Following up on a very informative discussion three months ago by Bernd, Oliver and others
http://forum.sunbeamalpine.org/index.php?threads/original-zenith-to-manifold-gasket.28354/. First, I want to say to Bernd and Oliver I am keenly disappointed the UK Sunbeam spares meet will not be taking place this year. To listen in on a conversation between you two (yes, I would have ease dropped without permission) would have been one of my 2020 European Automobile extravaganza's highlights. Oh well, there will be 2021.
Now taking off from some of what was communicated in the above sited thread I want to share some findings in my scattered and yet organized piles of Sunbeam parts. Questions may arise about Hartwell tuning and I will share what I have and await anyone who might chime in.
This is a photo of the my USA Promotional Harrington Le Mans at the March, 1962 Sebring race press trailer.
My HLM was specifically purchased by Greg Vederoff (a successful 50s/60s Porsche sports car owner/driver racer) for the 1962 racing season in the Pacific Northwest. Then Vederoff traded it to the Forsgren brothers (racing legends on the West Coast in the 50s/60's) early 1963 for one of their hand built race cars. The complete numbers matching engine was provided to me by the third owner from whom I purchased the HLM in 1998. He needed to install another engine (1725) after the #1 rod broke and excavated a hole though the original block at 51,000 miles, December 1, 1968. I still have all of the components from the original engine and this is what I found today.
Because this was the USA Promotional HLM I can assume that the original engine was tuned by George Hartwell. I would also assume that it was race ready minus the limited slip differential ordered from the factory by Vederoff. I believe, based on the complete engine investigation, it was a Stage III tuning.
Here are photos of what I have:
The engine incorporated flat top pistons most likely giving it the 10:1 compression ratio for stage III tuning.
The left over #1 piston after rod failure.
Comparing HLM intake manifold (Hartwell tuned) with twin Zenith 150s to a stock manifold. Note: The difference in inlet port sizes 35mm (no ridge) to 33mm (ridge for metal cylindrical insert) respectively.
Hartwell tuned on the right (no ridges).
Comparing HLM 1952 block (Hartwell tuned) with Stock 1592 block. Note: The difference in exhaust port sizes 35mm (ported/no ridge) to 33mm (not ported/ridge) respectively. Difference in inlet, Hartwell tuned is ported (no casting imperfections) and stock is not ported (casting imperfections).
Hartwell exhaust port and polished (top orifice) Stock exhaust port with significant casting ridges (bottom orifice).
Hartwell inlet (28mm) port and polished (bottom orifice) Stock inlet (28mm) casting ridges (top orifice)
The Zeniths have the throttle bracket reinforcement. I don't believe this was done by Hartwell.
Here is a shot of the original carburetor to a Hartwell manifold. I don't see the thicker gasket (mount to manifold) that you were referring to in your thread above Bernd. However, it is possible the Zeniths were removed and paper gaskets replaced the thicker example Bernd found in a drawing.
The head was significantly shaved (Note: At the bottom you can see exposed threads.) This probably led to a very high compression ratio and the demise of the rod.
I don't believe the shaving was done by the Hartwell team. I do have records showing there was a rebuild done at 20,000 - 21,000 miles by the Forsgren brothers in 1966 with valve replacements. They were very successful racing their hand built cars. However, my HLM was not raced by them it was used to tow there race cars to the track. I still have the tow bar system that was installed.
