cosworth yb naturally aspirated

[tvralfagtv6]

also posted on engine forum thread.

am doing a NA pintworth conversion i.e using pinto 205 bottom end and cossy
head. I have got bd 3 cams hydraulic followers and the standard flat top pistons,
has anyone done a similar conversion and what power did they get?
I assume the hydraulic lifeters go pete tong at about 6000 and that solid lifters are needed after that. I believe fiesta diesel ones can be used with a bit of mechanical ingenuity but which fiesta diesel? how much do they cost?

Background.

I want good solid performance all round the dial.not just at the top end.
I have been told that the 205 bottom end is good for 7000 and my change point and gearing/ mechanical synmpathy is suited to about 6800.
The motor is in a seven and with the standard injection motor on twin 45's it feels nice and surgey even if very limited revability and is deceptively quick for a standard cam / head.

185-190 bhp in a seven is the holy grail for me 150-160 reliable tractable horses with a nice high tec'ish exhaust note is my initial sights with upgrading to forged pistons and fully ported head to get the last thirty or so horses.

Any advice on skimming decking expected compression ratios with flat toppers instead
of the 600quid domed ones that i know i should have. Any one driven a normally aspirated
what do they go like? etc etc.Any info welcome .

[busa_rush]

Any reason to not use a Duratec ? More power, much cheaper etc ?

[tvralfagtv6]

the duratec is a 2000 grand option closer to 3000 if you add decent management etc etc.bellhousing engine mounts. I have a 205 block really good h and h moded distributor
excellent dellorto carburation light flywheel new clutch, starter etc etc. its all there to be used so to to speak. I've done some good deals on getting all the parts needed apart from the forged pistons at around 600 its amazing how the little bits on a cosworth add up.(still need a thermostat housing if anyone's got one) and you can see why I have gone this route, lots of things helped its case exhaust is on the same side etc etc.plus i couldn't get a duratec second hand...your opportunity sort of dictates your thought processes.

[KITT]

Have you looked at the Des Hammill book, How to Build and Power Tune Ford Pinto Engines. Top reading and has a whole chapter dedicated to converting Pinto's to NA Cossies

[tvralfagtv6]

its on order now

[andygtt]

don't see why the lifters go at 6000rpm.... my cossie turbo went to 7000rpm with std turbo cams and my bottem end was coped with way more power so id say it'd cope with more rpm if less power is present

[garyyb]

I did this conversion 4 years ago on my Westfield. I've got a web page about it, currently off line, which I'll dig out for you.

The lifters will need to be converted to solids if you're going to use a mechanical cam profile - I'm not sure what the choice is nowadays. I used Kent CW12's, which are BD3s, and have a mechanical profile. I converted my hydraulic followers to solid using shims and a lot of elbow grease grinding them down to achieve the correct gap. Shims supplied by Dave Andrews for something like £1.50 each.

I used a 2.1 pinto bottom end in a 205 block, standard pistons (flush with the top of the block deck) and got a CR of 10:1. a 2.0 bottom end will give you a pretty gutless CR, so you need to do something:

Expensive replacement raised top pistons
Skim half a mill off the block so that the pistons become slightly raised top. Not sure about the block strength implications of this.

I ported the head, without changing the valve sizes (they're plenty big enough) and found that on Jenvy 40's and the standard westfield exhaust manifold it made 160 lb/ft of torque and 195bhp. I never took the engine over 7000 rpm, but when on the Emerald rollers, Dave said the power was still climbing steadily through 7000, so it really wanted to be able to go up to 7750 odd. oh, I changed the con rod bolts to ARP too.

Are you aware of the cam belt problems you're going to run into and how to overcome them?

Gary

[tvralfagtv6]

Thankyou Thankyou , I Now have the des hamill book , ref the solid lifters I am doing my own at the moment, it is a lot of work.
i have two bd 3's only recently found out you can't use the hydraulics. Cr ratio is another bone of contentention the des book says you can expect10;1 with a standard 205 bottom end. ref the pinto bottom end i have been assured by the racers that 7500 rpm is ok all day so to speak,
any thing above and it goes wrong drastically quickly.
Ref the cam belt I have a complete set of cosworth pulleys wasn't aware of yet more WORK?

[garyyb]

I was also advised to solder up the oil feed holes in the lifters after conversion to solid to stop them filling up with oil. This makes the cam drive train lighter and more compatible with high RPM (less chance of valve float as the springs have less mass to lift)

I measured the combustion chamber at the time, but also made some small valve cutouts in the tops of the pistons for some extra clearance, which didn't help the CR. I can't remember whether the valves actually touched the pistons, or whether they were just too close for comfort.

I think you're okay on the pulley front. I did it a cheaper way and fitted a cos crank nose pulley, then a put a CVH camshaft pulley on a pinto aux shaft.

Gary

[tvralfagtv6]

How did the character of the car change from pinto to pintworth? and did Westfield do a manifold for it or did you convert your own?

[garyyb]

I used the standard westfield stainless Pinto manifold and welded on new flanges which were supplied by demon tweeks. I think the overall diameter of the headers was slightly too narrow. I also chose to keep the alternator in its standard position, which means the header for Cyl1 needed to make a shar turn after leaving the head, in order to miss the alternator. The plan was to sort out the exhaust and alternator properly at some point, but it never really happened. The exhaust was way too close to the alternator with this setup, and I used to get through an alternator regulator/brush pack every 6 months, despite exhaust wrap and ally shielding.

I was using the narrow tunnel chassis though, which positions the bell housing in the engine bay rather than the MT75 chassis which has the bellhousing in the tunnel and therefore moves everything back 6 inches. If you have the latter you'll be okay I expect.

The engine drove better than the Pinto it replaced. The pinto was on webber 40's which had a poor vacuum signals for the dizzy vacuum advance. These were replaced with Jenvey's and an Emerald M3D, and I found it much more tractable and economical. I used to commute to work in the car and found it easy to bimble around at 1500-2000 rpm, with loads of torque, and no stuttering/hessitation. It sounded fantastic on full throttle too!

Gary

[tvralfagtv6]

Gary I was planning to do exactly the same , mines in an all steel monocoque caterhood so the gearbox and bellhousing sits right in the tunnel with the engine way way back, it has great weight distribution. Glad to hear yours could bimble as well ,I do a lot of that in summer but I like it to be quick when i want it to be. the standard hood exhaust sounds a little tractory with a pinto.
Hoping that as funds allow to put a sweeter sounding box on it. I have had varying advice on head porting so may well go with standard ports to start with.

[garyyb]

I've finally got my old pages uploaded - having just moved house, life without ADSL is a pain! They're a mish mash of diary style present tense, and historical addition past tense writing. The thing that surprised me the most is that I reckoned the 2.1 bottom end and the YB head gives a CR of 9.5:1 - that's pretty poor.

This is all from the days before I discovered digital cameras too! I think I have some other photos somewhere... I'll have a look...

www.thincats.com/westfield/index.html

[tvralfagtv6]

cheers Gary looks good