bigfatls6

iTrader: (34)

I have a lq4 complete long block That I am going to install a cam in. I want to up the compression from the stock 9.4:1 so I would like t oknow what would be best to have the stock 317 heads milled and ported or have a set of 241s I have laying arround ported? Which ever head I use I want to run it on the stock lq4 short block. I have heard the 317s are basicly the same as ls6 or 243 heads but with larger chambers.

dwfronk

This may not help much but i am having my 317's ported but not milled due to a different set up. I have seen a LOT of ppl on these threads port and mill there 317's, but i dont know how many have a set of 241 heads laying around.

bigfatls6

iTrader: (34)

I have the 241s laying arround because they came off of the 2002 ss in my sig when I swapeed them for PRC stage 2.5 5.3 heads. The 241s are nothing special just have smaller chambers to get the compresion up. Im wondering how milling the 317s affect the flow numbers on them even when they are ported.

02*C5

iTrader: (1)

1. How much compression are you lookign for?
2. Whats your final objective with the LQ4?

bigfatls6

iTrader: (34)

The Lq4 is going in a fox coupe mustang that weighs about 3k. Building it as street/strip car. I mainly want to try to get the compression to about the same as a stock ls1. Im not that concerned with Hp numbers but I want it to run strong 1/8th and 1/4 mile. I don't want the low compression to affect my cam choice. When I have a problem with the stock lq4 I will use the block to build a 370 or 408. I also plan to put a 150 hp of nitrous on it .
The car will be a stalled a4 with 373 gears. Fuel injected haven't selected a intake set up for it yet.

02*C5

iTrader: (1)

Now if your looking for good flow I would really think of doing 243s. Me you I would sell the 317s and the 241s and get a set of 243s ported polished bring the chamber down to about 61CCs and you'll bring that compression up on the LQ4 to about 10:1 The pistons while the dish is not too deep, remember that 241s have 66cc chanbers and have a 10:1 compression with flat top pistons. The 243s with the 64CC chambers gives you 10.5:1 on flat tops. The 317s have 72/73CC chambers and it would be unsafe to try to mill them down to what you need to get what you are looking for.

Hope it helps.

wws699

iTrader: (3)

Unsafe? Could you explain in more detail.

Thanks

LTX355

iTrader: (15)

milling them to much will cause issues like bad valvetrain geometry if you dont take measurements, depending on cam tight piston to valve clearances and not to mention a weaker head due to excessive material being removed. not good if u plan on a 150 hit or better down the rd

ramdaspadhye

iTrader: (3)

TSP stage 2.5 5.3's or TEA's stage 1.5 or 2 5.3's

02*C5

iTrader: (1)

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Thats the case with the 317s to bring down your chamber CC to make a differece, there is only so much material you can take off around the chamber, you will have to take way too much of the deck and it will be very unsafe to run a head like this even with ARP studs you will encounter degradation with time and the heads can literally explode off your block. Specially if you are adding N2O or any other type of power adder.

ramdaspadhye

iTrader: (3)

You can safely mill up to .035 off the 317's... I say keep em and go turbo

LSxPwrDZ

iTrader: (4)

Stock compression on the LQ4 is advertised as 9.4:1 but actually calculates to ~9.56:1.

Here is a stock bottom end LQ4 compression calc breakdown using stock LS2/LQ4/LQ9 Head Gaskets:
72cc - 9.47:1
71.06cc (stock 317 chamber) - 9.56:1
71cc - 9.57:1
70cc - 9.67:1
69cc - 9.77:1
68cc - 9.87:1
67cc - 9.98:1
66.67cc (stock LS1 241/853) - 10.01:1
66cc - 10.09:1
65cc - 10.20:1
64.45cc (stock LS2/6 243) - 10.26:1
64cc - 10.31:1
63cc - 10.43:1
62cc - 10.55:1
61.15cc (stock 5.3 706/862) - 10.66:1
61cc - 10.68:1
60cc - 10.80:1
59cc - 10.94:1
58cc - 11.07:1
57cc - 11.21:1
56cc - 11.35:1

I'm running some 5.3 heads on my LQ4 stock bottom end in my TA in my sig. Only mods on the heads was to put the factory LS1 intake valves in place of the smaller 5.3 valves. Chamber volume didn't change which put my compression right at 10.66:1. It's a stick shift car with a G5X3 114lsa cam and a 3.73 gear which is way too tall for the 28" slick I run and best to date on completely stock rear and stamped steel suspension was 12.2@119mph NA and 10.91@128 150 wet shot. Vid in sig of the 10.9 pass.

wws699

iTrader: (3)

Thanks,

I was asking because I have some Stage 3 317's on my 408 with 12:1 compression and Diamond flat tops. How much do they mill off to get 12:1? I want to run more than 150 on the jug.

mark21742

With the 408 you are compressing so much more air than the stock 370 that you chambers can be a lot larger (milled less) and still net higher compression ratio. On my 404 with 61cc heads, dished pistons and valve relies om at 11:1... You might still be around 68-64cc chambers. I'm on my cell and don't have my comp ratio app on here to give you the exact cc of your heads


Goto wallace racing calculators, punch in your numbers and it will tell you what you have

wws699

iTrader: (3)

Thanks,

Bore: 4.030
Stroke: 4.00
Head Chamber (cc's): 67
Valve Relief / Dome (cc's): -2
Gasket Thickness: .051
Deck Height: 000


Now I understand why the OP should go with the 243's on his 370, gotta take to much material off the head to get the compression up. Thanks for the info

So would It be safe to assume that I'm ok to hit it with a 200-250 shot?

mark21742

I'd think your heads could take the shot with no problem as long as your timing and a/f ratio are tuned for it, and to be safe I'd run 100 octane unleaded or higher when you plan on hitting it with that big of a shot(just dump in a few gallons on race day).

One of my frends is running a 346 big cam(25x duration) with dome pistons and big valve ported and milled 5.3 heads on 112 octane unleaded race gas... 14:1 compression 350 combo 2 stage wet/dry shots and his motor holds together

Just curious what is your dynamic compression ratio sitting at with your cam?

wws699

iTrader: (3)

I wish I knew, I got a "Smokin deal" on the long block from a local member who purchaced an SS from a guy in Texas, the car ended up catching on fire so I got it for dirt cheap. All the info that I have about the setup I pulled off this site from the original owners posts, the rest of the little details I'm still trying to figure out.

How do you figure out DCR?

mark21742

same place different link at wallace racing calulators

I miss being home and the home computer lol kinda limited on my phone while driving