Barely bigger than valve cover bolts. Not a good gamble to take. They are cheap enough to justify the peace of mind.
Yes, the bolts are cheap BUT it's a bit expensive to have the rods re-sized for them. I have read the the weakest link in the Ford 302 is the stock oil pump drive rod, and the 2nd weakest link being the rod bolts. I already got a ARP oil pump drive rod, but was wondering if anyone here has any experience with the stock rod bolts breaking. (?) My original 302 went 183,000 miles, driven hard, and never broke anything. Anyone have any stories to tell?...
Dad's running stock bolts in the stock rods in his 302, turns 6800-7000 every pass with heavy cast 10.8:1 compression pistons. Knock on wood, it's still together. I ran almost 2 seasons on stock rods in a 302 turning over 8500-9000 with TRW 11:1 pistons that might as well have been made of lead. I tried to blow that thing up and I couldn't seem to hurt it in the burnout box.
T.L. the stock 302 rod bolts are a lot like the heads that Ford puts on their motors. THEY SUCK! Replace them for your own peace of mind! As always just my .02 Bossmav
Just have the rods reamed for the GM 11/32 inch bolts and put in the high strength units from ARP. Even the 250 six cylinder has 3/8 inch bolts. They were originally made for the 221 cu in V-8 from Ford that turned into the 302. They are the weak link as far as strength to load ratio. PaulS - just another opinion from an old man
I know that the ARPs are far better than stock...that's a given, but I am just wondering if the stock ones are "good enough" for an engine that doesn't make more than 250hp. This particular engine never sees over 5500 RPM. Does anyone on this board have any actual experience with rod bolt failure in a 302 ?? Just curious...
At 5500 RPM the average piston speed is only 2750 FPS. At speeds above 3200 FPS you should have 3/8 inch bolts. I have repeatedly turned a 289 to 5500 without problems with the rod bolts - the 302 is just a bit more. You can probably get away with it if the engine is balanced but you can gain reliability by using after-market 5/16 bolts without reaming the rods to accept the oversize bolts. PaulS
From what I'm told, that's an even quicker way to disaster than just using ARP 5/16" bolts. Supposedly, reaming the holes out to 11/32" removes precious metal from the cap and big end which is already small...and weakens the rod itself. As many 302's as we've had with stock rod bolts, and no failures whatsoever, I'd say the 5/16" bolts are just fine for a motor under 7000 RPM, as long as they're GOOD 5/16" bolts. The stock bottom end of a 302 is a hell of a lot stronger than people give them credit for. You'll usually break the block before anything in the bottom breaks, at least that's what I've seen from others' experiences.
we have stock rods and bolts in Tammy's car no problem so far....but we don't drag the car either, just a nice daily driver. It makes 295 RWHP@ 5900 RPM
no, that's what happens if you try to go to the 3/8 inch bolts. there are some options: C9OZ-6200-B heavy duty rod with oval head 3/8" bolts (for the over 7000 range) have the rods reamed for 11/32" bolts and install either ARP or SPS high strength bolts that are made for SB chevy (up to 7000 for short times) Stock rods and bolts for 5000 or less If you want to go all out you can get the TransAm 302 rods (D0ZX-6200-A) and special pistons (if you can find them; lower compression height and short skirts because the rods are as long as 289 rods) PaulS
