DOHC 4.6L V8 build

[2000StreetRod]

Fuel rails

The DivisionX fuel rails arrived today and are not exactly what I expected. The driver side (top in photo below) has a -8AN port at each end. There is a port that may match the fuel rail pressure sensor (FRPS) in the forward half and a plate that I think covers a 1/8 inch NPT port in the aft section. The allen heads on the aft plate fasteners are mangled and will probably be difficult to remove.

The passenger side (bottom in photo above) has a -8AN port at the forward end and a plug at the aft end.

The photo below is of the interior side of the rails.

The photo below is of the exterior side of the rails. Obviously, the rails were connected in the front. I was planning on connecting them in the rear but maybe there isn't room for that.

The seller told me they were in a return type fuel system. I'm surprised the passenger rail aft end was plugged. It was my understanding the Cobra and the Mach 1 fuel supply is on the passenger side. Maybe the feed was connected to the front of both rails and the return was at the aft end of the driver side rail.

I couldn't wait to see if the driver side rail would fit on the Mach 1 intake manifold.

It does but I would prefer to have the NPT port in a more accessible location if I connect a pressure gauge to it. In the next few days I'll remove the throttle body to confirm that the passenger side rail will install. Then I'll see if the driver side rail will install on the passenger side and not interfere with the throttle body with the FRPS installed. I need to look at blower installations to determine associated rail configuration requirements.

DivisionX makes a 90 degree FRPS relocation fitting for clearance when installing a Whipple 3.4L or 4.0L supercharger - larger than what I'll need but an additional reconfiguration option.

 

[CDW6212R]

Well you've done a good job taking it apart and finding what caused the failure. I'd want to upgrade to a stroker kit also once you need a crank and some rods anyway. Let us know what those end up running. The 302 stuff can be had for under $750, complete and balanced. That's why a lot of people end up going that route, given the decent kit price.

 

[2000StreetRod]

main bearings

I tried to remove the main bearing caps today but was unsuccessful probably because I don't have any impact tools. The side bolt heads are only size 13 mm and in my opinion that's too small for bolts requiring an excess of 150 lb-ft. Also, I should have soaked the bolts with P B Blaster for several days before attempting removal. I ended up rounding one of the bolt heads and mangled the corners of another even using a 1/2 inch 6 point socket which is a tighter fit than 13 mm. I also tried heat before rounding the one bolt head. Anyway, I was able to remove all six bolts of three caps. Number 1 was in pretty good shape.

Number 2 has a bad gouge.

Number 4 is badly pitted.

I'll take the block to a shop to have the remaining 4 side bolts removed.

 

[2000StreetRod]

oil dipstick and tube

The Mark VIII engine oil dipstick and tube arrived yesterday.

It will probably be many months before I can try it out.

 

[2000StreetRod]

fuel rail configuration

I confirmed that the passenger side fuel rail will fit on the driver side.

I also confirmed that the FRPS fits the fuel rail but that it can't be installed on the passenger side.

The intake plenum is resting on the FRPS electrical connector. Even if I purchased the 90 degree adapter and it fit a fourth of it would be behind the plenum. I would have to remove the plenum to replace the FRPS. So I'll install the FRPS rail on the driver side with the NPT ports near the firewall. The FRPS will only fit in one direction on the rail because its port is not centered between the mounting holes.

The base of the FRPS interferes with the plenum so I'll either buy the 90 degree adapter or cut down the base overlap to eliminate the interference.

 

[2000StreetRod]

main side bolts removed

I used my crane to transfer the block from the engine stand to the back of my Sport and drove to the shop where I plan to have the heads pressure checked, resurfaced, and a valve job with repairs as necessary. The cost for the pressure test is $80. The labor for the repair and resurface is $300 and parts are extra. The labor cost for bronze valve guides is $8/guide or $256. The shop owner advised me it wasn't worth the cost for my application (no racing - just street use). I also got the name of the machine shop the owner uses and I'll talk with them in a month or two.

The standard impact tool could not get the first main bearing side bolt loose with me pushing on the block with my feet while sitting in the vehicle between the front seat and the block and the shop mechanic pushing against the bolt with the impact tool. It wasn't powerful enough so they switched to a super heavy duty tool and broke the bolt loose. The tools below that I brought with me saved the day for the bolts I had mangled.

I was surprised the "sockets" didn't break because they were made in Taiwan and were made for a 3/8 drive. The hard part was separating the bolt from the socket after extracting the bolt. Total cost for removing the bolts was zero but the owner knew I would be coming back with the heads.

 

[Benjam]

He advised against bronze valve guides?

Benjam

 

[2000StreetRod]

An honest shop

The shop owner told me that bronze guides provide better cooling to the valves but since I only drive about 3K miles per year and the vehicle is strictly for street use there's no need for me to spend the money. A set of manganese bronze valve guides for a Mach 1 cost $190 plus the $256 to remove the old guides and install the new ones.

 

[2000StreetRod]

Crankshaft removed

Today I used the crane to transfer the block from my Sport back onto the engine stand. I was able to remove the remaining 4 main bolts and the two main bearing caps.
Main bearing number 3 looked pretty good.

Main bearing number 5 had some significant scratches but the sides looked good.

I removed the crankshaft so now the block is ready for the next phase.

 

[boominXplorer]

Honestly I would spend the money on the valve guides. Say you back out of the project, those heads are worth well over a grand with them. It's kinda like replacing the timing chains with good used parts instead new improved oem.

 

[2000StreetRod]

4.6L stroker kit dilemma

After doing more research I've realized that my aluminum block 4.6L V8 is like my 4.0L SOHC V6 with minimal displacement increase potential. According to mmr the maximum safe overbore for FI street use for the Teksid and cast iron blocks is 0.030 inches. My WAP aluminum block is thinner than the Teksid so I should limit my overbore to 0.020 inches. Even the Boss block max bore is limited to about 3.70 inches due to the cylinder spacing. When greater than that there is insufficient surface between the bores to achieve reliable head gasket sealing.

The 4.6L stroking potential is also disappointing. Increasing the stroke in a block requires reducing rod length or reducing piston compression height to maintain the stock block deck height. My stock specifications are:
Deck Height: 8.937 in.
Comp Height: 1.22 in.
Rod Length: 5.933 in.
Stroke: 3.543 in.
Wrist pin center to cylinder bore bottom at BDC: 0.465 in.
The overall assembly
height = comp ht + rod length + (stroke/2) or 1.22+5.933+(3.543/2) = 8.9245 in.
So the top of the piston is 8.937-8.9245=.0125 below the block surface

The stock (Mach 1) rod and piston is shown below.

The most popular aftermarket stroker crankshaft has a stroke of 3.75 inch which results in a displacement of approximately 5.0L with a overbore of 0.020 inch. For that stroke there are two configurations available. One is to maintain (or even lengthen to a standard length) the stock rod length and reduce the piston compression height. An example of this configuration is:
Comp Height: 1.112 in.
Rod Length: 5.95 in.
Stroke: 3.750 in.
Wrist pin center to cylinder bore bottom at BDC: 0.378 in.
The disadvantage of this configuration is the ring lands are thinner and there is no land for the oil control ring where the piston pin bore is.

This means less oil control and possibly less compression ring strength for FI.

The other configuration is to shorten the rod length and the compression height. An example of this configuration is:
Comp Height: 1.212 in.
Rod Length: 5.85 in.
Stroke: 3.750 in.
Wrist pin center to cylinder bore bottom at BDC: 0.278 in.
The disadvantage of this configuration is the rod angle at 90 deg BTDC and ATDC is greater and there is less distance between the piston pin and cylinder bore bottom.

That means more piston slap and increased wear.

To me neither of the above configurations is desirable nor worth the long term reliability decrease just to gain 0.4 liters. I'm approaching the same conclusion I did for my SOHC V6 - just use a supercharger to simulate increased displacement. However, for this block I still need a new crankshaft, forged rods and pistons to survive the increase in power.

 

[CDW6212R]

Wrist pin center to cylinder bore bottom at BDC

I agree with those judgements Dale. I've never really seen all of those specs, or in print together.

I would do as you seem to now, but I would like to compare the very common specs(limits) used for the stroker 302 parts.

I think the most critical dimension for stroking the 4.6 engines is the Wrist pin center to cylinder bore bottom at BDC. I'd love to know what that spec is for the OEM 302 and 351 blocks, plus the aftermarket Dart 302, 351, and the FMS Boss 302 block. I believe that the spec will be very interesting to compare for the 4.6 and the Boss 302 block.

I bet you that the same limitation of the Boss 302 block is what is hurting the 4.6 blocks, the piston cylinders are too short. You can build very reliable(oiling and long life) 302/347's and 351/427's with stock blocks, but the short cylinder Boss 302 block is dangerous to go beyond a 3.25" stroke(347 is 3.4").

The stroker 332/347 pistons and rods are shorter than the stock 4.6's(or 5.0's), in rod/stroke ratio, and oil ring lands. The problem I'm sure if that cylinder length, if it was say 1/4" to 1/2" longer, you could safely run a 4.0" stroke in the 4.6 blocks.

 

[CDW6212R]

What does it cost to sleeve all eight cylinders of a 4.6, and do any of the high end builders do that to gain more stroke? I bet that they do, but it's also very expensive.

 

[2000StreetRod]

cylinder sleeves

Cylinder sleeves were fairly common on European cars many years ago. My 1964 Alfa 2600 Spider had sleeves. If the pistons or cylinders were worn it was cheaper to buy a new set of pistons with sleeves than buy the pistons separately and have the sleeves bored to a larger size. No special tools were required for removal/installation of the sleeves. Many antique engines are restored to functionality with custom made sleeves since parts are no longer available.

I suspect race car teams use sleeved engines and they are readily available for modular Fords. I can purchase ($1325) a Darton set with a bore of 92 mm (3.605 in) that can be bored to 95 mm.

I think they have to be installed by a shop with a CNC mill/lathe.
The Ford Racing Boss 5.0L modular cast iron block has a bore of 94 mm with rough honed cylinders.

I've never seen the cylinder length specified in any shop manual.

 

[2000StreetRod]

Mach 1 owner's experience

I've just corresponded with a Mach 1 owner who pulled his engine because of a broken valve spring and wanted to check for interference damage. In 2008 the previous owner installed the mmr 3.75 inch stroker kit with 5.850 inch rods. The current owner purchased the vehicle almost three years ago. It was a daily driver for both owners and frequently driven hard (autocrosses and drag races). It has stage 3 heads and outputs 390 rwhp.

Anyway, he said that there was no excessive wear on the lower cylinder walls although he didn't pull the pistons to check the skirts for wear. He said if he were building an engine from scratch (like me) he would have no reservations in using the mmr stroker kit again. I guess I'll continue to research the issue and delay making a decision until I finally purchase a 3rd generation Explorer.

 

[CDW6212R]

See if you can learn what the lower piston skirt specs are. How far they do come out of the cylinder, and compare that to the very reliable 347 pistons used in thousands of 302 blocks. If they are similar, and you hear that the 3.75" stroker kit is reliable enough, I'd want that.

 

[2000StreetRod]

stroker - not an easy decision

I've spent hours reading the theoretical pros and cons of stroking the 4.6L and comments posted by Cobra/Mach 1 owners and it is difficult to reach a decision. Theoretically, the longer stroke with shorter than stock rods results in greater side thrust (increasing cylinder/piston wear) and longer stroke with longer rods results in decreased piston compression height (decreasing oil control). Increasing stroke increases TDC dwell time (improving intake and exhaust flow). Increasing rod length also increases TDC dwell time. increasing stroke also increases max piston speed. According to this article (Stroker Motors - Understanding the geometry behind the popular performance engine building practice) the manufacturers have determined that for street engines the minimum rod ratio (rod length/stroke) is 1.50 and that rod ratios between 1.65 and 1.80 are ideal. The stock 4.6L rod ratio is (5.933/3.543) = 1.67. Decreasing the rod length to 5.850 and increasing the stroke to 3.75 = 1.56 results in a ratio outside of the ideal limits. Even the longer rod of 5.950 results in a ratio of only 1.59. For comparison the rod ratio of a stock 302 is 1.696 vs 1.588 for a 302 stroked to 347. There are numerous 4.6L Mustang owners with the mmr 5.0L stroker kit installed but most seem to blow their engines before having them long enough for increased cylinder/piston wear to develop.

There is a lot of controversy among the 4.6L Mustang owners regarding the cost vs benefits of stroking. My summary is as follows:

1. The 4.6L max power increases more from a 5.0L bore than a 5.0L stroke because of less valve shrouding. Typical NA stroked engine max power increases range from 15 to 40 rwhp.

2. A FI engine benefits less from stroking than a NA engine.

3. A stroked engine with a positive displacement supercharger benefits less than one with a centrifugal supercharger.

4. Low and mid range torque increases are not noticeable for a stroked engine.

5. Even if the crankshaft needs replacement forced induction is probably more cost effective than stroking for power increase - especially at low to mid range engine speeds.

Below are dyno results for a 4.6L Cobra stroked to 5.0L with 18 psi boost from a Paxton Novi 2000 centrifugal supercharger.

 

[CDW6212R]

Concentrate on reliability over theoretical factors and limits. The 454 Chevy has horrible rod to stroke, but there it is as a reliable OEM engine. It's under the 1.55:1 level.

The power gained from displacement is worth it, for the cost, if the reliability is good. The 347 combination began as a seriously doubted engine, mostly for oil control and piston wear. Now after thousands have been built, and with optimized piston deck heights and piston lengths, those are very reliable. If the modular stroker kit has similar piston at the cylinder bottom specs, I'd trust them if there isn't a lot of negative clear examples with problems.

Look at the 347 versus the 332 stroker(it's not really a 331, the actual displacement is 332). The 347 has proven to be no less reliable as the 331(332). Given the tons of examples and theory about the possible issues, the 347 has proven to be a great choice versus the 332. The modular strokers are still kind of rare, so in a few years, enough examples will be available with results.

I think it comes down to the cost versus the stock parts needed, and the piston specs. What will a different stock crank and a few other parts(rod, rings, bearings) cost, versus the stroker kit?

 

[2000StreetRod]

Coyote 5.0L vs 4.6L

I found some specifications on the Coyote 5.0L to compare with the 4.6L.

************ Stock Coyote
************ 4.6L * 5.0L
Rod length: ** 5.933 5.933
Stroke: ***** 3.543 3.653
Rod ratio: *** 1.67 * 1.62
Deck height: * 8.937 8.937

Since the rod length and the deck height are the same then Ford chose to decrease the piston compression height rather than decrease the rod length. I wonder if a Coyote stock forged steel crank will fit in my 4.6L block. That would give me a displacement of 4.74L (289 cu in) with my stock bore of 3.55 inch. I've read that the Cobra 4.6L and Coyote 5.0L rods are interchangeable so that means the crank rod journals are identical. I've also read that the cylinder spacing (100.0 mm) is the same so maybe the mains are identical. If my cylinder bores are still within spec I might get by with no block machine costs. It might be cheaper to purchase a stock Coyote crank and aftermarket forged rods and pistons. That should be good to 500 rwhp with no problem surviving a future mild boost.

 

[boominXplorer]

I am not sure of the crank compatibility between it and the 4.6 but here is a low mile coyote with some good bearing damage at 20k mi that was in my work. Cause of damage unknown.