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| hyper pak compression ratio https://slantsix.org/forum/viewtopic.php?t=27633 |
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| Author: | Valleyant [ Mon Mar 03, 2008 11:23 pm ] |
| Post subject: | hyper pak compression ratio |
Hi, I read that the 170 was 10.5:1 and the 225 was 11.5:1. Was this achieved only with special high compression pistons? Thanks, nico |
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| Author: | SlantSixDan [ Tue Mar 04, 2008 6:34 am ] |
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High-compression pistons, yes. 10.5:1, yes. Don't think I've read that the 225 was 11.5:1. |
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| Author: | runvs_826 [ Tue Mar 04, 2008 9:08 am ] |
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The last 340 we built had 11:1 compression and we had to at least run a mix of 91 octane and av gas. So that would kinda suck to run av gas in your car from the factory. Course octane used to be higher with leaded gas. Kinda interesting to see what this E85 will bring us huh? |
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| Author: | 1969ronnie [ Tue Mar 04, 2008 5:46 pm ] |
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my info shows 11.5-1 with 195 h power at 5200 rpm. ron |
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| Author: | SlantSixDan [ Tue Mar 04, 2008 7:30 pm ] |
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Quote: my info shows 11.5-1 with 195 h power at 5200 rpm. ron
What is the source of this info you have?
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| Author: | runvs_826 [ Tue Mar 04, 2008 9:12 pm ] |
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Man, if that's true that's probably just as good or better than the super slant I run now. I guess the compression would help, but what else did the original hyperpak motor sport besides a bitchin manifold? I thought there was a special cam or something? |
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| Author: | Valleyant [ Tue Mar 04, 2008 9:28 pm ] |
| Post subject: | |
Hi, I read on allpar about the 11.5:1 in the 225. The stick shift cars even got a heavy duty clutch. It sounds like it was a well thought out package. I would love to see a '60/'61/'62 Valiant hyper pak in person maybe someday at the Mopar Nationals. nico |
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| Author: | SlantSixDan [ Tue Mar 04, 2008 9:42 pm ] |
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Quote: Hi,
Careful. There is no information quality control on Allpar. It contains a great deal of information, much of which is quite good and reliable, and some of which is factually lacking.
I read on allpar about the 11.5:1 in the 225. |
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| Author: | Doctor Dodge [ Tue Mar 04, 2008 10:17 pm ] |
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The Hyper-Pak was a well engineered package. The Valiants that used this combo of parts literally "clean house" on all competitors in the Datona races they ran in. NASCAR cancelled the "compact car" race after running it for 2 years and watching Valiants wipe-out the field. The Mopar engineers knew how to make the SL6 run... air flow and some compression. Here is the 'kit" that was offered to the public, no 'pop-top' pistons in this photo of the kit. DD 
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| Author: | Charrlie_S [ Wed Mar 05, 2008 4:57 am ] |
| Post subject: | |
Doc, I have heard conflicting things about the "hyper Pack" setup, can you answer these questions? 1) If I remember corectly the "NASCAR" cars had 170 engines. 2) The hyper pak was sold as a dealer installed option, or "over the counter". 3) Were there two different kits? One for the 170, and one for the 225? 4) If just one kit, which one?, Your picture shows pushrods, and the 170, and 225 used different pieces. 5) I would also think the "header pipe would need to be different, due to the different "deck hight", of the two motors. 6) Also wondering about the pistons. With the different deck hight, there really should be a different configuration of the top of the piston. Such as a higher distance from the pin to the flat portion on the top of the piston, and a smaller dome, for a 225 piston. Is there any chance you have the specs on a OEM HP piston? I have a set of NOS Jahns "pop up" pistons for a slant, and would like to compare the specs. |
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| Author: | SlantSixDan [ Wed Mar 05, 2008 5:49 am ] |
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I'm not Doc, but do you mind if I take a crack at some of these? The NASCAR Valiants did run 170s. Most of the reports I've seen say they had high-compression pistons for 10.5:1 compression which were not included with the kit sold over dealer parts counters. The reason the Hyper Pak was even offered to the public at all was so that it could be considered production/generally available equipment and thus qualify for installation on the race cars. In fact, there were a fair number of differences between what was provided for the NASCAR Valiants and what was made available to the public, so I don't know how rigidly the NASCAR "production equipment" rules were written, interpreted, and/or enforced. I used to have a very detailed report on the matter from the '60-'61 timeframe when the NASCAR Valiants were being campaigned — I'm sure I still have it somewhere, but don't anticipate it floating to the top of the heap any time soon. I've seen factory P/N lists and installation instructions for the Hyper Pak kit, and none of them has included pistons, nor have they listed more than one (170) pushrod or headpipe P/N, nor have there been any instructions like "On the 170, do ABC. On the 225, do XYZ instead." Keep in mind that this kit was produced and officially offered in '60- early '61 (remaining stock was sold after this timeframe until depleted), and the 225 wasn't available in Valiants until the middle of the '61 model year — it was nominally available in the '61 Lancer from the start of M.Y.61, but I do not know when 225s actually became readily available in Lancers. So there was little overlap between Hyper Pak availability and 225 availability. It seems likely that either the 225's stock pushrods were used with acceptable results due to the 225's lower RPM range, or aftermarket pushrods from e.g. Iskendarian were used in 225 Hyper Pak installations. Since the Hyper Pak was an aftermarket-only item (i.e., the only "official" installations were on the NASCAR 170-engined Valiants), there would've been nothing officially controlling the use of this or that or any other pushrod, piston, or any other component on non-NASCAR installations. As for the headpipe, it's not too hard to adapt 170 headpipes to fit 225s...ask Doc! 
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| Author: | Charrlie_S [ Wed Mar 05, 2008 6:19 am ] |
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That's about what I thought. I'm still curious about the pistons. I'm pretty sure an old Direction Connection, engine book I have, had a original part number listed for the pistons. I will have to try to find it. I would like to compare the specs to my Jahns pistons. One of these days, I will get around to checking the dome volume, and see if they would work better in a 170 or a 225. I suspect it will be a 225, since the compression distance, from the wrist pin CL to the flat part of the piston is .059 greater then a TRW replacemnt piston. I think even without any decking, the Jahns piston would be too high, in the 170. The dome on this piston is approx .300 high. Weight of piston is about 10 lbs  
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| Author: | Doc [ Wed Mar 05, 2008 9:07 am ] |
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I agree that all the development and parts for the kit were designed for the 170 and that the least understood part of the package are the pistons. I have seen many different compression ratios claimed and seen a few sets of "so called" "original" H-Pak pistons, one of those sets were made by Jahns and were "pop-tops" that resulted in 11.5 static compression in a 170. Another piston set I saw would produce 13 to 1 and my guess is that the "good ol" NASCAR boys were running that compression. Those old pop-top piston designs are cool looking but they really do not work well from a burn standpoint. The age of computer sims. shows that the dome blocks the flame travel across the piston head. DD |
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| Author: | Charrlie_S [ Wed Mar 05, 2008 10:42 am ] |
| Post subject: | |
Quote:
Those old pop-top piston designs are cool looking but they really do not work well from a burn standpoint. The age of computer sims. shows that the dome blocks the flame travel across the piston head.
Yeah, but since I have them, I will run them, one of these days.
DD |
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| Author: | LUCKY13 [ Wed Mar 05, 2008 12:36 pm ] |
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A little massaging on the dome, and the underside of the piston could get a burn pattern that was good, plus knock off some weight. Jess |
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