell ads talk about right-cast technology. That's pure bull-crap. I had about 1/8" port mismatch. After port matching it looked great. The machining was impressive, particularly clearancing the block for the connecting rods- very professional. Interior parts were as advertized- ARP bolts/studs and SS bolt kit for exterior components. The timing chain cover (black painted steel) was inconsistent with the quality of the engine so I changed it to a cast Al cover from Summit.
Based on my short drive in which I drove it easily for break-in, it seemed to have more power than my old 385 HP 350. It didn't idle too well or start well but I think it requires some tuning which I'll do this spring. That's a little disappointing since it was dyno tested & supposedly tuned by Bill Mitchell. Still have to complete the exhaust before putting it on the road which I expect to do withing a month or so. The "dyno sheet" is a joke. It's just a form with HP, torque & some other numbers filled in. I guess you have to go on faith. I was expecting a curve Like in a real dyno sheet but that wasn't supplied.
My biggest suprise was that the exhaust ports are raised. You can't use standard headers such as Hookers. I ended up with Stahl custom headers. There's no warning that you need special headers and no guidance from Bill Mitchell. Bottom line, impressive engine (so far). Worth the money. Service/tech support is substandard. You're on your own. Maybe they're geared to pros/racers who are familiar with their products, although they market the the engines (at least the one I got) as street engines, I would assume targeted to individual consumers.
Some pics below:

 

A couple of additional pics:
Lifter valley:


Installed engine:

 

Couple of comments, that's a pretty clean looking motor for something that has been on broke in and tuned on a dyno ?

How much raised are the exhaust ports, my Vic. Jr's have .3" raised exhaust ports and I used the standard Hooker Super Comps. Looks like you have a conventional exhaust bolt pattern ?

 

nice

 

maybe i will stick with one of the generals 383's- the zz383 looks impressive.

 

Yes, engine was clean, but it was definitely run before I got it, although I don't know for how long. Residual oil that I drained was slightly dirty & exhaust ports were coated with carbon- was obviously running rich.
Exhaust ports are raised a good 1/8" with respect to the header bolt holes. See pic below which shows raised ports using a Fel Pro 1404 gasket. You could mount Hooker Super comps by slotting the bolt holes but Hooker ports were too small. I don't know why they didn't raise the bolt holes along with the ports. That would have made it easier to find a header that would fit. The Hooker Super Comp ports would definitely require enlarging to match the head ports, especially the gobs of weld metal that were protruding into the ports. I actually bought a set of Super Comps but sent them back when I saw the problems they presented.

 

Wow that's crazy how did you explain this to Stahl ? And get headers that fit, that must have been a pain in the azz

 

I sent them a rubbing of the ports & bolt holes which they used as a template. The Stahl headers fit perfectly. They're a work of art, especially the ports- nice & smooth & they match the head ports as-built. No mods required.

 

Did you ask World wth was going on ? Looks like a mistake, they drilled the holes is the standard location for a raised exhaust port head.

At first I thought you had a dual pattern drilled in the heads but now it doesn't even look like that.

Who makes headers for those heads, which ones are they ?

 

Head over to www.chevelles.com and do a search. Poor assembly and even poorer customer service seems to be the norm, but you can find the details of each customer's nightmares there.

 

I discussed exhaust port/bolt pattern configuration with World Products when I discovered the problem. They didn't know anything about it. After inspecting a head in their warehouse, they agreed that ports were raised with respect to bolt holes but couldn't offer any advice.
I did an extensive search for headers and concluded that no one makes headers to fit. Also, no one makes gaskets to fit. You have to modify a standard exhaust gasket. You either have to modify off-the-shelf headers or get a custom set, like I did. I have to admit it's a strange set-up. I also discussed with a local racer who builds & races pro-stock & has seen just about everything, and he says he's never seen such a bolt pattern. Apparently all other raised port heads have the bolt holes raised along with the ports so you can use a standard header. On the other hand, I bumped into a fellow at Carlisle last year who said he was familiar with the unique raised exhaust ports from Bill Mitchell from his work on their engines. Bottom line, you learn by doing but I would have expected Bill Mitchell to flag the issue (no mention of this in any of their literature or in any car mag article about Bill Mitchell engines). Also I would expect Bill Mitchell tech support to have known about the port geometry and be able to help. No such luck.
So finally, after a lot of work, worry & expense, I've got everything together. After I complete the exhaust I'll get it out on the road & hopefully be pleasantly surprised by the performance. It's mated to a Keisler 5-speed so I'm looking forward to it.