Birdie2000
Club Member
I need to know the thread size of the 3 holes on the block that the motor mount clamshell bolts to. One of them got screwed up and I have to chase it with a tap.
Thread size for LT1 motor mount holes?
- Thread starter Birdie2000
- Start date
fastredgmc
Forum Member
probally 3/8 16
All generations of the original SBC v8 at least gen1 and gen 2 tpi,l98,tbi,lt1 etc are standard thread engines.
There are a few bastard years of the 4.3 v6 starting around 1999 or so that are metric thread engines.
This of course changed with the gen3 and up engines.
There are a few bastard years of the 4.3 v6 starting around 1999 or so that are metric thread engines.
This of course changed with the gen3 and up engines.
dave89iroc
Club Member
LT1 factory bolts are all standard thread, tho some bolts were metric heads..............
beertestr
Club Member
If it bolts to the block or heads, it's standard. If it bolts to a new part, like the accessory bracket, or intake... it's metric.
3/8-16 for the motor mount brackets.. cause it's to the block. 10x1.5 might be able to be forced in since 3/8x16 is like M9.5x1.6 once you convert to metric. I've seen that before.
Another example. Intake bolts - 3/8-16. Fuel rail bolts M6x1. TB bolts M8 or M10 x1.5 I forget, but not 3/8 for sure... Let's not forget that most of the plumbing is NPT... I think my 5.0 Ford was the same way, but it's been a LONG time since I tinkered with that motor.
I assembled an LT4 for a friend of mine with ALL NEW parts, and most of the bolts are not available from the dealer anymore, so I had fun with mounting the accessories and the accessory bracket. I lost track of how many runs I made to the bolt shops when I put it together.
Once I figured out the above rule, things were a lot simpler.
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