I've wrote up my experiences with this street stroker for anyone interested and to share information with my fellow Fordmuscle'rs. It was an interesting and fun project since my past experience has been with BBFs 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. I was also concerned about longevity and oil consumption of strokers. Restoring an entire car is not an inexpensive venture and I felt that sinking additional monies 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. The rod/stroke ratio of 5.155 / 3.6 or 1.43 seems small anyhow. 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 400-500 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.
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 stack 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 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 one 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 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. 11/32 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. Notching of the cylinder skirts may be 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 rod work was $650, far less than any 331 stroker kit on the market. Rings and bearings were 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 (1.5 x 1.25 port size). Flow is 220 cfm @ 0.5 intake and 180 cfm @ 0.5 exhaust. The intake volume was increased about 25% to 160-165 cc. The exhaust volume was increased nearly 50%. 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 superior torque especially at low and mid rpms. Final chamber volume was 60-61 cc. These heads will support the 331 to 6500 rpm just fine. 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 small 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. The lifter galley accumulated a lot of oil soaking the bottom third of the intake manifold gasket and causing a vacuum leak and the engine to suck a small amount of oil from the intake gasket (milling the heads and block probably contributed to this problem). I had to re-install my manifold with a thin coat of sealer this time. I'll be replacing my oil pump with a standard one also.
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 .020, 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 .020.
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 marking the manifold.
6. Be sure to use thread sealer on the flywheel bolts since the bolt holes lead thru the crankshaft into the crankcase on a SBF.
7. Check the TDC mark on the harmonic balancer for accuracy using a piston stop in cylinder one. Mine was off by 5 degrees and I re-indexed the timing marks. I used a reconditioned Ford harmonic balancer. A local shop highly recommended to stay away from fluid type harmonic balancers for a street engine. The engine rpms change too much on a street driven car for them to be effective and detrimental engine damage can occur when rpms change abruptly.
8. Don't forget to open up that top ring gap on Hypereutetic pistons.
'68 302 block
'65 289 rods reconditioned and strengthened (ARP bolts, magnafluxed and shotpeened)
Speedomotive hi-nodularity 3.25 stroke SBF crankshaft
Clevite 77 bearings throughout
Speed Pro file fit moly rings
Melling hi volume oil pump (went back to a new stock pump due to excessive oil volume and pressure)
Miloden windage tray
Canton 7 quart oil pan and pickup
'70 351W heads race prepped
Weiand Stealth 8020 intake manifold port matched
Doug's Headers Tri-Y headers (in conjunction with 165cc 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
Ford Racing tall valve covers
Holley 670 Street Avenger carburetor
Cloyes true roller timing chain
Rebuilt and recurved Ford distributor (16 deg BTDC initial, 34 deg BTDC final)
Flame Thrower coil
Magnacore spark plug wires
Reconditioned Ford 289 harmonic balancer using elastomer instead of rubber
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. The engine (without any load) is very responsive to throttling. Engine rpms climb extremely fast when the throttle is opened. This is the most responsive and fastest revving engine that I have ever experienced (granted my experience is mostly with big blocks). Rpm runs at 6500 have been performed with no problems. I hope to have the engine in the car within a month.
Engine power estimate at the flywheel:
402 ft-lbs torque @ 4500 rpm *
398 Hp @ 6100 rpm *
* Estimates based on open headers using 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 95% of this, i'll be happy.
Tracy Blackford: Corona, Ca
Restoring '65 Fastback Mustang
329 with speedomotive hi-nod 3.25 crank, stage II 289 rods, KB 322 pistons,
282S cam, and fully ported 351W 1.94/1.6 heads to top it off.
[ This Message was edited by: blkfrd on 12/21/02 2:02am ]