What Camshaft?

[gagvanman]

Hi all. I currently run a 1776 but will be tearing it apart in the new year due to low oil pressure when hot, issues.

Current specs:
Stroke 69mm
Bore 90.5

Cylinder Head:
CB performance 044 40 x 35.5mm 90.5 valves
1:1.1 rocker ratio

Carburettor:
Twin Weber ICT 34's
idle jet 55
Main jet 160
Air corrector 180
Emulsion tube f6
Float jet 150

I am not sure what camshaft it currently has, but was wondering which would be the best suited for the above specs? I want good drivability and fuel consumption, not worried about high top speed.

Thanks...

 

[ozziedog]

Stock sounds perfect to me. Have a word with Abel At Afonso motors and I’m guessing he’ll point you in the right direction if you tell him what you’re after.

Ozziedog,,,,,,,, Fuel consumption,,,, I’ve heard of that :mrgreen:

 

[Davydomes]

We have a similar set up (can't recall jets sizes). We also have a 6 Rib Gearbox. Abel did a great job on our engine and advised we removed the 100 Cam that came with it and revert to stock if we were not bothered about top end speed. This would help with the torque at the lower end and with the economy.

 

[atafonso]

Hi :mrgreen:


The cam will dictate the behaviour of your engine; it will give you loads of low end torque, but sacrifice power up top, could give you good power up top(having matching heads, carbs and exhaust) at the cost of much less low end torque; or you could have a cam that is a compromise between the two. So you can see that the cam is one of the most important parts in an engine build as it can make you love or hate your new engine.

Allow me to ask you a few questions so i can make you a suggestion.

How heavy is your Bus?
What is your cruising speed on motorway?
At what revs do you normally change gears?
How high do you like to rev?
What percentage of city and motorway driving do you do?

Abel

 

[ozziedog]

Hey Abel, where you been ??? Glad you’re still alive :mrgreen:

Ozziedog,,,,,good to hear from you. :mrgreen:

 

[gagvanman]

Abel, thanks for your input.

How heavy is your Bus?
Not sure, its a standard Dormobile early bay with lightweight furniture and 3/4 rock n roll bed (no spare wheel).
What is your cruising speed on motorway?
60 - 65
At what revs do you normally change gears?
Between 2k / 3k depending on engine load.
How high do you like to rev?
Never go above 4k
What percentage of city and motorway driving do you do?
50/50

 

[atafonso]

Hey Abel, where you been ??? Glad you’re still alive :mrgreen:

Ozziedog,,,,,good to hear from you. :mrgreen:

Hey Ozzie, good to talk to you too matey

All good, just crazy busy at work!! :shock:
I am still helping people but mainly on Facebook lol :lol:

 

[atafonso]

Abel, thanks for your input.

How heavy is your Bus?
Not sure, its a standard Dormobile early bay with lightweight furniture and 3/4 rock n roll bed (no spare wheel).
What is your cruising speed on motorway?
60 - 65
At what revs do you normally change gears?
Between 2k / 3k depending on engine load.
How high do you like to rev?
Never go above 4k
What percentage of city and motorway driving do you do?
50/50

Hey Gav

Ok, so based on your info, here`s my suggestion and why:

Cam- Stock. Yes, stock cam. Why? Because you never rev past 4k rpm, and the stock cam maxes power up to around that ish. Plus, there`s no other cam that will give you as much torque down low as the stock cam. Also is free, and you can use all stock valvetrain, which will make the engine more reliable, needing less maintenance and quieter.

Heads- Sell your CB`s (Your CB heads are too big for your needs and using them will hurt low end torque, and you won`t be able to use it to it`s full capabilities due to the rev range you use the engine) and get a pair of AA 500`s stock size valves. With a little clean up of the ports, they will flow much more than your requirements, plus they use long reach spark plugs which makes the head stronger around the plug area avoiding cracking. Also they have a modern heart shape chamber, very efficient. Chambers are 54cc`s, which will give you a compression of aroun 7.8:1 with a stock deck height of 1.25mm. Perfect for max efficiency.

Carbs- 34`s are great, i use them a lot, very reliable if usung a CSP Bellcrank linkage, setup and forget. Use a stock fuel pump, then hook up a gauge on the fuel line, then grind the pump rod until you get 2.5 psi fuel pressure. It will work as a charm! I use always 145 mains, 160 airs, F78 emulsion(works for me perfect), 55 idles. More than 20 combos with the same jetting, so more than proved.

Crank and rods- Stock are perfect, if you can, balance the rotating assembly for smoothness and more longevity.

Exhaust- If you can, use a 1 3/8" 4x1 header with a silencer of your choice. That will give you a few extra ponies.

This combo gives a solid 75bhp at the crank, but 100-105 ft/lbs of torque as low as 2k rpm, the engine feels really responsive, specially at low revs. Perfect for your application

Abel

 

[gagvanman]

Thanks Abel. I forgot to mention I am using a CSP Bellcrank link on the carbs and a 4 into 1 exhaust. I won't be ditching the heads just yet (cost me a lot of money last year) they are running long reach spark plugs and have 54 cc chambers. I did notice a big increase in torque and performance.

The main reason why I asked about the cam is that the engine is very lumpy on tick over and quite hard to get the timing right.

So when I strip it down to try and find the cause of the low oil pressure I might fit a standard cam.

 

[K@rlos]

Thanks Abel. I forgot to mention I am using a CSP Bellcrank link on the carbs and a 4 into 1 exhaust. I won't be ditching the heads just yet (cost me a lot of money last year) they are running long reach spark plugs and have 54 cc chambers. I did notice a big increase in torque and performance.

The main reason why I asked about the cam is that the engine is very lumpy on tick over and quite hard to get the timing right.

So when I strip it down to try and find the cause of the low oil pressure I might fit a standard cam.

What cam and ignition system do you have now?

 

[atafonso]

Thanks Abel. I forgot to mention I am using a CSP Bellcrank link on the carbs and a 4 into 1 exhaust. I won't be ditching the heads just yet (cost me a lot of money last year) they are running long reach spark plugs and have 54 cc chambers. I did notice a big increase in torque and performance.

The main reason why I asked about the cam is that the engine is very lumpy on tick over and quite hard to get the timing right.

So when I strip it down to try and find the cause of the low oil pressure I might fit a standard cam.

Gav, first you need to find out what cam you have in there, but having a bigger valved head with a stock cam means the velocity on the ports will be reduced at low rpm`s, so you will loose torque for sure down low, and won`t benefit of the larger ports and valves because you won`t be turning higher rpm`s due to your driving style and combo.
Don`t think it`s a downgrade to use smaller valves, you will have more down low torque and won`t sacrifice power turning 4k rpm`s. Also the engine will behave more like stock with the smaller valves and heads due to increased port velocity, making it easier to tune. Not a massive difference, but every little helps.

That`s just my £0.01 :mrgreen:
Abel

 

[K@rlos]

Thanks Abel. I forgot to mention I am using a CSP Bellcrank link on the carbs and a 4 into 1 exhaust. I won't be ditching the heads just yet (cost me a lot of money last year) they are running long reach spark plugs and have 54 cc chambers. I did notice a big increase in torque and performance.

The main reason why I asked about the cam is that the engine is very lumpy on tick over and quite hard to get the timing right.

So when I strip it down to try and find the cause of the low oil pressure I might fit a standard cam.

Gav, first you need to find out what cam you have in there, but having a bigger valved head with a stock cam means the velocity on the ports will be reduced at low rpm`s, so you will loose torque for sure down low, and won`t benefit of the larger ports and valves because you won`t be turning higher rpm`s due to your driving style and combo.
Don`t think it`s a downgrade to use smaller valves, you will have more down low torque and won`t sacrifice power turning 4k rpm`s. Also the engine will behave more like stock with the smaller valves and heads due to increased port velocity, making it easier to tune. Not a massive difference, but every little helps.

That`s just my £0.01 :mrgreen:
Abel

This^^^^ 1 of the best bus engines we’ve done is a 1968cc stroker with an Engle W110, stock rockers, ported stock heads, twin 40 IDF’s and 8.5:1cr. It’s in a pop top westy and it’s a torque monster! Idles like a stock engine, pulls like a diesel and tops out At 5500 rpm. Bigger isn’t always better, port velocity is critical for torque and the bigger the valve the less that will be at low rpms. If your not looking for high end rpm I’d sell your heads and buy a stock set. Their not being used to their full potential with what your trying to achieve.

 

[StefansBus]

Two things: Other than stock I think the CB2280 would also be a great choice of camshaft.It consistently gets rave reviews from people who use it on a mild set-up.

Second: I think if you normally shift between 2-3k then you may be running the engine at too low RPMS. It's air-cooled. It needs some fan RPMs for best cooling. I'd say shift it at 3.5 to 4k at and drive it not below 3k under load for any significant length of time. Especially things like up hill or towing.

I often shift at 4.5 in my 1776 CB 2239 and modified single Solex 34.

 

[Tofufi]

Second: I think if you normally shift between 2-3k then you may be running the engine at too low RPMS. It's air-cooled. It needs some fan RPMs for best cooling. I'd say shift it at 3.5 to 4k at and drive it not below 3k under load for any significant length of time. Especially things like up hill or towing.

I often shift at 4.5 in my 1776 CB 2239 and modified single Solex 34.

With that in mind, I fitted a Porsche 356 alternator/dynamo pulley. It keeps the fan speeds up as it is smaller.

Does help keep my bus cooler, although sitting at 3500rpm+ (70mph in 5th) for any time it does still get hot. Sitting at 3000rpm (60mph) it stays around 90-95c all day. Fitting an oil cooler is still on my to-do list.

I've got a 1955cc engine built by Abel. It has a stock cam and is lovely and torquey.