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853 to 243 headswap...

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Old 07-12-2006, 01:14 AM
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Default 853 to 243 headswap...

I've been reading through pages of threads concerning this topic, mainly discussing the gain in power between the 241 and 243 heads... My car has the 853 heads on it and I was wondering if I could hear some opinions on what I plan to do. What I really want to do is buy some AFR 205's and slap them on, but being that I'm not done with school yet I can't afford a $2300 set of heads...

What I can afford though, is a set of stock 243 heads. I plan on buying a used set along with some ARP head studs and some injectors (my car has the 26 lb/hr injectors ). From what I've read, this will bump compression up by about .4 and benefit from the better flowing head design. With my TR224 cam and full bolt-ons, would this be a wise choice for me to make? Unfortunately, money does play a factor so porting/polishing the 243 heads before they're installed is out of the question. The install would be done by me, so no install fees there.

I would like to see a 20rwhp gain out of the head install, is this a reasonable goal or am I over shooting? Also, would a set of 30 lb/hr injectors be up to the task? Any feedback is welcome.
Old 07-12-2006, 02:19 AM
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not trying to hijack but i too would like to know this...exact same predicament sp? that im in too....school sux..
Old 07-12-2006, 12:52 PM
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Anyone??
Old 07-23-2006, 12:13 AM
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what would the gains be from stock 853's to ported 243's.... flow #'s anyone got them?
Old 07-23-2006, 12:27 AM
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I would say 15-20 hp, and I think your injectors would be fine with your current setup.
Old 07-23-2006, 01:47 AM
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i did the swap. i used stock gaskets though. if i were you, id go with something thinner..a .040 or something. My tune was very shitty, it had knock and i got rid of my duals and got the stock muffler reinstalled. I swapped from the f10 114 to the f13 112 and an asp pulley and went from 377/372 to 396/366. Not much of a gain, but the tune and muffler had a lot to do with it. Ive got a new motor going to be installed next month, so i know these heads will flow a bit better than the 853s. Ill save up and get a better set in the future.
Old 07-23-2006, 01:52 AM
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I did the swap but i had a set of ported ls6 heads. I gained 40rwhp with my head swap i dont see why u would not get 15-20rwhp.
Old 07-23-2006, 01:56 AM
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how thin are the GM gaskets? had got a set of graphite victor reinz gaskets... should i go with something different
Old 07-23-2006, 02:03 AM
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Between 20 to 25 rear wheel horse power is what I have seen.
Old 07-23-2006, 02:16 AM
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I think the gaskets are like .054 for the stock graphites.
Old 08-02-2006, 04:48 PM
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For anyone that's interested, I've posted my results of the headswap in the dyno section. Here's the link:

https://ls1tech.com/forums/showthrea...00#post5285200
Old 08-02-2006, 09:46 PM
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I'm doing the same thing very soon. I have Cometic .040's, but I may have to go back to stock thickness gaskets, because from what I'm hearing my cam may be too tight P-to-V
Old 08-02-2006, 10:26 PM
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well i am going to be doing this soon. i am going to do a little porting myself. nothing major just getting rid of the rocker boss and a little cleaning up on the valve guide. hoping to gain about 20rwhp. i am also going to be milling mine alittle so i will be at 11.0:1.
Old 08-03-2006, 12:03 AM
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That is a pretty good gain were they ported at all?
Old 08-03-2006, 01:45 AM
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Ubergeist, no porting or milling at all on these heads. They were taken off a '05 GTO. All I did was swap a set of LS6 valves on the heads, clean the mounting surface with a scotchbrite pad and bolt them on.
Old 08-03-2006, 08:54 AM
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The heads will probably only gain ~15 HP. youre 853's dont flow too bad. Youll gain a bit of torque with the tighter quench and added compression. Id spring for the budget ported LS6 heads and gain 30+ HP for an extra 400 bucks...
Old 08-03-2006, 11:07 AM
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Thanks for the advice GuitsBoy, but I already did the swap and posted my results in the dyno section. I ended up gaining 35 hp and 25 lb/ft to the wheels with a set of stock 243 heads.
Old 08-03-2006, 11:30 AM
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Sorry I missed that! WOW, Those are impressive gains! Did you retune for the heads? My guess is that people who see gains that big are few and far between. Im very impressed though...
Old 08-03-2006, 12:14 PM
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No problem, my car was re-tuned for the new heads and fuel injectors. First pass made 396, second pass made 405, then on the third and fourth passes put down the 411hp. There was about 10 minutes of cool down time between runs, except for the last one which was only about 5 minutes of cool down.




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