194 to 250 Head Swap

[jjester6000]

The original 250 inline 6 in my 1974 gmc c1500, at this point, is worn out to the point that is burns oil like it's 2 stroke. This is most likely from totally shot valve guides (years of unleaded gas) and maybe a whipped cam lobe or twelve.

You must be registered for see images attach

I recently bought a 194 I6 for 40 dollars that is in absolutely AMAZING original condition (no sludge, original 3.56 bore, and even some crosshatching still showing in the cylinders).

You must be registered for see images attach

You must be registered for see images attach

I was wondering what it takes to swap the head into my original 250 in order to bring the compression up from 8:1 to 9:1(It seems that all the issues are top end, and I do know that the 194 head should fit).

You must be registered for see images attach

I don't think the 250 has ever been touched (and it has great oil pressure) so I want to do this without doing the rings or bearings.

 

[DoubleDingo]

I don't know much about I-6s but if the bolt pattern matches, it should bolt on. Unbolt your 250 head, put the 194 head on the engine, if the holes line up, get a new head gasket, clean up the surfaces and bolt it on. Don't forget to torque the bolts in stages to get them the torque-spec. Or just rebuild the 250 head.

 

[jjester6000]

I don't know much about I-6s but if the bolt pattern matches, it should bolt on. Unbolt your 250 head, put the 194 head on the engine, if the holes line up, get a new head gasket, clean up the surfaces and bolt it on. Don't forget to torque the bolts in stages to get them the torque-spec. Or just rebuild the 250 head.

I got all of the torque specs and the pattern sheet in my Chiltons book, I am just worried that the higher compression may increase blow-by to the point that I lose oil pressure. I probably should have asked that question in the first place; whether or not it is okay to go from a 8:1 compression head to a 9:1 compression without rebuilding the bottom end of the motor.

One more thing, I am pretty sure that my head bolts are not torque-to-yield, but do you think I should reuse them?

 

[DoubleDingo]

I'm not well versed in engine builds, but that makes sense on increasing the compression. Not sure if it will do that, if the rings are not doing their job or the cylinders need trued, then it would be best to just rebuild the engine. Maybe just install the 194 and rebuild the 250?

I may get chastised for this, but I have always reused my head bolts. Maybe if it was a turbocharged engine I'd replace them.

 

[4WDKC]

sounds like the engine is need of a rebuilt anyway. Put the head on if it works great, if it causes blow by swap in the 140 while you rebuilt the 250?

 

[78C10BigTen]

I may get chastised for this, but I have always reused my head bolts. Maybe if it was a turbocharged engine I'd replace them.

Anytime ive ever changed or pulled heads ive reused the bolts without issue... was it right, probly not. Did i fo it, yup

 

[Rickf]

If it was my project I'd set both heads side by side and measure everything. Are the tops of the valves the same? Do the rocker studs and bosses look the same? Are the 250 push rods the same length as the 194? You want to make sure the 250 has the same rocker & valve geometry. You might find some info on inliners.org.

 

[legopnuematic]

I'm not well versed in engine builds, but that makes sense on increasing the compression. Not sure if it will do that, if the rings are not doing their job or the cylinders need trued, then it would be best to just rebuild the engine. Maybe just install the 194 and rebuild the 250?

I may get chastised for this, but I have always reused my head bolts. Maybe if it was a turbocharged engine I'd replace them.

I have reused the head bolts on my 76 and 79. Just clean them up on the wire wheel and good to go. If they were torque to spec head bolts then I wouldn't, but as far as I know all sbc (w/stock or stock replacement) head bolts are not torque to spec/yield bolts.

Sent from my Moto Z (2) using Tapatalk

 

[jjester6000]

If it was my project I'd set both heads side by side and measure everything. Are the tops of the valves the same? Do the rocker studs and bosses look the same? Are the 250 push rods the same length as the 194? You want to make sure the 250 has the same rocker & valve geometry. You might find some info on inliners.org.

I am pretty sure everything lines up, the only difference between the 194 block and the 230/250 block is the bore and probably water jackets.

I have been told that the cam, pushrods, and rockets are the same.