Identifying Cosworth engine and 1988 Caterham 7

[Brasfort]

Recently acquired '88 Caterham 7 in Canada. I need to clarify the engine's specifications to determine ignition timing, Weber tuning, etc. Engine is a red top 2 litre Cosworth YB (I'm told), with Spanish Weber 45s and an old Bosch distributor with the vacuum advance welded over. The car is LHD, was imported from Holland and the only serial number I can find (KLC 0081L) doesn't reveal much.

Is there a site with serial number info? Were the YB's all turbo engines? If equipped with carbs, must the engines be re-tuned? Exhaust headers changed?
Cam timing different? Best distributor (appears Burtonpower has 1)? Thanks

Edited by Brasfort on Friday 27th May 17:59

Edited by Brasfort on Friday 27th May 18:00

[DVandrews]

All YB engines were originally forced induction, the only 4 valve NatAsp versions of the Pinto were Warrior headed.

The stock turbo cams were very mild and not really suitable for a powerful naturally aspirated engine. The compression ratio would also be too low with the stock turbo pistons.

I ran a NatAsp Cosworth YB in my seven for a number of years, first on DCO/SP 48s then on throttle bodies. You can check the jetting and choke sizes fairly easily on the Webers. The cam specification is what will mainly determine the characteristics of the engine and there are many choices, BD3s were a popular choice as were L1/BD3 combination and the more extreme F1 cams,

Dave

Edited by DVandrews on Sunday 29th May 08:30

[BertBert]

Presumably this engine must've been rebuilt with an appropriate compression ratio and cam profile to work naturally aspirated?

Also it must have had an appropriate exhaust made for the install - on the wrong side as it were in a caterham of that vintage.

Then the settings for cam and ignition timing, carb jetting etc would be specific to what the build is.

Not being any help I know, just musing!

[DVandrews]

BertBert said:

Presumably this engine must've been rebuilt with an appropriate compression ratio and cam profile to work naturally aspirated?

Also it must have had an appropriate exhaust made for the install - on the wrong side as it were in a caterham of that vintage.

Then the settings for cam and ignition timing, carb jetting etc would be specific to what the build is.

Not being any help I know, just musing!

The usual suspects for cams are (in order of aggression)

BD3/BD3
L1/BD3
L1/L1
F!/F1

If the engine is 2.1 and has decent cams/headwork/CR then it is on the cusp of change to 48DCO/SPs that will accomodate larger 42mm/44mm chokes.

Dave

[Brasfort]

Dave -

Cam markings show LYD5/LYD3 left-right. Can you clarify what those markings indicate?

Only compression check done showed 120 across the board. I don't know how much a turbo engine would vary from that. The exhaust headers appear quite home-made ( 4 to 1), which is not necessarily a bad thing, but I understand 4 to 2 is better or a lengthy 4 to 2 to 1.

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[Brasfort]

Dave,

If all YBs were forced induction, how does one determine precisely how a car is to be set up?

The engine module on this car is just running the spark. The Bosch distributor has a welded over vacuum advance; I'd like to replace it. Burtonpower says the distributor should be a FT295K with a side cap. I tend to agree but it would be nice to find a site that definitively lays it all out.

I'm told it's a 2.0 L and the DCOE 45s would match that. A site says the YB began as a N/A YAA concept with the turbo launched in '86.

[BertBert]

That looks a fairly scary/nasty exhaust to me. Overall you need to work out what you have got by inspection as it could be anything really.

To get anywhere I would have thought you need to identify the cams and the compression ratio (probably only done by taking the head off and doing some measuring)

[mickrick]

Interesting thread...

[DVandrews]

Brasfort said:

Dave -

Cam markings show LYD5/LYD3 left-right. Can you clarify what those markings indicate?

Only compression check done showed 120 across the board. I don't know how much a turbo engine would vary from that. The exhaust headers appear quite home-made ( 4 to 1), which is not necessarily a bad thing, but I understand 4 to 2 is better or a lengthy 4 to 2 to 1.

url]|https://thumbsnap.com/4uBKMEMM[/url]

LYD5 and LYD3 are the markings from the stock cams, so it’s likely that they are the original cams and they have been reprofiled to something altogether more interesting.

There is an article on my website that outlines how to set up jetting for various engine sizes and expected peak power RPM, the values it reveals would be a workable starting point.

An engine with pent roof 4 valve configuration with central plug would require around 30-32 degrees total advance from around 3500, static advance would start at around 12-14BTDC depending on cam duration (effective compression stroke), advance should then ramp from around 1200RPM. This would be a good starting point for an advance curve. If you can arrange 3D mapping of the advance then the engine will be much more drivable as part throttle would come alive (this is what vacuum advance does for you in clockwork systems).

There is also an article about ignition timing on my website that may be worth a read..

This is not self promotion but passing on of knowledge FOC

Www.dvandrews.co.uk

There are links from that main page (the page is a bit clunky as it has been around 24 years or so)

The exhaust is not working for you..

Dave

Edited by DVandrews on Tuesday 31st May 22:38

[Brasfort]

Dave – reading your notes from Pistonheads message re ignition timing, Weber tuning, etc., I think the jetting/emulsion tubes are all in the range. But my feeling is the distributor isn’t advancing enough – old Bosch unit, welded over vacuum advance, and I figure it needs to be sorted before the carbs can be tuned. From my research, a BurtonPower FT295K should fit with a side cap. I don’t know if you can confirm that. Also…DCO/SP – is SP for Spanish-made Webers? And similarly, the base setting for the idle mix screw is 1-turn out rather than 2 to 2.5 on Italian carbs? Final question – you say ‘exhaust not working for you’ – can you expand on that?

I appreciate your thoughts on these matters. I’m not well experienced in these areas. These cars are quite common there but not here.

1 final colonial comment – good to see the Queen enjoying the day. You people certainly know how to celebrate your royals.

James/Jacques.

[DVandrews]

Brasfort said:

Dave – reading your notes from Pistonheads message re ignition timing, Weber tuning, etc., I think the jetting/emulsion tubes are all in the range. But my feeling is the distributor isn’t advancing enough – old Bosch unit, welded over vacuum advance, and I figure it needs to be sorted before the carbs can be tuned. From my research, a BurtonPower FT295K should fit with a side cap. I don’t know if you can confirm that. Also…DCO/SP – is SP for Spanish-made Webers? And similarly, the base setting for the idle mix screw is 1-turn out rather than 2 to 2.5 on Italian carbs? Final question – you say ‘exhaust not working for you’ – can you expand on that?

I appreciate your thoughts on these matters. I’m not well experienced in these areas. These cars are quite common there but not here.

1 final colonial comment – good to see the Queen enjoying the day. You people certainly know how to celebrate your royals.

James/Jacques.

DCO/SP are sport versions of the DCOE and have no cold start mechanism amongst other small differences.

Be careful with the side entry caps, some of them have the conductive poles in a different position and will give cross firing problems, check the relative positions of those WRT to the distributor body.

I would go with an electronic distributor which is programmable if you can find one, that way you can determine / perfect total advance without impacting idle and progression. Ideally you should use a 3D mapped system with a TPS to determine throttle position.

The exhasut manifold primaries are way, way way too short to be effective, the ideal setup for a naturally aspirated engine with decent cams would be a 4-2-1 manifold with 30 inch primaries and 12 inch secondaries.

Dave

[andy97]

Plenty of people in the rally world converted turbo YB engines in to n/a configuration, with appropriate changes to the internals, often for use in Escort Mk1 and 2.