# Chrysler Hemi 1/4 scale



## driller1432 (Feb 19, 2018)

Here we go with hemi build.
Scaling off the real deal, did the crank awhile back did not take any pics of machining.
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Have a good start on heads with combustion chamber cutter made from drill bit
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The scrap head to scale from
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Next will be intake and exhaust ports and spark plug holes.


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## Cogsy (Feb 19, 2018)

That crank is a work of art. This should be another impressive engine.


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## petertha (Feb 19, 2018)

Very nice. What material did you make your model crankshaft from? 

Too bad about no pics, hope you document the rest of your journey for us because its a very admirable project. 
Can you describe some of the tooling you used - ex parting tool to rough? home cut HSS tools to finish? any lapping?


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## driller1432 (Feb 20, 2018)

Thanks Cogsy
And the metal I used for the crank came from a shaft from the draw works on a water well drill rig I once owned. I roughed out the crank on the mill with rotary table and tailstock with a fixture on each end to index rod journals then ground journals to final dimension on the lathe with tool post grinder. As my father owned an automotive machine shop for 52 years I have reground hundreds of crankshafts so it made sense for me to do it this way. Ill post pics of fixtures next time I go to shop. Thanks for your interest.


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## Hopper (Feb 20, 2018)

Very nice work there. Will be following this one with interest. I worked in a Chrysler factory back when a hemi was the hot money.


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## driller1432 (Feb 28, 2018)

Making valve seats on my new to me sherline mini lathe View attachment IMG_1250.jpg

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And spark plug tubes ........next head bolt and pushrod holes and topside of heads for spring seats.


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## driller1432 (Mar 4, 2018)

Getting close to finishing head machining .....oil drain back holes, oil feed passage..... water passage and valve cover surface to be perpendicular to spark plug holes then ready for seats guides and valves.

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## driller1432 (Mar 4, 2018)

Pictures x2 dont know why? sorry


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## stevehuckss396 (Mar 4, 2018)

heads look great. tons of work there.


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## driller1432 (Mar 4, 2018)

Yep a little more to do, at least I think Im past the point where I might screw up and have to start over! [emoji851]


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## stevehuckss396 (Mar 5, 2018)

driller1432 said:


> at least I think Im past the point where I might screw up and have to start over! [emoji851]



Don't think like that or you will be starting over! Hahaha!!


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## driller1432 (Mar 11, 2018)

Hi guys got the valve guides and seats installed now will cut down and cut angles in seats with a two step pilot that fits in guide and inner valve seat since the ID of the guide is only .115 also got a start on intake  valves tulip style from 
.500 drill rod View attachment IMG_1266.jpg
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## driller1432 (Dec 25, 2020)

Finally back on the Hemi getting the block roughed in, got past the nerve racking part as all the cylinder bores ended up in the proper alignment with crank center line and main bearing webs. Now need to finish hogging out crankcase then the lifter valley will have to be hogged out as well. Then cylinder bores taken to near finish bore for liners then the main bearing caps will be milled away and new ones made. Then align bore the main bearing bores. Now some questions like has anyone used split rod and main bearings? Is so what material was used? Used the washer that is approx same diameter as crank to check for enough clearance for crank the side walls of crank case will also be milled thinner as well.


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## gbritnell (Dec 26, 2020)

I don't think there is any other way to make trapped bearings other than to split them. I turn the bearing inserts to size then part them off and finish the length. From here there's 2 ways to go. First you have to make a fixture to hold them then you can split the with a very thin slitting saw and not worry about the small gap produced or you can split each bearing so that one half is perfectly cut in half and discard the other half. This method requires making twice as many pieces but you get perfectly split bearings. I then drill the cap and one half of the bearing for a brass pin to keep the insert fram spinning.
I have also used a third method which involves taking 2 pieces of rectangular stock and soft soldering them together leaving one piece a little longer so that when set up in a 4 jaw chuck the exact center can be established. First the inside is drilled and bored to size. I don't like reaming because sometimes the pressure of reaming will split the solder joint. Now the O.D. Is turned and the insert parted off. Now it's heated until it separates leaving just a minute space where the solder was.


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## gbritnell (Dec 26, 2020)

Not wanting to hijack your thread I'm going to start another on how I machined the connecting rods and split bearings for them. It will be in Tips and Tricks.
gbritnell


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## driller1432 (Dec 26, 2020)

gbritnell said:


> Not wanting to hijack your thread I'm going to start another on how I machined the connecting rods and split bearings for them. It will be in Tips and Tricks.
> gbritnell


That would be great can’t wait to see how you machine the rods and bearings I appreciate the help!


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## CFLBob (Dec 27, 2020)

Question if I may.  

The only engine that comes to my mind when I read "Chrysler Hemi" is the 426 CI hemi from the late 60s.  That would make this a 106.5 CI engine, which is still pretty big for a model.  

Is that right?


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## a41capt (Dec 27, 2020)

I read George’s split bearing thread first, and then saw yours.  That is a fantastic looking job to this point, and I look forward to seeing the remaining steps in your build.

Beautiful work!
John W


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## stevehuckss396 (Dec 27, 2020)

The bore and stroke of the 426 hemi was 4.25 X 3.75 = 425.5877 CID

1/4 scale would be 1.0625 X 0.9375 = 6.6498 CID


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## CFLBob (Dec 27, 2020)

stevehuckss396 said:


> The bore and stroke of the 426 hemi was 4.25 X 3.75 = 425.5877 CID
> 
> 1/4 scale would be 1.0625 X 0.9375 = 6.6498 CID



Ah!  Not dividing the 426 by 4, dividing bore and stroke each by 4.  That turns into scaling the displacement by (1/4)^3.  That makes sense.  Should have thought of that.

Thanks, Steve.


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## driller1432 (Dec 27, 2020)

CFLBob said:


> Question if I may.
> 
> The only engine that comes to my mind when I read "Chrysler Hemi" is the 426 CI hemi from the late 60s.  That would make this a 106.5 CI engine, which is still pretty big for a model.
> 
> Is that right?


You are correct it is the 426 elephant engine.


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## davidyat (Dec 28, 2020)

*The bore and stroke dimensions do come out to 425.58 CI. But wouldn't the volume of the cylinder heads add to the 425.58 volume making it a bigger engine? I thought that's why NASCAR engine builders have to CC the heads with a liquid to make sure the total volume doesn't go over specs. Or are the pistons dome shaped to compensate for this?
Grasshopper*


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## L98fiero (Dec 28, 2020)

davidyat said:


> *But wouldn't the volume of the cylinder heads add to the 425.58 volume making it a bigger engine?*


It's the swept volume that is counted for displacement figures, the head volume doesn't change.


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## davidyat (Dec 28, 2020)

*I've never heard of "swept volume". What is it?
Grasshopper*


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## L98fiero (Dec 28, 2020)

davidyat said:


> *I've never heard of "swept volume". What is it?
> Grasshopper*


Swept volume can be defined as the volume swept by the engine piston during one stroke. Swept volume is also the product of piston area and stroke. 
	

	




						What is swept volume?
					






					help.summitracing.com


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## davidyat (Dec 28, 2020)

*Thank you, I learned something today.
Grasshopper*


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## CFLBob (Dec 28, 2020)

I think I got this graphic here on HMEM but I don't remember anymore.  It might be helpful for some folks.







The displacement equation is for one cylinder, so you'd multiply that result times the number of cylinders in the engine.


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## bruski (Dec 28, 2020)

Bore X Bore X Stroke X .8754 X Cylinders


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## CFLBob (Dec 28, 2020)

I think you swapped a digit.  It's .7854.


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## Willyb (Dec 28, 2020)

Good job. Enjoying the build.
Willy


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## Noitoen (Dec 29, 2020)

davidyat said:


> *The bore and stroke dimensions do come out to 425.58 CI. But wouldn't the volume of the cylinder heads add to the 425.58 volume making it a bigger engine? I thought that's why NASCAR engine builders have to CC the heads with a liquid to make sure the total volume doesn't go over specs. Or are the pistons dome shaped to compensate for this?
> Grasshopper*



I think that is used to calculate compression ratio by measuring the chamber's volume.


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## driller1432 (Dec 29, 2020)

Thanks for all the replies. Last couple days spent hogging out lifter valley and drilling lifter bores. The holes for the fifth head bolt were drilled first then the lifter bores were drilled 
Because of the size of the lifter bores the boss for the head stud is very thin walled and one even broke thru. But the undercut on the bottom side of the boss has a lot of meat left so there should be no problem holding the stud  as the boss is about .250 in length. I thought about building the boss up with tig welding but it would probably make it worse! The reason for the stud going down is so there isn’t a bolt going thru intake port.  There is still a little more work in valley milling clearance for exhaust push rods which are at angles same as intake pushrods. So now a lot of work with rotary tool rounding inside corners  and smoothing every thing out. Next back to crankcase and getting main bearing webs to final width and milling away caps. Set heads on block for a quick look . I haven’t posted pictures of rockers and shafts yet but I have them all made.


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## ddmckee54 (Dec 29, 2020)

Noitoen nailed it, they CC the heads to determine the compression ratio.  Nascar has compression ration limits and they want to be sure nobody's cheating by using an engine with a higher ratio.

Don


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## Badhippie (Dec 29, 2020)

So you are going to have studs in the lifter valley as on the original engine design. They were bolts in the original engine but everyone switched them out for studs. Very nice work glad to see a fellow mopar nut in the crowd 
Thanks 
Tom


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## driller1432 (Dec 30, 2020)

Badhippie said:


> So you are going to have studs in the lifter valley as on the original engine design. They were bolts in the original engine but everyone switched them out for studs. Very nice work glad to see a fellow mopar nut in the crowd
> Thanks
> Tom


Hey Badhippie yes going to use studs for the fifth head bolt .


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## Bentwings (Dec 31, 2020)

davidyat said:


> *The bore and stroke dimensions do come out to 425.58 CI. But wouldn't the volume of the cylinder heads add to the 425.58 volume making it a bigger engine? I thought that's why NASCAR engine builders have to CC the heads with a liquid to make sure the total volume doesn't go over specs. Or are the pistons dome shaped to compensate for this?
> Grasshopper*


I don’t think chamber volum and comp ration will scale properly it would be best to adjust the piston and chamber to give a functional ratio according to the fuel being used if pump gas is suggest around 9.5 pistons and rings this size are not the easiest things to make as it is. Plain cast iron works for rings as you can simply crack them in your fingers the use a small fin file to fit them . The standard .004 in per inch bore diazepam still works ok. Even our model airplane engine one used this rule you wind up about .002 fitted gap. This size bore is pretty sensitive to gap so keep it snug. Since this would be liquid cooled... I think. It would have a better control of cyl temp than air cooled motors.
I thought of dyke rings on the engine I’m just starting but that’s a huge complication I don’t need. Tigh tolerance is one thing but with multiple operations on lots of parts is quite another. I would also consider a ring installation tool and make plenty of extra rings. Ductile iron is hard to control in this scale full size is easy but tiny is another story.
My 2 strokes had cylinder and pistons matched. Assembled the pistons had a slight stick at Tscheda as the engine warmed up clearances opened up. When this went away when cold it was time for a new liner and piston. Cr was pretty high bu lots of nitro was the rule in this days. I had a number of spectacular engine distractions. No fires but lots of pieces flying around. For small engines they made pretty Big Bang when they let go..


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