I recently assembled a new engine for my brother's '66 Comet. ALL parts were new.
- Ford Racing M-6009-363 363 cid crated shortblock, 4.125" X 3.40", with Mahle forged flat top pistons with generous valve reliefs
- Flo Tek 185cc 'Thumper' CNC ported aluminum heads w/ 2.02"/1.6" s.s. valves (rated flow = 278 cfm Int & 182 cfm Exh @ .600" lift)
- Ford Racing M-6051-R351 head gaskets and M-6014-BOSS ARP head studs
- Lunati Voodoo VDSF-282 hydraulic roller cam (231°/239° @ .050", .581"/.587" lift, 110° LSA); Rollmaster billet roller timing set; Installed @ 109.5° Int C/L
- Edelbrock Performer RPM Air Gap intake manifold (professionally ported by Joe Crane)
- Quick Fuel 650 cfm SS-series carburetor
- Jegs #20990 1.6 ratio 3/8" stud aluminum roller rockers; Jegs #20277 6.248" pushrods
- Boss 302 6-quart oil pan & 5/8" tube pickup, Melling Hi-Volume oil pump, ARP drive shaft, Comp 10W-30 Break-In oil
- Patriot 'Clipster' shorty headers
- Pertronix billet electronic distributor, Ford Racing 8.2mm wires, Autolite AR3932 spark plugs gapped at .035"
The engine was carefully assembled, with everything torqued to specs, and the cam degreed per Lunati's specs. The cylinder heads had been originally set-up by the factory for flat tappet use, so the springs, retainers and keepers were replaced with Trick Flow PAC dual springs (16315-16), Chromoly steel retainers (51400423) and hardened keepers (51400444) for use with the HR cam. The adjustable guide plates were maneuvered to get the rocker roller tips aligned on the valve stems.
When installed and fired, the engine started instantly and ran well. Pressures, temperature and leaks were checked. The initial timing was set at 16° BTC. The car was then taken for a drive of about 18 miles, and there were no issues with the engine's operation. RPMs were kept below 3,000. The exhaust had been cobbled together with 2.5" stubs, 20° & 45° bends to mate up with the previous dual exhaust system until the car could get booked into a muffler shop for a complete new exhaust system. There were leaks from the ball & socket collector flanges, so the head pipes were removed and re-positioned. NOTHING else was changed.
On the next run, there was only a minor leak from the passenger side exhaust, so another drive was attempted. Within half a mile there was a loud backfire, and the engine began running poorly. It did not want to rev-up, and had little power. It backfired several more times.
On examination, we found that the #7 exhaust rocker arm had broken in two down around the trunnion, with the polylock nut seized in its slot. The pushrod was bent. Any is not good, but it wasn't excessive. We checked the other rockers and all appeared to be still adjusted properly, except for the #2 exhaust rocker, which now had a slight amount of valve lash. We couldn't see anything amiss, so it was readjusted to zero lash plus one turn. A compression test was done, with all cylinders falling between 152-162 psi, so there were apparently no bent valves. The engine started fine, and again the car was taken out on the road...only to return within two minutes, farting and popping. This time, that #2 exhaust rocker arm was broken.
All of the rocker arms, pushrods and studs were then removed. What we found was that the ball on the lifter end of that #2 exhaust pushrod had broken off, and the end of the pushrod was badly mushroomed. Four of the other pushrods were now bent. Four of the other rocker arms had trunnions that would only rotate with a good effort, not freely as they should have.
The intake manifold was removed to attempt to locate the missing pushrod ball, and it was found sitting in the valley beside the lifter boss. And it was now found that the #7 exhaust lifter had a chip out of the upper rim, and that the snap ring had popped up from its groove, but luckily not gone anywhere. At this point we stopped work, unable to explain what was happening, and why?? The engine had been rotated dozens of times by hand for valve adjustment prior to startup. There was no interference that could be felt then, so what had changed?
If you've gotten this far, you know that I'm perplexed and frustrated. I could really use some help from those of you with engine building experience. What did I miss? What should I check?
Thanks for your time!
