Rebuild engine or what cross flow 1990 about 25000 miles

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Barry Thompson
Barry Thompson's picture
Last seen: 1 week 3 days ago
Joined: 17/04/2014
Rebuild engine or what cross flow 1990 about 25000 miles

My son who I have given my car to wants to get a new clutch fitted and as car burns oil we are wondering if should get engine rebuilt  about £2000 I believe,or get a sigma engine fitted    ? Money is tight for him and all will be done at a garage where the boss mechanic understands classic cars neither my son or I understand mechanics but I think whist clutch (WHICH ONE or part number. Best?   Car is super sprint 1700 ) is being fitted it seems sensible to ask about rebuild or whatever is logical    Any advice appreciated.   Thanks son wants to keep this car long term as it's a model with ever thing he likes including flared wingsand the engine noises and exhaust.pops and bangs !!

Golf Juliet Tango
Last seen: 4 hours 48 min ago
Joined: 17/04/2014

I understand the limitations imposed by one's wallet but if it is burning a lot of oil, I think it needs to be taken apart and rebuilt.

As your son says he wants the car to be a keeper, he needs to bite the bullet and invest for the long term.

Stephen, owner of a Supersprint Crossflow engined Seven (1996 car) with over 136,000 miles on the clock.  


Democratic dissent is not disloyalty, it is a positive civic duty

Ralph45's picture
Last seen: 4 hours 30 min ago
Joined: 31/08/2018

Keep it crossflow!

were the car mine I would definitely lean towards originality.

And we all know a set of carbs sounds better than any other form of induction!


Tazio's picture
Last seen: 9 hours 36 min ago
Joined: 17/04/2014

And get it rebuilt by someone who knows his crossflows.....

simon_h's picture
Last seen: 9 hours 41 min ago
Joined: 17/04/2014

Get it rebuilt by someone who actually knows older engines or fit a zetec. Sigma is not an easy fit but a zetec is much easier.

Ed White
Ed White's picture
Last seen: 2 days 15 hours ago
Joined: 18/04/2014

If there was ever an engine suitable to learn on, its a crossflow. It basically needs stripping, and the bottom end sent away for a regrind and new pistons fitting. Crank shells checked while apart, but could well be good. Has the oil burning come on gradually? Wherte are you?

OldAndrewE's picture
Last seen: 4 hours 16 min ago
Joined: 29/04/2020

I would say before rushing in to getting rebore, regrind etc the engine needs a strip down and thorough checking for wear by someone with the necessary equipment.  It could be down to bad wear on the inlet valve guides.

Obviously I am not familiar with the garage you are proposing to use but most garages will not do this sort of engine work themselves but farm it out to an engine builder/reconditioner.  You really need to know who will be doing the work.

You say you do not understand mechanics but if you want to try and learn (as has been said above) this is a good engine to learn on.  I see you are in North Dorset and that is too far away for me but there may be a member with suitable knowledge nearer who is willing to help


1985 S3 1700 XFlow.  Undergoing full restoration

rkeywood's picture
Last seen: 5 hours 46 min ago
Joined: 09/02/2021

On the clutch question I ended up back with a LUK standard clutch (available from Burton and others) for road and race. This was after trying several uprated clutches and on the recommendation of friends running FF1600s who were animal with their clutches. Basically bulletproof, lighter and needing less balancing than the AP and better getting off the line than a Helix. Also dirt cheap!

On the engine I'd suggest the starting point is what the original engine was. Is it a factory built car with a new Caterham built engine, kit built with new Caterham engine or built with a secondhand engine. 25k miles sounds a bit low for a bore / piston issue if it was a new engine but, as said, needs a strip to see what's what. I'd like to see whether it's been balanced, particularly whether the clutch has been balanced on the flywheel, and whether the valve seats are 'unleaded'. If it's a keeper and these haven't been done the now may be the time to do it.

If you're not in a position to pull the engine yourselves then I guess it needs to be a garage as a starting point but preferably someone who's worked on Caterhams before. Taking the engine out is pretty quick and easy if you've done it before but you don't want to pay garage rates for someone to spend the time finding their way around. Then it's a question of who's actually doing the engine rebuild and making sure they are familiar with old school engines.

DaveMorris's picture
Last seen: 2 min 22 sec ago
Joined: 17/04/2014

Barry, firstly - I'd keep it as a crossflow (but that's just personal preference). . . . . . and then . . before taking the engine out (which as others have said is pretty simple) or deciding on what needs to be done to the engine it is definitely worth doing a compression check (on hot and cold engine) and then posting up the results here. That info can be a good guide as to whether a new pistons/rings and a honing are going to be needed. (Feel free to ask me or the other x-flow owners on here how to do the check if you're not sure).

I agree with other posters above w.r.t. valve seats, although if a Caterham engine then the seats may already be hardened/unleaded ones. A well balanced engine always spins better and smoother, so if the engine is coming apart then it's well worth getting everything balanced (i.e. rods, pistons, crank, flywheel/clutch assembly) and then getting the flywheel/clutch/crank dynamically balanced as a unit. IF the engine doesn't need stripping then make sure that the flywheel/new clutch assembly is balanced - it's better than nothing. 

Obviously replace CRB when replacing clutch, and if you have any major rumbly noise from gearbox when engine running, in neutral and clutch pedal up then you might consider having bearing replaced on primary motion shaft on gearbox - the box being easy to remove when engine is not there. (indeed many would remove engine/gearbox as a unit and split them when out of the car). 

Happy to talk "semi-knowledgeably" on phone with you if you want. Unfortunately not really local enough to North Dorset to make calling round for a coffee/chat a realistic option.


robert green
robert green's picture
Last seen: 17 hours 34 min ago
Joined: 17/04/2014

Hi Barry! Andrew's son here. I'm so glad the car is staying in the family. If originality is key, rebuild the xflow, but speak to someone like Roger King for spec and maybe advice as to who should do the work. I had the same issue, and decided to go zetec as the exhaust and carbs stay in the right place. On the plus side you get a modern(ish) engine with more power and a good life span. Keep the carbs and it still sounds good too. Also, if you keep the original xflow it could go back in if someone wanted it original in due course.  Raceline are the people to speak to about zetec conversations. They did mine 15 years ago and it has been completely trouble free. A bit more torque to go with the power too! 
Rebuilding the xflow properly is probably still cheaper, but there won't be much in it. 
Best wishes, and thanks for your support of dad recently. It means a lot. 

TexasDreamer's picture
Last seen: 2 days 12 hours ago
Joined: 08/03/2021

Choice of clutch is very important to the character of the car. I replaced the clutch on my 1991 Crossflow  1700 with a Helix set (70-1605,40-2482, 60-3329). Before the new clutch it was easy to drive smoothly and easy for friends who were learning to drive a manual. Perhaps this was partly due to the worn out nature of the clutch. With the Helix, It's great to drive vigorously as the shifts are really quick. Takes a lot of concentration to drive smoothly. Getting off the line takes focus.

The working travel of the clutch is very short, about 3/8” at the clutch release fork where the cable attaches. The resistance to the pedal is very non-linear: Hard at the top of pedal travel then soft once the clutch engages. The net effect is a very binary clutch action. As the pedal comes of the floor, the spring grabs it right when the clutch is engaging and pushes your foot to the top of travel. The clutch is either engaged or dis-engaged unless you are VERY careful with the pedal. This makes the car very hard to drive smoothly. On the other hand, it makes it beautiful to drive aggressively.  

Perhaps I did something wrong in the installation? Do others with a Helix clutch have this experience? Welcome comments and suggestions. I'm considering pulling the engine and going to a different clutch so very happy to see the recommendation above of the LUK clutch.

Love my Crossflow as it makes beautiful music.


TexasDreamer, 1992 Caterham Super 7, 1700