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I have a freshly machined .040 302 block ready for assembly but have cylinder head questions. I wanted to use the original OEM Ford C90E heads, C8AE 2 barrel intake and Autolite 2100 carb and then modify down the road as a learning experience for my son and I. When I found out how much it would cost to rebuild these heads it now does not make sense as they need guides, valve job, decking and all new valves, springs, etc as some were damaged. Looking at $650 parts and labor not including rocker arms.

My goal with this project is to make more power than stock but not that much more as this will be driven by my kids sometimes who are teenagers.

I have looked at a lot of head options from rebuilding the stockers to inexpensive rebuilt E7TE heads, to rebuilt GT40 heads (not GT40P), to entry level aluminum in the $1,200 to $1,400/pair including valves/springs. What I don’t want to do is go too big on heads and sacrifice low end torque for high end HP. I enjoy 0-60 MPH sprints now and then but don’t care about the drag strip or high speeds, but really most of the time this car will just be cruising in the city with some highway trips. I suppose rear gears are an option as this only has 2.8:1 but without OD on the trans RPMs could be an issue.

Another big issue that I don’t fully understand is the effect of compression ratio and the available octane ratings (we only have 91 octane where I live). I have no problem using 91 octane as gas cost is not a factor. I have new 3 CC relief flat top pistons and the piston to deck clearance is .010. My stock heads I measured at 59 CC combustion chamber. With a “standard” gasket (using .041) this would yield a static compression ratio of 9.67 (8.27 dynamic with Comp Cam XE256H camshaft) which worries me on iron heads.

If I went to 64CC heads static comp ratio drops to 9.11. I also hear that if I go aluminum heads I can get away with more compression due to heat dissipation. I absolutely do not want a finicky motor that pings or requires timing adjustments or additives to keep from pinging.

There is some uncertainly as to the CC of the GT40 heads but most look to be about 64CC so I am thinking this might be a good compromise for me. Would the stock intake fit on these? This way we can add a new intake and 4BB carb later if we want more power. I realize that upgrading the cam and heads and keeping same intake and carb may net little to no improvement over stock as they are likely the bottleneck.

There is really not a budget for the project but I want to spend money sensibly for what the end goal is. If that means $2,000+ for heads, new intake and carb so be it, but it all seems a little overkill.
Looking for some suggestions. I have searched endlessly on google but feel like I am going in circles. Sorry for the long post. There is so much for us novices to try to learn!
 

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I'd suggest going on Ron Corral - I've been ionized... and look in the Windsor parts. You should have a pretty good chance of finding set of GT40 heads. You will have to pencil in pushrods and rocker arms but sometimes you can find good deals on bolt on rocker arms. I found a set of Crane 1.72 ratio rockers for $110, not on Corral. You can frequently find good deals on used Aluminum heads that have been freshened up. Another option for inexpensive aluminum heads I would use are the Flotek from Speedway. About $750 a pair. I read a review on them by a professional machinist who bought them for his car, on You Tube. Machining was very good and valves were good quality. These heads would work about the same as a mildly reworked set of 289 heads. You would have to add in the cost of roller rockers. These heads can be improved with some porting as they have a lot of extra material for porting but by that time you're into the price range of a good set of heads. They are basically a copy of the Ford GT40 aluminum heads. The Edelbrock Street heads are very good for the money.

I wouldn't assume a CR based on the head volume. There are several other factors such as how far the piston is down in the bore. A lot of times over sized pistons have a lower deck height to compensate for any increase in CR due to the larger bore size. The down side is it hurts quench and can increase detonation even though the CR was lowered. I really don't buy into the aluminum dissipating heat better that allows higher CR. I believe it's due to improved, modern combustion chamber design. Dave Frieburger of Hot Rod did a test on a SBC with Dart heads. same short block, 2 different set of heads. Identical in every way except one was aluminum the other cast iron. Both made the same power, both needed the same timing, neither one was more detonation resistant then the other.

You could even make the GT40P head work. It has a 60 CC chamber and with a little grinding on 65-66 exhaust manifolds will work.

Six Budget Ford Heads That Work - Car Craft Magazine

Comparing Aluminum And Iron Cylinder Heads - Car Craft Magazine
 
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If you want to stay budget minded, find a good set of E7 heads. If you look, you can find some bolt on heads for not a lot of money. You could step up to GT40s as well ( which are basically early 351W heads ). But for the money and fitting your scenario, some E7s might be the ticket.
 

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Not really addressing your question, but some focus on your cooling system might be a good investment. Overbore of 0.040" is not a slam dunk regarding engine reliability. Overheating with that overbore is not just a possibility, it's a likelyhood. Many folks have overheating issues with just a 0.030 overbore, let alone 0.040. So think about goving some serious attention to the assembly of a cooling system that has the best possible components.

I'd be thinking Griffin Radiator, FlowKooler water pump, electric fan(s), or a mechical fan that moves A LOT of air, a well designed fan shroud, 100% water w/ water wetter.


Z
 

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There is really not a budget for the project but I want to spend money sensibly for what the end goal is. If that means $2,000+ for heads, new intake and carb so be it, but it all seems a little overkill.
Looking for some suggestions. I have searched endlessly on google but feel like I am going in circles. Sorry for the long post. There is so much for us novices to try to learn!
Hmmm… I'm thinking you can save between $500-$1500 by doing this:

http://www.mustangbarn.com/PDFs/Port Matching.pdf
 

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If you want to stay budget minded, find a good set of E7 heads. If you look, you can find some bolt on heads for not a lot of money. You could step up to GT40s as well ( which are basically early 351W heads ). But for the money and fitting your scenario, some E7s might be the ticket.
e7 HEADS dont flow much air compared to some older castings. A set of well ported ones flow around 220 CFM at .500 lift. Relay done right will out flow some aluminum heads.
 

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- I'm convinced people who have overheating issues with a bored block have problems with the their cooling systems. I don't think the bored cylinders have anything to do with it. It just becomes an easy scapegoat when the engine runs hot. There are many thousands of engines running just fine with cylinders bored .030, .040 and even .060.

- I agree with 22GT. For your purposes, freshening up your current heads and doing some mild porting is the way to go. Seriously, $650 is chump change in the world of classic cars. And what's wrong with the factory rockers?

- With 91 octane gas, 9:1 static compression will be fine. Although, you must always run the 91 octane. You can't get away with running regular or it will ping.

- A bone stock 302 with 9:1 compression that's fresh and properly tuned will be more than enough for teenagers.
 

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Discussion Starter #9
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Seriously, $650 is chump change in the world of classic cars.

Indeed! This is part of the problem. I have no problem spending the $650, but I also have no problem spending more so deciding what to do is the tough part.

I got ahead of myself and did the short block before really knowing the whole picture and being told <10:1 compression would work. Then I researched more and started second guessing. I should have bought dished pistons to reduce compression ratio with the stock heads.
 

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I don't know why you are worried about 10.0:1 compression ratio. I've built numerous Shelbys and K codes with a verified 10.0:1 CR and never had any issues with them.

Z
 

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- I'm convinced people who have overheating issues with a bored block have problems with the their cooling systems. I don't think the bored cylinders have anything to do with it. It just becomes an easy scapegoat when the engine runs hot. There are many thousands of engines running just fine with cylinders bored .030, .040 and even .060.
......."
My experiences don't bear that out. Core shift is a known issue with SBF's of the 1960's-'70's. It often affects overheating when the overbore is 0.030 or more. I don't know the percentage of engines with this issue, but it's not a small number.

Numerous times I seen engines that ran cool at +0.020 but at 0.030 they were overheating.

Z
 

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Discussion Starter #13
I wouldn't assume a CR based on the head volume. There are several other factors such as how far the piston is down in the bore.


Thanks very much for the great info and links. GT40s are high on my list. My CR calc is accurate as I have the short block mocked up and have .010 piston to deck clearance + have measured CC on the chambers and piston reliefs.

There is so much disparity between what people think is too much compression. Stock C code motor was 9.3:1 and way up to 10 for the A code and 10.5 for the K. I guess gas was better back then....This is what got me off track thinking 9.7 was OK.
 

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If you ask me, regardless of what you pick up for used iron heads (unless you find some that have been gone through) you're going to be looking at spending $$$ on valves, seats, guides, studs, springs, retainers, keepers, shims, rockers, etc. Add your time for DIY porting and what do you have? A set of iron heads.

I'd go with a set of AFR165's (58cc) with stud-mounted stamped steel roller tipped rockers, a Weiand stealth intake with a Summit M2008VS600 carb and some reproduction HiPo exhaust manifolds. With the XE256H that should give you a snappy little motor.
 

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Another big issue that I don’t fully understand is the effect of compression ratio
ok let me explain how compression ratio works, and why you get more power with a higher compression ratio. lets take two engines, one with 8:1 compression and one with 10:1 compression.

first we must recognize that atmospheric pressure at sea level is 14.7psi, lets round that up to 15psi though to make the math easier. so when we compress the a/f mixture, assuming 100% cylinder filling, we take the 15psix the compression ratio, so we get;

15 x 8= 120psi

15 x 10 = 150psi

now when you light the a/f mixture off in the cylinder, cylinder pressure goes up by a factor of 10. not instantly though, but we will use that again to make things easy, so we get;

120 x 10 = 1200psi

150 x 10 = 1500psi

for a gross difference of 300psi. now we subtract the original cylinder pressure before we light the fire, we get;

1200 - 120 = 1080psi

1500 - 150 = 1350psi

or a net difference of 280psi. that means 280psi more pressure pushing down on the piston on the power stroke.

as for cast iron heads vs aluminum heads, now you are talking thermal load differences, the aluminum head dissipates heat faster than the iron heads do, so you can run higher compression, or more timing, or both, on the same octane fuel.
 

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cylinder heads

TG, why does it not make sense to rework the stock heads ? You can make a set of heads that do exactly what you want, and you're still spending less than new. At the $650 level, does that include hard seats under the exhausts ? Why replace the guides, it is usually very cost effective to line them with thinwall bronze liners......and what new valves are you getting at that price ? If I were buying new valves for those heads, I'd get the early 351W valves at least....1.84 intakes and 1.54 exhausts.....and it isn't fair to hold the price of new springs against the old heads, you need new springs anyways to allow for your new camshaft.....

And I wouldn't worry abit about going 040 over, we bore small Fords 060 over on a regular basis and we don't have trouble with them. If your waterpump and rad and fan are good you'll be fine.

LSG
 

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My experiences don't bear that out. Core shift is a known issue with SBF's of the 1960's-'70's. It often affects overheating when the overbore is 0.030 or more. I don't know the percentage of engines with this issue, but it's not a small number.

Numerous times I seen engines that ran cool at +0.020 but at 0.030 they were overheating.

Z
Were those racing engines? I'm not arguing with what you've seen, but sheesh. I just got back from the Rocky Mountain Mustang Roundup. There were a whole lot of 65-70 Mustangs there, most of which were driven to the event, and you can bet most or all those engines are bored .030 or more. No overheating issues; not even at the autocross.
 

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All kinds. They were engines that saw a lot of what I call severe duty. Some were juSt street cars that ere driven with gusto. Two of the HiPo engines were raced in the long distance endurance races in west Texas, basically flat out in top hear for about 150 miles. They didn't overheat, but did have issues later when they were overhauled and bored out some more. I always try to take an original bore out to the minimum where it will clean up, usually never more than 0.020", sometimes less.The practice of always going to 0.030" is one I don't understand.

Blocks can be sonic tested to determine if the casting is optimal or not. I don't think many machine shops do that.

Z
 

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Discussion Starter #19
ok let me explain how compression ratio works, and why you get more power with a higher compression ratio.

Nice write up and thanks. I do understand compression and the forces involved, it is more the combustibility and relation to octane. But never looked at it in the form of cylinder pressures.
 

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Discussion Starter #20
TG, why does it not make sense to rework the stock heads ? You can make a set of heads that do exactly what you want, and you're still spending less than new. At the $650 level, does that include hard seats under the exhausts ? Why replace the guides, it is usually very cost effective to line them with thinwall bronze liners......and what new valves are you getting at that price ? If I were buying new valves for those heads, I'd get the early 351W valves at least....1.84 intakes and 1.54 exhausts.....and it isn't fair to hold the price of new springs against the old heads, you need new springs anyways to allow for your new camshaft.....

And I wouldn't worry abit about going 040 over, we bore small Fords 060 over on a regular basis and we don't have trouble with them. If your waterpump and rad and fan are good you'll be fine.

LSG
The heads were rebuilt before by the PO and already have hard seats installed as well as bronze liners but there is a lot of play (like .030 on some). So need new liners, valve job, deck the head. The valves I have are very inexpensive and stock size of 1.78, 1.46. My issue is IF 9.7 CR is too high for iron heads then I have a big problem unless I can carve out 6-7 CC from the 59 CC chambers. So with all the work needed , seems to make sense to go to GT40 or an aluminum head with bigger chambers to get CR down nearer 9:1.

So my biggest unknown is some say 10:1 and other 9:1 to not ping on 91 octane. Not just in this thread but all over the internet.
 
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