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Discussion in '1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-' started by Grabbin' Asphalt, Aug 23, 2013.
I invite you to explain your logic.
I agree total lift is not the determining factor. Ridiculously high lift might require a more aggressive ramp rate to keep it off of the piston, but the major point here is that more important than lift specs are duration and then LSA/LCA. You're right about the non-stock heads and cam Nik, but I was actually just bringing to light that at some amount of lift, the lift figure does matter. The motor is non-interference, from everything I've been told. That being the case, there is a given lift below which there will never be PTV contact and above which it becomes a possibility.
Believe I'm gonna do the AFR 165cc milled and call it a day. Unless my mechanic has a nice used set of TFS 170's around.
I'm gonna throw in a monkey wrench. We identified the AFRs as having a slight advantage on a 302. That said, the TFS 170s are the same head Nik has on his 302 in a CNC'd 205cc form. They are way overkill for a 302, but the point is that with the TFS heads, you'd have a ton of room for growth if you ever went stroker or to a larger 351w setup.
In all honesty, AFR165s are a perfect fit for a 302. I had them on an old combo of mine that made 320rwhp with a ported cobra intake and custom cam. If I were to do another 302, I wouldn't be afraid of the AFR185s of the TFS fast as cast 190cc CNC heads. Anyway, I just wanted to get that out there for your consideration.
I'm a little late to the party and it's just as well. With moving and all, I don't have access to all of the magazine tech articles etc. that I've saved over the years. I will leave it at this though:
There's plenty of evidence out there to support the notion that there's no such thing as too much head for a 302. I can recall at least two instances where back to back testing was done with progressively larger heads on a stock bore 302. The moral of the story is that there was a significant improvement in power output as the heads got larger and larger. I don't recall the exact changes for each and every step up in head size but it's logical to assume that the inlet tract was modified to accommodate the increasing airflow as well.
Were it me... I'd get the largest/best head that I could afford that also has the smog cross over ports in the back (if required) and call it quits. If the motor is ever modified then the heads at least, already exist and don't have to be repurchased.
Well, I guess in that scenario, you're talking about the possibility that the cam would be out of time with the crank, and the valve would be at peak lift when the piston is at TDC. So, at that point, you've experienced some sort of engine failure, like the timing chain breaking apart or the cam pin shearing off, etc. So, I see what you're getting at, but assuming a properly running engine with no failures, peak lift happens when the piston is deep in the hole. SO, then, like you're saying and like I said above, in a healthy motor, piston to valve clearance issues are related to when the intake opening event and the exhaust closing event occur, and how fast their early/late (respectively) ramp rates are. That stuff is completely independent of peak lift, which is what I'm really driving at here.
Cool, but wouldn't it be kinda nice to know a peak lift number below which you can say with certainty that someone will never have a problem? I mean, if it takes .540" that's a pretty big deal, because there are lots of 302 cams that do not go that high. I guess it would still be complicated by other things like head milling, gasket thickness, flat top vs. factory notched pistons, etc... Ok maybe it's not such a great idea... I'd still kinda like to know, though.
So the shop may have a barely used set of 185cc or something. They're suppossed to be bigger than the 165cc but I'm either gonna buy those and slap them on my 302 or use the funds for a 331-ish size DD motor.
Get the Big Heads milled like mofo to help my 302ci??
If I get the 331-ish bottom end, my fully ported/milled Gt40p's will have to be used regarding low funds.
I guess if you're looking at an otherwise completely stock motor and just swapping the cam, it would be interesting to know at what lift it became an "interference" type motor. I bet it’s not a lot though, considering the stock cam is only like .450” lift.
Just my $.02, I’m not a huge fan of milling a ton of material off a cylinder head for a small motor. My reasoning is this- if you ever want to build a bigger motor and want to reuse the cylinder heads, you may have a problem getting the compression back into a pump-gas friendly range. That’s just me, though. I’m always trying to think ahead like that, for better or for worse, haha.
You'll get more out of a decent set of heads on a standard strok 302, than a set of sub par heads on a 331.
The 331 makes a bit more torque across the board than a standard 302, but not by a huge margin. They do however like to rev. Using a stet of cast iron GT40's (even ported), is going to limit that engines power potential in those upper ranges. I'm running a set of milled and ported GT40X's on my 331 and even though it gets from one end of the tach to the other in a hurry, I'm sure the heads themselves are holding me back considerably.
Also, not sure why the hard on for so much compression. Going from the stock 64cc down to 58cc is only gonna net you another 5-10hp or so....and also limit you to premium fuel all the time. Unless you can buy the head outright with the smaller chambers, I would bother spending the money having them milled down.
My Gt40p are already .030 so I'm kinda use to it and the throttle response is Amazing
Gearbanger is your dyno sheet posted, like to see your powerband??!!!
I'd build the 331 and keep the gt40s for a fun potent dd.
Sorry, no Dyno sheet's as of yet. Just finished putting it together a couple of months back. Going by my "Seat-o-the-pants" meter right now. It's definitely a strong runner though. Really rev happy and pulls like gangbusters above 3,000RPM.
I've got it backed with a Trick Flow Track Heat port matched to the GT40X's as well as a Comp XE274HR camshaft as well as a host of intake, exhaust and fuel system upgrades. Gonna make sure all of the little bugs are worked out of it and get a few more break in miles on the engine before taking it for a dyno session. Gonna need to clean up idle and drivability in a few areas.
I know I've really thought about that. They're heavily ported along with the ported Cobra intake as well. Main reason my Ecam is thriving now. What about this combo,
331+my Gt40p+ Cobra+xe264hr-12+ my chip retune
would not this DD scream on the streets??!!!
It'll be more powerful than a 302 of course, but not nearly as powerful as it could be with better heads and intake.
You'll probably make somewhere in the 300-310rwhp range with that set up.
I hit post before added the 264 cam sorry miss hit. Im at 280rwhp with just the Ecam now.
I've seen 305rwhp same set up on stangdawg 302 with that cam.
why not build a new motor from scratch and then sell the old one? I hate to say it, its not worth much with the parts you have listed but you will get some of the costs back. I just dont see taking a DD off the road to put new heads on as economical.
Id only have the funds to build the 331 short block and swap any parts over. I'm really gonna' consider this for more CI and upgrade heads later down the road.
is your current engine about to die? you seem sold on this one or the other idea when ideally you need a good top end/bottom combo. If you are going to spend money I vote top end. Nik's build is a prime example.
Hahahaha I know im all over, thinkin' turbo, stroker or heads. Motor is super good right now. Just trying to design my plan of attack for the future of this DD build. Maybe 6months to year away. Really thinkin' hard about CI 331-ish upgrade.