70caminoman

I found some info on one of the racing threads where Martin (former Tick employee) helped a user with some cam selection. Well I'm building a 2000 trans am for my wife and I want it to run as good or better than my car (70' Elco 355 NA SBC, 11.75 @ 113). Well, I was super impressed of with one specific member on ls1tech that has had incredible results with one of Martin's Tick cams.

https://ls1tech.com/forums/11-second...goes-11-s.html

He used the torquemax S1 cam in a basic bolt on car. My wifes combo is similar here is the summery of the build. 4l60e built to FLT stage 4 specs, yank ss3600 converter, 3.73 gear, drag radials, stock suspension. Engine: compression bump to 11:1 (milled 0.025" and 0.041" gasket), worked over 853's, ported LS1 intake (for now may move to Dorman lS6), ported TB, 85mm MAF, just a basic rebuild with the necessities and attention to detail. Exhaust, 1 3/4" TSP LT's, 3' y-pipe with dual cut-out's before the merge. SLP LM1 catback.

Here is what I was thinking around cams because I would like to grow a little bit in the future as far as the induction system goes. The S1 specs use comp LSL lobes from what I can tell and I calculated out the cam events as follows;

DUR 223IN 227EX 111LSA +2*ADV
0.610" 0.614"

@006
EX 25.5 ATDC IN 27.5 BTDC
71.5 BBDC 65.5 ABDC
53* overlap
@050
IVO is 2.5 ° BTDC ( - indicates ATDC)
IVC is 40.5 ° ABDC
EVO is 46.5 ° BBDC
EVC is 0.5 ° ATDC ( - indicates BTDC)
Overlap is 3 °
I looked at your other cams and it looks like he tried to achieve the same intake closing point to achieve max compression. I also liked the exhaust opening point so that the cam will have some upper rpm capability but not late enough to loose any torque. I wanted to try and give the motor a little more cylinder filling ability without hurting any of the low RPM characterisitcs of the S1 cam and here is what I came up with.

DUR 227IN 227EX 110LSA +3*ADV
0.614" 0.614"

@006
EX 25.5 ATDC IN 31.5 BTDC
71.5 BBDC 65.5 ABDC
57* overlap
@050
IVO is 6.5 ° BTDC ( - indicates ATDC)
IVC is 40.5 ° ABDC
EVO is 46.5 ° BBDC
EVC is 0.5 ° ATDC ( - indicates BTDC)
Overlap is 7 °

So you can see that the intake opens a little earlier giving it a little more filling ability and closes at the same time. While the exhaust events remain unchanged. it also has a little more overlap @57* vs 53*

The only thing that I am unsure of is what Patrick has spoken a lot about, which is the Overlap of a cam being biased straight up, or more towards the intake side. I understand that some people like to say that it has to do with how much advance is ground into the cam or adjusted to on installation, but that does not jive with me. To me overlap being biased towards either side can only have to to with the IVO and EVC events. At TDC during overlap period the intake is starting to open and exhaust is closing. Any bias to me only makes sense when you refer to those two events, not how much advance you put into the cam. In addition to that Patrick usually refers to how this bias helps the power carry past peak RPM.

Patrick feel free to chime in i really want to understand this!

Oh and in case anyone is wondering I have been a long, long time lurker. Usually don't post unless I can't find what i need and I am really obsessing about this right now.

Thanks for the help everyone
Eliot

Fbodyjunkie06

iTrader: (10)

Slumaro's car definitely works well. His combination as a whole works well and that is why his car runs the ET's it does.

Your wife's car sounds like a good starting point with the supporting modifications she has already. A 3600 stall and 3.73 gears will open up more doors in terms of camshaft selection.

With the heads milled .025" and a thinner .040" gasket you need to be careful with that 7* BTDC IVO event. IMO that's too early for the heads being milled and running the thinner gaskets and will have too little P to V.

I wouldn't go any earlier than 5* BTDC to keep P to V kosher. With the 3600 stall and 3.73 gears you could also close the intake valve a bit later to capitalize on inertia ram cylinder filling at the end of the compression stroke. I'd push it out to 41-42* ABDC.

When I spec camshafts for a given application, I look at the relationship the valve events have in regards to one another. Like for this application for instance, with a 41-42 IVC I would have at least a 47-48 EVO. I feel like if the relationship between the IVC and EVO is smaller than 6 numbers in a cathedral port application like this one, then the engine will not RPM as well as it could. I usually am anywhere from 6-10 numbers on a cathedral port application similar to this one. Since the IVC event determines how much mixture is trapped and the EVO event is the main factor in how much is expelled they have a symbiosis in relation to one another.

As far as biasing overlap to the intake side or the exhaust side, you are correct as that is based 100% on valve events. Where the intake valve opens and where the exhaust valve closes. I look at total cylinder displacement versus valve diameter to help determine how much overlap should be used. Usage of the vehicle, engine size and all parts being utilized play the biggest role in determining this figure.

As far as how it is biased, that is going to be based upon a lot of differing parameters. Intake manifold design, cylinder head flow at low lift, throat diameters, header tube diameter, collector diameter, vehicle weight, rear gear ratio, stall speed etc. etc. etc.

If you wanted a little more high RPM cylinder filling without hurting the bottom end of the SNS Stage 1, this is what I would do:

226/230 .612/.603 111+2

4* BTDC IVO
42* ABDC IVC
48* BBDC EVO
2* ATDC EVC

Hope this helps!