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What to do when the Supersprint engine gets worn and tired


AnkerB-S

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I looked in the technical guides and didn't find it.

I am really, really curious whether anyone can enlighten me on the options for me when the engine in my 1987 1700 Supersprint gets worn enough to warrand rebuild/replacement.

So my amateurish thoughts are as follows:

The valve guides and seals, and maybe the valves are what will go in the heads. New valve seats, valve guides, seals and valves should, with a thorough cleaning, get the head to perform as good as new. I assume all the parts are readily available. Are they?

Much harder with the block. Maybe a honing of the cylinders and new rings can prolong life as long as oil pressure remains good (does in my engine). Once the bearings get worn enough for oil pressure to suffer and the cylinders get worn enough to require oversized pistons it gets complicated. Are the pistons, cams and crankshaft readily available? Is it best to get a new 1600 block (the Formula Ford gang is keeping the demand alive, and they are surprisingly inexpensive), get it bored to 1700 cc and then install the Caterham-specific pieces (crank, cam, pistons, connecting rods?).

Or is it better to get a "new" engine? And, if it is, which ones are the least painful to get fitted.

I am a decent amateur mechanic. Know what I can do myself and when to hand the job over to professionals.

Any thoughts, pointers, opinions and advice will be appreciated.

Anker

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As I understand it the 1700 pistons came from a 1300 engine and would be fairly basic. (But you can always have some bespoke made)

The replacement engine of choice seem to be a Zetec. Raceline have most (if not all) parts off the shelf but it adds up.

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In the UK Burton Power are a source of Crossflow engine spares, simple engine that any competent engine builder can rebuild.

New blocks are available from Ford Motorsport in the US, and from Burton, they are superior to the original 711m and later AX Blocks, as are the new SCAT cranks.

Roger King on here is a very respected Crossflow Builder, now retired , also if you have Facebook, a good guy to chat to is Dave Gemzoe, he has a prescence on FB as Gemzoe Motorsport, and used to sprint a truly wicked crossflow, so there's not much he doesn't know aoit building a crossflow.

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  • Area Representative

there's loads of info and people out there that specialises in the crossflow, but today the work can be extremely expensive. I;d get it all diagnosed first to see if its head work or block (or both) then do some searching.

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I am not any more expert than yourself, but it seems to me that the deciding factor is whether you are happy with the power your crossflow provides.

If you are, I would try and keep the car as standard as possible by rebuilding your engine. Hopefully, if it is running well, you might just need new bearings and seals.

However, if you feel you will want more power in the future, it would almost certainly be cheaper in the long run to source a 2 litre zetec engine as they can be tuned to 180bhp without any major work.

Duncan

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The higher power, newer engine option is tempting. My main question would be how easy it is to hook up to the existing clutch and transmission. If that isn't possible the cost skyrockets as the necessary upgrades cascade down the drivetrain.

My path of choice is to follow Tony Ingram's suggestion and first determine whether it needs head work, block work or both. The power is fine, there is good oil pressure, no piston slap or big end knock. What is going on is exhaust smoke when the throttle is lifted when driving, which I suspect is caused by lifter seals and/or guides. If it needs that work I would also take a look at the valve seats and decide whether I need seats and/or valves replaced. If any symptoms of wear remain after the head work I'll tackle the block. All of this is long term. For the 2020 season I'll run it as is with some upgrades: carb mounting hardware, Aldon distributor, oil catch can. Also full service: replace all fluids except coolant, check, and if necessary, repair brakes and suspension. Winter 2020/2021 remove head and repair anything necessary. Drive 2021 season and then tackle whatever repairs are indicated the next winter, and so on and so forth.

It has turned cold again here in Massachusetts, so I haven't done the warm engine, dry and wet compression tests. So far I have done a cold engine dry compression test which showed even compression close to 150 PSI across all four cylinders, so there don't appear to be any broken piston rings or scored cylinders.

The responses to this thread have enlightened me and given me the names of several people who can further guide me down the happy path of Caterham ownership.

I was at a Porsche club party yesterday evening and discovered that there would have been quite a bit of competition to purchase my Caterham if it had been widely known that it was up for sale. I know one person who would have grabbed it and imported it to Spain and another who would have bought it and kept it locally.

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 My main question would be how easy it is to hook up to the existing clutch and transmission

I converted my 1993 X/flow to a Zetec in 2010/11 and can confirm that the engine simply bolts on to the same clutch, bellhousing etc, but you will need new engine mounts. The carbs and primaries still stick out of the same holes although the sideskin needed enlarging for larger diameter primaries.

I wrote an article in LowFlying in August 2012 detailing the process and the subsequent conversion to throttle bodies which can be seen here.

 

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I suppose it comes down to originality vs power. I did rebuild my xflow with forged pistons bored out to 1700 and rebuilt the head (although it was already quite new and converted to unleaded)

It did make a difference and it was a great engine.

However when I went down the "power" route, I decided the best was to sell and buy a later Duratec car.

Once modified (very quick and cheaper if you want big bhp) it will affect the value (in my humble opinion) in the long run.

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I have stuck to originality, my Crossflow has done well over 130,000 miles (the mileometer show 129,000 and something but the faulty speedo meant that six months mileage is missing). So a couple of rebuilds have taken place and it runs well (particularly when it has a fully functioning alternator attached, which is not the case at present).

 

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As Chris (aeroscreens) has said, the Zetec is a great engine and they are available cheaply, but the costs start to pile up when you add the essential Caterham-specific manifolding, fuelling, management, etc.

Having said that, a full rebuild of a crossflow isn't cheap these days either.  I'm in this boat myself as my crossflow is starting to get a little fumey, and I'm planning to rebuild it when the time comes as it's a key part of the car's personality for me.

If your bores are merely uniformly worn and not heavily gouged, you could most likely go from +090" to 83.5mm bores (a very small increase) for which forged pistons are available. If I recall correctly this will give an extra 9cc (1691 to exactly1700) along with lower mass and reduced friction. That's probably the max. rebore for a 711M block like mine, although thicker walled AX blocks can go a lot further. Other than that you're looking at the usual regrinding/refacing/etc. engine overhaul procedures. Pretty much everything you need for a rebuild is still available, but it does add up to a pretty serious investment.  When I started my 7 build 30 years ago there were loads of companies selling complete remanufactured and uprated 1700 crossflow engines in kit form for as little as £250, as it was the 'go to' engine for the majority of kit cars on the market. I decided to splash out and spent a whopping £650 on mine - about the current price of a decent set of pistons!

As has been said above, there isn't much that Dave Gemzoe doesn't know about the crossflow engine, I'd recommend looking him up.

Crudders

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The responses to my thread have been really useful and enlightening.

My 1700 Crossflow has 25,000 miles on it, and it was great to see that Golf Juliet Tango's has done over 130,000 miles on his, so there should still be a lot of life left in mine. This gives even more credence to the theory that the smoke is caused by valve guides and/or seals.

The crank vent has no catch can on it, just the hose going to the back of the transmission tunnel, and a bit of oil fumes come out when it is idling. It has been so long since I worked on older cars without AOSes that vent into the intake that I don't know whether it is normal. I have ordered a catch can since it seems a waste not to have one.

The car has seen a lot of autocrosses and has had a tendency to overheat in hot conditions, which doesn't surprise me when I look at the whimpy cooling fan sitting quite a bit behind the radiator. I have a new, modern, radiator fan that I will mount in front of the radiator and it should help a lot since it will be mounted right up against it.

It is always tempting to go with a newer, higher HP engine, and I am one to fall for the "big boat disease". I have a 35 foot ocean cruising sailboart from 1985 in my front yard that has never been in the water to show for it. It was out fifth boat in 7 years!

I am retired and can do most work on my car, and need to ensure that I have enough to live on the rest of my life, so the "keep the car original" advice seems prudent.

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Glad you're persuaded by the XF's charms Anker *thumbs_up_thumb*

A trailing, open-ended hose from the crankcase breather was common on many early cars but it's not ideal, as it will potentially suck in all sorts of grot when the engine is on the over-run at revs with a closed throttle. If you run that hose to a catch tank, make sure the tank can breathe but also can't suck in contaminants. In my old set up I had a small K&N breather filter on the Caterham supplied plastic washer bottle catch tank but now have an aluminium Mocal (Think Automotive) catch tank which breathes and filters through its cap.

There are people who have achieved huge mileages from XFs but 20-25,000 is where they often start to breathe heavily, due to the weight of the 1300 cast pistons originally used as a cheap and effective means of achieving high compression.

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The usual reason that a Crossflow gets a bit smokey at around 25,000 miles is that the piston rings give up. It's not their fault, they were designed for 55bhp and are having to cope with around 120bhp at much higher revs. Forged pistons have much better rings (I'm talking about Accralites here) that seal much better, for longer, and as a bonus run with much lower friction.

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Thank you, Roger!

I will really, really appreciate if someone with experience (hopefulle have done the job), can rattle through what needs to be done to replace the existing pistons and rings in a 1700 Superspeed with forged pistons. The best case, of course, would be a hone and simply replace the pistons and rings, but it sounds like a bore would be the realistic minimum. The Supersprint has a Caterham head and and a high lift cam, so anything relating to the Ford Crossflow head doesn't necessarily apply.

Since the Supersprint already is bored to just under 1700cc it would imply that it uses pistons that aren't regular Ford pistons. Am I correct?

Actually the absolutely bare minimum would be a hone and replacement of the rings, but that doesn't deal with the weakness.

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Your original pistons are ordinary 1300ccm Crossflow pistons, but at +.090" oversize which is the largest overbore size available in standard spec, and gives a capacity of approx 1690ccm. The forgings are 83.5mm (this is the most common size, but others are available) and give a capacity of 1699ccm. Only a small difference, but you will need a rebore. It is essential that you have your machine shop leave the new bores with a plateau honed finished. If they can't do it, go elsewhere because the rings on the forged pistons demand it - with good reason because these rings are far more sophisticated than those of the standard pistons which basically date back to the 1960s.

You will probably be OK with the diameter of the valve cut outs that come with the pistons, but you must check in case anything has been changed in the past. Bowl machining I can't advise on because I don't know what compression ratio you are aiming at. If you can tell me that, I can give you an approximation of the machining you need, but every engine I ever built had the pistons machined on an individual basis due to quite large variations in block height in production.

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I live in the continent of low octane gasoline, 93 in my state and 91 in a lot of other states. I will probably never fill it with 91. So I'm looking for a recommendation for compression. I did get a new Aldon dustributor and Ignitor set up for 83 octane thay O will install as soon as I return to the state of ice and snow (Massachusetts) from Florida where I am recharging this month.

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A few years ago, a former L7C member from Alberta ran a couple of tours for Caterham owners on the W Coast and invited members from the UK to join.  I think about 6 cars were shipped and I think all was absolutely splendid and they all had a jolly time!  One of the queries raised before they went was about the quality of fuel in the U.S.  I didn't know, but apparently there is a difference in how the fuel is rated, the following may help, in any case I think your fuel is the same as ours.

Europe vs the States

In Europe, gas stations describe different types of gasoline based on their RON rating. It is typical to have 100, 99, 98, 97 or 95 RON with prices varying accordingly. In the States the descriptions look a lot like RON, but they are not.

Pump gas

In the United States gas stations describe the types of gasoline based on the Pump Octane Number (PON). That number is the average between RON and MON. This causes many problems.

If a fuel is 98 RON then it will be 93 PON -> 93 PUMP
If a fuel is 95 RON and 87 MON then it will be 91 PON -> 91 PUMP


Brian

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