GM/Chevy 250 Conversion in 90/110/130

RDavisinVA

Technical Excellence Contributor
AC charged and blowing cold, just in time for the cooler fall weather!
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Adog

Well-known member
Cleaned and painted some parts while I wait for my rebuilt 250 to arrive. Bought a donor engine to grab manifolds, brackets, oil pan to move over. Kiddos voted for red and black (bulldog family) for the engine color.



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Adog

Well-known member
Engine is here .. looking forward to getting it on the stand and painted up. The holly sniper arrived as well. I now have most of main parts outside hoses clamps miscellaneous items.
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Brrrrt

Member
Engine is here .. looking forward to getting it on the stand and painted up. The holly sniper arrived as well. I now have most of main parts outside hoses clamps miscellaneous items.

Which a Holly Sniper did you go with?
 

Adog

Well-known member
Robert suggested the 2gc small bore I went with the black ...

Got her on the stand .. hope to get a coat of paint on soon and start assembly (never done this so lots of videos to be reviewed. Engine came with oil pump and various gaskets .

I ordered a bolt kit from alloy boltz that has all the fasteners however I believe it’s stainless Robert advises against stainless In his guide.

not sure what are best type of bolts to use for non load applications ...
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RDavisinVA

Technical Excellence Contributor
Interesting that they sent you a block casting without the mounting flange on the right side.
It is only used for LHD, so not a problem for RHD conversions.
 

Adog

Well-known member
Getting closer...

Timing cover/oil pump/ pan water pump and tstat are all sealed (Hopefully) and bolted up could not get crank shaft on all the way little over 1/8 to go (don’t want to hammer it on more than I have) It won’t budge so I am going to have to drill and tap the snout to get the pulley fully on. Set the engine to the #1 and dropped in the distributor made my marks on the engine for when I have to remove to prime the oil pump. This is my first go at something like this and hopefully will have it dropped in the defender as soon as Roberts kit arrives. The hd clutch /new fork and release bearing arrived from Ashcroft.
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Napalm00

Technical Excellence Contributor
Getting closer...

Timing cover/oil pump/ pan water pump and tstat are all sealed (Hopefully) and bolted up could not get crank shaft on all the way little over 1/8 to go (don’t want to hammer it on more than I have) It won’t budge so I am going to have to drill and tap the snout to get the pulley fully on. Set the engine to the #1 and dropped in the distributor made my marks on the engine for when I have to remove to prime the oil pump. This is my first go at something like this and hopefully will have it dropped in the defender as soon as Roberts kit arrives. The hd clutch /new fork and release bearing arrived from Ashcroft.
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before you drill the crank and upset any balance from the rebuilder. Pull the damper/pulley and hit it with some scotchbrite on the inside of the bore, then using a heat gun (not a torch) heat the bal until its almost too hot to touch, should slide right on the crank snout lubed with some grease. the fit is meant to be a slip fit from the factory, not an interference fit. dont hammer on it as you could damage the thrust bearings that locate the crank axially.
 

Adog

Well-known member
I will try ... I put it in the oven for 30 mins at 200 and couldn’t get it on. I just removed the pulley and noticed the timing cover seal was bent a bit .. I am guessing the key slid back and was the reason the pulley would go on all the way. I have to be honest I did hit it with rubber mallet with a block. Last 1/8 or so wouldn’t budge. I will try and heat it for longer but honestly I can’t imagine this sliding on without some leverage or force... I bought a jig that looks pretty hight quality to drill and tap. I ordered a new timing cover and I guess I will drop the pan clean and reseal with a new gasket to replace timing cover . I might use the key that came with the balancer instead of the one that came with The engine. Anyone in Atlanta I will be happy to feed you beer to help me get this thing on.
 

Napalm00

Technical Excellence Contributor
If you already heated it then there's some other issue. You're in the right ballpark that's for sure and don't heated any further than what you did because obviously the rubber would separate.

I agree with you that it sounds like the key slid upwards along the crank and probably kept it from going on, especially if the seal/cover now has a ding in it.

If you're already bought the jig to drill it I guess go for it but the factory designed this not to be like that. Has to be some other problem lurking. Getting a second set of eyes on it will probably help!
 

Adog

Well-known member
I honestly feel pretty good on drilling... the bit tolerance between the jig and bit was very tight. It slides tightly over the snout. I might heat again same time frame and grease the heck out of it and see what happens .. before I pulled the pulley I wanted to see if there was any play and there wasn’t so I am pretty confident no damage. (Fingers crossed)
 

RDavisinVA

Technical Excellence Contributor
We drill them all the time and have a jig for accuracy.
All the later Chevy engines are drilled and also most of the same period like the 292, but for some reason GM did a press fit on the 250 crank pulley.
I think the key being cocked caused the pulley to stop before going home.
 

Adog

Well-known member
I am going to give the jig a go later today. I like the fact that I can take it slow when pressing on. I purchased a grade 8 threaded rod and some washers and nuts. The jig drills out 1.75 inches and then you tap.. it’s a 7/16 so I figure 1.75 +- would be solid purchase to help pull the pulley on. I like the fact then I could put a bolt to ensure the pulley doesn’t come off.
 

RDavisinVA

Technical Excellence Contributor
With aftermarket pulleys, tapping the 250 crank is a good plan because you never know what sort of fit you'll have.
I would sand the inside if the pulley down a little.
With the bolt in place, it will keep the pulley synched once it is home.
The 292 was tapped for a 7/16 crank bolt and that is the size offered via the 12-bolt jig you have.
Use a torque wrench on the 7/16 crank bolt, to ensure you don't strip the threads.
You'll want to stay under 40 PSI to be safe.
If you are unlucky and strip the threads, I will send you the jig, tap, and a washer bolt assembly, for the larger bolt, but won't be able to ship it until early next week.
It's worth noting that the factory tapped the Iron Duke 4 cylinder engines with a larger bolt, while the 3.0 liter Mercruiser engines had a pressed pulley like the 250.
We've been tapping the 3.0 liter crank with the larger bolt for years on our 4 cylinder conversions, and now tap both the 250 and 292 conversions we do without any negative effect, so there are no down side to tapping the crank.
 

Adog

Well-known member
Good call on the torque wrench... hopefully heating and greasing will help .. oh and the key not moving up. By slowly tightening down the pulley I will be able to see that the key is set correctly and not jacking up the timing cover .... I will report back .....
 

Adog

Well-known member
Happy to report that I was able to drill the crank shaft with the jig to the recommended depth. I bought a bottle of cutting oil and used the w bit that came with drilling kit. Kept the speed of drill on low setting and about 200-300 rpm (guessing) cleaned bit and exit hole often and oiled every time as well. I was surprised how well it worked. I used a cordless Milwaukee . Still waiting on New timing cover and new seal. Will prob run the tap tomorrow. Took about 30-45 mins to drill
 

Adog

Well-known member
Awesome ... great now you are forcing me to install new fuel tank and fuel
lines ... been dreading it ! Still having nightmares of getting the old one out !
 
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