Ax Gt Head And Vtr Bottom End

[custard-rallye 25]

hi as title says in the middle of doing this now just a few questions for finishing tomorrow

 

• what size will i need to drill the jets to for it to run well
  

• will i need any other bits to make it run well
  

• will the gt gearbox go straight on??
  
• and if it does what clutch and flywheel will i use the vtr one or the gt??
  

 

any help would be great as im doing it first thing tomorrow cheers

Edited May 1, 2010 by custard-rallye

[custard-rallye 25]

anybody?

[allye 530 3 Cars]

Are you sticking with the solex? If so drill it out a hugely small amount! It won't idle as good though, if you have had the solex apart some ideling and fuel mixture adjusting will need to go on, a timing light will be very helpful as its almost impossible to get it right by ear. I pretty sure the gearbox will go straight on, not sure about the clutch though.

 

Ali

[calvinhorse 870]

I did the same conversion, i drilled my jet to 1.3 in a lathe. Would probly stand being drilled a bit bigger, not checked the colour of the plugs yet.

[Guest dean-191]

I'm pretty sure the gt 'box is too small for the 1600 flywheel/clutch, it bolts together ok but only with the 1360 flywheel. My advice would be to find a cheap ebay gearbox (£50 or so) from a post '91 car otherwise the 1360 clutch just might not take it. 1100 has a nice short diff so that might be the one to go for. As a point of note it seems a shame to strangle a 1600 with the tiny weenie ports and valves in the 1360 head. I had a manifold modded so i could use the 1600 head with a solex, but i used it on a 1360 bottom end so I've no idea on jets at all! The 1600 head is so much better than the 1360.

[calvinhorse 870]

i'm using the 1.4 clutch (valeo) and its holding up fine.

 

4800miles of pain

[miamichris 9]

Just out of interest Calvin, whats this engine set up like compared to a standard Xs?

[Guest dean-191]

A cheeky mod to get your clutch to hang on a bit better is if your getting your flywheel re-faced get the machinist to cut the mounting face 0.005" (about 1/8mm in new money) lower than the friction face. Just gives it a bit more pre-load and helps it hold on. It's also free if you're having your flywheel re-faced anyway!

[calvinhorse 870]

Miamichris- more torque for a start! You notice the slightly heavier engine but that only lasts 2 miles before you get used to it, the mid range is better and shifting from 3rd to 4th to 5th you get a real boost of power as you apply the throttle.

It really changes the car from a "nippy little base model" to a somehow "bigger" car!?

Its a great mod in my opinion but ideally needs management or remapped dizzy to fully iron out pinking

[custard-rallye 25]

Mine is going to get set up tomorrow

[custard-rallye 25]

@ Calvin horse did you need a vernier pulley to set it up as I read on axoc you need one ?

[calvinhorse 870]

No, the timing is set to .6 instead of .8

basically if you put the engine under heavy load or labour it, it will pink but i can drive round it.

Above 4k it doesnt pink.

I'm not sure how a vernier pulley would help this as its a problem caused by the ignition curve?

[burr_2000 1]

The combustion chamber on the XS head is about 28cc and the head on standard VTR about 32,5cc which is significant and not a way forward for performance, understand if its just temp until you find a suitable manifold for the bigger valve heads.

[calvinhorse 870]

Its just easy and cheap to use the xs head, its a power gain over a standard xs thats all.

[batespeed 0]

i thought the vernier pulley was needed to get the valve timing right, not the ignition timing ? is the vtr not a longer stroke, therefore the block is slightly taller, and the belt run from the crank pulley to the cam pulley is also longer. so in theory the valve timing may be half a tooth out. (obviously, you can adjust it but only by a minimum of one tooth without a vernier pulley or an offset woodruff key) and there may only be 4.5 cc difference between the combustion chambers, but the vtr has domed pistons , i think, so your compression ratio will be far too high ,with the domed pistons and the smaller chambers, that's probably why it pinks a bit. i think you can get a thicker head gasket, any one know what one ?

Edited June 13, 2010 by batespeed

[custard-rallye 25]

I put a triple lare metal head gasket on mine and it still pinked I might buy a vernier

[Sam 4]

I could never get mine to stop pinking when I done this and put a proper 1600 head on it in the end.

[burr_2000 1]

I can understand trying to get more torque, i think book spec is about 90-95 lb/ft of torque of VTR engine and about 95-100 bhp but the xs book spec was about 80 lb/ft with 85 bhp (from new ). Now i think running the VTR on a smaller head and on a carb you will be getting a lot less for your efforts. i still think a well set up xs with the lightweight alloy block is great.

[calvinhorse 870]

had a small breakthrough!

i was reading the new ppc and in the guide to fitting megajolt, it says if tuning a car with a dizzy you should always remove the vacuume advance otherwise it can cause pinking

 

i tried this and its helped alot, it now only pinks if you really load it up which i just don't do on purpose i just did it as a test..

 

im pretty sure it will use more fuel tho?

 

i just want to add that im not a mechanic and im only listening for the pinking with my ear out of the window, just because i can't hear it does'nt mean its not happening!

 

burr 2000- i think its something to do with the compression being raised so much? also are you going to pugfest? i would love you to take my car up the hill and see what you think?

Edited June 27, 2010 by calvinhorse