Technical Cam shaft replacement - is it an engine out job?

[smart51]

My little Fiat is running very well now, but it is noticeably down on power. I bought the 500R specifically because the 594cc engine has more go than than a 500, except mine hasn't. It's top speed is 60 MPH on a level road, suggesting about 18 BHP. As my car has the 28IMB carb, I'd expect 23 BHP, which translates to about 67 MPH. I've talked about this at length elsewhere on here, but everything on the outside of the engine is now new or thoroughly reconditioned. The only thing I've found wrong is the stroke of the push rods is about 0.5mm less than the book states, suggesting the cam shaft is worn. I've spent a few months considering whether to leave it or replace it.

How hard is it to replace the cam? Looking at the Haynes manual and various YouTube videos, I suspect the cam could be removed with the engine in situ. I suspect the tappets would fall into the sump if I did. Refitting the tappets means removing the head. So is it an engine out and full rebuild job?

 

[Bounding Bambino]

From a technical standpoint, yes you could do it all in the car. But honestly, with a floor jack to support the engine, these engines are very straight forward to remove which makes the R&R so much easier on a table or workbench.

2 things i would strongly suggest is, use original fiat tappets. The general consensus is they seem to be the best quality on the market, and tie in with a new cam. I strongly suggest you don't try to reuse the original tappets with a new cam, its critical that the tappets and cam "break in" properly when replaced as a set. Use a high zinc "break in" oil during its first run, and try and keep rpm's around 2500-3000 during its initial 15-20min startup.

While your in there, it would be an ideal opportunity to put in an performance cam instead of a factory one. There are many to choose from, with the 75/35 type being the most common. Also, might as well replace the timing chain also as a preventative measure, if you dont know how many km it has on it, its best to replace as they do wear and stretch over time.

Install wise, the cam and timing components are very straight forward compared to a modern car. Just be familiar with how timing align marks work for the cam to crankshaft, and distributor to cam.

 

[Goldnrust]

I agree with @Bounding Bambino ambino, yes you ‘could’ do it with the engine in place, but I don’t think it’s the right move unless you have a specific reason not to remove it, e.g. you’re doing this in a carpark of a block of flats and have nowhere to put an engine or health issues make the physically of removing it impossible.

Leaving the engine in the car I think you’ll spend more time trying work round the awkwardness than you would spend undoing the few bolts to pull the engine out.

Also this is a slippery slope. Faster is never faster enough! Give it a few months and you’ll have a fire breathing race engine. Haha.

 

[the hobbler]

From a technical standpoint, yes you could do it all in the car. But honestly, with a floor jack to support the engine, these engines are very straight forward to remove which makes the R&R so much easier on a table or workbench.

2 things i would strongly suggest is, use original fiat tappets. The general consensus is they seem to be the best quality on the market, and tie in with a new cam. I strongly suggest you don't try to reuse the original tappets with a new cam, its critical that the tappets and cam "break in" properly when replaced as a set. Use a high zinc "break in" oil during its first run, and try and keep rpm's around 2500-3000 during its initial 15-20min startup.

While your in there, it would be an ideal opportunity to put in an performance cam instead of a factory one. There are many to choose from, with the 75/35 type being the most common. Also, might as well replace the timing chain also as a preventative measure, if you dont know how many km it has on it, its best to replace as they do wear and stretch over time.

Install wise, the cam and timing components are very straight forward compared to a modern car. Just be familiar with how timing align marks work for the cam to crankshaft, and distributor to cam.

The camshaft CAN be replaced in-situ, but it is a 'head-off' job. The cam-followers MUST be replaced with, as Jacuqes pointed out, Fiat Factory items if possible. With the head off, the push-rod tubes can be removed and the cam-followers removed/replaced. The timing-cover will need to be removed to extract the cam. The fuel-pump will also need to be removed and the pump-operating-pin removed (to allow the cam to be pulled out passed it). I also would take the opportunity to renew the timing-chain assembly. If you can afford it, replace the push-rod tubes with the 'spring-loaded' variety and use the 'thin' red 'silicon' seals.
To undo and then re-torque the big 'end-of'crank' nut you will need to prevent the crank from turning. This can easily be done with one of the small flywheel locking tools placed between the ring gear and the side of the bell-housing. You will need to remove the flywheel under-tray and then place the flywheel-locking tool ON the ring-gear teeth and UP AGAINST the bell-housing wall on the off-side to unlock the nut and near-side to tighten the nut.
Cam-wise, I would suggest the 35/75/75/35 would be a good choice with what is basically a standard engine. Use a GOOD "engine build-up" lube when fitting the cam and followers---they are usually rich in Zinc. For a 'running-in' oil, Millers do a very good one---their CRO10W40-MSDS. This is available from 'Opie Oils'.
If you ARE going to do the job with the engine in situ, all you need to do is is to support the engine on a hydraulic jack (with a square of ply, or similar,between the head of the jack and the sump) and then take off the rear cross-member. You might find that you can remove the head and exhaust together. If there is no reason for taking off the exhaust elbows (from the head) DON'T---because if you do, there is an evens chance that some of the alloy thread in the head will come out with the bolt, which opens up a whole new bag of worms!

 

[smart51]

Also this is a slippery slope. Faster is never faster enough! Give it a few months and you’ll have a fire breathing race engine. Haha.

Yes, I know where that road goes! I don't go over 50 in it really, I'd just like to maintain 50 up a bit more of an incline than it will currently do.

 

[smart51]

A couple of you recommend 35/70 camshafts, which have a 290° duration. The stock cam for my year is 263°, plus there are 280° and 300° options. How much difference is there between them?

 

[Bleeding Knuckles]

Hi Smart, The principle difference if the effective Lift the individual cam provides at the valve. For instance my 'not so hot' engine runs with a
35/75-75/35 cam (290deg) giving a lift of some 7.25mm if we multiply this by the rocker ratio of 1.5 we arrive at 10.875mm At The Valve! The total effect must be (if necessary) adjusted to prevent valve spring binding of less than 25 thou between the coils at full lift. Also, I have found through experience that with the Panda head it is entirely possible that the valve stem spring cap underside will contact the valve guide at less than full lift unless modified. You must also consider the effective length of your pushrods as skimming effectively makes the pushrod longer and upsets the rocker arm position. For best performance the rocker arm should be parallel to the ground with the cam at half of full lift. On the other hand my 'Hot' engine uses a 40/80-80/40 cam (300deg) giving a lift of 7.70mm with roller rockers of 1.55 ratio giving some 11.935 at the valve - there had to be some very careful measuring and adjustment to get everything together. It depends on what you require, the wilder you go the more work and cost is incurred.
Ian.

 

[smart51]

Thanks Ian. I don't necessarily want to tune the engine, just get back what I've lost, though I'm not against finding a little more power while I'm at it. I wouldn't go for a 40/80 cam. I'd rather have some low speed tractability than high revving peak power. I'd probably choose between a stock cam and a 30/70, but I might be pushed towards a 35/75. I don't want to make problems that need to be solved though, like spring binding.0 What kind of real world difference does a 30/70 make over a stock cam?

 

[the hobbler]

Thanks Ian. I don't necessarily want to tune the engine, just get back what I've lost, though I'm not against finding a little more power while I'm at it. I wouldn't go for a 40/80 cam. I'd rather have some low speed tractability than high revving peak power. I'd probably choose between a stock cam and a 30/70, but I might be pushed towards a 35/75. I don't want to make problems that need to be solved though, like spring binding.0 What kind of real world difference does a 30/70 make over a stock cam?

Initially I fitted a 35/75/75/35 cam on my current engine---a 'normal' 652cc 126 engine, I suffered no valve problems at all. Does your engine have single or double valve springs? In answer to your question---yes, the 'wilder' cams CAN produce more power, but in order to utilise the 'wilder' cam fully, you have to start improving the head----bigger inlet valves, ported head etc. 35/75/75/35 cams are available from a number of sources, as is a timing-chain set and cam followers. "Axel Gerstl" or "D'angelo Motori" are good sources.

 

[Bleeding Knuckles]

Hi Smart, Any change/increase in cam duration (the length of time the cam holds the valve open) will be of benefit, I don't honestly know what the figures would be over a standard cam, but a 35/75-75/35 would be a modest jump with a standard carb and adjusted jetting and you could improve things slightly more with a 'sport' exhaust. As Tom (above) says a timing chain set and new followers Will be necessary if you have wear and tear on the cam lobes. Lay out what you need to achieve and price accordingly, it may (at first) seem a mountain to climb for modest results, but you will enjoy the end result even more.
Ian.

 

[Toshi 975]

My little Fiat is running very well now, but it is noticeably down on power. I bought the 500R specifically because the 594cc engine has more go than than a 500, except mine hasn't. It's top speed is 60 MPH on a level road, suggesting about 18 BHP. As my car has the 28IMB carb, I'd expect 23 BHP, which translates to about 67 MPH. I've talked about this at length elsewhere on here, but everything on the outside of the engine is now new or thoroughly reconditioned. The only thing I've found wrong is the stroke of the push rods is about 0.5mm less than the book states, suggesting the cam shaft is worn. I've spent a few months considering whether to leave it or replace it.

How hard is it to replace the cam? Looking at the Haynes manual and various YouTube videos, I suspect the cam could be removed with the engine in situ. I suspect the tappets would fall into the sump if I did. Refitting the tappets means removing the head. So is it an engine out and full rebuild job?

As a friend and I found out some years ago the camshafts do seem to prone to wear. We pooled together our spare cams and had about 20 available for a reprofiling project. We rejected a couple as too worn, often on just one lobe then the cam specialists rejected three more. So something like 25-30% failed the test.

 

[smart51]

As a friend and I found out some years ago the camshafts do seem to prone to wear. We pooled together our spare cams and had about 20 available for a reprofiling project. We rejected a couple as too worn, often on just one lobe then the cam specialists rejected three more. So something like 25-30% failed the test.

I've seem you say this on another thread, which makes me feel more comfortable with my diagnosis of my engine where I think the cam is worn. I've only tested the fuel pump lobe and the rear cylinder's exhaust lobe by looking at the stroke of the push rods. The exhaust lobe seems to be worn by 0.5mm from memory, though it's hard to be precise as my verniers wouldn't fit in the space between the rocker and the top of the engine bay. I have no sense on whether 0.5mm is a lot or not.

I'd be happy enough with a reprofiled cam if it was a cheaper alternative to the billet steel cams on sale. I doubt I'll do enough miles to wear out another cam. You had to collect 20 cams for it to be worth your engineer's time to reprofile them. I only have one so I'll guess it isn't a cost effective option. I don't suppose you have any of your 20 left over do you?

 

[Toshi 975]

I've seem you say this on another thread, which makes me feel more comfortable with my diagnosis of my engine where I think the cam is worn. I've only tested the fuel pump lobe and the rear cylinder's exhaust lobe by looking at the stroke of the push rods. The exhaust lobe seems to be worn by 0.5mm from memory, though it's hard to be precise as my verniers wouldn't fit in the space between the rocker and the top of the engine bay. I have no sense on whether 0.5mm is a lot or not.

I'd be happy enough with a reprofiled cam if it was a cheaper alternative to the billet steel cams on sale. I doubt I'll do enough miles to wear out another cam. You had to collect 20 cams for it to be worth your engineer's time to reprofile them. I only have one so I'll guess it isn't a cost effective option. I don't suppose you have any of your 20 left over do you?

At the time it was a project to make a sporty cam more affordable to the enthusiast owner and I had hoped to do it on an exchange basis so it could be repeated but we made too affordable and guys just bought them with no exchange so that aspect failed. Yes there was a set up fee which I had discussed with the firm and this was spread across the first 10. The remaining 4 were more expensive as the same fee applied.
Long time since I had my hands on them but two unused ones turned up last year. One was in a random batch of spares a guy bought and I was able to identify it for him. It is now fitted in a very sporty little 500 running around Hertfordshire.
If it were me I would buy a new 35/75 cam and go from there. For recent engine builds I got two from a firm on eBay for just over £200. They are also hardened by heat treatment so less likely to wear.

 

[the hobbler]

At the time it was a project to make a sporty cam more affordable to the enthusiast owner and I had hoped to do it on an exchange basis so it could be repeated but we made too affordable and guys just bought them with no exchange so that aspect failed. Yes there was a set up fee which I had discussed with the firm and this was spread across the first 10. The remaining 4 were more expensive as the same fee applied.
Long time since I had my hands on them but two unused ones turned up last year. One was in a random batch of spares a guy bought and I was able to identify it for him. It is now fitted in a very sporty little 500 running around Hertfordshire.
If it were me I would buy a new 35/75 cam and go from there. For recent engine builds I got two from a firm on eBay for just over £200. They are also hardened by heat treatment so less likely to wear.

I have fitted a camsshaft from "D'angelo Motori" (in Italy). They can either supply a camshaft on it's own or a "syched" camshaft which comes with a new chain and a crank sprocket. On this option the sprocket is already fitted to the cam sprocket----yes, you have to fit both the sprockets and the chain all at the same time, but it is not as difficult as it initially sounds. With the "camshaft on its own" option, you will still have to purchase a "sprockets, chain and gasket" set.
I appreciate that this is NOT the cheapest option, but I have never had a problem with the quality of "D'angelo's" products. I also agree with 'Toshi'---in the long run, the best option is to get a new camshaft from a known, reliable supplier

 

[smart51]

I've looked at D'angelo. They do about 40 different profiles of cam. Can't decide between a 30/70 and a 35/75? Split the difference with a 32/72! Their prices are fair until you see their £60 shipping charge. Nanni Ricambi AKA Fiat500sport have a sale on, but don't ship to the UK. I'm indecisive, partly because it will end up costing £400 and partly because I'm a bit daunted by the task. I'll probably do it, I just need to sleep on it a few more times.

 

[the hobbler]

I've looked at D'angelo. They do about 40 different profiles of cam. Can't decide between a 30/70 and a 35/75? Split the difference with a 32/72! Their prices are fair until you see their £60 shipping charge. Nanni Ricambi AKA Fiat500sport have a sale on, but don't ship to the UK. I'm indecisive, partly because it will end up costing £400 and partly because I'm a bit daunted by the task. I'll probably do it, I just need to sleep on it a few more times.

Do you have a relative or friend who lives in Italy (or Europe)?---if you do, get them to order it and get it delivered to THEM, and then they post it to you. I have done this on a number of occasions (I have 2 friends, both 500 owners, in Italy) and I assure you, this system works and will save you a pile of money with regard to carriage costs. The 36/75/75/35 "Synched" camshaft cost £203 and is the one that I would reccomend. Where about in Brum do you live?---I am only in Chester, could be persuaded to come down and help (if you want). I do assure you though, it is not that difficult a job.

 

[Toshi 975]

I've looked at D'angelo. They do about 40 different profiles of cam. Can't decide between a 30/70 and a 35/75? Split the difference with a 32/72! Their prices are fair until you see their £60 shipping charge. Nanni Ricambi AKA Fiat500sport have a sale on, but don't ship to the UK. I'm indecisive, partly because it will end up costing £400 and partly because I'm a bit daunted by the task. I'll probably do it, I just need to sleep on it a few more times.

I bought a few items from D’Angelo last year and got the €60 shipping charge. You will have to pay 20% VAT on the whole lot including the shipping charge then a service charge is added to that. The net result was that the original price in euros was doubled and converted to GB£ by the time the parcel landed on my doorstep.

 

[the hobbler]

I bought a few items from D’Angelo last year and got the €60 shipping charge. You will have to pay 20% VAT on the whole lot including the shipping charge then a service charge is added to that. The net result was that the original price in euros was doubled and converted to GB£ by the time the parcel landed on my doorstep.

Hence the use of a friend in Italy who sent the parcel of parts on as a "present" with an 'adjustment' as to the value!---sneaky, but in the light of "Brexit" stupidity ####!

 

[fiat500]

Hence the use of a friend in Italy who sent the parcel of parts on as a "present" with an 'adjustment' as to the value!---sneaky, but in the light of "Brexit" stupidity ####!

I don't call what you have done "sneaky"...it is "our" government that was sneaky. The statistic that I have quickly found says that customs duties for UK citizens and businesses increased by 42% in the seven months after January 1st 2021. This seems to have got worse over time. It would be acceptable if we had seen a similar increase in expenditure that benefits us all.

 

[smart51]

I've taken the plunge and removed the cylinder head. It all looks OK, save for the poor condition of one of the spark plug threads.