i was curious on why the rods in a high horse 427-435 used 3/8 bolts, and i've seen some rods with 7/16 bolts? are the 3/8's correct for my 68? would it hurt the value or would i gain anything going to 7/16? would it be stronger? thanks again. also is there a way to identify the correct rod to make sure its original for my L-71 for documenting purposes? matthew
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3/8" dimpled is correct
Nobody can see the rods once it's assembled, so any rod would be ok. Your engine was originally assembled with the 3/8" dimpled rods - they are fine for street/strip type use to 6500 RPM - I have even used the later standard type 3/8" rods (with aftermarket bolts) to 6500 RPM. The 7/16" bolt rods were designed because the 3/8" rods were failing in endurance type applications. The 7/16" bolt rods were also forged of 4340 steel as additional insurance. They are heavier than the 3/8" rods and would require re-balancing your engine.
Nowadays, I would pass on all the factory stuff - too expensive new, and not worth gambling on used stuff. Get a good set of aftermarket rods instead for $200 to $350 a set brand new. For street use, I would recommend the stock type "I" beam rods with a pressed pin. If you go with the "H" beam racing type rods, you may have to cut the block for clearance depending on your stroke.
Mark -
i used the 3/8" rod bolts in every drag race
engine i ever built because you save about 1# of weight off of the rotating assy which allows quicker revs. we ran those engines 7500 RPMs thur the traps with no failuresComment
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Re: dimpled rods
matthew-----
All 1965-68 big blocks used rods with 3/8" rod bolts, including L-88. All rods were manufactured of the same material but rods for SHP applications were specially prepared and can be identified by the "raised dimple".
For 1969, things changed just a little. Most big blocks continued to use 3/8" rod bolts. However, L-88 and ZL-1 went to 7/16" bolts and a completely different forging---much stouter than other big block rod forgings to that time.
1970-74 big blocks also used the same basic rods as were used for non-SHP 65-69 big blocks, EXCEPT 70-71 LS-6 (1970 for Chevelle only; 1971 for Corvette only) used a new forging with 7/16" rod bolts. These were not the same rods, at all, as used for 69 L-88/ZL-1, but they were nearly as strong. A further improved version is still available today under GM #10198922. Unfortunately, their cost makes them somewhat uncompetitive with aftermarket rods of equal or greater quality and strength.
So, in summary, the only big block PRODUCTION engines ever built with 7/16" rod bolt rods were 1969 L-88/ZL-1 and 1970-71 LS-6. That's it.In Appreciation of John HinckleyComment
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Re: dimpled rods
thanks so much to you guys. your experience and knowledge educates us ( younger generation ) that was never around these applications. i think i'll stay with my 3/8's, i don't plan on killing this thing after its done. just intend to have fun once in a while, and enjoy it with the occasional blast down the strip. after all thats the thrill of these monsters. ( so i'm told ). hats off to ya!!Comment
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if you have not owned the rods since new
when you have them reconditioned also have them magnafluxed for cracks. these thing are only good for so many cyclesComment
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Re: if you have not owned the rods since new
i checked on the GM #922 rods. WOW! you can get a set of high dollar rods for those prices. list $170.00 , i can pick them up for $105.00. (each)Comment
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A set of Eagle 3D H beams is only $400 *NM*
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with any rod new or used they should be checked
for alignment,the big end bore and the wrist pin bore should be parallel with each other. i have even new rods needed to be straightened to accomplish this. if the shop you are dealing with does not know what you are talking about find a new shop with the proper equiptmentComment
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