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Discussion Starter · #1 ·
Hi All,

I am replacing the Thunder Racing Stage III LS6 heads on my 427 C5R motor with the new AFR aluminum heads at minimal cost to me. The valve train, cam, and compression ratio (11.0;1.00) will all remain the same. The LS6 heads flowed a healthy 343 cfm at 0.500 lift. I am told that the AFR heads are the best available and will outflow, and outperform, anything else on the market. Any one of you Z06 performance predators have data or an opinion on this?? I am told to expect an additional 20 rwhp or so just from these heads. Thoughts? Thanks y'all... :coo: :D :jammin:
 

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Based on my research

ScDFaCHE,

The highest h.p. N/A 427, 225 AFR car I have seen was 565 rwhp. with a super big cam and big compression(LG).

I seen quite a few N/A LS6/LQ9 Head Cars put down close/over 600 rwhp. As a matter of course, MTI builds two 427's a week at 550+ rwhp with LS6 Heads with moderate cams. GNXGUY has one.

I doubt you will see a thing, unless your tune gets improved as well. Tuning is a realy big deal.

Take a look at the, "All Pro," heads or the C5R heads.
My understanding is Cartek has the All Pro's flowing to 380 cfm now and the Vette Doctors have the C5R's over 400 cfm.

I just re-read your post, they are not the best. Not even close.

There is a guy on the other forum now testing the All Pro's vs. the C5R's. Alan Futral and Carmen(Vette Doctors) have both built several LS N/a cars that run 8's and put down 680 rwhp n/a to the tires.

I have not seen even one AFR car run a nine and only one run a ten.

Looking at your numbers, your torque seems a little low.
 

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Discussion Starter · #3 ·
Grim Reaper said:
ScDFaCHE,

The highest h.p. N/A 427, 225 AFR car I have seen was 565 rwhp. with a super big cam and big compression(LG).

I seen quite a few N/A LS6/LQ9 Head Cars put down close/over 600 rwhp. As a matter of course, MTI builds two 427's a week at 550+ rwhp with LS6 Heads with moderate cams. GNXGUY has one.

I doubt you will see a thing, unless your tune gets improved as well. Tuning is a realy big deal.

Take a look at the, "All Pro," heads or the C5R heads.
My understanding is Cartek has the All Pro's flowing to 380 cfm now and the Vette Doctors have the C5R's over 400 cfm.

I just re-read your post, they are not the best. Not even close.

There is a guy on the other forum now testing the All Pro's vs. the C5R's. Alan Futral and Carmen(Vette Doctors) have both built several LS N/a cars that run 8's and put down 680 rwhp n/a to the tires.

I have not seen even one AFR car run a nine and only one run a ten.

Looking at your numbers, your torque seems a little low.
Thanks Grim....I've met Alan Futral and will see what he has that would do the trick. I am having the AFR heads flowbenched and if they are no better than my Stage III LS6 heads, then I will simply have the latter worked on by a guy in Houston (not MTI) that does work on Winston Cup NASCAR heads... I am happy with the cam, the idle, and the streetability of my Vette at this point. I am simply trying to dial-in and maximize what I've got. I agree 100% - tuning makes all the difference and Geoff Skinner has done a fantastic job with LS1 Edit. I don't want more power at the expense of either reliabilty or streetability. Does MTI do a good job with tubing kits?
 

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I would not tub unless you run drag radials and or do the quarter mile. It will add nothing to handling IMO and may in fact hurt it.

If want both linear adhesion and straight line performance I would go with carbon fiber wide rear fenders 2" wider. ACP(Kerry Hitt)(World Challenge Cars use him), Carvaggio(John) or Spector Works.

What size tires and rims?
 

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Although the flow numbers are not a large improvement from the MTI Stage III heads, they are definately better heads. I have the AFR 225's on mine and I am ultra happy with them. The flow number comparison was published earlier this year on a thread by AFR.

I believe they are some of the best and highest flowing heads on the market!

Mike
 

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If were going to go an F1R with huge boost over 14lbs., AFR would be my head of choice. Thicker and you would not cry if it cracked. It is easily replaced and will not take forever to obtain. I would have to agree with Mike on that one.

But these look cool as well.
http://www.allproheads.com/images/LS1-LS6.pdf

That being said, the owner of ECS uses LQ9's.
 

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I'll be looking for your results with the AFRs. Other than the FAST/90mm intake, I'm running essentialy the duplicate of your motor, but with Cartek Stage IV LS6 heads. I plan on upgrading the heads and intake once the smoke clears on the AFR 225/LS7 head questions. My goal is 6oo RWHP with good street manners.
 

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Grim Reaper said:
That being said, the owner of ECS uses LQ9's.

Truth be told, ECS is just beginning a project where they will be using the 225's for FI based application. This one in particular will be with a TT on a forged 383 (Jersey Jay). ECS had done several 346's (mine included) with the 205's N/A and we all have been quite satisfied with the end results. I do think you will soon see results from ECS on some large stroker motors with the 225's. In speaking with Chris Coriell and Doug Ring from ECS, they have been very happy with the quality of the AFR product as a pretty much a "plug and play" head.

Don
 

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You will almost definately pick up midrange....Flow numbers are not everything, velocity is also a key factor. I think the AFRs arethe best conventional heads on the market (...not including c5R). I will be interested to see some of the new Z06 heads (ported)/intake on these big cube motors though.
 

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Like I said before, I will wait for the actual dyno numbers, the guys running 8, 9 & 10's to use them and major vendors back East and in Texas. Bench flow racing means nothing.

Re the AFR's They are strong and well made.

Don
The one AFR, that ran the mid 10 was the 383TT, I believe. When they get it worked out it will be in the nines, but you could bolt ANY head to a TT and do the same thing.

Be curious to see what the results are.
 

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Grim Reaper said:
Like I said before, I will wait for the actual dyno numbers, the guys running 8, 9 & 10's to use them and major vendors back East and in Texas. Bench flow racing means nothing.

Re the AFR's They are strong and well made.

Don
The one AFR, that ran the mid 10 was the 383TT, I believe. When they get it worked out it will be in the nines, but you could bolt ANY head to a TT and do the same thing.

Be curious to see what the results are.
I know we are suppose to be talking about AFR 225's and a 427, but here is a thread I dug up from LG where he took one of his "race" cars, added one of his biggest cams with the AFR 205's and proceeded to knock out a 10.4x run @ 140+ mph. Of course, with 535 rwhp, the car was breaking stuff left and right. :yeadog:

http://www.z06vette.com/forums/showthread.php?t=70360

Now I know Lou got flamed on this car, seeing as it is a road race car and very different in terms of weight. But the bottom line is that the AFR heads (coupled to a big cam) do make real power, and if you can get that power to the ground, you will go fast. :thumb:
 

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Discussion Starter · #12 ·
marco383 said:
I'll be looking for your results with the AFRs. Other than the FAST/90mm intake, I'm running essentialy the duplicate of your motor, but with Cartek Stage IV LS6 heads. I plan on upgrading the heads and intake once the smoke clears on the AFR 225/LS7 head questions. My goal is 6oo RWHP with good street manners.
Thanks for all of the feedback on the AFRs. I asked my cousin who owns Legendary Muscle Cars in Long Beach, CA an who restores mid-year Corevettes and he says the AFRs are the finest out of the box heads available today.

I sincerely doubt you can get 600 rwhp from a NA 427 (either resleeved or C5R) without tons of compression or a very large cam or a combination of both. With stage 4-5 heads, the valves can get quite this and wear down. Soo you are exchanging reliabillity for pergapsa few more horses. High compression means no more getting gas at the local Mobil station and the big cam may not be streetable. Reliability also becomes an issue at that point. If I wanted 600 rwhp, I'd have dropped the compression, dropped the cam and bolted on either a Magnusson S/C or a Vortech S-trim S/C..then I'd have approx. 750+ rwhp and need another tranny...

Without the 90mm TB/MAF, you are seriously choking power from that 427. The 1-7/8" headers will also make a differendce on the exgaust side.
 

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Discussion Starter · #13 ·
marco383 said:
I'll be looking for your results with the AFRs. Other than the FAST/90mm intake, I'm running essentialy the duplicate of your motor, but with Cartek Stage IV LS6 heads. I plan on upgrading the heads and intake once the smoke clears on the AFR 225/LS7 head questions. My goal is 6oo RWHP with good street manners.
I will keep you all posted with the chasis dyno results....
 

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This is a thread where the 225's were tested along side of my old Stage III heads.....http://www.z06vette.com/forums/showthread.php?t=71306&highlight=AFR+225

Again, although there are increased flow numbers across the board, this was not my primary reason for switching to the AFR's. As Grim stated in an earlier post, these are very thick heads and are extremely strong. I've seem them side by side with my old ones and two other brands. The difference was very visible! My main reason was to bulletproof the heads as much as possible for high hp applications. I think with the AFR's, I've accomplished that!

Are they completely neccessary for N/A 427 engines??.....probably not, but it's nice to know that the heads will not be a problem in the future.

Mike
 

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Can I have someone post/host my JPegs on my three sets of flow numbers? I am mentally handicapped and retarded in this department.
 

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ScDFACHE said:
Hi All,

I am replacing the Thunder Racing Stage III LS6 heads on my 427 C5R motor with the new AFR aluminum heads at minimal cost to me. The valve train, cam, and compression ratio (11.0;1.00) will all remain the same. The LS6 heads flowed a healthy 343 cfm at 0.500 lift. I am told that the AFR heads are the best available and will outflow, and outperform, anything else on the market. Any one of you Z06 performance predators have data or an opinion on this?? I am told to expect an additional 20 rwhp or so just from these heads. Thoughts? Thanks y'all... :coo: :D :jammin:

Let me know how that works out!!

Chris
 
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