rally cam test

[Forest_rallying]

T

one thing that will be interesting is we will now have a bit of a side test going on,

ive skimmed a bit off the burton head so it will give the same compression ratio as the origonal big valve head, but thats not the interesting bit. Having just flow tested the old cracked head and the Burton is there is a pretty dramatic difference in airflow between the two . At @10" depression the Burton inlet flowed 14cfm more and the exhaust was up about 11cfm thats about 15% more, so will that translate to a 15% power increase?

last time round i thought the Rl31 came in a bit low powerwise @162 bhp, now if the perecntage in flow difference between the heads translates to the same increase in power this time the Rl31 will make 186bhp...................

When you first tested the cracked head you described it as a typical 1980’s Big Valve Head. The Power was approx 160bhp when you first tested the BLF 40/41 cam which was about what they were producing in period in that specification.

It’ll be very interesting when all tests resume to see what power figures you come up with now you have the updated head. In the early 80’s there was bugger all information on porting cylinder heads for the hobby builder and most of the specialists knew little more unless you were dealing with Holbay.

[Graham]

T

When you first tested the cracked head you described it as a typical 1980’s Big Valve Head. The Power was approx 160bhp when you first tested the BLF 40/41 cam which was about what they were producing in period in that specification.

It’ll be very interesting when all tests resume to see what power figures you come up with now you have the updated head.

Got part of an answer, i got the head bolted on today with the BLF40/41 and gave the engine a quick run up before i came home, i only got time do a few runs to do a mixture check and dial in the ignition timing. Cam timing is just by eye at the moment i will swing it on the vernier later, but power is definatly a few bhp up and midrange torque is well up

[Graham]

A bit more of a teaser for you, ive now swung the cam timing and the ignition timing a second time, i dont like giving out timing numbers but i finished on 31 degrees advance @ 4000 rpm which is within a degree of what it the cam had last time. Cant knock the results though power curve is the same, as you would expect, its simply higher.

[Forest_rallying]

A bit more of a teaser for you, ive now swung the cam timing and the ignition timing a second time, i dont like giving out timing numbers but i finished on 31 degrees advance @ 4000 rpm which is within a degree of what it the cam had last time. Cant knock the results though power curve is the same, as you would expect, its simply higher.

It’s nice to see the new head’s both up on power and torque, what were the actual figures as it’s difficult to make out off the graph.

[Graham]

the 40/41 jumped up 6 bhp to 165.

next up i installed the 4.75, that jumped up considerably to close on 180bhp, but then i had a few issues along the way such as having to weld up the exhaust manifold, then the balance screw unscrewing itself out of its linkage, that lost the rear carb full throttle, so despite tuning i wasnt gaining power, i had noticed the engine not really idling any more, but im not normally really bothered about idle as it doesnt effect peak power, that but by the time i had spotted the issues the screw was so far out it was hurting power. Throttle sorted we were back close to 180bhp so nearly 18bhp up on the first test, but .looking back i think power was still low for the engine spec and cam,

In cold light of the day looking back at the results im pretty sure something was still wrong, power was well up, unlike the 40/41 the 4.75 appeared to loose some torque with the head swap but i didnt realise that until overlaying graphs at the end of the day. thinking i was done with the 4.75 i moved onto the WR40.



For some unknown reason the WR40 is ground on a much smaller base circle meaning the adjuster posts need winding out 4 turns to fit it, this must compromise it compared to all the other cams but it was the same for the last test. Going by the last test the comparing the 4.75 to the WR40 it should of lost torque, but run away at high rpm, but it just didnt work AFR was good but it didnt matter how much i swung the timing or ignition and was thinking the whole test was a bad idea, theres probably plenty of good reasons no one else had tried to test so many cams back to back. With the base circle bugging me i admitted defeat with the cam and gave up with it. later on a found a nut missing off the front carb throttle spindle, that lost the front carb lost ful throttle but that it didnt effect the idle. i dont know the exact point that that nut went missing it might of even done so on the next cam.

the next cam up was a similar story, weld the exhaust yet AGAIN, find and fit missing spindle nut. i even checked dyno calibration, if anything it was 1 lbft high. so if there wasnt anything wrong with carbs, linkage dyno, afr or timing the engine had to be down on power.

a compression test gave the answer, rear cylinder were down on compression by about 70psi. im assuming a blown head gasket wall:

so fix the engien and start again, after i have tiled the kitchen floor.............

[katana]

LOLs - paid someone to do mine, best £300 I've spent for no backache or knackered knees!

[Forest_rallying]

Nice work Graham, shame about where the compression has gone. What gasket are you using MLS or Vic Reinz?

[Graham]

Nice work Graham, shame about where the compression has gone. What gasket are you using MLS or Vic Reinz?

as cyls 3+4 had exactly same compression, just 70psi lower than 1+2 id lay odds it is head gasket. its an MLS. The engine is still in one piece but heres my guess. its literally built from assorted off cast and reclaimed bits and has way more piston protrusion than i would ever normally run, using a really thick head gasket its got correct squish and piston/head clearance but my guess is its suffering from localised detonation, i cant hear it and the timing doesnt suggest theres an issue, but cometic MLS gaskets clamped with ARP's do not just give out unless somethings wrong.

next week i wil pull the head assuming theres no real damage i will then pull the pistons and deck them and use a more normal thickness gasket. hopefully theres enough crown thickness in the pistons because i already decked them for there previous life.

[Forest_rallying]

as cyls 3+4 had exactly same compression, just 70psi lower than 1+2 id lay odds it is head gasket. its an MLS. The engine is still in one piece but heres my guess. its literally built from assorted off cast and reclaimed bits and has way more piston protrusion than i would ever normally run, using a really thick head gasket its got correct squish and piston/head clearance but my guess is its suffering from localised detonation, i cant hear it and the timing doesnt suggest theres an issue, but cometic MLS gaskets clamped with ARP's do not just give out unless somethings wrong.

next week i wil pull the head assuming theres no real damage i will then pull the pistons and deck them and use a more normal thickness gasket. hopefully theres enough crown thickness in the pistons because i already decked them for there previous life.

If they are the pistons that you have put the fly cuts in then a few thou off the crowns shouldn’t be a problem. 10 thou protrusion and a 40 thou gasket is ideal.

[Graham]

If they are the pistons that you have put the fly cuts in then a few thou off the crowns shouldn’t be a problem. 10 thou protrusion and a 40 thou gasket is ideal.

i need to take about another 0.030 off them, yes they are the ones with the deep cutouts, but thats slightly miss leading, the deep parts of the cutouts are where piston crown is thicker

[Forest_rallying]

i need to take about another 0.030 off them, yes they are the ones with the deep cutouts, but thats slightly miss leading, the deep parts of the cutouts are where piston crown is thicker

I would think you should be okay machining 30 thou off the crowns. Did you have to machine the crowns for the long Rods or had the pistons already got a shorter compression height to match the Rods?

It’ll be interesting to find out what the cause of the low compression is on 2 cylinders, it does seem strange for a MLS gasket to let go like that. You would expect even the Burton valves to last a bit longer than a couple of Dyno sessions.

[Graham]

I would think you should be okay machining 30 thou off the crowns. Did you have to machine the crowns for the long Rods or had the pistons already got a shorter compression height to match the Rods?

It’ll be interesting to find out what the cause of the low compression is on 2 cylinders, it does seem strange for a MLS gasket to let go like that. You would expect even the Burton valves to last a bit longer than a couple of Dyno sessions.

the pistons were previously machined to suit a 86mm crank and custom length rods that were inbetween standard and normal long ones, but they are now in a different block with 136mm long rods. the block they are now in has been decked a couple of times too.

i wouldnt expect an MLS to just fail so quickly either which is why i think its detonation related. I cant see it being the head. Cylinders one and two produce EXACTLY the same compression numbers as do three and four, just lower, thats not going to be the head at fault.

Andy Burton races in one of the series i am eligability scrut for so i see him regulary and we get on well. He is quite open and honest with me about whats good and what has gone wrong. He has stopped just short of telling me where they have their valves made. Only saying that its somewhere in europe, adding that to his knowledge they have never had one fail. The flip side is i have had valves from G+S (who make REC valves) that have lost stellite tips so who can you trust?

[Forest_rallying]

The only reason I mentioned the valves is, I remember a regular poster on here that has a Dyno commenting on the quality of their valves, he quoted they were totally worn out after the Dyno session was complete.

It’ll be interesting to see what the damage is when you remove the cylinder head, let’s hope it’s nothing more than a torched gasket.

[Graham]

The only reason I mentioned the valves is, I remember a regular poster on here that has a Dyno commenting on the quality of their valves, he quoted they were totally worn out after the Dyno session was complete.

It’ll be interesting to see what the damage is when you remove the cylinder head, let’s hope it’s nothing more than a torched gasket.

i too recall dirks comment on burton valves, but im pretty sure they have changed supplier

[alladdin]

The only reason I mentioned the valves is, I remember a regular poster on here that has a Dyno commenting on the quality of their valves, he quoted they were totally worn out after the Dyno session was complete.

It’ll be interesting to see what the damage is when you remove the cylinder head, let’s hope it’s nothing more than a torched gasket.

i think that was the oil pumps from memory ? (Dirk)

[Graham]

i think that was the oil pumps from memory ? (Dirk)

he definatly said it about oil pumps, but i di have something of a recollection about valves. although arguably there is something of a difference betwenn wearing out and total failure.

hopefully i can get the engine pulled down over the weekend and i can have a 3rd go at doing this test, before i loose teh wil to live

[rallyrob]

hopefully i can get the engine pulled down over the weekend and i can have a 3rd go at doing this test, before i loose teh wil to live

You're doing a Grand Job Graham. Thanks for sticking at it.

[Forest_rallying]

i think that was the oil pumps from memory ? (Dirk)

It was definitely valves but possibly they were probably selling shit pumps as well.

[Forest_rallying]

These camshaft test must be really trying your patience now Graham with so many problems that keep getting in the way. Let’s hope you can get the engine back up and running without too much expense, I dread to think what money of your own you have put into this just to prove the outcome of the cam tests to us all on this Forum.

When things resume where are you up to with the camshaft selection and will you ever get round to testing the race cams?

[Graham]

These camshaft test must be really trying your patience now Graham with so many problems that keep getting in the way. Let’s hope you can get the engine back up and running without too much expense, I dread to think what money of your own you have put into this just to prove the outcome of the cam tests to us all on this Forum.

When things resume where are you up to with the camshaft selection and will you ever get round to testing the race cams?

The trouble is to get proper meaningfull results requires starting from scratch every time. Although this time i will proabaly ignore the 40/41 and start with the 4.75., from what ive seen the 40/41 is pointless against todays crop of cams. The only reason i have it was i swapped it for a newman 4.5.................

i pulled the engine apart today, its a bit of a mystry theres no signs of the gasket leaking on the block or head faces, the gasket itself looks fine, although it is possible for an MLS gasket to leak between layers and not be apparent. There are no signs of detonation. looking at the piston rings lands there no blow by evidence, but top rings on 3+4 do seem to have a little less ring tension.

As i dont have another mega thick head gasket i have just decked the pistons by 0.025" to allow use of a more normal thickness gasket. That will still leave them out the bores at TDC.

only thing i havnt done yet is check valve sealing, although there were no signs of it on the pistons its possible two valves have at some point just touched a piston and are not quite sealing.

yes i still plan on running race cams, the engine doesnt have race cam compression but im interested in power band i need to find a cam which will pull from 4K to 8 or a little more, sure if you tried hard enough you could rev any cam to 8 but i need one which even if past its peak will still make useful power that high up the rev range

[Miniliteman]

yes i still plan on running race cams, the engine doesnt have race cam compression but im interested in power band i need to find a cam which will pull from 4K to 8 or a little more, sure if you tried hard enough you could rev any cam to 8 but i need one which even if past its peak will still make useful power that high up the rev range

For usefull power that high in the rev range the head is more important than the cam. No high-rpm-flow = no power.

[Graham]

For usefull power that high in the rev range the head is more important than the cam. No high-rpm-flow = no power.

agreed, the engine im refering to wil have a decent head, or at least i wil be reworking an existing head to get it as good as i can

[Graham]

latest update on the test is, the valves are still sealing perfectly. When i had the pistons out i overlaid the top compression rings from cyls 1+2 over 3+4 and they matched exactly for dia and gaps, so despite me initally thinking there was a tension difference there isnt one.

So we are back to head gasket, with no signs of a blow on blow or head face or outer faces of the gasket i can only assume it was an internal blow between layers, ive never seen that on a cometic but i have seen it on standard manufacturers mls gaskets. With hindsight i undid the head with what was a realitively short breaker bar, shorter than i would normally use and they didnt seem to be overly tight. i cant rememeber if i retorqued the head bolts, BUT despite always checking i have never had head bolts clamping a cometic head gasket tighten up further after running an engine.

[Forest_rallying]

P

latest update on the test is, the valves are still sealing perfectly. When i had the pistons out i overlaid the top compression rings from cyls 1+2 over 3+4 and they matched exactly for dia and gaps, so despite me initally thinking there was a tension difference there isnt one.

So we are back to head gasket, with no signs of a blow on blow or head face or outer faces of the gasket i can only assume it was an internal blow between layers, ive never seen that on a cometic but i have seen it on standard manufacturers mls gaskets. With hindsight i undid the head with what was a realitively short breaker bar, shorter than i would normally use and they didnt seem to be overly tight. i cant rememeber if i retorqued the head bolts, BUT despite always checking i have never had head bolts clamping a cometic head gasket tighten up further after running an engine.

That seems a mystery Graham. I once had a Discovery 300 Tdi, when I bought it the chap said it had a full engine rebuild. After running it for over 12 months the head gasket blew a piece out of the back of number 4 cylinder. I removed the head to find a cheap and nasty. motor Factors gasket that looked similar to a std Pinto one fitted. I cleaned the block and head face by hand and fitted a genuine LandRover MLS gasket, the problem was solved and it ran for many years after that without any issues.

It seems strange that Pinto with only mild compression to a Diesel can blow a MLS head gasket. I hope you can soon get to the bottom of this problem.

[stevieturbo]

Were the head bolts tight ?

What is the block and head finish like ? MLS need/like super smooth.

Did you try a leakdown test to listen for where the air is escaping ?

[Graham]

Were the head bolts tight ?

What is the block and head finish like ? MLS need/like super smooth.

Did you try a leakdown test to listen for where the air is escaping ?

its not my first rodeo! 80lbft tight on a cabilbrated torque wrench thats costs more than a pile of pintos!

yes surfaces are fine to suit an MLS but as i already said its not blowing across either head or block face to its not a surface finsih problem.
Time was short so did not do a leak down test, At the time we deduced it was unlikely to be ring or bore related as there has no crankcase blowby. Additionally it would be highly unusual for a leak in the bottom end to give EXACTLY the same results in two adjasent cylinders. In any case i had already decided to reduce the compression hieght of the pistons, and having seen the rings and bores i can say 100% its not in the bottom end.

[Forest_rallying]

Generally a surface finish issue with a MLS gasket is down to water seepage out of the side of the block and that’s certainly not the problem.I use good old fashioned Wellseal to address that problem. I hope by decking the pistons and using a thinner gasket you have solved the loss of compression on 2 cylinders. If compression’s not going past either the valves or rings then it has to be the gasket not sealing somewhere. As Toyah once sang, It’s a Mystery.

[stevieturbo]

oscilloscope and pulse sensor in the crankcase would help pinpoint if a cylinder is showing more blowby than others

But if two cylinders are reading the same, it would kinda point to something that inherently links those two cylinders which would suggest blowing between them

[Graham]

pistons decked and back together with a fresh head gasket the compressions are back.

before everyone came in this morning i ran the engine up, same cam timing and jetting as when i last ran it, pulled out 182bhp from a GTS 2 much more like it, it was stuck in the mid 150's. Tomorrow with a bit of luck i can do some fine tuning and move onto some other cams

[Graham]

if you want to know the realistic maximum number of cams you can fit and test in a day its 6, i ran theses up
GTS2, GTS3, GTS4, GTS6. WR40, BF63.
its not just a case of fit the cam rev it up and move onto the next, some needed running in, plus to make the test a fair comparison you have to warm the engine up to the same temps for each set of tests, then theres all the cam timing swings, finally the results are all multi run averages, ive done something like 180 "pulls" today and used getting on for 60 litres of fuel.

im going to put the 4.75 back in and run it one more time, i have a GTS5 on the way and will run that when it arrives along with some race cams.

Ear defenders or not! and yes i had them on all day, my ears are ringing now. I will post some results when i get a chance to compile them but its clear most of the cams will allow you to time them for a bit more top end power or midrange. Doing that narrows the difference between the cams, but for all these tests i went with the best balance of power/torque, cant give you much by way of numbers now but heres a tit bit.

best power was GTS4 190bhp best torque BF63 163.7 lbft

lowest power BF63 180bhp Lowest torque GTS2 159lbft

so given theres only 10BHP and 4 going on 5lbft difference best to worst on todays testing you can gather the results were pretty close unless you are in the pub.

[Graham]

i snuck into work for a bit today and fitted another cam, i was going to put the newman 4.75 back in, but just for Leon, i used an ACTUAL RL31
peak power was very similar to when i last tried the 4.75 the midrange did differ a bit, but that could be down to many things not just the brand of the cam.

out of interest i then fitted an HT1, that was interesting in that it had good midrange, better than a lot of the cams, but bugger all low down, and it didnt really work at high rpm either just 3 horsepower up on the RL31, so no match for top end power on the GTS4. On the HT1 it was a bit rich at the top so i might of scraped slightly more power with a jet change, but more likely it wanted bigger carbs, and maybe im reaching the limits of the cheapo sportex/ashley 4,2,1 manifold currently fitted to the engine, for me the whole point of this test was to compare cams that might go rallying, if i have to change carbs or manifolds its no longer a direct back to back comparision.

in an ideal world i could re run the test with different exhaust or bigger carbs/chokes ( i used 45's with 38's) mapped ignition, injection or god knows what else, i would love to, but i need to get on with actually earning money

Next week when it arrives ( Burtons have stock so it should be pretty quick) i will run up the GTS5 and i will call the test done but as i said yesterday theres not THAT much difference between any of the cams, but then again the laws of physics are what they are and there are only so many variations on a theme.

[stevieturbo]

How much of a difference is there numerically, valve timing, lift etc between the cams in the first place ?

[Graham]

How much of a difference is there numerically, valve timing, lift etc between the cams in the first place ?

its all in kents catalog, but as we all know that doesnt always reflect true life.

but if you want to look it up, so far i have tested a GTS2, GTS3, GTS4, GTS6, WR40, RL31 and HT1 only the BF63 isnt in there thats on burtons site

[Forest_rallying]

It’s certainly good of you to take the time and expense to test all these cams. It proves that the Man that said you only need four different cams from mild Road to full Race in a Pinto was talking sense. I think Kent have far too many profiles that are just confusing people. I think it’s pointless testing the GTS5 as the camshaft looks very similar to the GTS2 profile. I think the GTS7 would have been a better bet and maybe compare it to the full Race ones that you’re going to test sometime.

I think at the moment with my engine I am going to stick with the ageing BF63 for the time being until I am convinced that there’s a more suitable replacement that won’t result in losing me mid range torque. It’ll be interesting sometime if you could post up all the results, although I do struggle seeing the graphs on my IPad with my rapidly failing eyesight. In the meantime get back to work and earn some Brass to pay for everything that you have spent to bring us these tests. Thanks again.

[Graham]

I think at the moment with my engine I am going to stick with the ageing BF63 for the time being until I am convinced that there’s a more suitable replacement that won’t result in losing me mid range torque. It’ll be interesting sometime if you could post up all the results, although I do struggle seeing the graphs on my IPad with my rapidly failing eyesight. In the meantime get back to work and earn some Brass to pay for everything that you have spent to bring us these tests. Thanks again.

will post some graphs but to be honest 7 cams on 1 graph looks a mess. BF63 had the best torque but weakest top end. WR40 gave close to the midrange of the 63 but hung on well at the top.

[Graham]

in numbers

GTS2 184bhp @6800 159lbft @4900
WR40 184bhp @6700 163lbft @5100
GTS3 182bhp @6700 163lbft @6300
GTS4 190bhp @6700 160lbft @5200
GTS6 186bhp @ 6800 160lbft @5100
BF63 180bhp @ 6500 163lbft @4900
RL31 182bhp @6700 163lbft @ 5100

as you can see despite quoted power bands not one cam gave close to giving any real power @7500 or higher, perhaps 48mm carbs would rev on better or maybe a bigger bore exhaust, but you cant knock 190 bhp on a small bore Ashley!

[Graham]

Before anyone comments, yes i did cock up when scaling the graphs i didnt get the same scale for torque/bhp so they dont cross at 5252, but that doesnt change the results.

For me the real suprises were just how strong in the midrange the BF63 was, and how good the WR40 was, its not a cam i had come across but Forest Rallying suggested it and i do seem to recall Vulcan using it, i can see why, because in this test its basically a RL31 with a bit more top end.

At some point i will run a dgas/single 45/split 45 test again, my gut feeling is out of this lot the BF63 will be the one to go for.

if anyone has a particular desire to see just two or three cams on the same graph let me know and i will see what i can do

[Graham]

righto, ive just run up the last cam for now, GTS5 its a good cam made same peak torque as BF63, although it came in a bit later and held on a bit longer so made a few more bhp at the top.

i was going to put the BF63 back in to do another single carb/splits test but im a bit sick of swapping cams, it wouldnt be so bad if i didnt have to reset the tappets every time, with only an occasional one not needing doing, so something is quite variable, i assume its the followers not the cams? so im going to do redo the split test on this cam.

as a side note ive now run in total 11 or 12 different cams not a sign of any cam wear on anything from kent cams, or the cheap cam followers that im using, which are actually the same as burton own brand or actual kent supplied

[stevieturbo]

different base circles, gonna need re-set every time.

Or are you changing followers too every time ?

[Miniliteman]

Graham,

what conclusions can you take from this test?
All cams sort of give the same power/torque in this spec engine.
Cams with less overlap at TDC give the torque at a lower rpm?
Would a higher spec head / bigger carbs / bigger exhaust give more bhp at least for some cams?

Grtz, Leon.