I've wrote up my experiences with this stroker for anyone interested and to share information with my fellow FordMuscler's. It was an interesting project since my past experience has been with BBF and I had not built a SBF before. It's long, but I had a lot of things to cover. Enjoy!
During the process of restomoding my 65 Fastback Mustang, I had discounted the idea of stroking a SBF and settling instead with a somewhat larger displacement 302 engine and iron heads. Why?…primarily due to cost reasons since the entire restomod would approach $25K. Could I justify a $1200 stroker kit and $1200 heads? I was also concerned about longevity and oil consumption of strokers ( 331 and 347 stroker kits at the time had pistons with pins that intersected the oil ring...now we have 5.315 rod kits ). Restoring an entire car is not an inexpensive venture and I felt that sinking additional money into a stroker kit and aluminum heads could not be justified especially when I consider how well the car ran with the original A code 4 bbl 289.
I have to admit that I made this decision before I really seriously started building my engine.
Anyhow, the time came to start working on the drive train. Dave Williams has a site with some very interesting and informative engine information (
http://www.angelfire.com/ar/dw42/ ). In particular, one story discusses a customer's desire to stroke a 289 to a 366 using 289 rods. Dave went to great lengths to balance the custom ground crankshaft given that a whole lot of material had to be removed from the counterweights to clear the bottom of the piston. Honestly, I think this was an extreme case of stroking a 289/302 and I would not feel the investment would justify the performance gain. This story got lodged in the back of my mind and was recalled some time later while designing my engine as you'll see.
At some point, I was surfing the web and noticed how inexpensive the speedomotive 331 stroker Hi Nodularity crankshaft was…$189…Wow, a stroker crank capable of handling 450-500 HP for $189…what's the catch? Essentially there was none. Yes, the crank was cast in China, but the final machining and magnafluxing is done in the states. I figured that having my 302 crank reground and magnafluxed was going to cost me nearly $100 so why not pay $89 more for a new 331 crankshaft. The journals mic'd out right on the money.
Ok, so I had a potential stroker crankshaft, but I still don't like the idea of a SBF stroker that has the oil ring intersecting the wrist pin (at the time, the improved oil control stroker kits were not available). What to do? It hit me, a 289 rod is .065 longer than a 302 rod. Maybe I could use inexpensive, plentiful 289 rods and find an off-the-shelf piston with a longer compression height and skirt that would work. Given the 302 deck height, stroke of the 331 crank and the length of the 289 rod, I needed a piston with a 1.426 compression height…great!…that's a longer than typical compression height for a stroker piston so maybe I can find a piston that has the oil ring above the wrist pin! In addition, a longer skirt may be less prone to piston rock in the cylinder. What about the rod/stroke ratio? 5.155 / 3.25 = 1.59, the same as a 347 stroker with 5.4" rods…cool!…and better than several 351W based stroker combinations!
So my piston search began. Low and behold, KB had a piston for a 351W based 383 stroker with 1.405 height and +6.5 cc volume (due to two generous valve reliefs). The piston is the KB322 and the oil ring is above the wrist pin. A little math revealed 9.9:1 compression with 61 cc 351W heads…perfect for a semi long duration cam of about 230 duration @ .050 ( I was at the time considering the Comp Cams 280H or 282S cam and I finally settled on the 282S). Wait a minute though, the wrist pin is a Chevy size pin, .015 larger than a 289 pin! Can the 289 rod small end be enlarged? After a few calls later to a couple of reputable shops the answer was "no problem". The fact that the piston was a little shorter than 1.426 meant that I had room to deck and true the block. A local shop recommended the deck be milled for the piston to be .005 below the deck due to thermal expansion and rod stretch during engine operation.
I bought a set of .030 KB322 pistons and the 331 crank and it was time to mock up a cylinder to see how things fit. I mocked up cylinder #1 in the original 289 block which was bored to .060 over years ago. Since the early 289 and early 302 blocks are identical, the old 289 block would do fine for a mock up even though the piston was a bit loose in the bore. I was looking for major fitment problems anyhow.
I rotated the mocked up cylinder and the bottom of the piston boss was hitting the crankshaft counterweights just like the 366 stroker mentioned above. I had to loosen the rod cap nuts about ½ turn to get the parts to clear…now what? Can I remove material to get things to clear? I called Speedomotive immediately and they said that it is common for them to have to remove material from the crankshaft in strokers. They also said that I should have about .065 running clearance between the piston boss and crankshaft counterweights. It turns out that there is plenty of counterweight material on the speedomotive crank that a lot can be removed and the crankshaft will still balance out without using expensive heavy metal. I removed about .075 from the counterweight faces with an angle grinder and I removed about .015 from the KB322 piston bosses. The width of the piston boss at the thinnest point between the wrist pin hole and the bottom of the boss was .220. The piston can be as thin as .200 safely as told to me by a local shop so I settled for removing .015. Be sure to re-check clearance after your done.
Using Ford 289 rods will probably not require notching of the cylinder skirts to clear the rod nuts since there is adequate clearance. Every individual engine should be checked to be sure that adequate clearance of at least .065 is present. ARP bolts, magnafluxing, and shotpeening are recommended upgrades to the 289 rods for operation to 6500+ rpm. Polishing side beams is optional for added insurance. Be sure to check the rod nut to cylinder skirt clearance after ARP bolts are installed. It is NOT recommended that full floating bronze bushings be installed in 289 rods since too much material has to be removed from the small end. Instead, press fitting the wrist pins is recommended. If your going to be pushing some serious HP, aftermarket 289 I beam or H beam rods can be had. I took the H-beam route after I found a set of Hawks H beam rods for only $295 from the Mustang Depot on ebay which was probably not a lot more than the cost of improving the Ford 289 rods. Notching of the cylinder skirts was required with these rods.
The engine machining was done and reciprocating components were balanced. The short block was assembled with no problems. Speed Pro moly rings and Clevite 77 bearings were used. ARP studs were used on the main caps. Total cost of the Speedomotive crank, KB pistons, and 289 rods is about $650 ($750 for H beam rod kit), far less than any 331 stroker kit on the market. Rings and bearings are about another $100.
The heads chosen were early '70 351W heads. The intakes were ported and gasket matched using FelPro 1262 intake gaskets (2.10 x 1.28 port size) and the exhausts were ported and gasket matched to Copperseal gaskets (1.48 x 1.25 port size). Flow is approximately 220 cfm @ 0.5 intake and 175 cfm @ 0.5 exhaust. The intake volume was increased about 25% to 160 cc. The exhaust volume was increased nearly 40% (thermactor hump completely removed). I had 1.94 / 1.6 stainless valves and bronze guides installed, screw in 3/8 studs, and 5/16 guide plates installed in the heads. Total cost of machining and parts on the heads were about $600. Far less than aluminum heads and flow that rivals some off the shelf units. The benefit of using the 351W heads is the intake port volume and high charge velocity during engine operation promoting excellent torque especially at low and mid rpms. Final chamber volume was 60-61 cc. I had a little trouble finding headers that had inlet ports that were as large as my ported exhaust ports. Doug's Headers Tri-Ys were a perfect match. Grade eight 7/16 washers and ARP 7/16 bolts were used to fasten the 351W heads to the 302 block.
Heads were installed using the Felpro 0.039 thickness hi performance gasket. A 5/16 wooden dowel was used to determine the correct pushrod length by trimming the dowel with a bench grinder until the Comp Cams Pro Magnum roller rocker tip was in the center of the valve tip @ ½ of total valve lift. The valve springs on the test valve were replaced temporarily with a weak spring (inexpensive thin wire spring picked up at a local hardware store ) that would not break the wooden dowel. The optimum pushrod length was determined to be 6.950".
While installing and testing the valve train, it was observed that the pushrods were just barely coming in contact with the outboard side of the pushrod hole that goes thru the head. The valve train had to be disassembled and the pushrod hole slightly enlarged at the top outboard side of the hole. This problem is caused by the high lift cam and outward movement of the rocker arm pushrod cup as the valve opens. If you use a high lift cam and stock iron heads, open up the pushrod holes slightly BEFORE the heads are installed. It was tedious enlarging these holes and preventing metal shavings from falling into the engine when the heads were on the engine!
Other lessons learned were:
1. Do not adjust valve lash (solid) or lifter preload (hydraulic) until the intake manifold is installed and torqued. I adjusted my valve lash before intake installation and the lash changed about .004 tighter after the intake was installed. Had to do it again.
2. Don't use a high volume oil pump if your clearances are within the standard tolerances. I did and the pressure at idle was 70 lbs and high rpm pressure was almost 100 lbs. I replaced my oil pump with a standard one and pressure was 35-40 lbs at idle and 65-70 lbs at higher rpms.
3. Be sure the guide plates are aligned properly. The guide plates control the rocker arm alignment and the contact point of the rocker arm tip to the valve tip. I had a couple of misaligned guide plates that were causing the rocker arm tip to be dangerously close to the front or back edge of the valve tip. Had to remove screw in studs and realign the guide plates. Be sure to use a thread sealer on the screw in studs as they go into a water jacket.
4. If poly locks are used, tighten the set screw first and then give the nut a turn to really lock it into place. I set my lash to .019, but I have to adjust the poly lock for .023 and then tighten the set screw. Finally, I turn the poly lock nut down to lock it in and this closes up the lash to the final .019.
5. Be sure to fully install your intake manifold and torque it to specs before marking it's location for port matching the runners. Use the same manifold gaskets that you will use in the final assembly and throw them away and buy another set after matching the manifold.
6. Be sure to use thread sealer on the flywheel bolts since the bolt holes lead thru the crankshaft into the crankcase.
7. If you use a rebuilt stock Ford harmonic damper, check the TDC mark on the harmonic balancer for accuracy using a piston stop in cylinder one. My rebuilt stock unit was off by 5 degrees and I re-indexed the timing marks. Later, I changed over to a Pro Race Street model harmonic damper.
8. Don't forget to open up that top ring gap as specified by the manufacturer on Hypereutetic pistons.
Parts List:
'68 302 block ( this block and my old '65 289 block have the same cylinder length of 5 1/8 inches...the debate rages on).
Hawks H beam 289 rods (Ford 289 rods equipped with ARP bolts and shotpeened would have fit the bill but I found such a good deal on these H beam rods that I went for it)
KB322 pistons
Speedomotive hi-nodularity 3.25 stroke SBF crankshaft
Clevite 77 P series bearings throughout
Speed Pro file fit moly rings
New stock oil pump
Miloden windage tray
Canton 7 quart oil pan and pickup
'70 351W heads ported and 1.94 / 1.6 stainless valves
Weiand Stealth 8020 intake manifold port matched to 1262 Felpro gasket
Doug's Headers Tri-Y headers (in conjunction with 160cc intake runners should help promote good torque response)
Comp Cams 282S flat solid lifter cam and lifters
Comp Cams Poly Locks
Comp Cams valve springs, retainers and locks
Comp Cams Pro Magnum 1.6 true roller rockers
Ford Racing tall valve covers
Holley 770 Street Avenger carburetor
Cloyes true roller Hex Adjust timing chain
Pertronix ignition
Rebuilt and recurved Ford distributor (16 deg BTDC initial, 34 deg BTDC final)
Flame Thrower coil
Taylor 8mm spark plug wires
Pro Race Street model harmonic damper.
Engine Results:
The engine was built and test run on a modified engine stand. After the initial 20 minute break-in, timing was adjusted and the idle mixture was adjusted. It is a very willing and fast revving engine (granted my experience is mostly with big blocks). I have the engine in the car now. I hope to have the car on the road within a few months.
Engine power estimate at the flywheel:
417 Hp @ 6100 rpm open headers (see note)
418 ft-lbs torque @ 4500 rpm open headers (see note)
387 Hp @ 6000 rpm w/dynomax mufflers (see note)
394 ft-lbs torque @ 4500 rpm w/dynomax mufflers (see note)
Note: Estimates based on Engine Analyzer 3.0 and Dyno2000 simulations which were in agreement with each other to within 5 HP and 5 ft-lbs of torque. If i'm within 90% of this, i'll be happy. HP and Torque numbers revised on 11/15/03 due to incorrect cam duration used at .050. HP and Torque numbers revised on 7/20/04 to include tight quench increase. Actual Dyno numbers available below.
10/23/04 Update: Went to a new dyno tune shop where they perform complete engine tuning. First run was 290 RWHP and 297 RWTQ. After adjusting timing and carb mods to correct a lean condition 308 RWHP @ 6300 and 307 RWTQ @ 3700. These numbers were at the rear after going thru a C4 auto trans and a 9" posi rear. The car also had a dual 2.5" exhaust system. A few days later, I found that my throttle was not opening all the way so maybe a few more HP were on tap. Estimating 20% drivetrain loss, it looks like its right in the neighborhood of 390 FWHP and 390 FWTQ. EA 3.0 estimate was 387 HP and 394 TQ with mufflers.
08/26/05 Update: Installed a custom tuned holley 770 street avenger and returned to the chassis dyno for a new run. The vacuum secondaries were sticking and not opening completely so I asked them to open them manually to get peak HP and torque with the new carb. Peak HP was 313 @ 6300 and peak torque is unknown because they didn't manually open the secondaries until 4500 rpm. The new torque curve was significantly higher than the old curve from 4500 to 6500 so the new peak torque figure could be approaching 315 to 320. The new HP curve was also higher by as much as 10 HP from 4500 to 6500. I fixed the carb and also put a 1" spacer under it. Someday i'll get it back to the chassis dyno.
12/10/05 Update: Converted from the problem plagued C4 to a T5z and the car runs excellent. What a difference a transmission makes. It really feels like more power is getting to the ground now. I hope to have a new chassis dyno done sometime before the new year.
1/11/06 Update: It's time to chassis dyno the car since the T5z conversion. I have also added a 1" spacer since the last dyno (elongated 2 hole with center separator). The new dyno numbers are:
335
RWHP@6400 and 337 RWTQ@ 3900 (SAE correction)
STD correction numbers were 345/347. I understand that magazine articles tend to use STD correction so I provided both corrections here. The dyno was the same dynojet used with previous chassis dynos.
I am very happy with these results. This puts me right at or very close to 400/400 at the flywheel (SAE correction) using a 15% or 16% drivetrain loss factor. <IMG SRC="/phpBB/images/smiles/icon_smile.gif">
The vacuum secondaries were still opening too slow so during the second dyno run they opened them up manually. Here is the dyno chart and the dip around 3800 is where they opened the secondaries manually causing a momentary rich condition. This is the STD correction chart. The lower numbers are from the previous dyno while I still had the C4 auto.
I may have to dump the vacuum secondary carb in favor of a 750 DP. Everything has been done to the carb to make the secondaries open as quickly as possible. The dyno guys mentioned that they have seen coated carbs (nickel or chrome) have partially blocked passages in the carb body where you can't get to them...lucky me...<IMG SRC="/phpBB/images/smiles/icon_frown.gif">
9/14/06 Update: Could not solve the slow vacuum secondary problem so a couple of months ago I converted the carb to mechanical secondaries by putting a small nut and bolt into the linkage slot. I didn't have much hope of this working since there is not accel pump on the secondary side, but guess what...it worked great. The only time I get noticable hesitation is when it's cold...problem solved.
Crank was dropped a week ago to get it resurfaced. I visited a road course in late June (2nd time out) and oil starved the engine and wiped a couple of bearings. Warning...the Canton 7 quart pan is not a road racing pan. I bought a new 9 quart Canton road race pan to replace the existing pan...live and learn.
dyno chart
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