289 & 5.0 oem head, rocker ratio, compression and porting comparison - Ford Mustang Forum
 
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289 & 5.0 oem head, rocker ratio, compression and porting comparison

289 & 5.0 OEM HEAD, ROCKER RATIO, COMPRESSION AND PORTING COMPARISON



I wrote this at the request of a Moderator. Please notify them if you see any errors.

This post contains some [but not all] of the differences between the standard non GT40, GT40 and GT40p cylinder heads as well as some other info for those that are interested in hoping to improve the performance of their 289, 302 or 5.0 engine.



If you are wanting to replace non GT heads with either model of GT ones just to get more flow, you may strongly consider simply getting yours ported. The E7te’s can easily be modified with larger valves then ported to a point where they flow a stupefying 30% more then they do unported. This is also 16% more than the highest flowing stock 5.0 heads which are the venerable GT40p’s. See more info in the head flow section further below.



IDENTIFICATION

The GT series heads are easily identified by thin raised lines cast into end of the heads. The GT40’s have 3, 1 1/2” tall lines, the GT40p’s have 4 and the non GT heads have none. The GT40 heads also often have “GT” cast into them on the outside by the outer plug holes and the GT40p’s often have GTP cast in the same location.

The 60’s and 70’s heads are identified by casting numbers located under the valve covers. Casting numbers starting with C = 1960 through 1969 and E = 1970 through 1979. See the head chart further below for more info.



CYLINDER HEAD MATERIAL

With the exception of the modular engines, all the factory V8 heads are cast iron.



WILL CHANGING HEADS CHANGE MY COMPRESSION?

This can be determined by comparing the combustion chamber size on your existing heads with the ones you want to install. See chart below for more info. In general, most if not all Ford V8 engines have compression levels that are less than optimal for a performance engine.

The generally approved compression level for a naturally aspirated engine running around 93 octane is around 8.0 dynamic. This averages out to around 9.5:1 static on most moderate or lower performance street builds.

To determine the combustion chamber size that will give you the optimum level of performance for the fuel octane level you are planning to use, use one of the many free online compression calculators. One from Keith Black pistons is in the link posted below.



COMPRESSION CALCULATOR

These calculators always calculate compression at sea level unless an elevation option is selected. Below is the link to just one of many free ones online.

https://www.uempistons.com/index.php...0f0f44946247ce



MILLING HEADS TO INCREASE COMPRESSION

Before milling heads for the sole purpose of increasing compression, it is necessary to do a volume test of the combustion chamber. This can be done by a shop for a nominal fee. Heads on most non modular V8’s can be milled around .028 inches from STOC before any intake fitment problems might occur.

Milling them around .028 inches from STOCK [uncut original] will reduce chamber size by around 4cc’s. This will increase static compression by around .5:1. This increase in compression will increase horsepower and torque by approximately 2.5% throughout the entire operating range.



MILLING THE BLOCK TO INCREASE COMPRESSION AND REDUCE POTENTIAL FOR DETONATION (0 decking)

“0 decking” refers to the distance from the top of the piston to the machined surface on top of the block. This process not only increases compression, but it also reduces the potential for detonation. I suggest to NOT machine the block to less than .005 inches from the top of the piston. My reason for not going to absolute 0 is, because heaven forbid, if for some reason you ever needed to surface your block again, you would still have room to do it. Even though it is possible to actually run the top of the piston slightly above the block, it is NOT RECOMMENDED. One of the things doing this can do is reduce the quench area to less than optimal. The optimal quench distance/clearance is around .035 inch.



COMPRESSION VS ELEVATION

An engine will loose approximately 5 psi of cylinder cranking pressure for every 1000 foot increase in elevation.



HEAD FLOW

The table below, shows the flow rates of the heads in stock, and some, in ported form.

The amount of porting done, and the quality of the work, can vary greatly, therefore, the graphs are for general comparison only and your results may vary considerably.

Although the exhaust valves are slightly smaller in the GT40p heads, the exhaust flow is the same as the heads with the larger valves. At least part of the reason for this may be due to the absence of thermactor “bumps” in the GT40p’s exhaust ports.

Another option to seriously consider if one has E7TE heads and is looking for higher flow is to simply port your existing ones or buy them ported and fully rebuilt from the site below. See flow comparisons in the chart below.

From powerheads.com. Price $895.00 exchange.

“ALL E7 5.0 HEADS INCLUDE COMPETITON CNC PORTING, SOLID BRONZE GUIDES, 5 ANGLE MACHINED SEATS, 1.90’’x 1.60’’ FORGED SS SWIRL POLISHED VALVES, .530’’ LIFT SINGLE VALVE SPRINGS WITH CM RETAINERS AND VITON OIL SEALS. PROFESSIONALLY ASSEMBLED AND VACUUM TESTED TO ENSURE VALVE SEAT INTEGRITY.”



HEAD FLOW TABLE

Flow numbers below around .050” are far less significant than those above those numbers. This is because there is not much if any intake flow occurring at that lift due to the pressure of the end of the exhaust stroke trying to force air back up the intake tract. This process is called reversion and is caused by the natural overlap of the intake and exhaust lobes on the cam.

Head Type………..….In Valve Ex Valve ..In.100 .200 .300 .400 .500 .600 ...Ex.100 .200 .300 .400 .500 .600

289 64 thru 67 ….....1.78 …….1.45 ………….45 ...91 .132 .154 .168 .166………...41 ..71 ….95 .110 .120 .124

289 ported ............1.94 .......n/a .........n/a .121 .173 .205 .215 .222 .......n/a .101 ..126 .146 .159 .172

E7TE-AA ..........….…1.78 …….1.46 ………….55 .101 .140 .150 .164 ……….....…..42 ..78 ..102 .110 .114

E7TE-AA Pwrhead ….1.90 …….1.60 …….....64 .123 .175 .204 .217……..…….…….63 .110 ..151 .170 .175

GT-40 Cobra ..........1.84 …...1.54 …..…....54 .107 .157 .183 .192 .196 .........47 ..94 ..119 .128 .128 .129

GT-40P Explorer ….…1.84 ….…1.46 …........61 .128 .169 .195 .196 .193 .........52 ..90 ..123 .135 .139 .142


The link below contains the flow rates of several OEM and aftermarket heads in both unported [stock]and ported form.

Ford Head Flow Data and Specs



THERMACTOR BUMPS IN EXHAUST PORTS – The GT40p heads do not have any.



HOW MUCH PORTING/AIR FLOW IS BEST FOR MY SETUP

The various components of an engine work together as a package. The flow amount of the heads should match the requirements of the engine displacement, cam, intake etc. Since this is a complicated calculation to make, it is best determined by a professional engine builder. In other words, just because one increases the flow of their heads, it is no guarantee that the overall performance will be improved. Unlike beer and women, more is not always better.



POCKET PORTING/VALVE BOWL BLENDING

This process will provide the biggest increase in flow and depending on the amount of work being done, one can expect the costs to be between around $150.00 - $300.00

WARNING - Porting is both an art and a science. It is possible to actually reduce flow in some areas of valve lift if done incorrectly, therefore, it is strongly recommended that if one wants to do anything more than just a mild clean up of casting flash and/or the removal of the bumps in the exhaust ports designed for the thermactor air pump, I again strongly recommend that one has the work done by a professional.



THERMACTOR [AIR] PUMP HOLES

These can easily be plugged if desired. If you don’t need to thread a bolt into the hole, you can use a socket [allen] head screw. These socket head screw can also be used on the 60’s and early 70’s that had air injectors in the heads. See some plugs in the links below.

http://www.summitracing.com/parts/tfs-51400265



PISTON TO VALVE CLEARANCE

The intake valves of the GT40 and GT40p heads is larger than the others. The exhaust valve in the GT 40 is larger than the others. The exhaust valves in the GT40p heads are the same size as the other non GT heads. Because of the larger valve sizes of these heads one should check the piston to valve clearance whenever switching from a smaller valve head to a larger one. I don’t think that there will be a problem providing the cam does not have more than around .500 inches of lift and the block and heads have not been surfaced more than around .020 inches total between them.



1.6 VS 1.7 ROCKER ARMS

If your heads have sufficient flow [more than stock E7te’s etc] AND you have a stock or close to stock cam, you will gain around 6% more hp and torque by replacing the stock 1.6 rockers with 1.7 ones. Doing this will also raise your overall operating range slightly [maybe 200 rpm].

If you already have a high perf cam, you can do the calcs to see if you will benefit from doing this or not. It is not recommended to do this on steep ramp cams like the comp XE series or some of the Lunati’s. See article below for more info.

5.0 BUILD 400 HP WITH STOCK CAM

Ford 302 V8 Engine Buildup- Car Craft Magazine



VALVE SPRINGS

I have heard that some people have had trouble finding high performance aftermarket springs that will fit the 5.0 non GT, GT AND GT40p heads without machining the spring pads on the heads. This would be the case if one were to use dual or triple springs however there are numerous springs that will be a direct fit, A FEW ARE LISTED BELOW. The cam mfg’s like Comp Cams, Lunati, Cower and Howards etc. all have several springs to choose from. One needs to measure their trapped spring height before they can calculate which spring will work best with their camshaft.

When installing any camshaft that is larger than stock, it is important to get the proper springs for the cam. The factory springs that come with the GT40p heads are very weak/lite and therefore should NOT be used for any application other than a stock Explorer or ornamental decoration. The stock GT40 springs aren’t much better.

Below are just a few springs that can be installed with no modifications to the head.

Trickflow spring upgrade kit p/n TFS-2500100.

Crane Beehive spring kit p/n 44308-1.

Alex's Parts (alexparts.com) is another great place to look for a drop-in spring package.



WHICH HEADERS FIT WHAT

The GT40P heads are the only ones that have special header requirements. This is partially due to the location [angle] of the spark plug. The plug sticks straight out on these heads which interferes with some headers. On some of the headers that the plug does not interfere with, the plug may still be close enough to the header that the boot from the plug wire may contact the header. If the plug wire boot does NOT contact the header, it may still be so close to it that the heat from the header might melt the boot.

There are a few options to correct this problem which are as follows:

1. Use heat resistant plug wires that have a 90 degree boot.

2. Use plug wires that have a ceramic boot.

3. Buy ceramic boots for the wires.

4. Add thermal “socks” to the boots.

5. Use shorter plugs with 45 degree boots.



The following list of headers contains both direct fit and "should/might" fit headers with no modifications and no interference with the spark plug or spark plug boot on GT40p heads. Some other brands might fit with some modifications. Call manufacturers for more info.


Ford Racing P shorty’s verified

The top 4 listed half way down the page fit 86 thru 93 with not mods and 79 thru 85 with minor mods.

https://www.fordracingparts.com/part...KeyField=10535



MAC P verified

MAC Ford Mustang 5.0L 1979-1993 Unequal Chrome ShortTube Headers


MAC unverified but should fit

MAC Ford Mustang 5.L 1979-1993 5 Speed Ceramac Long Tube Headers



BBK unverified but should fit 86 – 93

BBK : 1986-1993 Ford Mustang 5.0L Equal Length Shorty Headers[]=1387&car_motor_key[]=1439&car_motor_key[]=1411&car_motor_key[]=1438&car_motor_key[]=1413&car_motor_key[]=1419

BBK : 1986-1993 Ford Mustang 5.0L 1-5/8€ Shorty Headers - BBK[]=1387&car_motor_key[]=1439&car_motor_key[]=1411&car_motor_key[]=1438&car_motor_key[]=1413&car_motor_key[]=1419

BBK : 1979-93 Mustang 1-3/4" Long Tube Headers[]=1387&car_motor_key[]=1439&car_motor_key[]=1411&car_motor_key[]=1438&car_motor_key[]=1413&car_motor_key[]=1419

BBK : 1979-93 Mustang 1-5/8" Long Tube Headers[]=1387&car_motor_key[]=1439&car_motor_key[]=1411&car_motor_key[]=1438&car_motor_key[]=1413&car_motor_key[]=1419

BBK : 1979-93 Mustang 1-5/8" Long Tube Headers For Automatic Cars[]=1387&car_motor_key[]=1439&car_motor_key[]=1411&car_motor_key[]=1438&car_motor_key[]=1413&car_motor_key[]=1419



SPARK PLUGS

All the heads mentioned here use a 14mm diameter spark plug. The E7TE heads use a short (0.460&quot reach plug while the GT-40 and GT-40P heads use a long (0.708&quot reach plug. Both types have a tapered seat (no washer used) with a 5/8" hex.

I suggest to never run a plug that is hotter than the manufacturers recommended rating for your particular engine irregardless of what cylinder heads you are running. Plugs that are 1 step colder are recommended for high performance engines and engines with high compression especially if they are operated in outdoor temps above around 70 degrees because they help reduce the potential for preignition.



HEAD SPECIFICATIONS AND APPLICATIONS

The 302 section of the list below is for all 302 engines for the time period specified, not just Mustangs. The E7 heads were only installed thru 92 and 93 on some models.

289 STD . 65–67 …….…..ALL .. 54-55 … 1.67 – 1.45
302 ………...…. 68 …..…4 BBL … 52-54 … 1.78 – 1.45
……….…….. 68-69 ……..2 BBL ... 61-63 .. 1.78 – 1.45
……..…..……70-72 …….......? .… 57-59 … 1.78 – 1.45
………....…..79–84 … D9AE-AA …67–70 … 1.78 - 1.46
……….…….…... 85 …. E5AE-CA . 67-70 … 1.78 - 1.46
……….………..… 86 …. E6AE-AA . 62-65 … 1.78 – 1.46
……...….... 85–95 …. E5TE-PA . 62-65 … 1.76 – 1.46
……...….…. 87–95 …. E7AE-AA . 62-65 … 1.76 – 1.46
……...…..… 87–95 …. E7TE-AA ....... ? … 1.76 – 1.46
…….…...... 87–95 …. E7TE-PA . 60-64 … 1.76 – 1.46
COBRA .….….. 93 ... F3ZE-AA . 60-63 … 1.84 – 1.54 … GT40
COBRA …. 94–95 …. F4ZE-AA . 60-63 … 1.84 – 1.54 … GT40
EXPL …... 96–97.5 . F1ZE-AA . 63-66 … 1.84 – 1.54 … GT40
MOUNT .. 96-97.5 . F1ZE-AA . 63-66 … 1.84 – 1.54 … GT40
EXPL ……. 97.5-01 . F77E-AA . 58-61 … 1.84 – 1.46 … GT40P
MOUNT .. 97.5-01 . F77E-AA . 58-61 … 1.84 – 1.46 … GT40P

351 W .... 85–86 …. E5AE-CA . 67-70 … 1.78 – 1.46
…………..… 87-95 .... E7TE-PA . 62-65 … 1.78 – 1.46
LIGHTN ... 93-95 …. F3ZE-AA . 60-63 … 1.84 – 1.54 … GT40
COBRA R ...... 95 ……………….? ………..? …………………..? … GT40

The 351 heads use 1/2” head bolts and therefore require a bolt adapter kit to install them on 289 and 302 engines because those use 7/16” bolts.

http://www.summitracing.com/parts/TFS-51400419/

http://www.summitracing.com/parts/ARP-454-3605/

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post #2 of 3 (permalink) Old 03-18-2014
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post #3 of 3 (permalink) Old 04-17-2016
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I'm sure it was listed before, but exactly where on the head do you find the part number??

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