trying to understand camshafts

[JPSmit]

I get what my cam does in terms of timing. how does an uprated camshaft help?

is this something worth following up?

https://tinyurl.com/yghmany

 

[Guest]

A real BRIEF explantion.

A "performance" cam opens the valve higher and holds it open longer allowing more air/fuel charge in and exhast out. It also usually means worse fuel economy, but not always. Usually you give away performance in one area to gain it in another. Ultra high top end power means loss of bottom end power and vise versa. It's all about what you want to do with the car. For me on the street, I'd prefer bottom and mid as I seldom ever wring my car out. Torque is fun, it's the stuff that puts you back in the seat.

Would I put this cam in my car? Maybe if the price was right.



I don't like the way this guy gives specs at all.

 

[twas_brillig]

I suggest that you not buy a cam until you've thought through the whole process.

Stapleton in "The Midget A-H Sprite High Performance Manual" comments 'Camshafts for 1500 engines: For the 1500 Midget there is a much narrower choice of cams, due to the fact that this engine not only had much less development than the A series, but was fitted in fewer models of car. Ultimately, it doesn't lend itself to high rpm usage and is hard pushed to match a good tuned A series. But there are cams for the 1500 engine, and Kent Cams has four cams to choose from (plus a race cam), of which its TH5 looks to be the best, having a power range of 2200-7000 rpm. This cam is available as part of kit which includes suitable cam followers and valve springs. APT in the USA also has a range of cams worth considering."

If you want something to worry about: Terry Horler, in "Original Sprite and Midget - the Restorer's Guide" provides this advice about the 1500 engine:

'Crankshaft end thrust was controlled by half washers in the upper rear main bearing housing only.
This last feature was to prove a weak link. Wear rate with half washers could often be rapid, especially on cars used extensively in traffic where prolonged use of the clutch would press the crank against the thrust washer. Ultimately, the rear washer would become so thin that it could fall out of the bearing housing, followed shortly by the front washer as the crank moved forward. Provided nothing went bang as these washers fell out, crank movement could then allow untold damage to occur - there are tales of connecting rods removing themselves from the engine."

I know I'm supposed to wiggle the crank and check for end play on our VW engined dune buggy occassionally, but I didn't know that some of the LBCs want thier booty wiggled as well.


Doug

 

[Hairyone]

1500 cams, does anyone have any suggestions on a good cam for low to mid torque?

hi-jacking your post: for a 1275 with the standard head (valves 29mm inlet, 34mm exhaust). HIF44 carb with a little work done on it & the manifold (as per David Vizard's book).
Has anyone any suggestions for a cam to provide a good street car, i.e. low to mid torque?

The 1275 in my frow at the moment

 

[aeronca65t]

JP-
That cam you're looking at is "remanufactured", which means it is reground. Some regrinds can be OK, but others may be "soft" and wear quickly. It can be kind of hit or miss with regrinds. The camshaft undergoes more friction than any other internal part in your engine, so it's important that they are truly hard. You're better off to buy a cam ground from a billet instead of a regrind (and with new lifters as well).

I raced my 1500 for two years with a stock cam. That's because it's not the type of engine you want to spin real high anyway. Most "hot" cams tend to make the engine perform better at higher RPMs. For a street or even autocross 1500, I stick with the stock cam.

That's because hotter cams "keep the door open" longer (longer duration of intake valve being open) so that more fuel mix can enter the cylinder. They also keep the exhaust valve open longer to allow more exhaust flow. And they lift the valve higher (off the seat) to help flow too. More extreme cams will also increase "overlap" (keep both valves open at the same time for a fraction of the cycle), to promote good flow at high RPM. All of these things tend to make an engine run worse at low RPM, which is where most street engines operate.

As was stated above, you need to watch thrust washers on these engines. Even keeping strict 5800 RPM redline, I change thrust washers every 20 hours of operation (and they are always worn).
And more important, the 1500 is a long stroke engine. High revs tend to eat rod bearings in these engines. Again, mine get changed every 20 hours and they show even more wear than the thrust washers.

I'm running a ~Kent TH2~ which is basically a hot street cam. It is designed to provide better flow from 2500 RPM to redline. My engine "lives" at 4500 to 5800, so this works fine with me. It's a "295" cam (which is the crank degrees of opening duration). The regrind that your are looking at is "285" which is pretty similar. My Kent also has a modest increas in lift. Not sure about the numbers on that eBay cam.


By the way, when BL engineers first put the 1500 in the Midget they ran several of them at a track for testing. The test involved running the cars at top speed (93 mph) for one hour. After the test, all the cars had rod bearings that were so worn they all needed to be replaced. So what did they do? Nothing! Most of the cars would be exported to the US and it was decided than "Americans don't drive like that anyway."

 

[Guest]

1500 cams, does anyone have any suggestions on a good cam for low to mid torque?

hi-jacking your post: for a 1275 with the standard head (valves 29mm inlet, 34mm exhaust). HIF44 carb with a little work done on it & the manifold (as per David Vizard's book).
Has anyone any suggestions for a cam to provide a good street car, i.e. low to mid torque?

The 1275 in my frow at the moment

Don't go that route jus' cause I said it. It's all how you drive it too. Some folks like'ta wind 'em up. That's just ~MY~ persoanl preference for ~MY~ particular car. I might be more inclined to wind a 1275 UP. Hap should have some good suggestions for ya.

 

[SilentUnicorn]

I am running a TH2 in my 1500. Pretty happy with it.

m

 

[Hap Waldrop]

JP, the cam on a 1500 is same as most of our engines, David Anton makes two street cams for 1500, I would say stay in the .400" lift area, and the duration in the 270-280 range for the street. Here's trick with 1500 when rebuilding and repalcing a cam, go with the Triumph 1300 cam, and then you can put cam bearings in your 1500 block, all BL did with the 1500 to delete cam bearings was make the cam journal big enough to fit the block minus cam bearing, so you can convert your 1500 block to cam bearing by simply getting the 1300 cam, and cam bearings from the 1300 Spitfire. The thrust bearing deal, it's not ideal, but it can be easily managed by keeping your foot off the clutch pedal at red lights, racing Triumph 1300 and 1500 don't have any thrust bearing issues, but they don't sit at red light, do they.

The poor ole 1500, has never really been given the love by the masses, but make no bones about, it has plenty of potential, Steve Sargis is proving that on the race track now with it, Sargis is easily the best American amatuer Triumph racer to ever hit the track. People build 1380cc A series hot rod engines all the time, but no one show the lowly 1500 the same attention, getting 1600cc out the 1500 is not that hard, and if the same love is shown it as the 1275s and 1380s, then a hot rodded 1500 would kick their butt. The 1550 as stated will not out rev the A series engine, but it will easily out troque it and has much greater HP potential. Mostly it was never raced and developed because the rulebooks didn't favor it well.

 

[Guest]

JP, the cam on a 1500 is same as most of our engines, David Anton makes two street cams for 1500, I would say stay in the .400" lift area, and the duration in the 270-280 range for the street. Here's trick with 1500 when rebuilding and repalcing a cam, go with the Triumph 1300 cam, and then you can put cam bearings in your 1500 block, all BL did with the 1500 to delete cam bearings was make the cam journal big enough to fit the block minus cam bearing, so you can convert your 1500 block to cam bearing by simply getting the 1300 cam, and cam bearings from the 1300 Spitfire. The thrust bearing deal, it's not ideal, but it can be easily managed by keeping your foot off the clutch pedal at red lights, racing Triumph 1300 and 1500 don't have any thrust bearing issues, but they don't sit at red light, do they.

The poor ole 1500, has never really been given the love by the masses, but make no bones about, it has plenty of potential, Steve Sargis is proving that on the race track now with it, Sargis is easily the best American amatuer Triumph racer to ever hit the track. People build 1380cc A series hot rod engines all the time, but no one show the lowly 1500 the same attention, getting 1600cc out the 1500 is not that hard, and if the same love is shown it as the 1275s and 1380s, then a hot rodded 1500 would kick their butt. The 1550 as stated will not out rev the A series engine, but it will easily out troque it and has much greater HP potential. Mostly it was never raced and developed because the rulebooks didn't favor it well.

told ya... (Gotta love Hap!!!) :wink:

Hap. is the 1300 cam any cheaper? Any better grinds? Could you turn a 1500 down to use 1300 bearings, or are the lobes too big?

 

[Morris]

spitbits.com did have some affordable 1300 cams. I briefly looked into having my stock cam turned down... but it after you turn ALOT of metal off, you have to machine new oil flow channels and have it hardened. Gets real expensive, real fast.

 

[Hap Waldrop]

As Morris stated, you can turn down the 1500 cam to work with the 1300 cam bearing, but it's way easier just to buy the 1300 cam.

Rick Cline a well know Triumph racer devised a low cost race engine recipe years ago using the 1500, you use TR6 pistons, a standard TR6 piston is a .040" over 1500 piston as for bore size, ok with that thought, you could then you use TR6 pistons in .060" over, that would give you a .100" over 1500 or 1593cc. Now with the TR6 pistons in the 1500 you have to deck a good bit off the block, like .200", but I've have already built two .040" race engines like this and had zero problems. Port the head, (the 1500 already has some decnt valve sizes compared to the A series, 1.44" intake and 1.17 exahsut) then bump the compression to about 9.5-10.00 to 1 with a good performance street and set of Euro spec twin HS4s or a side draft Weber, a header and look out , you got a ligitimate 1380 killer. There is no doubt in my mind this motor would easily have 10+ HP more than you can get out of street A series 1380.

 

[Guest]

There is doubt in my mind this motor would easily have 10+ HP more than you can get out of street A series 1380.

Did you mean to say "no doubt"?

 

[Morris]

Hap... it feels so good to hear someone say something nice about the 1500. I think I am tearing up.

 

[Hap Waldrop]

There is doubt in my mind this motor would easily have 10+ HP more than you can get out of street A series 1380.

Did you mean to say "no doubt"?

Yes, my fingers can never catch with my mind

 

[Guest]

haooens to me sometimes too. Too much ADD.

 

[SilentUnicorn]

As Morris stated, you can turn down the 1500 cam to work with the 1300 cam bearing, but it's way easier just to buy the 1300 cam.

Rick Cline a well know Triumph racer devised a low cost race engine recipe years ago using the 1500, you use TR6 pistons, a standard TR6 piston is a .040" over 1500 piston as for bore size, ok with that thought, you could then you use TR6 pistons in .060" over, that would give you a .100" over 1500 or 1593cc. Now with the TR6 pistons in the 1500 you have to deck a good bit off the block, like .200", but I've have already built two .040" race engines like this and had zero problems. Port the head, (the 1500 already has some decnt valve sizes compared to the A series, 1.44" intake and 1.17 exahsut) then bump the compression to about 9.5-10.00 to 1 with a good performance street and set of Euro spec twin HS4s or a side draft Weber, a header and look out , you got a ligitimate 1380 killer. There is doubt in my mind this motor would easily have 10+ HP more than you can get out of street A series 1380.

<span style="font-style: italic">drools all over that idea..</span>


Thanks for that recipe Hap


BTW what do you use for a cam?


m

 

[JPSmit]

Thanks all - especially Hap for your input. I'm not quite sure I understand so let me try to recap.

1. Standard TR6 Piston = .040" over 1500 piston (why wouldn't I just use a .040 over 1500 piston?) I don't understand the jump to .060?

2. Do you use the TR6 Connecting rods or the Midget connecting rods?

3. If you shave off .200 off the block, do you shorten the pushrods also?

4. Do you use a standard crank? - does this have to do with the connecting rods you use?

5. As was just asked, is this with a hotter cam also? the 1300? Does the timing gear just bolt on the new crank? Any machining for the 1300 bearings?

I'm sure I'll have many more questions but this is a start

thanks all

 

[Bob Claffie]

Back in the days of yore I built a 1300 for a racing Spit and used GT6 pistons for the .040 bored oversize Spit. At that time there was no rework needed for either the pistons or block. Apparently the process to create the 1500 was less simple. Likewise, as mentioned above, in a racing application thrust washers were not problematical. We used a 10 or 12 hour maintenance schedule which worked out pretty well too. Between practice, qualifying and the race itself, new bearings every 5 or 7 races kept failure to a minimum.. Bob

 

[Guest]

( A guesss) The 1300 might have a longer rod due to a shorter stroke, thus making up for compression height differences...but this is just a guess. Then again, it might have a shorter deck height.

I know NOTHING about these engines !!!!

Hap, what's a good book for the 1300/1500 on internal specs, model differences, interchenge etc...?

 

[billspit]

I know the Mk II or early MK III Spitfire had a very good camshaft profile. I have a MK IV engine in storage that has cam bearings in the block. Not sure if the cam that was in it is a good profile or not.