Twin cam conversion

gjgnz · Post by **gjgnz** » Wed Oct 11, 2006 5:58 pm

Sorry, I realise this has been covered before, but I just wanted to claify a few things about doing the twin cam conversion. Let's assume I have both a complete Starion engine and a complete VR4 engine with loom and ECU. Having searched through the old posts it seems to me that these are the main changes that are needed:

Use Starion block, VR4 head, pistons, front case and timing setup?
Balance shafts need to be removed?
Custom exhaust manifold and downpipe
New throttle cable
Move throttle body to front of manifold
Custom intake piping
Make recess in firewall for cam angle sensor
Replace Starion loom and ecu with VR4
Thermostat needs to be moved
Custom lines to run VR4 powersteering pump?

Have I missed anything? Any further info would be great.

Starion VR4 · Post by **Starion VR4** » Wed Oct 11, 2006 7:53 pm

No thats it.... other than loosing yr hair

:beer :beer :beer

TWIMCAM BOY · Post by **TWIMCAM BOY** » Fri Oct 13, 2006 1:59 pm

thats covered everthing mate, you only need to press the firewall in about 2 or 3 mm. GOOD LUCK with the conversion if ya need any help pm me i be more than happy to help!

JAS · Post by **JAS** » Fri Oct 13, 2006 4:19 pm

I moved the motor and box forward half an inch so the CAS cleared the fire wall. Instead of cutting the fire wall. I slotted the holes where the mount bolts to the engine 5-6mm, and 5-6mm for where the mounts bolt to the rubbers, and then used some seatbelt spacers to space out the gearbox crossmember from the gearbox. I had to remove the studs that come out from the gearbox and replace them with longer bolts. All pretty easy.

Just a different option :D

merlin · Post by **merlin** » Sat Oct 14, 2006 7:42 am

some of the previous comments did not match my experience, so heres what I found:
the TC timing belt is wider than the single cam belt, which required the use of the VR4 oil pump pully (wider), which did not properly fit to the staz oil pump assembly. I dont remember the details exactly, i think it fouled the casing.

Anyway, to use the VR4 oil pump pully required the use of the VR4 oil pump assembly (ballance shafts were previously removed). This all went together fine, keeping the staz water pump, so the plumbing all faced the right way etc. I almost forgot, the staz/L300 water pump needs a bit of metal removed to give clearance to the tensioner pully. Not a lot, but it does foul unmodified.

All was proceeding well, untill I tried to fit the staz alternator.
Nope, it wont fit the VR4 oil pump caseing.
Use the VR4 alternator, which is a multi-peak pully.
No problem, fit the VR4 harmonic ballancer.

You cant fit the VR4 power steering pump, theres no mounting tabs on the staz block to do it. Note I think some later 4G63/64 blocks do have the required mtg points. As i dont have aircon, I used a power steer pump of a Nissan RB engine (multi-peak belt, matches the VR4 crank pully), and mounted the PS pump where the aircon compressor used to sit.
Mark Boxal has the template for the adaptor plate to do this.
Just a 10mm thick flat item, drilled and tapped to suite.

It all worked! And this leaves lots of room on the exhaust side for headers/turbo/inlet plumbing. 3 inch inlet plumbing too!

UPDATE 1:
The blown ACL head gasket was partly caused by insufficent head tension.
It was torqued down to the requsite specification, however, the VR4 head bolts are about 1 turn to long for the staz block, or the washers are not thick enough, and the bolts were binding in the block.

UPDATE 2:
The exhaust valves had hit the pistons at some stage, probably when the belt tensioner moved, alowing the cams to advance a bit.
The ex. valve pockets in the piston tops did not match the VR4 head.
Something else to watch for. My pistons came from the US and may have been for an eclipse.

JAS · Post by **JAS** » Sat Oct 14, 2006 8:46 am

I moved the P/S pump (I used a Galant one) where the alternator is mounted and moved the alternator (starion one) over where the A/C compresser was (its New Zealand, you dont need A/C over here).
Hers a pic, note what Ive done with the thermostate housing.

Show Image: http://www.fr33z3.net/starions/Apr06/31egine.jpg

Im not saying its better that what other people have done, it just suits me. :D

evoJB · Post by **evoJB** » Sat Oct 14, 2006 5:15 pm

merlin wrote: I used a power steer pump of a Nissan RB engine (multi-peak belt, matches the VR4 crank pully), and mounted the PS pump where the aircon compressor used to sit.
Mark Boxal has the template for the adaptor plate to do this.
Just a 10mm thick flat item, drilled and tapped to suite.

How do i contact him for this template.

fr335tyl3r · Post by **fr335tyl3r** » Sat Oct 14, 2006 6:53 pm

mrb1 from these forums = mark.

silo · Post by **silo** » Mon Oct 16, 2006 2:24 pm

TWIMCAM BOY wrote:you only need to press the firewall in about 2 or 3 mm. GOOD LUCK with the conversion if ya need any help pm me i be more than happy to help!

Can someone measure the position of the cas in relation to the firewall?
I havent got my TC motor yet and my car is getting painted soon, so don't wanna damage new paint. I realise it will be an approx! THANKS :beer

flav · Post by **flav** » Thu Oct 19, 2006 12:39 am

Has anyone had any head gasket issues using the vr4 head on the staz block?

WANTSOM · Post by **WANTSOM** » Thu Oct 19, 2006 11:35 am

I think Merlin did but a Cometic should fix that

flav · Post by **flav** » Thu Oct 19, 2006 11:54 am

Yeah, i have an evo cometic and a VR4 cometic. The vr is the one you need but the evo one almost does the Job.

DanVR4 · Post by **DanVR4** » Thu Oct 19, 2006 1:26 pm

flav wrote:Yeah, i have an evo cometic and a VR4 cometic. The vr is the one you need but the evo one almost does the Job.

They're the same thing according to the back of my packaging

flav · Post by **flav** » Thu Oct 19, 2006 4:36 pm

errr, i have them both in font of me....miles appart.

Starion VR4 · Post by **Starion VR4** » Thu Oct 19, 2006 6:59 pm

Ok People, getting the water to the VR4 conversion, the pics tell the story.

Austarion

Twin cam conversion

Twin cam conversion

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