Increase speed and power

[lgurley]

I recently purchased a SIV which had been converted to use a Toyota motor and tranny. I have a spare 1725 and tranny. I will be changing back to all Alpine.

I am a novice at this. I will not be racing but since the engine and transmission are already out of the car I would like to have it rebuilt to run well at highway speeds for long trips.

Do you have any tips about using larger pistons, different valves, shaving the head, changing the stroke, and things of this nature or anything else that will help.

Thanks,

Larry

 

[RootesRacer]

I recently purchased a SIV which had been converted to use a Toyota motor and tranny. I have a spare 1725 and tranny. I will be changing back to all Alpine.

I am a novice at this. I will not be racing but since the engine and transmission are already out of the car I would like to have it rebuilt to run well at highway speeds for long trips.

Do you have any tips about using larger pistons, different valves, shaving the head, changing the stroke, and things of this nature or anything else that will help.

Thanks,

Larry

Cam and carb changes are your biggest bang for buck.
You can pick up an easy 15 to 20 bhp with these alone.
Carb would be a 32/36 or 38/38 2bbl weber on a SIV solex intake.

Stroking the engine will require different rods, or pistons or both.

Flat top pistons will increase your compression, or at least allow you to do some choice combustion chamber mods to increase flow (without loosing compression ratio). Look into the vizard chamber mod if you go in this direction.

Going beyond just the cam and carbs begins to look like cubic dollars.

 

[alpine_64]

While everyone in both your posts has mentioned the obvious stuff, cams (delta), head mods (vizard) and carbs.. there are a few other things you should look at that are as important.. and should be done regardless of you trying to get more power or not:

3 angle valve grind
chamber match the head
smooth out the intake and exhaust ports and port match the head
balance and polish (optional) the rotating assembly
lighten and balance the flywheel

these will all make even a stock spec motor more reliable, smoother and efficient. Alpines respond well to careful assembly and prep

 

[SIVAllan]

How to know how much to lighten a flywheel?

What area(s) are milled to lighten?

I too am a novice. I see the stage II example on lightening a flywheel. It that a fair
example for street use?

At some point, light becomes too light, and a motor won't idle, needs reving to make up for needed mass on the flywheel (right?).

Is there some way to know the magic amount to lighten beforehand?

Thanks in advance,

Allan

 

[jumpinjan]

Answer - Use a Lemans flywheel

The factory 1600 flywheels can be chopped to Lemans specs and I had many turned on a CNC machine. The finish is superb.
I wrote a 2-part article on how to build a Lemans 1600 engine for the club's newsletter.
Jan

 

[64beam]

The factory 1600 flywheels can be chopped to Lemans specs and I had many turned on a CNC machine. The finish is superb.
I wrote a 2-part article on how to build a Lemans 1600 engine for the club's newsletter.
Jan

What is the difference between the 1600 and 1725 flywheel's? Can the 1725 flywheel be machined the same as the 1600's?

Thank you, Robin.

 

[V_Mad]

How to know how much to lighten a flywheel?

At some point, light becomes too light, and a motor won't idle, needs reving to make up for needed mass on the flywheel (right?).

Is there some way to know the magic amount to lighten beforehand?

Thanks in advance,

Allan

I think the optimum 'lightness' of the flywheel is a trade-off is between throttle response and vibration etc or NVH. Not sure if idle is really affected much. If you like to drive fast, and dont care much about NVH, then go for light! Take advice from those who have done it. Thats the only way you will know how far to go!

In this context, light means 'easy to spin'. Technically this is low moment of inertia (MOI), or low resistance to angular acceleration. So removal of metal near the perimeter is most effective. Bear in mind also that the flywheel needs to retain sufficient strength for the clutch/starter to work with without distorting under heat etc.

Aluminium flywheels are available for some engines, to reduce MOI without losing strength.

 

[Jim E]

The flywheels all interchange but... the SI requires a different pressure plate or an odd ball anyway. I like the SII type FW that carries the bigger clutch, you can also use the Volvo disc MGB pressure plate on the SII FW. The Volvo/MGB set up is lighter, cheaper than the stock set up and has more clamping force than the late 7 1/4 inch clutch pack. Oh and if you can figure out how to run a roller throw out bearing instead of a carbon unit it opens up a whole bunch of pressure plate choices. You can then run a complete 140 series Volvo clutch pack [dics and pressure plate] and these in reman are cheap or if you are really laying down some power there are after market clutch packs you can run with this set up.

I have turned a bunch off a SII flywheel and not noticed any increase in engine vibration but that could be because the rotating assemblies were well balanced. I use a brake lath to turn them. Did have a turned FW spit a ring gear, not sure why but it sure did.

You have to be sure your release arm and the thing it blots to give enough travel when you start mixing up clutch and fly wheel bits, and you want to do this before you put the engine back in the car. Basically the early FW requires the early throw out bearing and release arm set up.

As most know I have a CD with all the HIPO Alpine info I have gathered, this includes prep notes from a racer, bunch of Vizard stuff, some factory stuff, chevy rod conversion and it is starting to have more V6 stuff. Might have a copy of the UK Alpine guide left which has some good stuff in it or at least makes for an interesting read.

Does not take much to wake the four up but do not expect more than 80 HP to the ground.

 

[AlpineIan]

I recently purchased a SIV which had been converted to use a Toyota motor and tranny. I have a spare 1725 and tranny. I will be changing back to all Alpine.

I am a novice at this. I will not be racing but since the engine and transmission are already out of the car I would like to have it rebuilt to run well at highway speeds for long trips.

Do you have any tips about using larger pistons, different valves, shaving the head, changing the stroke, and things of this nature or anything else that will help.

Thanks,

Larry

All these engine mods are great, but if you are looking for long legs on the highway, just add a 3.70:1 rear end.

 

[gordonra]

All these engine mods are great, but if you are looking for long legs on the highway, just add a 3.70:1 rear end.

Does anyone in the US has the 3.7 ring and pinions, and if more than one supplier, who has the best price?

 

[AlpineIan]

The best way to get them is new from Rootes Post Spares in Holland. www.rootesparts.com. Very hard to find used. I think they onlt came on the '69 Alpine automatics... is that correct?

This rear end in combination with an OD unit will make the Alpine cruise at 80mph with ease. I put one in Chris Bell's SV without OD and he loves it!

 

[jumpinjan]

What is the difference between the 1600 and 1725 flywheel's? Can the 1725 flywheel be machined the same as the 1600's?

Okay, here's the correct data:
Lemans flywheel - 19.0 lbs
Stock 1600 - 23.5 lbs
Stock 1725 - 22.0 lbs
Chopped 1725
per Lemans - 17.5 lbs

A homemade
chopped 1600
(w/too thinned
near ring gear - 19.5 lbs (the backyard hack thought it was chopped enough, but its still not as good as the factory Lemans flywheel....These Rootes guys knew what they were doing!)
Jan
I'm probably going to get another batch of chopped 1600 flywheels to Lemans specs, so if your interested stay in contact with me.