Taphee6

iTrader: (2)

Yes, this is an opinionated question. So, whats you opinion. Is 11.77:1 to high for pump gas (93) octane?

Thanks in advance

Also, can you double check my math

Bore 4.060
Stroke 3.82
Deck height .007
-2cc dish piston
gasket .060
cylinders 8
head CC 59.45

ShevrolayZ28

iTrader: (4)

That's a lot of compression. What is your DCR?

TchargedLS1TA

iTrader: (9)

Isnt the LS7 a 11.5:1 pump gas motor?

Patrick G

iTrader: (14)

Totally depends on dynamic compression. You could be running a lazy cam with big duration (like a 240/248 115LSA) and only have 7.8:1 dynamic compression. This would be OK on pump gas. Or if you were running a 220/220 110LSA +4 cam, this might put your dynamic compression above 9.0:1 and the motor would rattle its *** off on pump gas. Again, depends on cam timing. As a general rule of thumb, you can run up to between 8.3-8.5:1 on 91 octane and 8.5-8.8:1 DCR on 93 octane. FWIW, the DCR with the stock '98-00 cam is 6.9:1.

Beast96Z

iTrader: (21)

Pick a cam with a IVC that will put you in the 8:3-8:5 range and you'll be fine.

PREDATOR-Z

I'm running my 370 cid with ~11.7x SCR and 8.6x DCR on 94 octane (US rating), 98 (RON rating), no issues at 26* timing.

cws T/A

iTrader: (3)

what DCR does Pat G's cam put a Stock 00 ls1 at , can I mill my 241's

Patrick G

iTrader: (14)

It brings the stock DCR of 7.0 up to 7.9:1. If you mill your heads, that could bring your DCR up to the magic 8.5:1 level.

cws T/A

iTrader: (3)

Think this combo would pull 400rwhp my stock 241s , milled for 8.5 DCR + your highlift torque cam + fast 90/90

SStrokerAce

iTrader: (2)

Nope your screwed 11.75:1 is all you can do on pump gas.

Bret

gollum

iTrader: (1)

Good question.

Patrick G

iTrader: (14)

If your car is a 6 speed with all the bolt-ons and a good tune, it should hit 400+rwhp with ease.

DAPSUPRSLO

iTrader: (14)

Remember, it's not just dcr that comes into play either. It all depends on the cylinder pressure your motor generates. The lsx manifolds are probably more sensitive to compression considering they work much better in the midrange then the single plain/sheet metal intakes and more time for detonation will be present in the midrange then in the higher rpms. So basically if you have a high rpms type setup (via intake tuning) you can get away with a little higher dcr i'd think. Also, your heads combustion chamber, heat range on the plug, yadda yadda all in the combination will make or break your tolerance for pump gas.

Hell, if you didn't ever go wide open throttle you could probably get away with 13 to 1 on pump gas but as soon as you go wide open, unless your cam is silly silly late on IVC then you're going to have a pop corn machine

Taphee6

iTrader: (2)

If I remember correctly on my current set up cylinder pressure is 200.

JL ws-6

iTrader: (50)

I went 11.8 to 1 on my new build, not concerned with it being too high one bit. It will be fine.

DAPSUPRSLO

iTrader: (14)

Yeah, but that's during a compression test though. Now think about all the effects that intake tuning and exhaust tuning cause at different rpms on cylinderfilling resulting in more or less pressure in the chamber, which can't be measure with a compression test