A Visit with Len Hoffman.

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Jivermo
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A Visit with Len Hoffman.

Post by Jivermo » Mon Jun 26, 2017 10:26 am

My wife, Janet, planned an itinerary for a trip north for us, and we were to be in Watkinsville, Georgia, at a B and B. This rang a bell, and I realized that Len Hoffman had his shop in this town. As it turned out, he was less than a mile away from where we were staying. I dropped him a line, and he invited me to stop by when we were up there. We arrived on a rainy day, and I called him.
Len's shop is tucked away, behind a Shell gas station, by a motorcycle shop. It's difficult to locate, from his address, so I called him from my car, and he came outside and waved at me. I drove over, and he invited me inside. I walked into a very clean environment, filled with the tools of the modern machinists trade. Len and another fellow were busy, working in some racing car heads. I knew that he had a lot of work to do, but he graciously offered me "the nickel tour".

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Of course, I was interested in his air cooled work, so he told me about his Blueprint Special head work, and brought out a modified AMC head to show me. Here, in his own words, is what he does:

In 2007 we stopped servicing used VW T4 bus heads. By that time around half of the castings we saw had severe cracks down in the exhaust ports and/or other evidence of heat related damage. It no longer made sense to put large amounts of time into servicing them when we can buy new, better castings.

As replacements we offer our Blueprint Special’s.

We start with a pair of new AMC 2.0 heads, strip the sub-par valves, seats, guides, springs, and retainers and toss them in the scrap barrel.

The Blueprint Specials are machined to accept new high temp, super durable valve seats that are fitted tight with the proper interference fit. The tungsten carbide exhaust seat material we use is wear rated up to 1800*F.

They’re built with new quality parts proven to be durable and reliable. The valve guides we use are silicon/manganese bronze and are extremely wear resistant.

The valves are tough aftermarket stock 2.0 size (39mm x 33mm) O.E. replacements.

The heads are machined and built with pride to factory specifications. Valve stem ht’s are set to +or- .005” for consistent valve train geometry.
Combustion chamber volumes are stock at ~49.5cc’s.

These heads come equipped with a .8mm raised step in the cylinder registers. This step simulates the O.E. head gaskets thickness and allows them to be deleted per VW instructions without installing spacers under the jugs to restore the unswept volume and deck height lost with the deleted gaskets. This raised step counts as deck ht and is added to the deck ht in the cylinders for determining the total deck.

Example: If you have .25mm deck in the jugs at T.D.C., add that to the .8mm step in the heads for a total deck ht. of 1.05mm. This is the deck value you use for C.R. calculations.

The Blueprint Specials are the best stock specifications heads available, and come with a limited 1 year warranty.

Most 78 models came with Oval Port heads, but some late production year busses came with Square Ports.

We charge $1,425.00/pair for oval ports.
Square ports sell for $1,495.00/pair.

For an additional 25.00 we will machine a notch in the #3 spark plug well for a cht probe to nest under the spark plug. This is popular for guys who want to monitor the temps on that cylinder. This makes plug changes easier without destroying the probe. The plug well on these heads is deep and makes it tough to nest the probe without putting a sharp bend in it. For 50.00 we’ll machine a notch in all four spark plug wells for more comprehensive monitoring.

For serious heat protection we recommend a pair of coatings that have proven themselves in race applications time and again: a heat insulating ceramic coating of the combustion chambers, exhaust ports and tops of the valves as well as the underside of the exhaust valve, and a black exterior coating that aids in the heat shedding process. The most critical of these coatings is the ceramic insulation, which greatly reduces the temperatures of the aluminum. We’ve been using this coating on track/race applications for years and have seen it protect heads from major distortion/warpage caused by elevated exhaust gas temps (EGT’s) as high as 1450F*!

Aside from aiding in the shedding of heat from the fins, the black exterior coating, which is a slippery, Teflon like substance, also aids in preventing oil and debris from clogging the small airways that carry cooling air through the fins.

The added cost of the ceramic insulation alone is 225.00/pair. Add the black exterior coating for an additional 240.00.

These coatings will help protect your investment and improve reliability in heavily loaded highway situations where lengthy, full throttle driving is the norm, like climbing mountain roads or driving into stout headwinds. It is exactly this sort of driving that pushes up EGT’s to dangerous levels and lead to damaging heat soaking and head warpage.

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Here Len showed me how they peen the head area to strengthen it.

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An example of the ceramic coating he offers as an option for better heat handling qualities. He also has the black exterior coating, but told me that if you can afford but one, this is the one to get. He also showed me the Manley valves, which is one if his valve suppliers.

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A closer view. The coating looks really good, and consistent.

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He showed me a Chinese made copy of a head, that he was experimenting with, but I got the impression that he felt the AMC product was superior, because it is beefier. The Chinese copied the Porsche design exactly, while the Spanish one is heavier.



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I could have spent a lot more time speaking to Len, as he is really open about his work, and passionate about what he does. I knew he was busy, so I took my leave. I enjoyed meeting him very much, and the quality of his work looks really good. His shop is clean, air conditioned and well lighted, and well organized. He is expecting a shipment of AMC heads in several weeks, and will be making a run of his Blueprint Specials. He is a real interesting guy, and it's good we have some folks like this around for a resource, in my opinion. If you're ever around Athens, Ga., he is worth a visit. Jimbear, sorry I
missed you on this go around, and you as well, Hobug. Maybe on the return trip, and I'll give more notice, for a bite at that Chops and Hops!

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asiab3
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Re: A Visit with Len Hoffman.

Post by asiab3 » Mon Jun 26, 2017 10:42 pm

Ian, thank you for taking the time to stop by! It's always refreshing hearing about people who give a damn, and aren't looking to hang their hats up at a moment's notice. Plus, now I can put a face to the name! :)

Robbie
1969 bus, "Buddy."
100k miles with me.
279k miles on Earth.

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Re: A Visit with Len Hoffman.

Post by Jivermo » Tue Jun 27, 2017 4:36 am

You're welcome, Robbie. I'm thinking that it would be a very interesting article, to sit down with Colin and Len, and write up the ensuing discussion.

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Re: A Visit with Len Hoffman.

Post by sgkent » Tue Jun 27, 2017 9:31 am

It is a great article. Len does know his stuff. He is also a very warm compassionate person, although he is leery (like many of us are) of those who promote less than A+ quality work.
Thank You -

Merlin The Wrench

Machine Work/Shop Recommendations: http://kentcomputer.com/77VW/machinework.pdf

Pointers on rebuilding an engine: http://kentcomputer.com/77VW/rebuilding_a_vw_engine.pdf

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Re: A Visit with Len Hoffman.

Post by Mr Blotto » Fri Jun 30, 2017 5:14 am

Jivermo wrote:
Mon Jun 26, 2017 10:26 am
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Very cool. I didn't know that Page from Phish also rebuilt top quality heads! :joker:

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1978 Sage Green Westy - 2.0 FI - SOLD WITH 109887 miles :-(

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Re: A Visit with Len Hoffman.

Post by Jivermo » Sat Jul 01, 2017 5:52 pm

Len has some further clarification on those Chinese knock off heads. Here, again in his own words:

"AA Chinese 2.0 914/4 Knockoffs
by Hoffman
These heads are based on the 039 101 371A heads that came on 2.0 914/4’s and 1976 912E’s. They are often referred to as 3 stud heads due to the fact that they feature 3 intake manifold studs, unlike all other Type4 heads which have 4 studs. Since their release earlier this year we’ve fielded a lot of questions about these heads. Naturally I purchased a pair to investigate for myself. In this article I’ll address my observations of this single pair.

First though I feel the need to clear up some misconceptions and misinformation that have been circulating and have made their way back to me recently. First, that because my company supplies heads for Raby Aircooled Technology there is apparently an assumption flying around that Raby will be switching to these heads on his custom Type4 engines. Nothing could be further from the truth. The heads that we supply for R.A.T. are bespoke variations of our AMC based LE-200 model heads and are engineered to work with bespoke pistons designed by Charles Navarro of L.N. Engineering. There is no plan, immediate or distant, to make a change, even if the AA heads did have as much “beef” as the AMC heads (which they don’t). The second misconception circulating is the notion that I’ve “signed off” on them. Let me be clear, the fact that I worked up a pair of the AA heads for testing does not serve as an endorsement of them, tacit or otherwise. Nothing could be further from the truth. While I am hopeful that these heads will prove themselves over time, it’s going to be a long time before I step forward with an actual endorsement. We have over fifteen years of positive experience with the AMC heads. It's going to take a while before we develop that level of comfort with these, or any other replacement heads.

Now for some analysis, keeping in mind that I have only worked with one pair so I have no idea how repeatable these will be. As knockoffs go, overall they make a pretty good visual first impression. There are some exterior details that aren’t as exquisite as the German originals, but that’s no surprise and not particularly alarming. The first thing that jumps out is that AA dispensed with the 15mm O.D. exhaust guides, opting instead for the 12mm size used on the intakes. This sits well with me, but does eliminate the option to run 9mm exhaust valve stems. Something we haven’t done for years on any but our transporter heads, so no problem there.

After a thorough visual inspection we mounted them in our CNC machine for some reverse engineering to see how they compared to our programmed specs for factory heads. Overall I was pleased with those results as bore and chamber centers and heights were spot on. We did find that the intake ports were rough as corn cobs and out of position, especially the #2&#3 ports, relative to the manifold stud pattern which was properly positioned relative to the registers (thankfully). This means port matching, at a minimum, will be critical for good performance and even cylinder filling from cylinder to cylinder.

Once we were done reverse engineering, we CNC machined valve seat counter-bores using the same feeds and speeds with the same tooling as we use on AMC heads. The chips and machined surfaces were identical in appearance to the AMC heads and the machined dimensions were within .0002" of what we get with the AMC's. That tells me that they at least have similar machinability, which is encouraging regarding alloy characteristics, but hardly conclusive in predicting durability.
As for the critical features, the chambers are perfect repops and chamber volumes after our finish work were within .5cc’s and came in at 58cc's, about average for an uncut O.E. head. That’s excellent. On the down side the pushrod tube bores were ~.002” small, which was good since the machine work to them was rough as a cob and require honing to smooth them out so they won't tear o-rings. The fly-cut finish was okay, but the height from chamber to chamber varied by .0025”. Our finish work is within .0005"

The exhaust ports are pretty much dead nuts copies of the O.E. heads but with a rough texture. After polishing and blending they flow about the same as an untouched stock port, which is good when comparing to other O.E. T4 heads (1.7&1.8) but bad when comparing to what we get out of our AMC heads, which come from Spain with tiny ports and lots of meat around the outside of the port that allows us to carve a far superior shape, one that we've developed over years of testing. There's room for some improvement, but not enough to match our proven shapes as AA chose to copy pre-smog heads, which have a lot less material around the exhaust ports.
Unfortunately there are also several other areas of these heads that would benefit from more material. But that goes back to the fact that these are in most ways true knockoffs. Those of us who’ve been around long enough already know that the original 2.0 914 heads were lightweights and prone to cracks. IMO these castings are too faithful to the originals.

Because they are lightweight castings of an unknown alloy I sent this first pair out for thermal coatings to the chambers and exhaust ports.

My verdict is still out on these castings as far as durability goes. My hunch is that they are going to do at least as well as 40Y.O. castings that have been run through the ringer. That said, I'm willing to build them out with quality parts if people are interested, but I'm not willing to put a warranty on them beyond my workmanship."

For more details, see Len's website...there are more pics there, as well.

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Re: A Visit with Len Hoffman.

Post by Amskeptic » Tue Jul 04, 2017 7:28 am

Thanks for this, Jivermo.
There seems to be hope out there in fits and starts and spotty bits of blue sky that we may have a trickle, a misting of barely acceptable new parts wafting through the abandoned dirt streets of air-cooled Volkswagendom.
Colin
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 91 414 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,113 miles

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