Slant Six Forum :: Twiggy - Long Rod Aluminum Block Engine Build-up

I got to agree with where you put your timing events, should work good.

But the cams duration has me a little puzzled. Are you sure thats not the other way around Intake 244 exhaust 266. It would make more sense to me then. But I am not to good at making sense anyway. Then having the higher lift on the intake side to go with the short dur. In other words soemthing like this.

Intake 587 lift /244 @.050
exhaust 553 lift/ 266@.050

That kinda cam I am use to using, but with a reverse split like you are listing I have not ever used.

I also dont have much expeirance with diff cams in the /6, or any other long stroke small bore engine.

I assume with your expeirance you have found this type cam to work good in the /6, or you have listed the durations backward by mistake. Dont get me wrong, I am in no way saying that what I listed is what you need. I just want to know for sure what your cam is so I understand what is going on. If the way you listed it is correct, then it is a odd cam. But maybe not for a /6.

Thanks for the info

Jess

Author:	slantasaurus [ Mon Aug 13, 2007 10:40 pm ]
Post subject:
Thanks for the info, knowlage is power.

Author:	AndyZ [ Tue Aug 14, 2007 6:33 pm ]
Post subject:
A picture certainly is worth a thousand words. I can't wait to see this thing run! See you in Redding. AZ

Author:	Doctor Dodge [ Wed Aug 15, 2007 8:56 pm ]
Post subject:	Piston Installed...
The #1 piston went in with-out any problem. I found-out that we are .008 off "blueprint". This engine is suppost to be zero (0) deck height and it actually has the piston sticking out of the top by .008 Looks like my machinest took a little bit more off the deck and / or the main line bore... either way, I will have to redo my calculations to find the new static compression. (it should not change much) DD

Author:	Dart270 [ Thu Aug 16, 2007 6:37 am ]
Post subject:
Seems like that should be no trouble. I have a motor ready to go together that is 0.015" out of the hole. I figure with a 0.050" head gasket, that should be plenty of room to the head. Lou

Author:	slantzilla [ Thu Aug 16, 2007 7:07 am ]
Post subject:
Seymour had a Bruner motor that was +.020". When I put the first piston/rod in the 2.5 motor I did last spring it was +.200". That was an issue.

Slant Six Forum https://www.slantsix.org/forum/

Twiggy - Long Rod Aluminum Block Engine Build-up https://www.slantsix.org/forum/viewtopic.php?t=23948	Page 9 of 25

Author:	Doctor Dodge [ Sat Aug 18, 2007 11:06 pm ]
Post subject:	Degreed the Cam...
I installed and degreed-in the special dual pattern grind from Erson, 266 Intake & 244 exhaust. Everything came out pretty close to the card specs with the cam installed straight up. As you see, I do my cam degreeing with 1 piston installed and use a section of cylinder head with light tension test valve springs. This makes everything real easy to turn with a nice smooth motion. Set the lash to your cam card's lash numbers or set the lash at .050 if you want to see the events at .050 It is great to have a cam with a longer intake event, I actually retarded the cam 4 degrees to get the "blowdown" (exhaust opens) event to happen a little later (55 BBDC) and this also got the overlap event a little more centered around TDC. Straight-up overlap: Intake opened @ 27 BTDC - Exhaust closed at 13 ATDC. With 4 degrees cam retard: Intake opens at 23 BTDC - Ex. closes at 17 ATDC. My guess is that the overlap event will "even-up" a bit more once the timing chain stretches a little. FYI, this cam was ground with 4 degrees advance and on 110 lobe centers. DD

Author:	LUCKY13 [ Sun Aug 19, 2007 4:24 am ]
Post subject:
I got to agree with where you put your timing events, should work good. But the cams duration has me a little puzzled. Are you sure thats not the other way around Intake 244 exhaust 266. It would make more sense to me then. But I am not to good at making sense anyway. Then having the higher lift on the intake side to go with the short dur. In other words soemthing like this. Intake 587 lift /244 @.050 exhaust 553 lift/ 266@.050 That kinda cam I am use to using, but with a reverse split like you are listing I have not ever used. I also dont have much expeirance with diff cams in the /6, or any other long stroke small bore engine. I assume with your expeirance you have found this type cam to work good in the /6, or you have listed the durations backward by mistake. Dont get me wrong, I am in no way saying that what I listed is what you need. I just want to know for sure what your cam is so I understand what is going on. If the way you listed it is correct, then it is a odd cam. But maybe not for a /6. Thanks for the info Jess

Author:	dakight [ Sun Aug 19, 2007 5:48 am ]
Post subject:
I see that you are using an aluminum hub, nylon tooth cam gear. I thought those were undesirable, please explain.

Author:	argentina-slantsixer [ Sun Aug 19, 2007 7:34 am ]
Post subject:
Quote: I got to agree with where you put your timing events, should work good. But the cams duration has me a little puzzled. Are you sure thats not the other way around Intake 244 exhaust 266. It would make more sense to me then. But I am not to good at making sense anyway. Then having the higher lift on the intake side to go with the short dur. In other words soemthing like this. Intake 587 lift /244 @.050 exhaust 553 lift/ 266@.050 That kinda cam I am use to using, but with a reverse split like you are listing I have not ever used. I also dont have much expeirance with diff cams in the /6, or any other long stroke small bore engine. I assume with your expeirance you have found this type cam to work good in the /6, or you have listed the durations backward by mistake. Dont get me wrong, I am in no way saying that what I listed is what you need. I just want to know for sure what your cam is so I understand what is going on. If the way you listed it is correct, then it is a odd cam. But maybe not for a /6. Thanks for the info Jess jess, this is RDP cam. (Reverse Dual Pattern) in a 6 cyls you've a 120Â° spread between events unlike the V8's. Local chrysler used as much difference as 296 intake 260 exhaust. Couple of details is that intake ports are the biggest limitation on the /6 head, and your typical slant exhaust port has a larger percentage of flow compared to your average mopar SB head.

Author:	Bren67Cuda904 [ Sun Aug 19, 2007 8:07 am ]
Post subject:
Quote: I see that you are using an aluminum hub, nylon tooth cam gear. I thought those were undesirable, please explain. Looks like he's keeping the weight down here too.

Author:	Doctor Dodge [ Sun Aug 19, 2007 8:09 am ]
Post subject:
It's nice to see that people are following along and thinking about the combination. The reality of any good engine build-up is that it is a process where you have to check, think about and recheck everything that gets bolted onto the assembly. You quickly find-out that you have to make decision base on incomplete or less the ideal information. You are constantly faced with making trade-offs and compromises. This is especially true with "non-mainstream" engines like the SL6 where we don't have a lot of "out of the box" proven combinations to simply purchase, assemble and go. Anyway... yes the cam is interesting and defies "conventional wisdom". (V8 CW ) The numbers are correct, this is a "reverse dual pattern" cam grind where there is more duration (and lift) on the intake lobe. Here is the detailed profile sheet: http://www.dutra.org/pictures/engine/er ... am60bd.jpg It has taken me many years to discover that the SL6 likes more intake cam duration and lift... especially in the milder "street strip" configurations. I have tried a number of SL6 cams that are the conventional dual pattern (more more lift & duration on the exhaust) and these don't seem to work as well. (seat of pants and time slips = more incomplete information) The good news is that there is more & more agreement around this concept and from what I'm finding, from degreeing a few of these reverse dual pattern cams, it is a lot easier to get them and set them so the valve events end-up where the inline 6 likes to see them. As soon as the engine fires-up and I get lash and idle quality data, I will most likely order another one of these cams, ground with zero (0) advance and on 108 lobe centers. (more overlap) The aluminum top (cam) timing gear... let the discussion commence! I have never installed one of these into any engine I have built, I always take them out and they never go in... this may be another first for me! The main reasons I checked my set-up with one: - This gear is really light weight, 304 grams total. (10.6 onces) - I have a NOS gear, in perfect condition, zero wear. - Mopar put a bunch of these into production engines. - Smokey Yurick liked to use them in race engines. Truth be told... I have prep'ed and degreed two top (cam) gears and will have to quickly make a decision on which one I will use. DD

Author:	slantzilla [ Sun Aug 19, 2007 8:16 am ]
Post subject:
Using stock gears was the rage in the old days until they got to crazy valve spring pressures. The reasoning was two-fold. First. the thought was that the nylon/aluminum did not transmit harmonics to the camshaft. Second, they figured that the chain would "stretch" at high RPM, retarding the cam for a little more power. You also have to remember that the engines were torn down and rebuilt after every race, so longevity was not a real issue.

Author:	SlantSixDan [ Sun Aug 19, 2007 10:30 am ]
Post subject:
My thinking: They put those nylon-over-aluminum cam sprockets in \6s, small V8s, and big V8s starting around 1967. Sure, after years and miles, they will wear while an all-metal one won't, which means more and faster camshaft retard with age and mileage, and for that reason the conventional wisdom is "might as well put in an all-metal set while you're in there". But, it's not like the nylon/aluminum sprockets fail in 10k or 50k or 75k miles, the careful degreeing-in means you're already way ahead of the factory's loose and sloppy "just slam it in" tolerances, and I doubt this particular engine will spend a whole lot of miles and decades with any single cam setup, so I don't see anything especially unwise about using nylon-over-aluminum in this engine. And yeah, you get a nice weight savings with it!

Author:	Dart270 [ Sun Aug 19, 2007 10:53 am ]
Post subject:
I just looked at Doc's cam card and he made a typo above - 266 int and 254 exh (not 244). I have an Erson 280/270, 0.460", 226/220@0.050", 109 LSA that I'm going to try in a street motor with a nice head and 8.8:1. Would like a little more comp (9.5), but that's what I have in this setup. The fast guys who have tried lots of cams almost all use more int duration on a 225. Lou

Author:	greasy 225 [ Sun Aug 19, 2007 4:39 pm ]
Post subject:
Damn, I wish I woulda paid better attention now! I spoke with Tom at erson only very briefly about the long duration intake cam, he said with what Im wanting in mine the .280 would be a good choice. Now that I've read the logic twice, it makes much better sense now. -Jesse

Page 9 of 25	All times are UTC-08:00
Powered by phpBB® Forum Software © phpBB Limited https://www.phpbb.com/