PDA

View Full Version : Superchargers and aluminum heads?



69MACH1
02-20-2006, 11:55 PM
I have been wanting to upgrade the cast iron heads of my Mustang for some AFR 185's for some time. I was discussing this with a very experienced but old school engine builder friend of mine whose opinion I respect and he strongly cautioned against it. I have a blown, injected and stroked 351w with ported cast iron heads. The engine is well built with over 15,000 trouble-free miles on it. When fresh it was putting 550hp to the wheels. Honestly I do not need tha much more power but I would like to take some weight off the front end. I want to open track the car later this year and loosing weight is a good thing, especially from the front end. All this being said, I do not want to sacrifice long term reliablility for 30lbs., my car afterall is air conditioned. I like the AFR heads because they are high quality, locally made and have a 3/4" head deck. I also have a hydraulic roller cam so the engine does not rev. over 6 grand so I do not think I need the larger ports. Does anyone have any experience or opinion on the matter?

Thank you,

DeltaT
02-21-2006, 01:44 PM
There's so many cars out there with various power adders and aluminum heads, mine included (blower and nitrous) that I'm wondering what old school direction your friend is coming from. Do it if you want. Probably not worth it just for the weight, though. The most I've seen come off a car by changing heads was 50lbs but they were Corvette aluminum heads which were designed mostly by accountants (light weight = less aluminum = cheaper cost). Most head changes yield you only 20-30 lbs.

Jim

Y-TRY
02-21-2006, 04:27 PM
I don't really see the angle your friend is coming from, either. While a good set of iron heads can be as powerful as aluminum, the aftermarket heads will always flow better than ported factory heads. Maybe he's thinking factory aluminum as being not strong enough? I dunno. But you'll have no issue with strenght or flow from the AFR's

I, too, am an AFR fan. I say do it.

jdpepper
02-21-2006, 05:41 PM
I can see where your friend is coming from, if its not broke don't fix it. But if it was me, I'd have a set of aluminum heads on it.

Z06killinSBF
02-21-2006, 05:46 PM
I would go with the 205's though. Since the ports are bigger, they must weigh less right:hammer:

WS6
02-23-2006, 07:05 PM
what is your engine compression ratio and how much boost is the blower providing? if i had to guess i would say your compression ratio is down and your boost is up. if thats the case going to the aluminum heads could cause you issues with the fact that given two identical engines one with AL heads and one with cast iron heads. the cast iron headed engine will produce more power because the heads retain more heat allowing for a better combustion of the fuel. this is of course so long as the compression ratio is such that you dont need aluminum heads. so im betting thats his concern. i would think however if these AFRs flow much better than your current heads then a retune would be in order and the simple fact that the heads flow better will compensate for any loss of power due to loss of heat by going to the aluminum heads. however i could be talking out my ass right now.

simply having aluminum heads and a blower is not a bad thign in general. it may be for your aplication though. why not ask your friend why he says that?

also i second the going with the bigger CC runner heads. if your a stroker with a blower you can benefit from the larger runner volume. you might have to up the boost a little but its better than choking it off.

69MACH1
05-05-2006, 12:47 AM
Thank you for the input. The concerns of my friend have to do both with reliability and performance. He has a machine shop in Costa Mesa and works on everything from Fiats to multi engine offshore racing boats. He stated that keeping heat in the combustion chamber is one of the keys to making power as Trey pointed out, the aluminum head does not keep the heat in as well as the cast iron head, thus lost power. Second with with the boost that my car runs, distortion of the head becomes a problem which leads to blowing head gaskets. This is something that I have not had a problem with and I really do not want to start having a problem with. Lastly he said, also with as much boost as I am running head flow is not as big of a concern because you are able to "push" it through.

This past week I spoke to the guy who built the engine; initially he was excited about the idea of heads but after discussing it and him remembering some details about the heads he was not so sure. I knew it has Ford Motorsport N351 heads; 195cc intake, 2.02 intake, 1.60 exhaust and 10 degree valve angle. These were developed by Robert Yates and are spec for a 351W for NASCAR, and circle track racing. He reminded me that they were heavily ported by a well respected cylinder head guy. However he did say if I did find a better set of head that I would be able to run more timing which would liven the engine up more; not like it is dead.

Last week I called AFR; I cannot run the 195's because of the unique exhaust flange that is on my car for the N351 heads. I can run the 205's though because they can use the same flange and he thought that these would flow better than what I have no matter how well they are ported. My only concern is combustion chamber volume and maintaining compression with a different head.

Trey, static compression on my car is 8:1, not high and reasonable considering it will hit 15psi of boost.

Talking to the guy who built the car I got the impression I would be better off keeping things the way that they are and spend money on a good tune, getting a chip burned and getting rid of the engine management system that it currently is running. I will be re-ringing the car with some Hellfire rings and inspecting everything. Most likely the heads will need some work, so I will have to make a final decision then.

ProdigyCustoms
05-05-2006, 02:57 AM
What the hell is he smoking. Back to school would be the right thing for him. Man I hate it when people speak just to see there lips move! It is bad enough when a youngster does it just to sound smart, but when a old timer does it............

For the record, Go aluminum everything! As much as you wallet will allow!

You can tell him I said he should shut up and not give anymore advice!, Lol!

flynbyu82
05-09-2006, 03:51 AM
Um, I just wanted to chime in and say b-e-a-utiful car !! :)

I also plan on running aluminium heads in my boosted engine ...

WS6
05-09-2006, 05:21 PM
id leave it be honestly. your thoughts of getting a better engine management system is a good idea, unless the current one just needs someone to tune it properly. sometimes the simple computers work the best. for instance a speed density ecm from a 90-92 vette or fbody makes a great EFI swap ECM. however you've got to find someone who still does GM Eproms and knows how to tune SD. so that's an idea.
also remember you've got 15k trouble free miles and 550 rwhp. loosing weight off the front end is a good idea to pursue that wouldn't require reworking the engine. are there other parts that can removed? maybe inner fenders removed or switched to plastic or fiberglass? fiberglass body panels possibly? i just like to leave well enough alone if its working great and it sounds like it is.

my thoughts on the compression and boost are like this. you can pump 15lbs of boost into an Al headed engine with 9.0 compression easily. at 8.0 now you'll either have to get a smaller CC head or change the pistons. i dont know fords, but if you can bump compression and retain the flow numbers you currently have aluminum heads may be worth while., but again id look elsewhere first.

these are my thoughts on knowing engines in general and not knowing fords. i could be completely off since we are talking fords.

WELTERRACER
05-14-2006, 08:45 AM
aluminum heads all the way... they keep the engine even safer at high boost levels and the engine cool..

I agree with frank..

Cheatin'Chad
06-14-2006, 05:18 PM
You'll have ZERO problems because they heads are AL. THOUSANDS of AL headed engines running N2O,Blowers and Turbos in this world with zero problems.

pdq67
07-04-2006, 02:19 PM
I want to say that somebody recently posted over on Team Chevelle a thread that discussed aluminum head "lifting" b/c of high combustion pressures!

I think the Machinists and Pro- engine builders got into the thread and finally came to the conclusion that deck and head surface finish has to be dead-nuts on as well as the best headgasket that you can find used to keep aluminum heads from "lifting" between the head-bolts under extremely high combustion pressures!!

(Again, I wanna say a 14 to 1 CR., 555" BB and 300hp NOS'ed on top of it????)...

This was noticed by water coming out under pressure sideways between the head and deck...

Please look into this over there if you are still interested!

pdq67

RSX302
07-06-2006, 12:28 PM
69MACH1, I checked out your set-up, I bet its very fun. What cam are you running?

I've been a Ford guy for a while so here's my 2 pennies.
First off it does boil down to your pocket book. If i funds are limited, I agree with staying with what you have and work with the EPEC tune to get a little more. Cam change? run something as close to 0 deg overlap and 280/290 dur (example: CompCam Blower Grind 35-306-8) The EPEC system is not a bad system, just no more. As I remember their is still support out there for it.
Just a note, keep an eye on your injectors and install a A/F meter and an EGT if you don't already have.

If you decide to go with the AFR185's, you will get a lower acting CR due to the aluminum heat transfer. Therfore with Aluminum heads you can run a little more CR than you would with Iron. This is one way to raise CR. Do you have 63cc heads now? Go down to 58cc or 54's maybe? I'm flowing 725hp through my AFR185's with a 302ci at 14psi boost intercooled. ~9:1 CR and 91 oct Pump Gas. Although mine is a turbo I will gain the hp that you drive the pully with. With your non intercooled set-up 8.5 CR should be fine. Wtih 1/2" studs, you will not need to worry about lifting these heads or distortion.

Head flow is not a concern with boost? Not necessarily true. Minor Intake restrictions can be tolerated because of boost, but exhaust needs to be open and free flowing. This is why more cam duration is run on the exhaust side than intake.

67speedfreak
07-08-2006, 02:24 PM
With a blower motor normaly you don't want extra heat. A blower compresses air and there for causes heat. The hotter the air intake the better chance for detination.
If head sealing is a concern oring the block and heads.

Colvindesign
08-28-2006, 01:48 PM
The only concern I could imagine is differences in expansion rates, meaning the Aluminum will heat up and Expand at a different rate than the Iron.

Since I have not noticed if you put a specific boost amount, at outrageous boost levels, there have been cases of cylinder head lift, where the head bolts actually stretch out enough for the hed to separate, and for some reason it usually happens on Aluminum headed cars. But again this has been with outrageous boost levels.

Otherwise, the flow comments he mentioned are all wrong. The 185s would hinder the true capability of your engine, and the 205s (or larger) would be better suited to your engine. Put it this way, yes you are pushing air through, but would you rather push it through a straw, or a hose? Your turbo will work more efficiently with better flowing heads. However if you do not have the intake matched and the throttle body, etc all set up to match, you will still not realize the capability of your engine.

One of the first cars I built was a 1992 Mustang LX (302 stock bottom end) with TFS-R stage 3 heads, something we were told would way outflow the engine, then we port matched a Cobra intake, added a larger throttle body, and exhaust. With a few other mods (like an E 303 cam) and not even getting a tune, it laid down over 425hp to the wheels. We were told by many people it would make less hp than stock because the heads were too much. Since we had it all matched from the air filter through to exhaust, it worked quite well together.

I would highly recommend 205s or better on your set up, as long as you get everything on the same page. I am not sure how the stock 351 heads are, but I imagine they don't flow as well as the AFRs, even with the porting.

Plus if you do some port work on the AFR's you will get pretty good gains.