Has anyone looked into this or has had 853 heads CNC ported and milled to up compression and has had good results? What would it be comparable to? I'm in the early research stage of possibly changing my heads to get more power, as it's the current choke in performance for me in my NA cam build. Other than new valve stem seals, dual springs and Ti retainers, and cleaning up old carbon build up, I'm still on my stock 853 heads. Currently at 397WHP and 400WTQ is good fun for the street but I think I'm getting used to it by now and doesn't thrill me as much as it used to anymore. I'm looking to do an effective and cost efficient heads upgrade and want some guidance and what should be my honest expectations of torque and power gains.

Goal: +40whp, hopefully +50whp. I don't think I can justify the heads expenses and work for anything less. If optimized 853 heads are a waste of time, money and energy then I'll ditch the idea altogether.

Current mods:
Stock 853 heads
JEGS/Elgin/Sloppy "Stage II" .585/.585/228/230/112LSA.
TSP 1-3/4 Long Tubes and decatted X pipe
Magnaflow XL mufflers w/ bypass mod
42# injectors
K&N Cold Air Intake
LS6 Intake Manifold
Supporting: SD Dual Valve Springs, Hardened Push Rods, LS7 lifters, Trunnion Upgrade, Melling High Pressure Oil Pump, 160F Tstat, LS2 timing chain
93 Oct, Dyno tune
Current Power: 397WHP/400WTQ on DynoJet

 

Can't speak for gains on 853 heads, but on LS7 heads, it's pretty well accepted that there's virtually no gain from porting, and all the HP increase comes from the increase in compression from milling them. Granted, they are very different heads.

I would think port matching with the intake and exhaust manifolds would yield as much or more HP than porting the passages, but idk for sure.

 

You’ll need a good aftermarket head if you want to gain 40-50hp

 

That's what I'm gathering so far from what I've been researching. I'm looking into the PRC 2.5's of TSP. Some seem to be at or below the 1.5k range. I just have to research what would seem to be the best suited head for my cam and my NA goals and of course budget. PRC 225cc As Cast and PRC 2.5 CNC'd LS6 heads seem to flow very similar, at least CFM wise.

 

If you spend $1.5k on heads plus the new head gaskets and bolts you’re pushing past $2k easily plus retune.

I’m guessing you’d get tired of that too fairly quick. The hp gains aren’t the same as the torque gains.

Maybe spend the money towards a used supercharger kit? That should entertain you for a while longer.

 

Per the Texas Speed Tech in my email to them looking at their CNC package for these heads.

”I would rather you pass on the Heads find some 243s from a ls6. For the price you pay for us to port 241s they will flow the same numbers as a stock 243 head.”

So passed on that. And then thought about sending in a good set of 5.3 small bores. But i the ended up going with the PRC 225s...I got them decked and set for higher compression and with their set up no worries with PTV clearance.

 

Have you dyno tuned yet after the PRC 225's? What other mods you have and what were your results?

 

Still in the middle of my build. Working on getting engine back together. Should be a little over 400HP and close to 400TQ to the tire through an M6.

 

You may get 50 rwhp with a FAST92/LS2 tb and Advanced Induction Ported 853s and maybe half the torque.

 

I need some help guys. So I did this time-consuming, comparative analysis for kicks and giggles to see if I could see an easier clear winner for me. After all this comparative research, I haven't reached a good conclusion other than just getting 243's and rebuilding them with AI is not good value compared to the rest. Purely on a dollar per average CFM gained, I'm gravitating towards TSP PRC 2.5 CNC'd LS6 or AI CNC'd 232cc 243's. Again this is all a very generic and meaningless study since it's never really just about CFM, but also about an optimum combination. I wouldn't like to lose any torque that's for sure, and I'm already at 400ftlbs of wheel torque. Thoughts?

 

I did 436rwhp/415rwtq on a Futral 228/230 112+4, TEA Stg 2 5.3s ~59cc chamber, Kooks 1 3/4, 3" X pipe, no cats and necked it down to 2.5" after the X as I wanted to keep velocity up for torque, everyone wants to do 1 7/8" and 3" to the over axle pipes now. I was on a LS6 intake. ported stock TB and Halltech TRAP intake.

Another recent build with good results:
https://www.corvetteforum.com/forums...1-results.html

 

I built my 02 Z with these parts and got 450 RWHP

Patriot Performance Stage 2 Heads. Increased compression.
Home Ported FAST 90 & Home Ported 90mm TB
England Green Whiplash Cam
42 lb/hr injectors
VARARAM.
1 3/4" Stainless Works LT SS Ceramic coated headers
3" CAT BACK system with High Flow Random Tech CATs
Tuning

 

youll tire of intake/head gains porting in an afternoon. Call Mamo be honest in your expectations. Spend once.

 

I'm not familiar with Mamo. I don't know, I think a 40whp bump will feel great. I'm making pretty good N/A torque right now and where I would like to see more gains is up top. My torque just quickly tapers down after 6-6.5k. I can literally feel it on the pull (and read it on my dyno graphs) how it slows down the rate of acceleration past 6k. I think I could benefit here with the heads. A supercharger kit is simply out of my budget, even a used one unless it's a bargain. I also like the idea of knowing I have maximized/optimized my bolt-on LS1 N/A setup so now I'm getting that itch that I've left N/A power on the table because I don't have better heads.

 

Tony Mamo (Mamo Motorsports) was an engineer with Air Flow Research (AFR). He designed most (all?) of their LS head products. He's independent now. Definitely a leader in the LS head design & porting field.

 

I have read the flow charts 243 heads outflow them all pretty much. No use porting a old 853.

 

Your statement and this chart are very much in disagreement.

 

https://www.lsenginediy.com/ultimate...r-heads-guide/


also i didn't see where a 853 had ever outflowed the 243 before or after CNC with your chats maybe I am missing something.

 

So far, my runner up is the TSP 2.5 CNC LS6 (243) heads, with TSP providing their seasoned heads, followed by the TSP 2.5 CNC 5.3 heads as 2nd runner up. Just not worth it for me to go hunting for a donor plus shipping, when they can provide castings and it ends up being close to the same $ (unless you get a steal for used 243s). The intake CFM on the TSP 2.5 LS6 heads is just phenomenal at least based on the charts.

PS: I didn't put them on the Excel table, but I just noticed that Ai's 706/862 5.3 heads flow tremendously especially on the exhaust CFM (269CFM at .600). I just don't know how I could really benefit more from such a high exhaust CFM vs. having a higher intake CFM on TSP's 2.5 LS6 heads, and Ai's CNC services are up there in $.

 

Indeed some new new 243 heads are already costly at 700 bucks for performance heads from gm. I ordered a set about a month ago.Plus another port and polish job to maximize flow. I have some 853 In my garage I would indeed let go for cheap. There straight and just need to be rebuilt and cleaned. I dropped a bolt in one of them when I was removing it. There near perfect 853 original cathedral ports round exhaust hook up. I looked into flow because I’m building a ls9/ls6/ls2/ls1 Frankenstein compound boosted c5.