Ben16SS

I’m building an lq9 with 243 heads so essentially an iron block ls2. My question is what kind of dynamic CR am I looking at with this cam? I’ve tried a few different calculators and some seem to put it over 8.5 which is no good for pump gas. but this is what tick recommended so I am assuming I’m calculating wrong. Any help I’d appreciated thanks all!
The car is a 73 firebird. It will have at least 3:73 possibly 4:10 gears haven’t decided yet.
car will also have a manual transmission.
Tick Performance "SNS" torqueMAX Stage 2 V2 Camshaft for LS2 Engines
Standard Lobes: 231/235 | .625"/.605" | LSA111+2

Bob570

Your DCR will be well within what's safe on pump gas. Unless you've cut those 243 heads way down.

Ben16SS

what formula do you use to figure this out?

Bob570

Sorry, I don't actually know how to calculate DCR. But if you have the same compression as a stock LS2, you're going to be fine.

Ben16SS

Have you run this cam before or what are you basing that off of?

RedXray

I'm running the TSP v4 which is almost identical spec wise (231/234 .629" .615" 111+2). Both the SnS & v4 has the intake closing at 44.5 ABDC. The sooner you close the intake valve the more dynamic compression you build. I'm running a static 11.2 compression in a LQ9 with PRC heads and have no issues with knock on 93 octane. The online dynamic compression calculators need the duration specs @.006 to work correctly and sometimes those specs are hard to come by.

Darth_V8r

iTrader: (4)

It is pretty complex. You have to start with the IVC at 006, which tells you to where the piston it in crank rotation. Use sine/cosine functions to get how far down in the cylinder the piston is. Use that position to figure out your cylinder volume at IVC. Then use your volume at IVC / volume at TDC to figure dynamic compression ratio

Ben16SS

That cam does look very similar. My main concern is I only have 91 octane where I live. Yeah the intake valve closing point was what I noticed that initially concerned me.

RedXray

You didn't post what vehicle you have. The more the load the more sensitive it's going to be toward knock. You can tune for 91 octane if you keep the static reasonable. Work on the quench and try to avoid using a thicker head gasket like the LS9 unless you're going boost or nitrous. Are you planning on doing the tune yourself or...

99 Black Bird T/A

iTrader: (4)

I don't think it will be an issue.

FWIW - I have a carb'd Dart 400 Small Block Chevy SHP iron block that has roughly similar cam timing 230/236 LSA 110+2 with 10.85 to 1 static compression. It will ping if it's 95+ degrees in the summer on very low/no humidity day without octane booster at light throttle low rpm. That's with no electronics and ~34 degrees of timing on 93 octane.

Your iron LS2 with 243 heads will want even less timing and has precision fuel control w/knock sensors. I don't think you'll have any issues provided the car/truck has a little bit to gear to help it get rolling from a stop.

jlangley

iTrader: (8)

The Wallace racing calculator for dcr seems good. As previously mentioned you need ivc at .006 not .050.

Ben16SS

sorry I updated my post. Car is a 73 firebird 3:73 gear minimum and a manual transmission
as far as tuning goes I will be running a Holley terminator x system.

72tutone

I too was looking at this cam. I asked summit racing and they recommended a few cams. But, the tick looks appealing. I'm running 799 heads as well on factory lq9 flat tops.
It seems for our compression ratio with heads are anywhere from 11-.11.2 scr in this combo. But, having combed over this to death, it seems anything over 40 ABDC IVC @.50 will put us close to the 8.5 DCR. So, anything over 40 ABDC should be good.
Ive also emailed tick about what cam recommendation and they said the exact same one but I believe it was the ls1 model with 227 intake

But the ls2 231/235 will put your ABDC @ 44.5 which is a good number. The 227/235 puts me at 40.5 abdc. Which is right on the cusp of 8.5 dcr.

I emailed back the rep who I was talking to me, Chris Henson and asked for the .006 seat to seat and havent heard anything back.

My BTR stage 2 turbo cam was 226/231 113+4 cam and at .006 it was 281/286 adv duration and a 69.5 IVC .006. This puts me right around 8.5.

So knowing that information, I think somewhere 40+ ABDC should be ok. Now the piston to valve clearance scares me now too. From what I hear with the cam vendors they will not accept a return if its been installed. I'm not sure how else you go about checking p-2-v without the cam installed. I'm sure a whiz bang math guru will explain how to do otherwise.

But if you run this cam, let me know if it clears and it works out for you