Discussion
Well the OHC redblocks are essentially the same block as the OHV ones, just with a different head. They even still have the OHV camshaft in the block to drive the distributor and oil pump. Bore spacing is not one of the problems you run into when trying to use an OHC crank in an OHV block, and the B30 has the same bore spacing as the fours, so I think we're OK there.
Oil and water passages I'm not totally certain about... it's the sort of thing that does tend to undergo minor modifications when a manufacturer converts an engine to OHC. I don't have a good idea about it from looking at stuff other people have done, because said "stuff" would mostly be people doing their own OHC conversions on fours, and they don't bother, they just use the whole engine. Something is telling me that the water passages don't quite match up but it's not so bad that you can't modify things so that they do. Not quite sure where I've got that from. Oil passages... well if they don't they don't, but I don't see any difficulty in blocking them off altogether and plumbing in an oil feed using external pipework.
Bottom pulley is unlikely to be a major difficulty, OHC bottom pulley setup tweaked in my lathe if necessary (I think it is necessary, but as I already have the lathe, not a problem.)
Alignment of the heads is the big one. I can make up a jig to bolt onto the manifold faces and the block face to align it initially, the problem as I see it is making sure it retains the alignment after being cooked welding. It does make me wonder if it would be worth looking at epoxy instead. A correctly prepared epoxy bond with aluminium is stronger than the metal, it's just the question of finding a grade of epoxy that will take the temperature. Araldite won't do it
but I think there exist high-temperature grades that might.
Camshaft... plenty of people have cut and joined motorcycle camshafts, at least... so it ought to be possible!
K-Jet, ah well, this is where it really runs into the pigeon stuff
The reasons I want to do it, my principles of getting parts off other things rather than buying new, all sorts 
Part of the idea is "I wish Volvo had done this themselves", and if they had K-Jet is what it would have ended up with.
It's easy and cheap to get the complete set of parts required off scrap cars... buying the whole car if necessary, it's on plenty of cars that are worth no more than scrap value.
If I go for the engine management idea then it'll never get anywhere as I'll be sidetracked for ages into designing and building the thing. Yes, I know you can buy them, but I also know what the electronic parts cost to build them from scratch, and embedded control systems are something I particularly enjoy making. It would be fun, but it would take ages, and it would probably cost more getting hold of the electromechanical components to go with it than it would to get hold of a complete K-Jet off a scrap car.
K-Jet installations on things like 80s Volvos and Golf GTIs don't give me any cause to think negatively of the system. It may not be the ultimate for peak power, but with an automatic box the engine hardly ever gets a chance to rev out anyway. It's reliable and reasonably economical. People do seem to be fond of replacing it with Webers, but I'm not sure that's down to anything much more than either making full race engines or simply not understanding it.
Oil and water passages I'm not totally certain about... it's the sort of thing that does tend to undergo minor modifications when a manufacturer converts an engine to OHC. I don't have a good idea about it from looking at stuff other people have done, because said "stuff" would mostly be people doing their own OHC conversions on fours, and they don't bother, they just use the whole engine. Something is telling me that the water passages don't quite match up but it's not so bad that you can't modify things so that they do. Not quite sure where I've got that from. Oil passages... well if they don't they don't, but I don't see any difficulty in blocking them off altogether and plumbing in an oil feed using external pipework.
Bottom pulley is unlikely to be a major difficulty, OHC bottom pulley setup tweaked in my lathe if necessary (I think it is necessary, but as I already have the lathe, not a problem.)
Alignment of the heads is the big one. I can make up a jig to bolt onto the manifold faces and the block face to align it initially, the problem as I see it is making sure it retains the alignment after being cooked welding. It does make me wonder if it would be worth looking at epoxy instead. A correctly prepared epoxy bond with aluminium is stronger than the metal, it's just the question of finding a grade of epoxy that will take the temperature. Araldite won't do it
but I think there exist high-temperature grades that might.Camshaft... plenty of people have cut and joined motorcycle camshafts, at least... so it ought to be possible!
K-Jet, ah well, this is where it really runs into the pigeon stuff
The reasons I want to do it, my principles of getting parts off other things rather than buying new, all sorts Part of the idea is "I wish Volvo had done this themselves", and if they had K-Jet is what it would have ended up with.
It's easy and cheap to get the complete set of parts required off scrap cars... buying the whole car if necessary, it's on plenty of cars that are worth no more than scrap value.
If I go for the engine management idea then it'll never get anywhere as I'll be sidetracked for ages into designing and building the thing. Yes, I know you can buy them, but I also know what the electronic parts cost to build them from scratch, and embedded control systems are something I particularly enjoy making. It would be fun, but it would take ages, and it would probably cost more getting hold of the electromechanical components to go with it than it would to get hold of a complete K-Jet off a scrap car.
K-Jet installations on things like 80s Volvos and Golf GTIs don't give me any cause to think negatively of the system. It may not be the ultimate for peak power, but with an automatic box the engine hardly ever gets a chance to rev out anyway. It's reliable and reasonably economical. People do seem to be fond of replacing it with Webers, but I'm not sure that's down to anything much more than either making full race engines or simply not understanding it.
I see what you mean, a 924 quattro does sound like the sort of idea I'd go for if I was more oriented towards German cars
I also know what you mean about the flap thing on the fuel distributor, I feel a bit the same about it myself... which leads me to think of things like removing it altogether and operating the metering plunger from an actuator servoed to an ultrasonic doppler flowmeter...
I also know what you mean about the flap thing on the fuel distributor, I feel a bit the same about it myself... which leads me to think of things like removing it altogether and operating the metering plunger from an actuator servoed to an ultrasonic doppler flowmeter...
Welding up the coolant passages doesn't seem to be stopping that chap
Part of my thinking is the "this is what Volvo should have done" bit they did an OHC conversion on the fours, so they should have done it on the six... I'm thinking it should give around 200bhp, and I am given to understand that beyond that you begin to run into problems due to the length of the crank, though I have not been able to find anything that goes into detail or any source of stronger cranks.
They're excellent, I like having them around
Part of my thinking is the "this is what Volvo should have done" bit
they did an OHC conversion on the fours, so they should have done it on the six... I'm thinking it should give around 200bhp, and I am given to understand that beyond that you begin to run into problems due to the length of the crank, though I have not been able to find anything that goes into detail or any source of stronger cranks.wildoliver said:
What's the deal with the pigeons though.........They are sinister little beasties.
Sinister? They're excellent, I like having them around Marquis_Rex said:
Pigeon said:
Camshaft... plenty of people have cut and joined motorcycle camshafts, at least... so it ought to be possible!
K-Jet, ah well, this is where it really runs into the pigeon stuff The reasons I want to do it, my principles of getting parts off other things rather than buying new, all sorts
You'd have to probably get camshafts recast from blanks for each of the 3 cylinder banks- to take into account the new firing order.K-Jet, ah well, this is where it really runs into the pigeon stuff
The reasons I want to do it, my principles of getting parts off other things rather than buying new, all sorts I was thinking of joining two suitably cut-down four-cylinder blanks and then having the result ground with six-cylinder timings.
Marquis_Rex said:
Also- is this lot chain driven?
I'm not an engine chain drive designer, but after many a lengthy conversation with Wheeljack- he showed me just how difficult it is- and what has to be considered. I dont think the issues are neccessarily insurmountable.
No, it's a belt. I was reckoning on taking the whole lot, pulleys and tensioner assembly off the front of the OHC engine and looking for a heavy-duty belt...I'm not an engine chain drive designer, but after many a lengthy conversation with Wheeljack- he showed me just how difficult it is- and what has to be considered. I dont think the issues are neccessarily insurmountable.
Marquis_Rex said:
Do the water ways and oil ways match up- or would they after the head chop?
An OHC engine needs more oil in the top end (as I've learned painfully with my Challenger- but thats another story)- does the OHC head have an oil spray bar?
No, it doesn't. It has an oil feed which comes up around one of the head bolts and goes through galleries to the camshaft bearings. The camshaft actuates the valves directly, it is vertically above the valves and bears on bucket tappets. The cam carrier part of the head casting is more or less shaped like a bath, with transverse partitions for the camshaft bearings and the tappets sticking up through the bottom to as little height as necessary, so all the oil that escapes from the sides of the camshaft bearings then drains onto the upper faces of the buckets.An OHC engine needs more oil in the top end (as I've learned painfully with my Challenger- but thats another story)- does the OHC head have an oil spray bar?
The OHV head arranges for the oil feed to the rocker shaft in the same way but I'm not sure which bolt it uses. I figure it's not a major worry anyway because it's easy to plumb in an external oil feed.
There's no reason why it shouldn't be possible to fit an oil spray bar but camshaft wear is not a noted problem with these engines and since the cams would still be operating under the same conditions I am thinking all I need to do is make sure the oil pump is capable of supplying the requirements of 1.5 four-pot heads.
The water passages... I said above I wasn't sure, I've now checked it out and they don't match up. On the OHV engine they are smallish circular holes in the triangular spaces between the head bolts and the points at which the bores come closest together. On the OHC engine they are pairs of more or less triangular apertures in the spaces between the cylinders, the head bolts and the edges of the block.
I'm not sure why they've done this - whether it's to allow for a greater potential to increase the bore size or whether it's to increase flow...
If it's just for bore size potential then I think there's no problem in simply drilling holes in the appropriate place in the OHC head and blanking off the originals. This would also be bringing the water into the head closer to the exhaust valves, which should be beneficial... but I have my doubts as to whether the flow would be adequate.
I am thinking the thing to do here is to increase the pumping capacity of the cooling system and provide an additional external water feed to the head.
Marquis_Rex said:
Are the combustion chambers of a similar design or would you have to get pistons especially made to suit your desired compression ratio (no big deal).
Very similar... both heads have valves arranged centrally along the centre line of the engine and simple bathtub chambers. The OHV combustion chamber is a very simple "Hornby train set oval" shape with parallel sides, the OHC one is more of a "chain drive with unequal pulleys" shape, still with straight sides but with a larger radius curve at the inlet valve end. It is possible to overbore the OHV block to accept OHC pistons which would keep all the in-cylinder geometry factory standard.Marquis_Rex said:
I like K Jet and it take care of itself.
Its no Hotwire system but people often talk about its losses but I wonder just how bad they are compared to L Jet with that terrible air measuring 'barn door' which is of a small area and quite hard to push or carbs with their velocity stack-venturis.
One of the bigger issues with K Jet is its intolerance to agressive overlap/wild cams.
I am thinking that the curtain area of a K-Jet "flapper" is pretty huge...Its no Hotwire system but people often talk about its losses but I wonder just how bad they are compared to L Jet with that terrible air measuring 'barn door' which is of a small area and quite hard to push or carbs with their velocity stack-venturis.
One of the bigger issues with K Jet is its intolerance to agressive overlap/wild cams.
I wasn't planning on using an aggressive cam, I'm thinking either the same profile as Volvo used on the K-Jet engines or the Volvo "K cam" profile, which is nothing to do with K-Jet, it is the one which offers the lowest increase in tune over the standard production cams, still gives decent bottom-end performance and I believe does not upset K-Jet.
Which reminds me, I must follow your suggestion of joining turbobricks and get that question asked about the B30 crank...
The thing about this idea is that it isn't just about increasing the power output. My estimate is that the power output will be something under 200bhp, going on what the standard OHC fours do. I could probably get the same or better result in pure power terms by fitting triple SUs on a Penta manifold in place of the standard twin Strombergs on the restrictive preheater-thingy manifold, a free flowing exhaust, larger valves and a K cam to the standard OHV configuration, with a lot less buggering about.
I am thinking more in terms of rewriting history "what would it be like if Volvo had done this"...
When the 240 series replaced the 140 series, the major mechanical change was that the four-cylinder engine was converted to OHC. It worked very well and they carried on using that engine for nearly 20 years.
In the six-cylinder variants, though, the 260 did not feature an OHC conversion of the preceding model's engine. It had that horrible 90 degree V6 which apart from eating camshafts was as rough as a badger's arse, and was a definite backward step in terms of refinement, a 260 is like a tractor compared to a 160. The 160 purrs, the 260 goes dugga-dugga-dugga. Also, unlike the fours, it actually had less power than the engine it replaced.
In my opinion the 260 should have featured an OHC version of the B30, and I want to make "the engine that Volvo should have made" so we can see what it would have been like.
The thing about this idea is that it isn't just about increasing the power output. My estimate is that the power output will be something under 200bhp, going on what the standard OHC fours do. I could probably get the same or better result in pure power terms by fitting triple SUs on a Penta manifold in place of the standard twin Strombergs on the restrictive preheater-thingy manifold, a free flowing exhaust, larger valves and a K cam to the standard OHV configuration, with a lot less buggering about.
I am thinking more in terms of rewriting history
"what would it be like if Volvo had done this"...When the 240 series replaced the 140 series, the major mechanical change was that the four-cylinder engine was converted to OHC. It worked very well and they carried on using that engine for nearly 20 years.
In the six-cylinder variants, though, the 260 did not feature an OHC conversion of the preceding model's engine. It had that horrible 90 degree V6 which apart from eating camshafts was as rough as a badger's arse, and was a definite backward step in terms of refinement, a 260 is like a tractor compared to a 160. The 160 purrs, the 260 goes dugga-dugga-dugga. Also, unlike the fours, it actually had less power than the engine it replaced.
In my opinion the 260 should have featured an OHC version of the B30, and I want to make "the engine that Volvo should have made" so we can see what it would have been like.
Marquis_Rex said:
Ok, I'm a bit pressed for time as I'm about to go out and fit roller high ratio rocker arms on my challenger.
I've been following that, sounds like quite a saga...Marquis_Rex said:
My appologies, for some reason I thoght the B30 was a V6.
In which case I'm sure it should be alot easier in terms of the cam drive- just carrying over pretty uch, especially if the blcok deck height and position of the idler pulleys can be duplicated etc etc. How is it tensioned?
Belt drives are also easier to mess with than chains.
It is tensioned by a spring-loaded movable pulley on the "slack" side; you fit the belt, allow the spring to pull the pulley into the belt, and then tighten a nut to hold the pulley in that position.In which case I'm sure it should be alot easier in terms of the cam drive- just carrying over pretty uch, especially if the blcok deck height and position of the idler pulleys can be duplicated etc etc. How is it tensioned?
Belt drives are also easier to mess with than chains.
As well as driving the camshaft in the head it also drives the original "camshaft" from the OHV incarnation of the engine, which is still there to drive the distributor and oil pump. The OHV engine has a gear drive to this shaft, with a fibre gear on the camshaft for quietness; these have something of a reputation for coming loose after a couple of hundred thousand miles and it is recommended to replace them with the steel gears from the marine version of the engine, although plenty of engines don't have the problem.
This arrangement is a possible source of niggling but awkward problems; if I left the original drive in place it would require a large overhang on the end of the camshaft so the belt would clear the drive casing which would be inelegant to say the least. It would be much nicer to do the complete conversion, but since the original gear drive is of course lubricated it would require fitting an oil seal to the end of the shaft and repositioning the front oil seal on the crankshaft, which might be awkward.
Marquis_Rex said:
From what you say the design is direct acting with all the valves inline- so not a cross flow head?
Yes, direct acting with all valves in line. Not a crossflow head in the manner of something like the Jaguar XK where there is more or less a straight line path from inlet port to exhaust port with both valves open, but it does have the inlet and exhaust ports on opposite sides of the head, whereas the OHV engine has them all on the same side. The less cramped arrangement of the ports in the casting has allowed them to make the ports in the OHC head a larger diameter, and I think also the exhaust port in particular approaches the valve at a much more appropriate angle.Marquis_Rex said:
Do you hope to weld up the two cylinders from the OHC 4 cylinder head to the other 4? now you've inspired ME to do something to my BMW project but thats another story!
Do tell...I was thinking more in terms of 3 + 3 cylinders rather than 2 + 4, but yes, that's the general idea
I would really want to get two heads on the bench in front of me before making the final decision so I could see which option would make it easier to make the cuts and to fit the two bits together.Marquis_Rex said:
I think what BBq and wildoliver say, makes rational sense in a kind of function approach, but this project doesnt sound like its a rational thing- more to do with passion and the 'journey' being more important than the end result. 
I've done similar things also- I wanted to do a 4 valve straight six for my BMW E21 3 series, but NOT by simply dropping in the modern fully mnapped 328i engine- as I wanted it with dizzy drive and how BMW would have made it if they produced it and I used to get alot of flack for that. I also wanted to use a purely mechanical plunger pump fueling system rather than K jet or some mapped affair and I got alot of flack for that also- just stick to your guns and do what makes you happy/fulfilled
Sounds exactly the same sort of thing I've done similar things also- I wanted to do a 4 valve straight six for my BMW E21 3 series, but NOT by simply dropping in the modern fully mnapped 328i engine- as I wanted it with dizzy drive and how BMW would have made it if they produced it and I used to get alot of flack for that. I also wanted to use a purely mechanical plunger pump fueling system rather than K jet or some mapped affair and I got alot of flack for that also- just stick to your guns and do what makes you happy/fulfilled
I can dig that. It's sort of recreating an alternative bit of history that didn't actually happen, but might have done.Marquis_Rex said:
I think 200 Bhp is ambitious from a 3 litre non cross flow Volvo engine: Its not impossible, as you can go for a more agressive cam and shift the power torque compromise toward top end power- but it doesnt sound like this is what you want to do. 200 BHp from a 3 litre is the kind of numbers BMW would get from their excellent flowing-fast burning shallow 2 valve hemis with good torque around the late seventies. if you reduced intake and exhaust losses- you could possibly approach this figure without an agressive cam- if you were willing to compromise on exhuast boom and intake noise (which would probably sound great anyway).
There are examples of high BHP/litre engines with this combution chamber/port arrangement: The original 1.6 litre 1588 cc VW golf GTi, but that used an agressive cam and was peaky with peak torque at 5100 rpm and peak power abouve 6000 rpm.
Yes, the picture I have of the combustion chamber shape of that engine is very similar to the Volvo one, but the Volvo head doesn't have such a cramped port layout and probably flows better.There are examples of high BHP/litre engines with this combution chamber/port arrangement: The original 1.6 litre 1588 cc VW golf GTi, but that used an agressive cam and was peaky with peak torque at 5100 rpm and peak power abouve 6000 rpm.
Looking at the power figures for the OHC fours in K-Jet form as used in the 240 series, the 2127cc variant has a compression ratio of 9.3:1 and gives 123bhp @ 5500rpm, the 2316cc variant has 10:1 compression and gives 140bhp at the same revs. So if I bore the B30 block to accept the pistons from the 2127cc four - which it can easily take - and use the same 9.3:1 compression ratio, a simple x1.5 gives an initial estimate for power output at 184.5bhp.
Making the somewhat less justifiable assumption that that part of the power increase between 2127cc and 2316cc fours which is not proportionate to the capacity increase is due to the increase in compression ratio, the estimate for the OHC six rises to 194bhp if I go to 10:1 compression.
It may be a bit questionable to express these estimates to 3 significant figures
but I think "something under 200bhp" is a reasonable way to put it... and given the nature of the project, they are not targets, they are just an idea of the sort of area I'm likely to end up in.Marquis_Rex said:
The difference in projects such as these and my BMW stuff I've done for years is that you really have to be innovative and a pioneer in your own right. There's very little availiable. I used to hate the Ford guys- they had everything- special pistons were availiable for the Essex and Cologn engines, cam profiles, especial cam profiles etc etc. I had to get stuff custom made for my BMW all the time, and I had to populate my own knowledge as people didnt really know stuff about them. It wasnt too bad, as I work in engine R and D, with access to flow benches etc etc.
You'll have to be equally innovative. Now I'm playing with American stuff- its all easy-almost too easy. Everything is availiable off the shelf. roller lifters, rockers with needle bearings, disc brakes, rack and pinion steering set ups etc etc.
good luck
The situation for special parts for Volvo engines is actually pretty good - for the fours, both OHV and OHC. What you can't readily get is much by way of parts specific to the I6. Pistons, rods, valves, what-have-you, no problem... camshafts, crankshafts and heads, not a lot there. You'll have to be equally innovative. Now I'm playing with American stuff- its all easy-almost too easy. Everything is availiable off the shelf. roller lifters, rockers with needle bearings, disc brakes, rack and pinion steering set ups etc etc.
good luck
A significant difficulty
is keeping track of minor changes to unlisted but significant dimensions during the production histories of the various engines. There are various combinations of parts which one would think ought to be possible but turn out not to be because of some unexpected minor difference. In particular the transition from OHV to OHC, while being in mechanical terms nothing more than boring it out and sticking another head on, with all major dimensions remaining the same, did involve a lot of detail changes to the block casting - pushrod tunnels removed, different waterway pattern in the deck, bolt holes for ancillaries in different places...A big part of the project will be sorting out the details to minimise the number of special parts and special operations required. The more of it I can do myself the better...
Marquis_Rex said:
The 90 degree V6 sounds like its uneven firing to get the crank/piston balance. So it probably fires 150-90-150-90. The other way to get a 90 degree V6 balanced is do what Mercedes and Audi do now and offset the crank pins. Its unlikely a modern engine would ever do the uneven firing thing. In the 19070s it was common however, with Masserati and this Volvo, I think Buick chopped a V8 and did the same thing.
Yes, the engine was originally intended to be a V8 but they got cold feet in the 1973 fuel crisis and chopped two pots off. The original version had uneven firing but in the 80s they revised it with offset crankpins to give even firing intervals.It's an engine which seems to polarise opinion a bit, it seems to me that people who (like me) have come across it in Volvos aren't usually so keen on it whereas those who know it from its more glamorous French sporting applications view it with more favour
I get the feeling that Volvo themselves weren't too keen on it and sort of tried to push it to one side when the 700 series came out; only one of the 760 models actually had the V6, for the performance variant of the 760 they used the OHC four with a turbo on it to give more power than the V6.Marquis_Rex said:
I would be interested to hear what that uneven firing sounds like. I know the uneven firing of a conventional V8 leads to its beautiful burble- and introduced some interesting harmonics. I can also believe, no, I know this kind of uneven firing will lead to powerloss- due to charge robbing/interference issues-could even lead to a rough idle. I always thought it would be characterful. So bored of anodyne corporate refined motors 
In a Volvo it's heavily silenced and it doesn't sound like much really. It doesn't feel very smooth from inside a 260 though...For me this is perhaps an instance when it's not always a good thing to know too much... I can only really appreciate an uneven exhaust note when it's coming from something with separate inlet and exhaust tracts for each cylinder, like a Moto Guzzi. When the unevenly-firing cylinders are sharing tracts what I hear is the sound of charge robbing and interference... my prime thought is always "those cylinders are not all operating under equal conditions". I can be a bit obsessive about balancing things sometimes and it spoils the sound for me.
Marquis_Rex said:
Interesting that you say it eats camshafts, I heard the 90 degree Buick V6 has chain drive issues, due to un equal loading on the chain drive.
It basically has marginal lubrication to the top end and the oilways tend to block up and starve it. Then to add insult to injury, when you come to do the repair the various covers interlock in an infuriatingly backwards sequence so you end up having to take off a chain of nominally unrelated parts before you can get at anything...Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff