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Post by racingelvis on Mar 5, 2015 10:00:45 GMT -6
I have a ton of stuff fromm DDI from back in the day. Updates, performance tips etc. Here is one of them
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Post by racingelvis on Mar 5, 2015 10:03:18 GMT -6
couple of cool things about this, the 295 experimental mod engine is my 295 wedge motor ddi magnum sled that jay sr. owned. that will be hopefully receiving a restoration coming up and the last paragraph about the 73 magnum heads, this caught my eye, so what did the magnums come with for heads, i have only seen these part #'s for the 73 sr heads? ??. only other sr f/a head i have seen is the 71 sr head. i doubt they came with those. Attachment Deleted
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Post by red19lite on Mar 5, 2015 11:35:24 GMT -6
couple of cool things about this, the 295 experimental mod engine is my 295 wedge motor ddi magnum sled that jay sr. owned. that will be hopefully receiving a restoration coming up and the last paragraph about the 73 magnum heads, this caught my eye, so what did the magnums come with for heads, i have only seen these part #'s for the 73 sr heads? ??. only other sr f/a head i have seen is the 71 sr head. i doubt they came with those. View Attachment mybe one was for gas other no for methanol
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Post by magnumed on Mar 5, 2015 13:29:59 GMT -6
Here are the two different heads, more cooling area on the left set. Both sets are the part number in the letter. A lot of people don't know this. The 71 sr heads next picture have no part number cast into them and much less cooling area.
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Post by racingelvis on Mar 5, 2015 13:45:56 GMT -6
thanks ed, i understand now, i thought there was a different part # head that i never seen before.
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Post by red19lite on Mar 5, 2015 15:51:58 GMT -6
Here are the two different heads, more cooling area on the left set. Both sets are the part number in the letter. A lot of people don't know this. The 71 sr heads next picture have no part number cast into them and much less cooling area. are the combustion chambers the same on both sets of heads? cc? both plugs 1/2 in reach?
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Post by magnumed on Mar 6, 2015 19:37:16 GMT -6
Kevin I finally got them measured, the ones I have are identical.
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Post by red19lite on Mar 6, 2015 22:10:53 GMT -6
ed, I thought they would be different, being there was a couple years between build,s most of the time things like that change a little, where all free air tohatsu 440 were oringnally for mehtonal fuel? thanks kevin
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ddi stuff
Mar 7, 2015 0:43:28 GMT -6
via mobile
Post by magnesium on Mar 7, 2015 0:43:28 GMT -6
71's were methanol. In 72 methanol was banned by a lot of racing organization's. There was a kit Rupp offered to change 71's to gasoline for the 72 season with Tillotson's,modify the tuned pipes,etc. Apparently Gene Bloom ran a CDI in 72. 73's ran on gasoline.
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Post by magnumed on Mar 7, 2015 6:45:44 GMT -6
ed, I thought they would be different, being there was a couple years between build,s most of the time things like that change a little, where all free air tohatsu 440 were oringnally for mehtonal fuel? thanks kevin I checked the two different style 73 heads. I will check the 71 heads next. Ed Sent from my SPH-L720 using proboards
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Post by magnumed on Mar 7, 2015 9:38:43 GMT -6
71 SR heads are the same as the 73SR heads in the combustion area. I also check the cylinders, both NOS. The porting looks the same except the 73 exhaust port is larger and a touch higher, the 73 intake port is larger and lower, approximately .014. The 71 piston skirt is approximately .014 shorter on the intake side as well. The 71 SR must have been a beast at the track. None to be found. I think a lot of them bit the dust when converted to gas. They have less cooling area on the heads and cylinders. Designed for Methanol not regular gas.
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Post by magnesium on Mar 7, 2015 15:39:09 GMT -6
The two 1971 440SR top-ends that I've found don't show signs of overheating. One did run on gasoline for a very short run. The owner was a welder who decided to follow Rupp's advice, welded the crank himself.....bang The other top end may have run successfully on gas but I have no way of finding out. Ignition timing would have to be reduced to run gas. Methanol has an octane rating of 100! Both left-hand cylinders had broken fins from belt /clutch failures. One head had ring damage. I'd say that they kept revving them higher until failure. For years I've believed that Methanol had 3x the refrigerating effect of gasoline. Last night I realized I was wrong, it has more than 6x the cooling effect. CH3OH absorbs 3x as much heat (over gas) by volume, but you burn twice the amount of fuel, so it's 2 x 3= 6x! Turns out that methanol is still evaporating by the time the spark lights it. The "explosion" evaporates the rest. Remember that the cooling happens at both sides of the piston crown. Those ported pistons increased the cooling of the piston crown, too. The 73 would benefit just as much as the 71. Remember that everyone was trying to get more cooling air to the motor of the 73's. Anyone who likes drag racing knows why fuel cars do burn outs. They're getting the engine internals warm enough to evaporate all the fuel they guzzle. (They could just warm the tires with electric blankets) The alcohol 2 strokes fall on their faces unless you warm them up.
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