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tstkl

15+ Year Contributor
3,881
64
Feb 10, 2005
SoCal, California
Hey Guys,

I have an incredibly Frankenstein status car, so this bolt could be from pretty much ANY USDM 4g63T (1g/2g/evo). Despite all the custom parts I am fairly certain this is a genuine mitsubishi bolt as I almost exclusively use mitsubishi hardware on my builds and have a very large reserve from all the cars I've parted out over the years. Anyone know what it is or where it's from?
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Some additional details that may help:

The bolt is an M5x0.8 thread and measured 9.5mm ignoring the washers. I believe it would be listed as an M5-0.8 x 9 in CAPS but had no look searching for that. It could be M5-0.8 x 10 theoretically. The last few threads are slightly damaged. This leads me to believe it was pulled out from where it came from. At first I was thinking it was aluminum deposits but now I'm thinking the threads are slightly stripped. The bottom of the bolt is not damaged so it is not the head of a longer bolt.

It was found on the ground directly under the front of the engine. The car is a 1988 conquest with a 1g 7 bolt 4g63, a 2gb cylinder head, an evo 8 front case/oil pump, an evo 8 intake manifold and a 91+ throttle body. The bolt is not from the TPS sensor, ISC motor, or the 95 style cam position sensor trigger wheel. Additionally it is not one of the 3-4 long bolts on the alternator that hold the two halves together, although it could perhaps be another bolt on there. The car was on the dyno having the engine broken in at the time. I am using AEM adjustable cam gears and the bolts for the cam sensor trigger wheel backed out and ran into the head/valve cover. Unfortunately despite the AEM cam gear having the bolt holes and threads for the trigger wheel it is not compatible with the OEM bolts as they have a ~2.8mm grip length while the trigger wheel and washer stackup to about 2.3mm. So all four bolts backed out on me, one of them broke, bounced around a little and eventually got squeezed between a pulley and the belt itself before fully penetrating through the belt. In this process the tensioner pulley also loosened although it appears the valves did not contact the pistons after an initial visual inspection with a bore scope. The broken cam position sensor bolt was found directly next to the bolt shown in the photos, so I suspect it followed a similar exit path. All four trigger wheel bolts are accounted for and are round phillips head screws, not hex head like this one photo'ed. Additionally it is not from either the cam position sensor or crank position sensor themselves as those are m6 bolts and accounted for. I have extensively torn the front end of the engine down as I am upgrading from 1gb timing tensioner hardware to evo 9 timing tensioner hardware and have yet to find anything that seems reasonable. It is conceivable that it is from the chassis side but I haven't seen anything yet. Based on how short the bolt is it can't hold anything terribly meaningful, but I'm a bit thorough with my builds. I would guess it's holding some sort of thin sheet metal like the metal back sides of the timing belt covers however again those bolts are M6 and longer. I was under the car a few times throughout the day so while it is theoretically possible it was left over from a previous mitsubishi on the dyno (this happened at RRE) I believe it is unlikely as it wasn't obstructed by anything that would have prevented it from being seen. Any help would be greatly appreciated.
 
That's actually a really decent guess, albeit wrong. My transmission is a 1998 T-56 with a custom "bill housing" I'm using a tilton integrated throw out bearing/slave cylinder so I actually have three "inspection covers". For the one blocking the hole where the clutch fork would normally go I actually used nearly identical bolts to the one in question.

Also, I believe the fact that it's a Philips head means it's grade 4, which mitsubishi almost never uses for engine components (except apparently cam trigger wheels)

Keep em coming
 
yeah I'm pretty sure it's something engine related. When the trigger wheel bolts went it shook the engine pretty good and the two bolts were literally right next to each other under the oil pan. The car has a bit of an aerodynamic shield under it (most conquests have lost them by now) which would kind of funnel anything from the front of the motor down to that area. I'm pretty confident it would have come from the engine bay, and most likely hard mounted to the block.
 
@DSMPT Yup, definitely M5x0.8. I have a thread checker like you find in the hardware stores and it threads right in.

@TK's9d2TSi I'll check but I don't recall anything that small. They're popups so it wouldn't be anything similar to a 2g but perhaps a 1ga.

@steve people are going to think I fought in 'nam one day if I can't find charlie's home...
 
@DSMPT Yup, definitely M5x0.8. I have a thread checker like you find in the hardware stores and it threads right in.

@TK's9d2TSi I'll check but I don't recall anything that small. They're popups so it wouldn't be anything similar to a 2g but perhaps a 1ga.

@steve people are going to think I fought in 'nam one day if I can't find charlie's home...
Left is M6x1.0, right is M5x0.8. What socket size does the bolt have?
I can only imagine M5x0.8 bolts under the hood are the ones on throttle body for TPS and ISC. The ones for TPS has a flat/lock washer, 90 throttle body has a bit shorter bolts w/ larger washer for TPS than 91-94 throttle body. But the TPS bolts should have a dot on the head, so that's not the TPS bolt.
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The larger ones I've seen holding up splash shields the smaller on some of the timing belt covers and tins.
I bet with CAPS we could track down a few more places but I don't have access to my CAPS system here. (assuming the Win95 machine will still boot)

I thank the powers that be everyday I wasn't sent off to hunt down and kill people @ 18.
 
Left is M6x1.0, right is M5x0.8. What socket size does the bolt have?
I can only imagine M5x0.8 bolts under the hood are the ones on throttle body for TPS and ISC. The ones for TPS has a flat/lock washer, 90 throttle body has a bit shorter bolts w/ larger washer for TPS than 91-94 throttle body. But the TPS bolts should have a dot on the head, so that's not the TPS bolt.
It's M5x0.8.
The larger ones I've seen holding up splash shields the smaller on some of the timing belt covers and tins.
I bet with CAPS we could track down a few more places but I don't have access to my CAPS system here. (assuming the Win95 machine will still boot)

I thank the powers that be everyday I wasn't sent off to hunt down and kill people @ 18.
Any luck with CAPS? where is "here" relative to "there"? good excuse to put some miles on the stealth?

I was thinking the other day that I may have seen some bolts this small on the coil pack, however I'm running evo 8 coils and wires so it wouldn't be from those either...
 
It does look like a TPS 2G bolt. Tricky to remember exactly I might have the original bolts at home still as i try swap as much out to socket cap or stainless ones as i remove them.
 
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