Cam Headaches & Interpreting specs.

[Anonymous]

This is an E-mail I sent to C.O.M.E cams after looking at their internet site, with replies marked.

Like your grinds. Im a bit confused about one the CSBH-450 (is a 208 215 at 50) says it is used to make over 300 hp in the ST2 engine, the 351 Clevo. It also says that it is used in the ST3 Holden and ST3 Chevs.
On milder versions of these engines.

When I looked at the dyno (their dynoe comparisons)
comparisons on these engines (presumably as it says with this cam) the peak for the chev and holdens with the ST3s was well over 5000 rpm but for the ST2 clevo it was only 4750rpm. This makes me think it is not the same cam but another being used in the ST3.

Reply. "These are different cams".

I am intending to pull down my Ford 250 2V engine (Different head
casting is a pre-crossflow) out of my 4 speed manual Cortina. Im not
happy with the cam I bought from Camtech its a 204/204 at 50 .420 lift 1.5 ratio. Its similar to your HVH 308 I think. I believe mine peaks at about 4000rpm and has no hope of making power at 4700rpm as Camtech said.
Thing is, Im not going to buy a cam unless I can be sure it peaks
between 4600 and 4800 rpm, preferably 4600. I noticed you have one that is a 205/214 at 50 and it says it is the equivalent of the HVH 308 is a
203/204 at 50 similar specs to what I have.
I like the 205/214 (think it will go higher than HVH 308) but I am still
very wary of getting something similar or same as a I already have. Maybe the CSBH-450 (want dual pattern) would be OK so long as it is a 4750 "peak" cam, not over 5000rpm.

Reply below.
"You need our CLH-191 or our CSBH-462 grind to peak as high as you are
asking. That assumes you have large enough induction and compression
ratio to feed the engine. The cam is only one link in the chain."

My Coclusion
Both the cams they recommend are a lot higher duration than anticipated to get the peak HP at the level I asked for. The specs on these cams are CLH-191, 217/218 at 50, 435/440 lift, 114 lobe sep range 1800-5300rpm. The CSBH-462 is a 218/222 at 50, 461/461 lift 112 lobe sep range 2200-5500 plus.

 

[aussie7mains]

Either of those two will give peak power around 5000rpm, you are using mechanical tappets I hope.
Ive run bigger cams than that in 2vs and they will go to 6500 with webers or similar, but a word of warning they wont be happy with a slushie, go toploader of BW single rail, use 250mm clutch from AU OR similar.
Your cortina will be plenty fast once sorted out. You would be well advised to get a LSD, unless massive one wheelers are you thing.
2v definately work better with triple webers or dellortos, then you can run even more cam without loosing low down manners.
A7m

 

[addo]

Jeff, what about triple HS-8s, compared to the D'Os or Webers?

 

[Anonymous]

Thanks Adam and A7Ms
I have decided to stop playing around with the Cortina and get it to "GO". Im just not sure how far to push the limits. To tell you the truth I am new to all this and am surprised at how well it performs now up to only 4000rpm. It puts the AU and a BA (auto) to shame at low rpms.
Im obviously no where near its limits yet (nor do I want to be) but pushing to around 5000 rpm seems reasonable (with bit more head work and bigger valves).
The number of CAM obtions out there is staggering (they dont advertise them all) and even ones that appear very similar can behave very differently. I dont know how anyone makes a decision. Every time I think Ive got it all worked out, I learn something unexpected and it puts me back to the drawing board again. I am after something a bit different.

A7Ms (or others)
I dont think my 500 Holley will work with these cams in a 250 2V. Do you know if a 465 4bbl or something else like it will.
Any other suggestions.

 

[Anonymous]

What are mechanical tappets?

 

[Anonymous]

Got this quote from Wade cams web site. I assume this has something to do with mechanical lifters.

Q: Which type of cam should I use, Hydraulic or Solid?

A: It really comes down to what you are using the engine for.
Is it a competition engine or one which will be used mainly for every day use?
In most cases, if the engine isn't going to be used above 5500 RPM then a hydraulic profile should be adequate.

If however, the engine is going to be used around the 6000 - 6500 rpm range, then you can still use what is known as Anti Pump Up Hydraulic lifters.
Revving the engine higher than 6500 rpm would require using solid lifters.

 

[aussie7mains]

OK
Triple webers or dellorto have a big advantage over all other types as
They can be infinatley tuned.
When you have isolated runners with one carby throat per cyclinder you dont get adjact cylinders disturbing carburation, especially with large overlap cams IE a can like the old fasioned 35-70 waggot idles rough as guts with single or triple SU, but with triple webers is like a shopping trolley, smooth as silk.
Triple dellortos are my preference, they will give best torque.
Tim your 500 will work with the 220degree cams (about a 30-70) but it may be a bit too big and a 350 would be better, maybe something like a 350 venturi on a 500 throttle might be best compromise. Sixes like twin carbs like two weber down drafts even a couple of stockers on a suitable manifold should work well.
disco and I cut up a couple of stockers with twin dvg to try but never got onto a car. This should actually work well.
Solid lifters are definatley my preference even with 5000rpm, they always seem to give better torque with less duration, hydraulic is ok, but solids are the ducks guts, pity they will add a bomb to your costs.
Hope this is of some help
A7m

 

[xctasy]

Wow A7M, some great stuff there!

I've been thinking about what I think is reversion in high lift, lower duration cams with 350 and 500 cfm #2300 carbs. I've always believed it is best termed as a 'reverse pressure wave travelling up the intake manifold, upsetting stable air/fuel atomisation'

I've felt that this problem is due to too much signal. However, my thinking, for the first time, is now that on a 2-bbl synchronised carb, a greater signal may be a good thing.

Looking at a stock 350 PN 7448, there is a 1.4375 divided by 1.1875 signal, or 21%. On a 500 PN 4412, there is 1.6875 divided by 1.375, or a 22.7% signal.

When you mix'n'match a 350 venturi body to a 500 throttle, you get 1.6875 divided by 1.1875, a massive signal of 42%. Does this fix carby spit back entirely?

Just curious, because on 390, 660 tunnel rams and even 450 cfm spreadbore Holleys on stock 350's with high intensity cams, people find signals above 35% cause reversion. 1150 cfm Domiantors with bigger throttle plates, used in Pro-Street Racing, run just awfully when the signal is more than 15%.

 

[Anonymous]

My sister has an EAII, with CFI and a 4-speed. Without any problems, too

Anyway. I am curious about running straight gas through dual throttlebody injectors. I have a suspicion it'd be more boost friendly due to the point at which the fuel is added to the intake charge, ie not onto the backside of the intake valve, but into the plenum, where its got a greater chance of fully evaporating, hence cooling the mix down that much more..

I wouldnt mind doing some calcs on that one actually, does anyone know the specific heat value of LPG, or propane in general? My chemistry books dont seem to list it..

 

[addo]

Happy metrication!

http://www.propaneplus.com/propane_info.htm