3.9 later intermin Serp Engine project

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Prophead
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3.9 later intermin Serp Engine project

Post by Prophead » Wed Sep 25, 2019 5:48 pm

Continuing on from my previous post....I've gone and got a late 3.9 interim longblock i.e. serp front end and block casting with provision for cross bolting (but not actually cross bolted).

Allegedly the engine has been 'rebuilt' but until it arrives I wont know to what extent. In the meantime I want to start to make a plan for what is to be done with it.

1. Check cylinder liners for slippage & have block pressure tested.
2. Get it drilled and tapped for cross-bolted mains - I'm really hoping I get lucky and it has the correct main caps for this. If not, anyone know if they are available?
3. Get rotating mass balanced.
4. If required hone and new rings

Performance:
Increase CR; Block decked and use tin gaskets
Fast road cam; contenders are Piper 285, V8D Stealth, Kent H214 or H218, Viper Typhoon - Will I need pocketed pistons for valve clearance?
Duplex timing chain
Stage 1 head work

Serpentine ancillaries:-
Just going to be running an alternator and waterpump, so will have to use an idler pulley in the power steering location for belt routing to drive waterpump. Anyone running something like this, if so what did you use?


Porsche 924 GTv8 Track-day car project
Porsche 944 2.5 Lux gone but not forgotten

richyb66
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Re: 3.9 later intermin Serp Engine project

Post by richyb66 » Thu Sep 26, 2019 8:12 am

I'm running just and alternator and water pump on a serp setup and I repositioned the standard tensioner.

I posted some pictures in this thread:

viewtopic.php?f=12&t=15309&p=117028#p117028

Done over 8k miles on this setup with no issues.

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Prophead
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Re: 3.9 later intermin Serp Engine project

Post by Prophead » Thu Sep 26, 2019 5:37 pm

richyb66 wrote:
Thu Sep 26, 2019 8:12 am
I'm running just and alternator and water pump on a serp setup and I repositioned the standard tensioner.

I posted some pictures in this thread:

viewtopic.php?f=12&t=15309&p=117028#p117028

Done over 8k miles on this setup with no issues.
Thanks very useful.
Porsche 924 GTv8 Track-day car project
Porsche 944 2.5 Lux gone but not forgotten

richyb66
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Re: 3.9 later intermin Serp Engine project

Post by richyb66 » Thu Sep 26, 2019 8:33 pm

Here's another more detailed picture.

Image

The spacer is 20mm thick. It's bolted on through the centre of the tensioner into a hole drilled and tapped in to the lifting eye and also in to the head with a longer bolt through the existing lifter eye hole.

Not visible is the blind hole in the spacer that engages the cast boss on the tensioner that stops the fixed part of the tensioner rotating.

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SimpleSimon
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Re: 3.9 later intermin Serp Engine project

Post by SimpleSimon » Tue Oct 01, 2019 8:50 pm

X bolting not necessary IMO unless your building a balls out screamer or aiming for big power numbers , no need to change main caps on many 3.9 int blocks they already have the full width caps fitted block and caps just needing jigging and drilling for X bolting :wink:
TVR Chimaera RV8 Serp & Megasquirt MS3X

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Prophead
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Re: 3.9 later intermin Serp Engine project

Post by Prophead » Wed Oct 02, 2019 7:01 pm

The engine is going in a track-day car, whilst it's not going to be a screamer or mega power, it will get driven hard in its upper rev bracket so thought it a good idea to get the cross bolting done.
Porsche 924 GTv8 Track-day car project
Porsche 944 2.5 Lux gone but not forgotten

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