Best Camphase to suit engine's

[engybenjy]

naah it closes at 71 now at .006" so advertised is about 283 degrees it works out now that the dynamic comp ratio is almost the same as the old static comp ratio.The lobe seperation is on 114

[engybenjy]

picture of work in progress

[Holden202T]

"Green is nice!!" what is that your using for ccing fluid ?

[engybenjy]

I just use water with a bit of radiator inhibitor in it. Runs ok with the glycol in it and cheap and easy to clean up. I am midway through doing a 202 as well and I see you do a bit with methanol I have been helping a local racer with his speedway car on methanol and it goes good seems to be rounding up a few of the V8s as well.

[Holden202T]

good to hear hahaha

[VX L67 Getrag]

WOW this thread has still been moving I forgot about it, hows the boat motor going now?

Is there a list of different GOOD cam specs anywhere in particular for VS 5 Litre & what are the main diffenerences of the common cams like 284 Vs 286 & similar to them?

I've only really put 2 cam's in my cars before 1 was a TQ20 (from memory) in my old Euro Pack VB that was supposed to have a 253, that I may have put a 308 in it & used a 253 eng number (maybe... lol).
The other 1 was a purposes built motor stroked harrop 355 + a bit that I had running HI comp dual throttle body gas research in my VR Calais, wish I still had that car as I sold it because the trans guy swore he'd be able to build T700 strong enough to handle but every 6 months pretty well on the button for 2 years so 4 tranny rebuilds it kept loosing 3rd gear, but if I still had it I would love to see what actual power it was putting out & get teh drive train sorted out!

Anyway I still have all the cam specs floating around & I will post them up when I find them to see what experts think!

[engybenjy]

Took the boat out last week to test it on Nhilacootie and it goes nice pulls my fat customer out of the water on a single so that is good. The cam is a little bigger for the application than I would have selected but it was in there and it was ok so it saved him a couple of dollars. We used the skiier as the dyno and advanced the timing to get the most response off the line but when you get on it up higher in the revs it was pinging so I brought it back to the shop and did some tweeking. First of all I have dissmantled the dizzy and did some welding and filing to reduce the overall advance, it has now got 24 at idle and a total of 33 on the mechanical on top of that I felt the secondaries were opening a bit to slow so I have adjusted that a little (Quaddy) The other thing I have done is modify the wedge adaptor under the carby by welding a divider in it, my idea there is to keep the dual plane manifold dual all the way to the carb. So it hasn't been in the water yet but I believe he is taking out on monday so I will know soon enough and will be sure to report.

I will write and tell you what my ideas have been on the camshafts and some of my theories when I get a break tonight or tomorrow

[engybenjy]

Allright so camshafts, how do you know what works and what doesn't. I have been working on this for years. there must be a way of selecting cams for any engine that will work. right here goes.
for pushrod engines
your have your advertised duration - this is the period that the valve is open from completely open to completely shut or what I call seat to seat duration. In crankshaft degrees
duration at .050" this is the period that the valve is open from .050" lobe lift to .050" closed. (this is important)
the lobe separation or centres is the angle between the maximum lift of the inlet to the maximum lift of the exhaust in cam degrees.
maximum lobe lift is maximum lobe lift- easy
maximum valve lift is maximum valve lift- easy
now if you had for example a blue racer 976810 you would have these specs adv. dur. 272 /.050" dur. 206 with a valve lift of .448"
thats all the specs they have on the web but to get your lobe lift you can divide the .448 by 1.5 (thats your rocker ratio) and you will see that it has a lobe lift of .298".
Consider what the purpose of the engine will be ie street / circuit / etc.
my experience is that on the street people enjoy driving their cars if they have a well tuned mild engine more than a maxed out race style engine. thats up to you.

lets imagine for a second that you were in a controlled class and the above cam was the control but you were able to do whatever you liked to the rest of the engine. and you were not limited by budget of course.

1. match the compression up to the camshaft, this is the oldest and most reliable hot up of them all. first you need to understand the differences between static and dynamic compression ratio. most engine builders know what static comp ratio is ei 10 to 1 etc. understanding dynamic comp ratio is key to getting your engine sweet every time you build it. Dyn. comp rato is the compression ratio you get when you calculate the compression ratio from when the inlet valve is actually closed not from bottom dead centre. if you dont get that do a wiki search or ask me and I can try and explain again.

ok so when does the inlet valve close on our control cam? easy . On my engine I am going to run my inlet lobe centre at 105 degrees after top dead centre. we know that the advertised duration is 272 degrees of crank rotation so half of 272 is 136 so that means the lobe centre is exactly 136 degrees after the valve starts to open. so the inlet valve closing event is 136 degrees after our 105 centre. Does that make sense? therefore the inlet valve closes 61 degrees after bottom dead centre.

that means that the remaining 119 degrees of crank rotation is what we use for calculating the dynamic compression ratio and because the piston speed changes we can use a dynamic compression ratio calculator to do the math or you can dummy up the engine and physically measure the remaining stroke but that sucks. somewhere back at the start of this thread I made an attachment with some maths on it download that and put your 5 litre specs in it using the inlet valve closing value of our 61 and a desired dynamic ratio of around 8.2 and see what you come up with.

this should tell you what your targets are in terms of a static comp ratio.. sweet now you have that sorted we can talk about other stuff that will maximise our control cam.

[VX L67 Getrag]

Can't wait to hear how it went after the NEW adjustments & again your showing you skill over me with my rebuild I sent the dizzy off & had it re-graphed by ignition developments back in the day (screwed if I knew how to do it).

I'm quite annoyed I can't find my exact camshaft sheet I know I had it but mis placed it for now (strange as I have a folder with sheets for everything bought & invoices down to new genuine sump bolts).
Anyway I found a sheet that I've asteriksed a cam so guessing it must be close to it!
it reads advertised int duration 293* ex 295* @0.050" int 238* ex 246* cam lobe lift int 0.345" ex 0.357" & had rockers 24744-16 so I think 1.6 ratio so should have been int 0.552" ex 0.571" with a lobe seperation of 106*.

as I said it was a stroked 308 to 355 with 20 or 30 thou oversize hypertectic dished pistons & measurements I have here vol = 727.65, CC = 8, Dish = 17 & head = 51
so I think was around 9.767 comp ratio

hopefully I will find the spec sheet around but the engine was strong enough to tear the diff carrier for the IRS!

[engybenjy]

i will punch those specs into my calculator and have a look