Cylinder Heads

[Guest Petemate]

Hi all

In my local scrappy there are a number of injection pinto-engined cars, both Grannie and Sierra. His prices are usually reasonable, and I would like to obtain the head from one with a view to using it on my 2B (at present standard with stepper-motor carb). I have heard of some builders using the injection type head with a carb with good results. Having got so far with my build, and not wishing to go the injection route, I would like to do this if nothing else to replace my present head which is too old to have hardened seats. Any ideas regarding ignition timing etc? There is of course the facility of retarding with the plug in the loom. Any info gratefully received etc etc.

Pete(Oldgit)

[Big Jim]

Why do you ask about ignition timing? The cyl head from the injection shouldn't make any difference to your ignition timing, you set that to suite the system that you have.

The only problem with using the inj head, is the shape of the inlet ports, they are pear shaped, the manifold that you have has round port faces, and a good quality gasket from your local Henry's place won't make the seal, you need to buy a cheap & nasty one from your local accessory shop, there's more paper to it, poorer quality, but at least it will allow you to get a seal between your manifold and the head.

[Guest Petemate]

Thanks Jim

You confirmed what I was thinking, that it will be fairly straightforward. Thanks for the tip re the gasket. As for the seats, am I correct in thinking that all the inj heads have hardened? (I sheepishly feel I should have researched and avoided that question)

Cheerz

Pete(Oldgit)

[Guest Daz]

Pete,

 

I have just gone down this route, for just that purpose. I understand that all the injection heads are for use with unleaded, and despite the pear-shaped inlet ports the head has better gas-flow properties and is good for another 4-5 bhp. I got a complete injection head from my local scrappy for about £20 back in Aug/Sep last year but have just finished fitting it today. I have also added a FR30 Cam (towing cam for extra torque, ie acceleration) and a solex twin-38 choke carb to complete the ensemble.

 

I had the same set-up as you to begin with but sourced a new dizzy, engine management unit, coils and all associated wiring at the same scrappy for a tenner. I love that scrap yard!!

 

Now the problem. Anyone feel free to give advice. I have fitted everything and got the engine running. It runs sweet as a nut while cold, but when the auto choke (hot water type) switches out the idle 'hunts'up and down - it fades away to 500 rpm then kicks back up to 2000 then falls off to 500 rpm again. I am not an experienced mechanic by any stretch of the imagination and I am after some guidance on what to check out. I suspect something with the carb as I fitted it as it came from the scrappy. I reckon it needs jetting and setting up properly.

 

Daz

 

ps Pete, I have moved house. I am still at Wycombe and plan to do some touring of Oxfordshire in the summer weekends. I will pop in some time and have a shufty at how you are getting along.

[Guest Petemate]

Hi Daz

Thanks for the info. Since posting last night, I did some research into the old RHOCaR site and was pleased to see that the injection heads are unleaded (well, I will ensure I get a later one, and will check the code on the head)

It sounds to me like the idle jetting needs altering - I would hink that as the head has bigger valves than the one the carb was intended for, a rolling road session would be worth every penny. I have now psyched myself in advance for that!

Cheerz

Pete(Oldgit)

P.S. let me know when you plan to call - I may be under the knife.

[Peter Bell]

Hi Daz, I am not sure about the Solex 38 but I have a Webber DGAS which is fitted with a LOVE diaphragm, not all have them. No you are wrong it stands for low vacuum enrichment! What it does is as the engine is about to slow right down and the vacuum drops in the manifold it pumps in a big squirt of fuel like the accelerator pump (it looks a bit like it too on the side of the carb with a vacuum line to the base of the carb) and off the engine goes again. It could be this causing the hunting so disconnect it as you should not need it anyway, block up the tube, and then set up the slow running as usual.

Peter

p.s. the main jets will probably be too big as well as I expect the carb is from a 2.8 or 3.0

[Guest Simon cooper]

The LOVE diaphragm that you call it also has effect at quick throttle openings when the manifold vacuum drops to nil as the air "stalls" in the carb venturi. It should be left connected. This is not the cause of the hunting but the effect that you end up with. The usual cause is a partial blokage on the idle circuit normaly in an idle jet. As previously mentioned, blow them through and set idle speed to about 850. Also check that both mixture screws are out by the same amount. If any adjustment are made then they should be repeated to the other side.

Simon

[Guest Daz]

Thanx for the comments.

 

Daz