Cam Timing For Pts Max Torque Cam And Other Engine Spec Help Needed&#3

[Chris H 10]

Hi, i've picked up a cheap pts 7048 max torque cam and vernier wihich is going into a budget rally engine i'm building.

 

Does anyone know what it should be timed up to? I've done a search and caan find the same questions but no answers.

 

Does anyone have experience of this cam, by the sounds of it, you need to up the compression to make the most of it.

 

Havent decided wether to use a 1.9 motor with 1.6 pistons or build a 1.6 engine but as far as i'm aware there are no easy ways to get the compression up without forged pistons on a 1600.

 

Car will be running Webber alpha ecu and 45mm tb's

 

The engine will also be having some std size longmans group A "penny on a stick" valves, double valve spring kit, titanium tretainers. Magnex manifold

 

I have a blueprinted skip brown 1900 gpn engine (that makes 151bhp onthe webber alpha), a std 115bhp b6d, a std 105bhp 180A engine and probably lots of other bits floating about.

 

I have an absolutely mint head that i'll be building up with the above bits.

 

All the bits i've bought owe me less than £150! I'm just trying to build a fairly quick engine that will replace my 105bhp engine in my rally car......whilst i've had class wins in it...there is only so much fun you can have with that little power!

 

So...can anyone suggest cheap and effective bits to swap about? What should the cam timing be? Any other advice welcome

[welshpug 1,626]

the answer to higher compression in a 1.6, flat top 1.9 pistons, from the 405 SRI and some BX engines not sure if you'd need cutouts in them but I don't think you do.

[Chris H 10]

That's an option then. Are these pistons easy to find?

 

I also have an engine thats allegedly from a 1.9 auto but it hasn't got the engine code plate on it......do the 1.9 auto engines have a spacer plate between the sump as this hasn't!

[welshpug 1,626]

no they don't tend to have the spacer plate as far as I know

[Chris H 10]

no they don't tend to have the spacer plate as far as I know

 

So it could be an auto engine then....are there anything useful in these engines?

[petert 554]

I use to run that cam. You definitely need 11:1 minimum. I'm not sure why you'd build a 1.6 if you could have a 1.9L. You can also use Mi16 pistons and rods. These pistons have the added advantage of being lighter, full floating and centre the rods. I can't recall the lift @ TDC figure for that cam but it should be on a 106º centreline. ie the maximum inlet lift should occur 106º after TDC. This is somewhat difficult to measure accurately due to dwell on the top of the lobe. You need to verify your centre with points either side. Do some research if you're not sure what I mean.

 

The double springs are a wise choice. Using that cam with standard springs boarders very close on spring bind. What seat pressure are you going to run?

Edited April 7, 2012 by petert

[welshpug 1,626]

Rallying class cutoffs and the competition Pete, good 1600's are still fairly rare whereas there's dozens of high powered 2.0 cars out there.

[Chris H 10]

Quite right welshpug, i already have a reasnoably competitive 200bhp mi16 205 (well i would if it didn't need a reshell due to insufficient talent) and i'm planning to use my other car wnich is already a 1600 and have actually managed to get some 1600cc class awards even with its crappy 105 bhp engine! Its nice to have a choice of car depending on the event!

 

petert, i thought 106 deg was where i should start with the cam so that nice to have someone confirm the same. What do you mean be seat pressure by the way? The valves, springs and retainers were all came to me via an ex-longmans head builder ....his brother was using the same cam and was planning to build a new head wit these bits but ended up going mi1600 instead!

[petert 554]

When you assemble any half decent head, you always make sure there is sufficient valve spring pressure to keep the valves shut and to control the valve as it's closing. Putting double springs into a new head needs to done properly. That means measuring the installed height and measuring the spring pressure to suit, adding/subtracting shims etc. Sure, you could slap it together and hope for the best, or spend a little time and maximise your efforts and the result. Something like 100lbs seat and 240lbs open would be suitable if you want to rev it to it's potential.

Edited April 7, 2012 by petert

[Chris H 10]

Cheers for that, it makes a lot of sense. Need to do some measuring of free height, installed spring height and full lift height and rate checking then and work it out :-)

[petert 554]

What about using Mi16 pistons/rods, deck the block/liners and the 0.7mm Cometic gasket for a 1.6? That must get the CR high enough.

 

Sorry obviously you can't use Mi16 rods for a 1.6. However, a quick calculation reveals that the thinner head gasket with flat top pistons gives approx. 11.3:1 on std. 1.6 bore and stroke.

Edited April 8, 2012 by petert

[NNN 1]

Are the 1.6 pistons dished as the 1.9s¿? If so xu7jp4 pistons could be a good option... they are flat and they seat almost at deck height... and the rods are the same as 1.6s...

[Chris H 10]

The 1.6 pistons are dished but thave a smaller recess than the 1.9 hence they up the compression. Xu7jp4 pistons could be worth a look.....are they from cars like the 306xsi etc? Have to see what i can find a sensible price. I don't want to get carried away with expensive bits as this was always suposed to be a budget engine.

 

Will i need to co for a competiton head gasket if i'm running 11-1 or higher compression ratio?

[petert 554]

You need this gasket:

 

http://forum.205gtidrivers.com/index.php?showtopic=128397

[welshpug 1,626]

XU7 pistons wont work I'm afraid, they sit on the very same rod as an XU5 so have quite a short compression height

 

(well, same part number, but they do have a piston oil jet hole in the side and a corresponding hole in the big end bearing to supply the oil jet)

 

pictured is an XU7 rod+piston combo in an XU7 block but with an XU5 crank, at TDC.

 

[petert 554]

I'd just use the 1.6/CTi pistons. They have almost zero deck height and together with that thinner gasket and head skim you'll have no trouble hitting 11:1.

Edited April 10, 2012 by petert