65 dart 225 rebuild.

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RoadRage

RoadRage

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I posted a few pictures of my slant 225 rebuild and was told just from the pictures that there was no way I could get 320 horspower from a SL6. One Person said at best I had about 7:1 and maybe 100 hp. Well can someone explain to me how thats possible, seeing that the factory specs for my engine was 8.4 and the max HP rating was 145. Are you guys saying that rebuilding a slant makes less HP? Just a few things that were done. Block decked 25k, head milled 110k, bored 40 over with flat top pistons. 3 angle VJ. Head ported polished. Balanced blueprinted, cam is erson 224 410. Weber 500 cfm 2bl carb with clifford intake and headers, roller rockers to be installed. Here are the factory specs from ALLPAR.COM
Engine 225 cubic inch
Carburetor Single barrel Single barrel
Bore and Stroke (nominal) 3.4 x 3.125 3.4 x 4.125
Bore spacing (CL to CL) 3.98 (1-2, 3-4, 5-6);
4.0 (2-3, 4-5) 3.98 (1-2, 3-4, 5-6);
4.0 (2-3, 4-5)
Firing Order 1-5-3-6-2-4 1-5-3-6-2-4
Compres. Ratio (nominal) 8.5 8.4
Cylinder Head Material Cast iron Cast iron
Cylinder Block Material Cast iron Cast iron
Cylinder Sleeve None None
Number of mtg. points (Front) Two Two
Number of mtg. points (Rear) One One
Engine Installation Angle Lateral 0°, Up 3° Lateral 0°, Up 3°
Taxable Horsepower 27.7 27.7
Publishing max. bhp* @eng. RPM 115@4400 145@4000
Publishing max. torque * (lb. ft. @RPM) 155@2400 215@2400
Weight (piston only ) oz. 16.4 16.4 So if these are factory specs how can my rebuild not have more than what this says? I will have it dyno tested to see where it stands. I will post results when this is done. I am not a engine builder but it seems to me that the head work alone will increase the HP by 50! With my understanding of how much it was milled and flat tops that puts it at 10:1.
 
Sounds like it should pull pretty well. Looking forward to seeing how it does.
 
Sure. Let me try to answer your first question about the factory compression ratio, since that's the root of the issue.

Chrysler was really inconsistent about certain machining tolerances. Cylinder block deck heights were taller than spec, combustion chambers were larger than spec. That 8.4:1 compression ratio was an advertised rating. See that word advertised? Yeah. Marketing. These engines usually blueprinted (true measurement) closer to 1/2 to 1 full point below their advertised rating.

Also, as I believe it was explained to you before, the 225 does not even have its own cylinder head. When the 170 was first made, all the parts were designed around the 170. When the 225 came about, Chrysler simply used the 170 head on the 225. The slant six was never a production performance engine, so Chrysler saw no need to redesign another cylinder for the larger 225. So the 198 and 225 use a cylinder head designed for the much smaller 170. Small, restrictive ports and small valves. In order to be optimal for the 225, a complete head redesign would need to be done up to and including moving the ports to optimal places and reshaping them and including bigger valves. That was never in the cards.

Yes, you can have bigger valves installed and have the head ported, but how much more do you honestly think you are going to gain? A stock 225 is "about" 145 HP. You said originally your engine was 325 HP. That's an addition of 180 HP from stock. .......AND you don't have head porting listed in any of your mods. A naturally aspirated 225 does good to produce 1 HP per cubic inch. THere are some exceptions, but that's about the "going rate".

You used stock pistons in your build and you state the block was decked .025". Well, those pistons sit over .100" in the hole at TDC. Yes, you had the head milled a lot, and that's good for compression, but might be bad for detonation. Since the piston sits in the hole at TDC, there's no quench. Quench happens when the flat part of the piston gets close to the flat part of the cylinder head. Quench is good for a couple of reasons. It helps create turbulence in the combustion chamber, aids in more complete combustion and allows more compression to be run on a given octane of fuel. The way your engine is built, you have no way to achieve quench. But that's not a deal breaker, because the slant was never a quench engine anyway. Making it a quench engine "just helps" a little.

I am building what's called a long rod 225. That's using a longer (7.005") 198 connecting rod in the 225 with a 2.2 4 cylinder Chrysler piston to achieve zero deck height. But, in order to get any quench, I am still going to have to mill the head pretty good. I may try angle milling it. Taking more off one side than the other to help remove more from the flat side of the combustion chamber. I have a long way to go yet so "we'll see".

The bottom line is, while certainly you have a snappy 225, there's just no way in the world you have 325 HP as much as you want it to be true. I am going into my build thinking that if all things work out "like I want" I might end up with 250 HP......but, "probably not". LOL
 
Oh and a GOOD ported head with bigger valves MIGHT be good for 30 HP. But nowhere did you list yours is ported. If it is, we'd need to see flow numbers to give you a "better guess". Even then, you "AIN'T" hittin 325.
 
RustyRatRod said:
Oh and a GOOD ported head with bigger valves MIGHT be good for 30 HP. But nowhere did you list yours is ported. If it is, we'd need to see flow numbers to give you a "better guess". Even then, you "AIN'T" hittin 325.
Click to expand...
Read again i said the head was ported and polished!
 
RustyRatRod said:
Sure. Let me try to answer your first question about the factory compression ratio, since that's the root of the issue.

Chrysler was really inconsistent about certain machining tolerances. Cylinder block deck heights were taller than spec, combustion chambers were larger than spec. That 8.4:1 compression ratio was an advertised rating. See that word advertised? Yeah. Marketing. These engines usually blueprinted (true measurement) closer to 1/2 to 1 full point below their advertised rating.

Also, as I believe it was explained to you before, the 225 does not even have its own cylinder head. When the 170 was first made, all the parts were designed around the 170. When the 225 came about, Chrysler simply used the 170 head on the 225. The slant six was never a production performance engine, so Chrysler saw no need to redesign another cylinder for the larger 225. So the 198 and 225 use a cylinder head designed for the much smaller 170. Small, restrictive ports and small valves. In order to be optimal for the 225, a complete head redesign would need to be done up to and including moving the ports to optimal places and reshaping them and including bigger valves. That was never in the cards.

Yes, you can have bigger valves installed and have the head ported, but how much more do you honestly think you are going to gain? A stock 225 is "about" 145 HP. You said originally your engine was 325 HP. That's an addition of 180 HP from stock. .......AND you don't have head porting listed in any of your mods. A naturally aspirated 225 does good to produce 1 HP per cubic inch. THere are some exceptions, but that's about the "going rate".

You used stock pistons in your build and you state the block was decked .025". Well, those pistons sit over .100" in the hole at TDC. Yes, you had the head milled a lot, and that's good for compression, but might be bad for detonation. Since the piston sits in the hole at TDC, there's no quench. Quench happens when the flat part of the piston gets close to the flat part of the cylinder head. Quench is good for a couple of reasons. It helps create turbulence in the combustion chamber, aids in more complete combustion and allows more compression to be run on a given octane of fuel. The way your engine is built, you have no way to achieve quench. But that's not a deal breaker, because the slant was never a quench engine anyway. Making it a quench engine "just helps" a little.

I am building what's called a long rod 225. That's using a longer (7.005") 198 connecting rod in the 225 with a 2.2 4 cylinder Chrysler piston to achieve zero deck height. But, in order to get any quench, I am still going to have to mill the head pretty good. I may try angle milling it. Taking more off one side than the other to help remove more from the flat side of the combustion chamber. I have a long way to go yet so "we'll see".

The bottom line is, while certainly you have a snappy 225, there's just no way in the world you have 325 HP as much as you want it to be true. I am going into my build thinking that if all things work out "like I want" I might end up with 250 HP......but, "probably not". LOL
Click to expand...
So Chrysler just flat out lied about all there spec? Yes I said the head was ported and polished!
 
I think the point of the discussion, is as RRR said, the slant head has never been improved upon for any real performance. Sure milling, and port/polish helps.. but... sure, the right cam, better piston, bigger carb, valves?, headers all this helps but it is, ..what it is....
We will see.
 
RoadRage said:
So Chrysler just flat out lied about all there spec? Yes I said the head was ported and polished!
Click to expand...

Even so, 30HP more than stock would probably be a good guess as to added power from the head.......but no one would "just" port and polish and instal large valves without "other" work as you have done. I imagine a decent estimate where you are with power is probably somewhere close to 1 HP per cube. Maybe. Find a chassis dyno somewhere and make some pulls. But get ready to be disappointed. I believe if you come up with 150-175 HP at the rear wheel, you'd be doing good.
 
RoadRage said:
Read again i said the head was ported and polished!
Click to expand...

If you can supply flow numbers, I can plug it all into desktop dyno and give you a pretty close estimate.
 
RustyRatRod said:
Sure. Let me try to answer your first question about the factory compression ratio, since that's the root of the issue.

Chrysler was really inconsistent about certain machining tolerances. Cylinder block deck heights were taller than spec, combustion chambers were larger than spec. That 8.4:1 compression ratio was an advertised rating. See that word advertised? Yeah. Marketing. These engines usually blueprinted (true measurement) closer to 1/2 to 1 full point below their advertised rating.
Click to expand...
I can't remember how many slant engines I have taken apart to rebuild. I have never, ever, found one that was at least 8.0 to 1 from the factory. All were less then 8.0-1.
 
Charrlie_S said:
I can't remember how many slant engines I have taken apart to rebuild. I have never, ever, found one that was at least 8.0 to 1 from the factory. All were less then 8.0-1.
Click to expand...

Right. It's the same with everything else, too right up to the 426 Hemi. Course, they had better than 8:1 but all were still low compared to what they were rated.
 
shoulda just turboed it and a small shot, might get the majik 325, for a couple of milliseconds.
 
Have to agree with the comments here, a 300 horse NA slant is possible, but to get there you will need: very good port flow, compression in the 11:1 range,
a lot of cam and slant built to get RPMs above 6000.

Dyno Sim will give a reasonably accurate torque and HP curve, if good data is entered. So post the flow numbers and specific cam data and either Rusty or me will enter the data.

And Rusty, concerning "I am still going to have to mill the head pretty good." On the long rod motor I am building, with a very light clean up cut on the block deck surface, the pistons are at zero deck height. Using a non milled head with a combustion chamber cc value of 57 - 58 cc's, The calculated compression ratio is 10.6 to 1
I am planning to run e85 so I believe I am about maxed out on compression. If you will be running race gas, you can go higher on compression, but that brings another set of head gasket sealing issues into play.

Just something to consider.
 
my68barracuda said:
Have to agree with the comments here, a 300 horse NA slant is possible, but to get there you will need: very good port flow, compression in the 11:1 range,
a lot of cam and slant built to get RPMs above 6000.

Dyno Sim will give a reasonably accurate torque and HP curve, if good data is entered. So post the flow numbers and specific cam data and either Rusty or me will enter the data.

And Rusty, concerning "I am still going to have to mill the head pretty good." On the long rod motor I am building, with a very light clean up cut on the block deck surface, the pistons are at zero deck height. Using a non milled head with a combustion chamber cc value of 57 - 58 cc's, The calculated compression ratio is 10.6 to 1
I am planning to run e85 so I believe I am about maxed out on compression. If you will be running race gas, you can go higher on compression, but that brings another set of head gasket sealing issues into play.

Just something to consider.
Click to expand...

Yeah I knew it was gonna be high. Was hoping not that high. LOL I'll probably have to just get by with enough to make the head flat, because I am GONNA zero deck height the beeotch. Naw this is a pump gas only motor so I need to be careful.
 
I had my block bored .0450 over and used the long rods in my rebuild and am close to 10:1 compression ratio.
 
RustyRatRod said:
If you can supply flow numbers, I can plug it all into desktop dyno and give you a pretty close estimate.
Click to expand...
I borrowed the snap on cylinder pressure gauge from my engine builder today Im checking the pressure on each cylinder will that info be enough for you to guess the compression? I will have it chasis dyno at blue cat dyno in louisa ky. Info to come soon.
 
lilnoah said:
I had my block bored .0450 over and used the long rods in my rebuild and am close to 10:1 compression ratio.
Click to expand...

I am doing the same. Did you zero deck height your block? I don't know where I am yet, because I am still very early in the game.
 
RoadRage said:
I borrowed the snap on cylinder pressure gauge from my engine builder today Im checking the pressure on each cylinder will that info be enough for you to guess the compression?
Click to expand...

Yes, I can come close if you've included or do include all the camshaft specs.
 
ok ill double check the build sheet

i want to say it was custom ground at 224 410!
 
I have torqstorm supercharger and I am going to end up putting in EFI tank and pump along with Holley Sniper to control timing.
 
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