On the rollers tomorrow....

[escort new boy]

30mm chokes are two small, 38s are normally what people choose but can do with 36s

[Toby]

30mm chokes are two small, 38s are normally what people choose but can do with 36s

 

Oh yeah, I hadn't noticed them, they are small! Unusual to find in 45's. Had the carbs come off a smaller engine?

[SmokeEm]

They came off a bog std RS2000 I think. Got em off the bay. Peter at Sanspeed said I need 34mm chokes but not to fit them without raising the compression. Its all so bloody confusing.

[Toby]

They came off a bog std RS2000 I think. Got em off the bay. Peter at Sanspeed said I need 34mm chokes but not to fit them without raising the compression. Its all so bloody confusing.

 

Ok so....the reason he has suggested this is because....ready?!?

 

When the piston (and exhaust but that's another story) sucks at the inlet valve it draws air and fuel into the engine, the smaller the pipe (port / choke) it sucks it through, the higher the gas speed at any given rev. Eventually the port / choke will be a restriction to the engine revs and the power (a derivitive of torque) will fall away.

 

Your engine with the small chokes is creating a high gas speed, which is why you say it drives nicely. This high gas speed helps the low engine speed "inertial" filling (and low speed torque). Inertial filling is how it is possible to continue to fill the cylinder with the inlet valve open and the piston on it's way back up the bore. If you look at cam timing figures you can see the inlet valve is still open way after the piston passes the bottom of it's stroke. The air and fuel mixture has weight and therefore when travelling at speed, doesn't want to stop so continues pouring into the engine despite the direction of piston travel!!

 

By increasing the choke size you will reduce this inertia by reducing the gas speed for any given rev, this will improve breathing at the higher end of the rev range and spoil it lower down. By increasing your compression you put a little back into the engine low down. The risk of pinking at low revs, depite the increase compression, is reduced because of the reduced inertia, and pinking is less likely to happen at higher revs as the charge has less time to be heated by the surrounding engine parts, which is a contributing factor to pinking.

 

This is why an engine is a sum of it's parts. You can't usually change one thing and get enormous improvements as all the parts work in unison.

[SmokeEm]

bloody hell Toby. Now i'm really confused

 

I kind of get what your saying but and I also know why he's suggesting bigger chokes but what i don't understand is how he could know that the compression ratio is too low. I'm sure you've seen one of sanspeeds graph's? Just a bit of red ink on a heart monitor thingy

I know the block is a 20 type, not 205, I know the pistons are flat topped but I do not know what the head was from. Is there a way of checking?

To cut it short, I can't understand why everyone else that has the same or very similar spec, can get 140-150bhp and i get 119. It's not as if I've done anything unusual. It's all standard stuff. I have had it suggested to remove the sierra electronic ignition and either fit aldon stuff or back to points. I realise this would allow a better advance curve but it deffo wouldn't be 30bhp gain - not even with 34mm chokes etc surely?

[escort21]

If they said your compression was low then skim the head 40thou

[BIG G]

dave if it is a transit head the torque you have got will come in lower in the revs as a transit needs low compression to pull away with loads on board. this is done by lowering the compression the engine becomes more efecient at lower rpm as the cylinder has more mixture in it. as toby said that is why the transit has the crappy VV carburetor on it with a small choke to get the speed up so that chamber will fill.

As for the head you have if its not a injection head get one as the voice of expeirience here will tell ya dont throw good money after bad..

If you want as well as skimming it i'll port it as well what ever you decide bud i'll help you out

[SmokeEm]

dave if it is a transit head the torque you have got will come in lower in the revs as a transit needs low compression to pull away with loads on board. this is done by lowering the compression the engine becomes more efecient at lower rpm as the cylinder has more mixture in it. as toby said that is why the transit has the crappy VV carburetor on it with a small choke to get the speed up so that chamber will fill.

As for the head you have if its not a injection head get one as the voice of expeirience here will tell ya dont throw good money after bad..

If you want as well as skimming it i'll port it as well what ever you decide bud i'll help you out

 

Thanks Gordy mate. I'll keep em peeled for a cheap injection head. My cam has only done 5000 miles so it should be ok to reuse.

[Vista]

I have a head in the garage, no cam and it's not an injection head but has had some porting work done to it in the past by a previous owner. It's also had all the valves dropped out cleaned up and lapped in.

 

It was on my car when I bought it and made around 130 bhp at the flyhweel. I kept it when I had a new engine built, interested?

[danny69]

Are you sure he didn`t mean that you are losing compression rather than the comp ratio being low?

Just a thought.

[SmokeEm]

I have a head in the garage, no cam and it's not an injection head but has had some porting work done to it in the past by a previous owner. It's also had all the valves dropped out cleaned up and lapped in.

 

It was on my car when I bought it and made around 130 bhp at the flyhweel. I kept it when I had a new engine built, interested?

 

I might be Scott. As Gordy suggests I would be better off trying to source an unleaded injection head, so if I struggle, I may well take you up on that. Thanks mate.

[SmokeEm]

Are you sure he didn`t mean that you are losing compression rather than the comp ratio being low?

Just a thought.

 

Positive - we discussed it at length.

[Toby]

 

I kind of get what your saying but and I also know why he's suggesting bigger chokes but what i don't understand is how he could know that the compression ratio is too low. I'm sure you've seen one of sanspeeds graph's? Just a bit of red ink on a heart monitor thingy

 

Yeah he's probably not telling from the graph, more seat of the pant's and how the engine reacts (or not) as he puts ignition into it. Also by the rate of the revs falling off, and return to steady tickover.

 

 

I know the block is a 20 type, not 205, I know the pistons are flat topped but I do not know what the head was from. Is there a way of checking?

To cut it short, I can't understand why everyone else that has the same or very similar spec, can get 140-150bhp and i get 119. It's not as if I've done anything unusual. It's all standard stuff. I have had it suggested to remove the jelly mould electronic ignition and either fit aldon stuff or back to points. I realise this would allow a better advance curve but it deffo wouldn't be 30bhp gain - not even with 34mm chokes etc surely?

 

No you're right you are back to needing the combination of parts. It is probably missing due to poor head flow and lack of compression as well as small chokes. If the ignition is set to around 30 degrees of full advance then you wont gain any top end by swapping your ignition system. You may gain drivability but in the 1/4 you're probably only interested in everything over 4,000rpm and full advance anyway. Spend wisely!! Oh and bare in mind you're only at the strip for 15 or so seconds and that you have to live with the car 52 weeks of the year!!

 

Take BigG or Vista up on sorting a better head out for you. What nice boys!!

[SmokeEm]

 

I kind of get what your saying but and I also know why he's suggesting bigger chokes but what i don't understand is how he could know that the compression ratio is too low. I'm sure you've seen one of sanspeeds graph's? Just a bit of red ink on a heart monitor thingy

 

Yeah he's probably not telling from the graph, more seat of the pant's and how the engine reacts (or not) as he puts ignition into it. Also by the rate of the revs falling off, and return to steady tickover.

 

 

I know the block is a 20 type, not 205, I know the pistons are flat topped but I do not know what the head was from. Is there a way of checking?

To cut it short, I can't understand why everyone else that has the same or very similar spec, can get 140-150bhp and i get 119. It's not as if I've done anything unusual. It's all standard stuff. I have had it suggested to remove the jelly mould electronic ignition and either fit aldon stuff or back to points. I realise this would allow a better advance curve but it deffo wouldn't be 30bhp gain - not even with 34mm chokes etc surely?

 

No you're right you are back to needing the combination of parts. It is probably missing due to poor head flow and lack of compression aswell as small chokes.

 

Take BigG or Vista up on sorting a better head out for you. What nice boys!!

 

I'll keep an eye out for an injection head but if i can't find one, I'll take Scott up on his kind offer & ask Gordy to skim it & port it some more

 

I know this is a 'How long is a bit of string' question Toby, but Peter said 34mm chokes whilst others insist this is too small? What do you suggest? Are they too expensive to buy some 34mm, 35mm etc & take the lot to the rollers next time?

[Toby]

 

I'll keep an eye out for an injection head but if i can't find one, I'll take Scott up on his kind offer & ask Gordy to skim it & port it some more

 

I know this is a 'How long is a bit of string' question Toby, but Peter said 34mm chokes whilst others insist this is too small? What do you suggest? Are they too expensive to buy some 34mm, 35mm etc & take the lot to the rollers next time?

 

 

You'll loose power faster than you'll gain it by going too big on everything. If parts of seconds matter to you, make the compromise, if not Peter has seen a LOT of Pintos.

[Toby]

And yeah, they're expensive!!

[SmokeEm]

 

I'll keep an eye out for an injection head but if i can't find one, I'll take Scott up on his kind offer & ask Gordy to skim it & port it some more

 

I know this is a 'How long is a bit of string' question Toby, but Peter said 34mm chokes whilst others insist this is too small? What do you suggest? Are they too expensive to buy some 34mm, 35mm etc & take the lot to the rollers next time?

 

 

You'll loose power faster than you'll gain it by going too big on everything. If parts of seconds matter to you, make the compromise, if not Peter has seen a LOT of Pintos.

 

Point taken. 34mm it is. Just seen them for about £14ea - This bloody 'Hobby' is getting expensive

[Vista]

Point taken. 34mm it is. Just seen them for about £14ea - This bloody 'Hobby' is getting expensive

 

All the best hobbies are expensive

 

Oh and my 45's run with 40mm chokes.

 

The head isn't going anywhere mate, yours if you want it and when you want it.

[SmokeEm]

Point taken. 34mm it is. Just seen them for about £14ea - This bloody 'Hobby' is getting expensive

 

All the best hobbies are expensive

 

Oh and my 45's run with 40mm chokes.

 

The head isn't going anywhere mate, yours if you want it and when you want it.

 

Thanks Scott. Incidently, if you are running 40mm chokes, what's your full engine spec & power result?

[Vista]

It's a stroked big valve 2.2 with a race head from a local race engine builder. Electronic ignition, Kent RL31 cam with vernier pulley, lightened, balanced and all that mallarkey.

 

Initially it gave 163bhp at the rear wheels but after some jiggery pokery with the distributor to alter the advance curve when last on the rollers at the beginning of summer last year produced 171bhp at the rear wheels at 6100rpm. Less than some builders quote for their 2.2's but I specifically requested a flexible cam that pulled from low down and had a wide power band and wasn't going to make it a pig in day to day use .

 

Shamelessly plugs engine build thread from last year

 

http://www.oldskoolford.co.uk/phpBB2/vi ... ni&start=0

[Toby]

It's a stroked big valve 2.2 with a race head from a local race engine builder. Electronic ignition, Kent RL31 cam with vernier pulley, lightened, balanced and all that mallarkey.

 

Initially it gave 163bhp at the rear wheels but after some jiggery pokery with the distributor to alter the advance curve when last on the rollers at the beginning of summer last year produced 171bhp at the rear wheels at 6100rpm. Less than some builders quote for their 2.2's but I specifically requested a flexible cam that pulled from low down and had a wide power band and wasn't going to make it a pig in day to day use .

 

 

That's a very good figure at those rev's, so probably around 195 ish at the flywheel.

 

Have you seen the Jem engine in Retro Ford Mag this month? I think that's more like 160 odd at the flywheel from a 2.1, a realistic figure and definately not too sad!! Nice, drivable engine.

[BIG G]

Theres a place in Reading called euro carb that stock Chokes.

I run 38s in my 45s remember research and buy once

[SmokeEm]

Theres a place in Reading called euro carb that stock Chokes.

I run 38s in my 45s remember research and buy once

 

[Fiesta Steve]

Get your old chokes bored out and save yourself some cash

 

Vista, get 48's on that 2.2, I rekon it will drive even better. 40mm chokes in 45's aren't so good

[escort new boy]

Get your old chokes bored out and save yourself some cash

 

My Dad has a spare set which he is doing this with