Last night I started disassembling what I thought was a 500, it came out of a eldorado. Upon using my boroscope I found it to have the butterfly dished pistons in it. I've been running a .030 500 for the past 2 summers. And was planning on modifying this one for more performance. Is there that much difference between the 500 and the 472? Would the shorter stroke actually benefit us in a drag application allowing the engine to rpm faster? I'd like to hear about some 472 builds and the results from them. Cjay
Are you considering the G body as a street/strip racer?
More cubes and stroke in the same rpm range would win out over rev/$$.
For rpm to be an advantage you'd have enough into the engine in light parts and induction to negate the shorter stroke once again.
I suppose it depends on your proposed build and parts starting with already.
If you think about it, the top end taps out at a similar power level but with more cubes there's more torque and less rpm.
You'd need more gear and dollars to equal the wheel torque and show an advantage with hp acceleration.
More cubes and stroke in the same rpm range would win out over rev/$$.
For rpm to be an advantage you'd have enough into the engine in light parts and induction to negate the shorter stroke once again.
I suppose it depends on your proposed build and parts starting with already.
If you think about it, the top end taps out at a similar power level but with more cubes there's more torque and less rpm.
You'd need more gear and dollars to equal the wheel torque and show an advantage with hp acceleration.
robocop
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- 1987 Cutlass Supreme 2 door with 500 Cad/Turbo 40
Turn the crank in for a 500 crank.
Yes, it would be a street/strip grudge racing deal. I figured the torque would be down a little with the stroke reduction.
But the upper hp would be close. Plus I'm using a little nitrous on it. I was already having a problem hooking the car with all the bottom end torque the 500 was making. And this was with a 2.73 gear Figured the 472 would tame the leave down but still haul the mail upstairs.
But the upper hp would be close. Plus I'm using a little nitrous on it. I was already having a problem hooking the car with all the bottom end torque the 500 was making. And this was with a 2.73 gear Figured the 472 would tame the leave down but still haul the mail upstairs.
I liked 472's in my G bodies for exactly the same reasons.
There are plenty of times in which the extra size doesn't help.
The same limitations apply to revving either of them and if you don't put the effort into feeding the bigger beast it isn't helping anyways.
There are plenty of times in which the extra size doesn't help.
The same limitations apply to revving either of them and if you don't put the effort into feeding the bigger beast it isn't helping anyways.
dave brode
Well-Known Member
Cjay,
The pistons in 68-70 year 472s look similar to those from '70 500s. If you can't take it apart now, you can measure the stroke with a wire through the plug hole.
Dave
The pistons in 68-70 year 472s look similar to those from '70 500s. If you can't take it apart now, you can measure the stroke with a wire through the plug hole.
Dave
Dave, I'll be taking the top end off in a day or 2. I'm hoping it is a 500, but if it's a 472 I'm not gone worry. The nitrous will make up for the shorter stroke. Checked my other eldo engine, it too has the big butterfly dished pistons in it. I've got some old MTS catalogs and they advertised a 484 street sweeper kit that was 14 lbs lighter than stock. Wonder how they did that and the reliability factor. I think Courtney used the 484 engine for the streamliner used to set the speed record at bonneville. Guess they can't be too far off pace.
How they did what and the reliability factor?
What exactly is 14 lbs lighter?
Extreme effort builds can overcome cubes or stroke, and often use various attributes to advantage.
I don't think this applies the same to the mild street/strip versions we are talking about.
What exactly is 14 lbs lighter?
Extreme effort builds can overcome cubes or stroke, and often use various attributes to advantage.
I don't think this applies the same to the mild street/strip versions we are talking about.
I'm not sure exactly what Al meant about the lightening modifications. He just stated that the rotating mass was less to get the engine to rpm faster, not higher. Sometimes lighter doesn't mean stronger is what I was getting at about the reliability factor. As far as extreme builds I always try to stay conservative but it never ends up that way. Originally this was supposed to be a 1500.00 project but.... I'm here now and there's no turning back. So, it goes where it goes as far as cost.
I thought maybe the rotator was being referred to.
A crank will tolerate more abuse when the pistons and rods are lighter.
An engine will fling itself apart from rpm long before the power level destroys them (NA).
Back to your original questions...definitely a lighter rotator will rev up faster and that can exceed dyno figures due to the way measurements are taken..
Inertial correction is rarely factored correctly out of dyno testing. Nature of the beast.
As you know, once you begin grinding off large amounts of a crank journal and using lightweight parts, things jump a level in cost.
To that line of thought...aftermarket BBC and Mopar rods are cheaper than Cadillac marketed equivalents if you don't mind some math and working with a willing machinist (depending on the build level).
A crank will tolerate more abuse when the pistons and rods are lighter.
An engine will fling itself apart from rpm long before the power level destroys them (NA).
Back to your original questions...definitely a lighter rotator will rev up faster and that can exceed dyno figures due to the way measurements are taken..
Inertial correction is rarely factored correctly out of dyno testing. Nature of the beast.
As you know, once you begin grinding off large amounts of a crank journal and using lightweight parts, things jump a level in cost.
To that line of thought...aftermarket BBC and Mopar rods are cheaper than Cadillac marketed equivalents if you don't mind some math and working with a willing machinist (depending on the build level).
MadMax
Member
Agree with you 8ad-f85 - "To that line of thought...aftermarket BBC and Mopar rods are cheaper than Cadillac marketed equivalents if you don't mind some math and working with a willing machinist (depending on the build level)."
With our mini modified tractor engine rules of 500 cid, I have settled on a .100" over 472. Cylinder wall thickness is still .085-.125". I understand over square engines make more power per cube than under square. Currently building one with Mopar 6.900 rods and Mopar pistons - cutting more valve reliefs when I get the cam and measure everything. Getting the crank rod journal reground to 2.375" and then balanced. I am a firm believer in getting crank balanced. So far I have not had a bearing issue - use belt driven external oil pump - with external line from oil pickup to pump.
Must mention that I have scrapped a lot of pieces along the way.
With our mini modified tractor engine rules of 500 cid, I have settled on a .100" over 472. Cylinder wall thickness is still .085-.125". I understand over square engines make more power per cube than under square. Currently building one with Mopar 6.900 rods and Mopar pistons - cutting more valve reliefs when I get the cam and measure everything. Getting the crank rod journal reground to 2.375" and then balanced. I am a firm believer in getting crank balanced. So far I have not had a bearing issue - use belt driven external oil pump - with external line from oil pickup to pump.
Must mention that I have scrapped a lot of pieces along the way.
Well, pulled the top end off tonite. Mr. Brode you are the 'Man'. It was as you said...it is a 500. I was informed that the 1970 500s came with the binocular pattern in the pistons. This one has the butterfly pattern in the pistons. So I wonder if the compression ratio is still 10:1? The 69 472 with the butterfly pattern pistons is 10.5:1. Well, I guess I don't have to worry about the 472 now although I do have a 69 472 partially dissembled already.
Another question for my knowledgeable friends....did the swirl patterns work in the aid of producing better combustion? I've been trying to locate info on the results of their use.
Another question for my knowledgeable friends....did the swirl patterns work in the aid of producing better combustion? I've been trying to locate info on the results of their use.
I think you misunderstood what I was saying. According to Kruzick the designs in the top of the pistons were to help promote better combustion. Creating a swirl in the combustion chamber to better burn all the air and fuel. What I am seeing is combustion over the whole piston top. Not just on one side or the other. This engine has the 250 closed chamber head on it.
I thought you may have meant that you were seeing burn patterns deposited on the piston or head, which is one way to watch the effects of any chamber and port mods.
Any type of mixture motion is very helpful at lower rpms. It's fairly well documented and tested.
The beauty of a performance build is that we are effectively changing the rpm range we run it in to a higher one, negating 'some' of the need down low.
Any type of mixture motion is very helpful at lower rpms. It's fairly well documented and tested.
The beauty of a performance build is that we are effectively changing the rpm range we run it in to a higher one, negating 'some' of the need down low.
dave brode
Well-Known Member
You don't have to call me Mr, Mr.
Is if good 'nuff to go back std? Good deal if so. The advertised compression ratio numbers were all lies. The 68-70 472s and the '70 500 are just over 9-1, and 9.4-1 tops with a tight quench and 76cc chamber. Most "76" cc heads will be a tad bigger. The dish volume in the 70 pistons is apx 33cc.
Dave
Is if good 'nuff to go back std? Good deal if so. The advertised compression ratio numbers were all lies. The 68-70 472s and the '70 500 are just over 9-1, and 9.4-1 tops with a tight quench and 76cc chamber. Most "76" cc heads will be a tad bigger. The dish volume in the 70 pistons is apx 33cc.
Dave
Sorry Dave didn't mean to ruffle your feathers. Sounds like there was a lot of misinformation being given out back then. Wrong tq/hp numbers, wrong compression ratios, good thing Cadillac didn't get involved in the Hp wars of the late 60's and 70's.
The bores look good, no ridge in the top of the cyl. This engine I'm thinking didn't have much over 100,000 mi.
Dave, do you have any info about whether the different patterns in the pistons were effective? I know JW and Don used the 'Altoids' box design in their Engine Masters engine.
The bores look good, no ridge in the top of the cyl. This engine I'm thinking didn't have much over 100,000 mi.
Dave, do you have any info about whether the different patterns in the pistons were effective? I know JW and Don used the 'Altoids' box design in their Engine Masters engine.
dave brode
Well-Known Member
Hi John,
No ruffled feathers here. Maybe my choice of term was extreme. Most factory compression ratios were lies. LOL It seems that the higher the ratio, the bigger the lie. I'm not leaned enough to comment on the piston design. Good find on the nice std block! And the sought after '70 to boot.
Dave
No ruffled feathers here. Maybe my choice of term was extreme. Most factory compression ratios were lies. LOL It seems that the higher the ratio, the bigger the lie. I'm not leaned enough to comment on the piston design. Good find on the nice std block! And the sought after '70 to boot.
Dave
Looking at the combustion pattern on the pistons, the burn looks very good. It covers the whole piston top. And especially in the butterfly recess. Makes me wonder why there aren't more oversize pistons based on them. I suppose the compression ratio wouldn't be high enough for performance usage.