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Before I build it - Thoughts on an 1883cc motor for my 356A

Posted: Wed Jun 06, 2018 4:47 am
by David Twiss
Registry Members

I’ve had the components for a modified 912 based motor in their original packaging awaiting a suitable donor car for almost 20 years!

You know how it is…………….. work, family and other projects always seem to take priority.

Early this year I acquired a matching numbers, RHD Aussie delivered 1959 356 A coupe. I guess you’d call it a barn find as it has been off the road since 1964.

It’s in remarkable condition, silver exterior with a green interior and has never been restored. It hasn’t fully escaped the ravages of time however and I have commenced a suitable sympathetic restoration

The plan is to store the recently rebuilt matching numbers “ A” motor and rebuilt matching number “A” gearbox and in their place transplant a 1883cc 912 based motor and Skirmants built 741 gearbox .

For added braking power 60mm Carrera front drums are also to be installed.

Before I assemble and install the 1883cc motor, given the length of time I’ve had the components and as technology marches on I’d like to ask registry members about their experiences with similar configured powerplants

I am on the right track?

Are these LN 1883cc motors reliable?

Are there any tips you can give me?

I am also planning to go twin plug and in doing so up the compression to 11.1. (Petrol here is 98 Octane).


Motor (Type 616 1883cc)
• 912 Crankcase Blueprinted back to standard and converted to Full Flow Oil by Competition Engineering
• Scat 74mm Billet light-weight knife edged crank
• Carrillo Rods
• LN Engineering 90mm B Nikasil Barrels with JE Pistons (10.5 Comp) .
• ARP Head Studs
• 912 Cylinder Heads modified by Vic Skirmants. Includes: Porting heads, manifolds, combustion chamber re-contouring, 8 new race valve guides, 4 new Datsun style 40 mm intake valves, 16 new Datsun valve spring keepers, 4 new 34 mm with 8 mm stem exhaust valves, 8 new racing valve springs, 8 new Titanium valve spring retainers, 8 new valve lash caps, Valve spring shims as required,
• Dual 44mm Webers, Manifolds, Air Cleaners and Crossbar Linkage
• Elgin Camshaft – Grind 7208 – 19
BAS Stainless Steel 4 into 1 Sebring Exhaust
• 912 Rocker Assembly – Short Exhaust Rockers Ground and Shot Peened by Vic Skirmants
• Chrome Moly pushrods
• New 200mm flywheel lighten to 14Lbs
• Alum oil cooler
• Vic Skirmants Oil Pump Cover with Oil Line Outlet and Relief Valve
• Remote Oil Filter Adapter
• Alloy Finned Oil Sump Cover
• Old Skool 912 Alloy Finned Rocker Covers

Any feedback is greatly appreciated.

Cheers

David

Re: Before I build it - Thoughts on an 1883cc motor for my 3

Posted: Wed Jun 06, 2018 8:04 am
by C J Murray
Hello David,
The first question is — how do you intend to use the car? Second question — are you an aggressive driver or a smooth relaxed type of driver? To be satisfied with your engine build you must be honest with yourself when you answer those questions unless you just want to look at the car parked in the garage and brag how much trick kit your car has bolted to it. Answer those questions and I could give a detailed answer.

There is no reason for a transmission change.

Twin plug ignition is a joke. It is an expensive way to accomplish nothing, creates heater issues, and makes a plug wire mess.

Lightened flywheels are a mixed blessing on the street. They make driving in town a little more difficult and they increase the vibration characteristics of the engine and an 1883 vibrates more than a 1600/1720.

Weber 44s work very well on Solex manifolds with adaptor plates and blended to 44mm. Most Weber specific manifolds are poorly designed.

Re: Before I build it - Thoughts on an 1883cc motor for my 3

Posted: Wed Jun 06, 2018 12:33 pm
by Roger Shapiro
David,
I have a 1883 in my Roadster. Here a couple of things you should do.
1) Skip the twin plug. Take CJ’s advice.
2) be very careful about overcarbureting those 44s. UNLESS you are going to use all those 7000 rpm all the time, get a set of 34mm venturis.
3) Stick with the mildest cam (less lift) and least stiff valve springs (like factory spec) you feel comfortable with. A happy engine with a 3K to 6K rpm range is a thing of beauty.
4) THERE IS NO REPLACEMENT FOR DISPLACEMENT.

Re: Before I build it - Thoughts on an 1883cc motor for my 3

Posted: Wed Jun 06, 2018 2:42 pm
by John Lindstrom
My two cents is invest $$ into the car before you even think about the engine. Go through the entire car to ensure that it will start, stop, turn, brake, handle, etc. Safety first Batman. Then, and only then, put a bad boy engine in it. If you really want to enjoy it, like it sounds that you do, put a roller pedal in it and solid transmission mounts! Don’t forget a fire extinguisher and race helmet.

Re: Before I build it - Thoughts on an 1883cc motor for my 3

Posted: Wed Jun 06, 2018 3:39 pm
by C J Murray
Roger Shapiro wrote:2) be very careful about overcarbureting those 44s. UNLESS you are going to use all those 7000 rpm all the time, get a set of 34mm venturis.
Roger is correct. Depending on how the car is used you may even want to go with IDF40s with 34 mm venturis. I had an 1883 with IDF44s with 36 mm venturis and it worked but would have been better with less carburetion. IDF44 36 mm work fine on my 2133 and are definitely not undersized for that application. 34 mm venturis are plenty big enough for an 1883.

Re: Before I build it - Thoughts on an 1883cc motor for my 3

Posted: Fri Jun 08, 2018 4:40 am
by David Twiss
Thanks Guys.

I'd say I'm an enthusiastic driver!

All my cars are toys, they are not daily drivers but are brought out to enjoy a spirited drive when the mood (and weather!) takes me!

Each has been tastefully and subtly modified to suit my driving style and tastes.

However with the 356 A as originality is coveted the matching numbers motor (down to the carbs and ancillaries) and gearbox freshly rebuilt will be benched.

There will be nothing undertaken which cannot be reversed back to factory spec's

I have a Skirmants built 741 sitting in the garage (so I'm going to use it) and a set of lovely 60mm drums up front will be installed.

I was interested to hear the almost uniform recommendation not to go down the twin plug route...............I've taken this on board. Interesting as there are obviously twin plug devotees out there!

Likewise the advice on carbs and venturi's is duly noted!

Now LN 90mm Nickies versus the Shasta alternative?? Any thoughts as I've hear conflicting views on Nickies, that they are prone to smoke after spirited driving over time? I brought my Nickies 15 years ago and they have been sitting in the garage all that time. Clearly they have been on the market a long time so have any problems arisen over time?

Cheers

David

Re: Before I build it - Thoughts on an 1883cc motor for my 3

Posted: Fri Jun 08, 2018 7:26 am
by Martin Benade
One question, is the look and noise from the exhaust system what you want, over nicer torque curve and HP from a stock style muffler? It is a tradeoff.

Re: Before I build it - Thoughts on an 1883cc motor for my 3

Posted: Fri Jun 08, 2018 7:55 am
by C J Murray
I have used Nickies in 1883(10k miles), 2133(24k miles), and two 1622(8k rpm racing) engines without one problem. I have used Shasta a number of times without problems. Use the Nickies that you already have.

Camshafts and CR are a critical decision. I would use a mild camshaft and moderate CR. The bigger the cam the more CR required and the worse the car drives at slower speeds. As camshaft duration goes up the engine makes less power below the point of peak HP but more at and above peak power RPM. High lift cams are very tough on the valve components and cause high maintenance requirements.These are facts not opinion.

I had an 1883 with 7008 cam, IDF44/36 carbs, and 10:1 CR. If I were doing that engine today I would drop the CR to 9.5 and the venturis to 34 or better yet use a stock SC cam and 9.0 CR and Weber IDF40/34.

The big bore engines require an open mind where ignition mapping is concerned and the fully adjustable 123 Tune with vacuum advance is a great asset.

The goal is to achieve the greatest average HP throughout the RPM range not the highest peak HP number.

Re: Before I build it - Thoughts on an 1883cc motor for my 3

Posted: Sat Jun 09, 2018 2:25 am
by David Twiss
Thanks again Gentlemen

A few more final questions

1. Okay so I don't go down the twin plug route so what ignition system do you suggest I employ?

2. Martin you raised an interesting point regarding exhaust systems. I note the Willhoit used a factory style sports muffler on a number of his motors. I don't know whether he sells them or if he gets them from someone else. Are there any alternatives out there?

Cheers

David

Re: Before I build it - Thoughts on an 1883cc motor for my 3

Posted: Sat Jun 09, 2018 7:10 am
by C J Murray
Are you doing a 12 volt conversion?

Re: Before I build it - Thoughts on an 1883cc motor for my 3

Posted: Tue Jun 12, 2018 7:18 am
by David Twiss
C J Murray wrote:Are you doing a 12 volt conversion?
Yes CJ ...........I plan on doing a 12 volt conversion


Cheers

David

Re: Before I build it - Thoughts on an 1883cc motor for my 3

Posted: Tue Jun 12, 2018 7:46 am
by C J Murray
With 12 volts you can use an MSD triggered by the distributor of your choice. A strong spark will help you through your trials and tribulations of dialing in your jetting and ignition curve or ignition mapping in the case of the 123 Tune w/vacuum.

Re: Before I build it - Thoughts on an 1883cc motor for my 3

Posted: Wed Jun 13, 2018 1:41 am
by David Twiss
Thanks to everyone that responded to my questions.

Later in the year a couple of buddies and I are attending RENNSPORT and the 356 Carmel Valley bash so we hope to see you all.

Cheers

David

Re: Before I build it - Thoughts on an 1883cc motor for my 3

Posted: Wed Jun 13, 2018 9:57 am
by gregorycampbell
Hi David,

We will be at racing at Rennsport with a Devin and Elva. Looks like we have roadsters, outlaws, big bore motors, and Devins in common! Please ensure to drop by.

Gregory

Re: Before I build it - Thoughts on an 1883cc motor for my 3

Posted: Wed Jun 13, 2018 11:16 am
by C J Murray
Pictures of the Devin D please.