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| Do you need large valves? https://slantsix.org/forum/viewtopic.php?t=14170 |
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| Author: | sixty4dartgt [ Fri Aug 26, 2005 4:52 pm ] |
| Post subject: | Do you need large valves? |
Is there anyone running low 15's or faster with stock valves? My car seems to fall flat @ 4000 rpm. I am going to advance the cam, but my dad was thinking the valves were restricting the cam (it's a MP 268 - .460 lift). I think this is a med/mild cam. Right now I have a new valve job with stock valves and the head is shaved .060. I ported it with a dremel. I want to get a upgrade with larger valves, more compression and port polish professionally done. But, I wanted to see what I could get out of this set up first. Does anyone have a recommendation for someone to do the port/polish. All of the local shops around here will install the valves and shave the head, but they don't port or polish. I was thinking about BPE Racing Heads in Palentia, CA. www.bpeheads.com Thanks |
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| Author: | Charrlie_S [ Fri Aug 26, 2005 6:28 pm ] |
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I am running a head with stock, untouched ports and stock valves. But I am on nitrous, which carries it's own oxygen. Run low to mid 13's. |
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| Author: | sixty4dartgt [ Fri Aug 26, 2005 11:25 pm ] |
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Thanks for the reply. I would love to run 13's, but I don't want nitrous or turbo. I think 15's or 14's can be had with "natual air". Anyone doing it this way with stock valves? |
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| Author: | Dart270 [ Sat Aug 27, 2005 4:01 am ] |
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Certainly people have gone in the 14s and 15s with stock valves. If the engine falls that flat, I would suspect timing curve or carb tuning. These can have huge effects. Of course, you are better off with bigger valves and some good port work as a starting point. Your cam is also not very big. My guess is you can hit 15s fairly easily with your setup and correct tuning. If you have not mapped your dist advance curve, that is job one. Dont' throw expensive parts at it just yet...  Lou |
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| Author: | Guest [ Sat Aug 27, 2005 6:10 am ] |
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Cam timing could be causing this also. Were is the cam installed? Sounds like it is advanced to much! The more you retard the cam the higher the RPM, but it takes low end power away. This is wye it is so important to degree the cam. :lol:Jim Cox |
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| Author: | argentina-slantsixer [ Sat Aug 27, 2005 7:38 am ] |
| Post subject: | |
Don't advance your cam, retard it. Advancing it will cause your mill to fall flat out even sooner. |
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| Author: | sixty4dartgt [ Sat Aug 27, 2005 9:32 am ] |
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Dart270 - OK I was already planning to put in a recuvred distibutor next week. Jim Cox - I did degree the cam. It is at 105*. This is the cam I got from Menko. I do not have paperwork for it, but from what I found on the internet, it should be at 104*. So that means it is 1* retrarded, right? I was going to put it to 104*. Should I leave it? Anyone running/has run one of these cams? I don't know if the valve lash makes a big difference, but I have mine at 28 intake and 32 exhaust (per the info I found above). |
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| Author: | sixty4dartgt [ Sat Aug 27, 2005 10:59 am ] |
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So here is the info I found. http://www.victorylibrary.com/mopar/mpcam-tech-c.htm#6 I also found out that jharris (Joel) was running the same cam with stock valves and was in the low 15's. I sent him a PM, but he hasn't posted in 2 years so ... This is the post from Sept '03 that I got the below quote from. http://www.slantsix.org/forum/viewtopic ... ght=#32651 Quote: I bought one of these cams a few years ago and on the box it recommended .018" lash intake and exhaust. There was an instruction sheet in the box that recommended the lash be set at .022" int. and exh. The Mopar Performance catalog recommends .028" int. and exh. I called Mopar Performance Techline and they said that the lash spec's are not set in stone. The guy said that if you tighten up the lash you will get better performance but you will shorten the life of the cam. I currently run mine at .022" and it is fairly quiet and performs well. I hope this helps.
I guess I will set my lash at .022 and get the distributor recurve straight, then see about the cam.Joel Thanks for the replies. 
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| Author: | Dan Trump [ Sat Aug 27, 2005 9:56 pm ] |
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just a dumb question, but when you put that cam in, did you upgrade your valve springs? if you left the stock ones in it wont rev either.. Good Luck, Dan |
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| Author: | sixty4dartgt [ Sat Aug 27, 2005 10:04 pm ] |
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Yes sir. I put in 340 springs. |
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| Author: | Charrlie_S [ Sun Aug 28, 2005 5:49 am ] |
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This might be a stupid question, but what carb are you running? Didn't see it mentioned. A 1 bbl will only go to about 4000-4500. A 2 bbl should work OK. A 4 bbl, if the secondaries are not opening, will cause this problem also, since the primaries are generally smaller the a 2 bbl. |
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| Author: | sixty4dartgt [ Sun Aug 28, 2005 7:21 am ] |
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I am running a Edelrock 500. I also thought maybe the secondaries were not opening. I thought it might be my linkage. I checked it the other day and it's OK. I can change the spring however. There are 5 different sizes. I had the 3 strongest in there at different times. Maybe I should try the weaker springs? |
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