Mopar R5 Block

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tinman2

tinman2

Too Broke for Missiles, Switching to Guns
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I got in on the R3 discussion thinking that's the block I had a chance to buy. Later, after looking for more info, I realized that it was an R5 block with the open deck that I looked at.
I realize that it is not what I need for a street car. But, I bought my first real modified street car in 1974. It was a 65 Falcon, with pretty trick 289, 4 speed, 4.10 gear. It would pull hard up to 8000rpm. Then in January, 1976, I bought a 67 Camaro drag car. My go-to car builder took a stock short block 302, threw on some decent racing heads, intake, big headers, etc. I was dropping the clutch and changing gears at 8000rpm. So, that's what I like.
It never occured to me to build a high winding small block mopar until a friend offered me a new R5 block and a new crank. He also had one new head, maybe W7 or later... not sure. Dang. That must have gotten my hormones pumping. I started looking for info, some on this website, and realized that sourcing parts wasn't going to be easy, and I figured the costs would quickly spiral out of what I would consider reasonable for me.
 
tinman2 said:
I got in on the R3 discussion thinking that's the block I had a chance to buy. Later, after looking for more info, I realized that it was an R5 block with the open deck that I looked at.
I realize that it is not what I need for a street car. But, I bought my first real modified street car in 1974. It was a 65 Falcon, with pretty trick 289, 4 speed, 4.10 gear. It would pull hard up to 8000rpm. Then in January, 1976, I bought a 67 Camaro drag car. My go-to car builder took a stock short block 302, threw on some decent racing heads, intake, big headers, etc. I was dropping the clutch and changing gears at 8000rpm. So, that's what I like.
It never occured to me to build a high winding small block mopar until a friend offered me a new R5 block and a new crank. He also had one new head, maybe W7 or later... not sure. Dang. That must have gotten my hormones pumping. I started looking for info, some on this website, and realized that sourcing parts wasn't going to be easy, and I figured the costs would quickly spiral out of what I would consider reasonable for me.
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The R5 is an exotic block. I know very little about them except one word applies for sure….

Expensive!
 
When you look at a normal block, just the block, you see the surface of the block where the cylinder head will reset on and be bolted to.

On this block, there is no deck, just open to the naked cylinders and cooling passages. You can see all the way down.
 
rumblefish360 said:
When you look at a normal block, just the block, you see the surface of the block where the cylinder head will reset on and be bolted to.

On this block, there is no deck, just open to the naked cylinders and cooling passages. You can see all the way down.
Click to expand...
Weight saver?
 
Some of these old Nascar blocks were selling for prices years ago that were hard to pass up, but I did. I don’t know if he’s a member here but he raced an altered at Norwalk several times while I was there. That small cubic inch engine loved rpm and sounded totally different than most drag racing engines. He was capable of doing much of the needed extra work converting it over so for him it was a great deal.
 
I’m pretty sure they were built W8 and later type heads. A little W8 action, though
 
Yessir! If you listen to how hard it starts pulling by the sound it makes up on the top end, it sounds almost identical to a well tuned super stock hemi.
 
R5 is a block used with P7 NASCAR heads.
I know several guys running those motors in drag cars.
They have an extremely short deck. The heads are terrific.. 400 cfm terrific
Short deck deal, not for everybody and won’t fit in a stock A body front end.

you can buy these as complete motors very reasonable. Starting with just a block wouldn’t be the way to go.
 
Heads to wide rod stock engine compartments?
 
They do have that deep skirt block I forgot about…
 
rumblefish360 said:
They do have that deep skirt block I forgot about…
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good buddy local to me had one in a 68 Dart. Mild restrictor plate Busch motor. Ran 9.40’s at 143
Putting a much stouter cup motor in a Dart Sport right now. Has aftermarket K, still a chore getting it in. This should run MUCH better than the one he used to have. Can’t wait to find out here soon. We race together a lot
 
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WOW! We need some pics of that exotica when you’re able, if you don’t care!
 
Garrett Ellison said:
WOW! We need some pics of that exotica when you’re able, if you don’t care!
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it isn’t exotic at all. If you look around you can buy complete 750 horse plus motors for under 10k…. Need headers and also tranny adapter( getting harder to find) and carb.
They run nice in front of 904’s with loosened up 8 inch verts that flash 6500-7000k.
My buddy posts on here, he might post a video when it’s in the car running, I will ask him
 
The guy I bought my R1 from (RIP Mike) bought four or five of them. He told me they were the cheapest HP to be had and very reliable. He said the converter was the key to making them work.
 
tinman2 said:
I wouldn't be surprised. And I don't understand the open deck. Yet.
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The open deck was to allow coolant all the way to the top of the bore. Some of these blocks had 1 inch thick decks. IIRC the X had .750 thick decks. So there isn’t any coolant up there.

In the early 2000’s guys were playing with them and I know a couple of them made up inserts to press into the open deck. IIRC they said they had big blow by numbers with the open decks and they thought the tops of the bores didn’t have enough support and were moving around.

I’m not sure what the final conclusion was on that. I never asked and they never said.
 
Given the shorter deck height, it looks like the Darton MID sleeve system for a third would work pretty well in that. Those allow for nearly full coolant flow around the top of the sleeve (swirl cooling, just a channel around the top with oval holes all the way around to underneath) but still have support to the deck walls.
 
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