[Healeys] 100 engine rebuild

WILLIAM B LAWRENCE ynotink at msn.com
Mon Nov 6 14:22:42 MST 2017


I just started my engine after about 2 years of rebuilding. Sounds great.

I installed 88.5mm pistons from Denis Welch. They are sized precisely enough that the machinist just has to bore to the nominal size and they fit. They incorporate new tech metric piston rings to minimize blowby. So far they are performing as advertised. They also sell these pistons in 88mm and 89 mm. I think there is a lot of meat in the block and I've heard of people overboring them to 0.100"

I also installed their performance head gasket which is a MLS (multiple layer steel) design. This is supposed to eliminate the typical leak at the number plate.

I'm running an iron head which had never been cut and tested with no cracks. How many of those have you seen recently? I'm running an 8.5:1 compression ratio.

I'm using a set of H6s that I built up from spare parts on a set of Denis Welch manifolds with their heat shield. For jetting I just went with the 100M spec OA6s. I plan to run it on a chassis dyno to check the mixture and adjust the tuning (Burned a couple pistons a while back so I'm very leery of pinging.) I've added a set of 2-3/4" velocity stacks and a  Pipercross double air filter. This will just fit under the shroud but I've got to have a hatch fabbed into the shroud to allow for servicing. Fortunately I've found a good sheetmetal guy who is refurbishing the shroud as we speak.

The camshaft has been ground by Iskendarian to their Z-99-E4 specification (I have been running this specification for over 10 years). It has durations of 260 degrees and a valve lift of .425". These numbers are a little more radical than the 100M/S grind, but it runs smoothly without a noticeable lope. I sent them a used camshaft and they ground it and heat treated it for $135 plus shipping. I bought Denis Welch's vernier cam sprocket and I've set the cam timing ahead 4 degrees to optimize low end torque. I am building the car for long distance touring and with 3.54:1 final drive gears I doubt if it will spend much time over 4,000 RPMs.

Good luck with your project.

Bill Lawrence

BN1 #554

From: Healeys <healeys-bounces at autox.team.net> on behalf of warthodson at aol.com <warthodson at aol.com>
Sent: Sunday, November 5, 2017 7:32:16 PM
To: healeys at autox.team.net
Subject: [Healeys] 100 engine rebuild

I am beginning a complete 100 engine rebuild & am looking for advise.

- I would like to build an engine that will produce as much power as is possible consistent with the following specifications:
Fast road driving, not road racing. Premium fuel, not racing fuel. In the USA Approx. 91-92 octane rating. I think that results in about 9.5:compression. What compression ratio would you recommend?
The engine will include:
-an aluminum head
-Carbs: twin H6's

I also need a new cam recommendation & am considering either Denis Welch "#DW1 or #DW4 cam? Suggestions, please.

Also, I would like to over bore the engine. Is there any reason to not bore it out to 89mm, other than that might not allow for any future over bore?
What piston sources  would you suggest for this application?
Any related suggestions, recommendations or questions would be appreciated!

Gary Hodson
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