SladeX

A few questions on the PRC 5.3 heads, basically the goal is a car that drives and pulls hard on the street without breaking the bank. AFR 205 is out due to price. Cam is TR224 0.561 112 and installed already.

So I've got the PRC 5.3 in mind and wondering of I should mill them or not. Anything extra that can be done before they get made up for me like going for smaller cc or something.

Also since this is budget, LS7 lifters sound good for an upgrade?

Car is a 98, so valve covers, coil brackets, PCV are taken into account. Just want to know if anything else needs to be done. I've got headers, underpulley, LS6 intake, ported TB, true duals.

Chevy406

iTrader: (12)

Milling the heads to 64cc chambers and using a .040" Cometic head gasket will net you roughly 11.0 static compression and 8.5 dynamic compression, plus a very nice quench distance. LS7 lifters are an excellent choice for you.

TVWilkes

The PRC 5.3L heads will have 62 cc when you buy them. This will give you roughly 10.7 compression. I would mill them about .015. This will kick up the compression to 11 to 1. I would also run a .04 Gasket. This combo will make some nice streetable HP.

SladeX

sounds good so far... mill to 64cc and use 0.040 gaskets.

MrElectric03

iTrader: (71)

No milling needed...the heads are 62cc out of the box. I would use the comression calculators to be sure of your ratios but with a ,040 you should be golden. With your current mods and a tune to make the most of those parts I would say you are looking towards 420rwhp.

davered00ss

iTrader: (4)

As stated above, no need to mill the 5.3 heads.

Post your results when you get them. I would like to know how those heads do with the TR224.

ZMONSTER!

iTrader: (9)

running a similar cam, on 59cc 5.3's numbers in sig
edit: Im getting some detonation...

jsteele90

iTrader: (13)

my buddy has the 1.5 ls6 heads and a 228r making 439hp

TXZ28LS1

iTrader: (5)

ive seen a few guys on this site running a 224/224 cam with some 5.3 heads and were just making crazy power.

Jon@Texas-Speed

iTrader: (18)

I would do a light mill on the heads something like a .010-.015" and throw a Cometic .040" on with the heads. Get the compression up to 11:1 like mentioned above that the car should make for an awesome street/strip combo. We have done this on several cars now with great results. The throttle response and low end is very nice and the car will make power across the entire RPM band while essentially driving like stock. Let me know when you are ready to order and I will make sure we get you setup with everything you need.

Jon Reynolds

PREDATOR-Z

Milling .015 (if the heads are 62cc) will give you 59cc
That and .040 gasket will yield ~ 11.7:1 Static Compression (SCR) and ~ 9.3 DCR (Dynamic)
wich will force you to run premium and has a too high Dynamic compression. This can lead to detonnation and motor failure.

I used .005 out of hole but yours can be .007 out and make it even worse.

My recommendation NO mill and stock gasket MLS, that will yield ~ 10.7:1 SCR and ~8.6x DCR wich is well within the safe margins for today's fuel on the market

Mark

SladeX

So in worst case scenarios, run 91 octane or even worse 89 octane (problems with stations down south and out west and you can't seem to find 91 let alone 94, running 62cc chambers for a 10.7 static DCR would be the optimal scenario?

Also, under the circumstances, can I get away with running my Comp 7.4 pushrods? Just need to know if its too much preload with the LS7 + 7.4. Worst case scenario is that I remeasure and buy again, but I know that lifters have a preload range so I'd like to know if I'd be safe within it. Currently with the TR224, I needed the 7.4 to get the valve train quiet.

Jason 98 TA

iTrader: (4)

We've shipped tons of 224R camshafts & 5.3l heads with .040" gaskets. If you'd like I could fax you a copy of our 228R dyno sheet with PRC 5.3l heads. That combo made really good power & the 224R is within 4-5hp of the 228R!!!

Jason

Jon@Texas-Speed

iTrader: (18)

That's funny, I'm showing 11.2:1 Static. Don't forget when you are calculating your compression that our chambers are slighly larger due to CNC'ing the chamber. We have run this combo several times without any signs of detonation on 92 octane gas.

SladeX

Any chance you could scan the dyno sheet and PM it to me? Fax isn't hooked up to a landline and I work off my cell for most things.

ZMONSTER!

iTrader: (9)

Well Im running the new 5.3's at 59cc's and Im getting detonation. Kinda wish I hadnt gone so far on the milling! But oh well my choice live and learn!
EDIT: no more detonation! Just needed fine tuning runs fine now!

PREDATOR-Z

So what are the true size of the 5.3 stage 2.5?
Mine were 63cc measured (not all equal)

At 63cc with .040 I get 11.2 but still ~8.88 DCR, still too high for common gas, will require lower advance timing therefore negating the gain in compression.

8.5 > 8.7 is safe more is hit or miss depending on quality of gas and location (temperature, DA, humidity etc...)

SladeX

So... what cc do I want? Isn't stock 67cc, and I think these heads come in at 67cc initially, but can be milled...

ZMONSTER!

iTrader: (9)

59 will work, but you need a VERY tight tune in order to avoid detonation. I would go a little less for saftey sake

SladeX

ok so I want 62 or 63 cc then

the tune I will do myself, I have my current tune bang on for driveability no det even if I floor it in high gear and low rpm, I was pretty nuts about getting all detonation out. I have the AFR bang on for 12.7-12.8 from 2500-6500 so I think I'm good.