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  #31 (permalink)  
Old 11-17-2012, 09:02 PM
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put the same cam in 4 degrees early for a sooner response,or use 1 size smaller cam

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Old 11-18-2012, 06:53 AM
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With newer flat tappet cams they already have aggressive ramp rates for the material and the design of the lobe to lifter geometry. Using a 1.6 rocker increases this ramp rate, meaning that it will cause the valve to open farther and then close in the same amount of time. This increases stress on the cam lobes and lifters. If you are just talking about using a roller rocker on a flat tappet set up, you can do it. In this case since you didn't spend a bunch of money on the rest of the valvetrain I don't see a big need to spend a bunch of money on the rockers.

As for the cam you are talking about, if the cam card says 2500-whatever, this is just a broad-generalized guesstimate made by the manufacturer. You also have to understand that these guesstimations are made based on an engine of 350 cubic inches. You are planning on a 383, those extra 33 cubes eat up some of the range on the cam (the larger the displacement, the more duration is needed to produce the same effect). So as a general rule of thumb you can take about 500rpm off the guesstimated ranges. If the cam card says 2500-6000 then it will be closer to 2000-5500.

I didn't look into the cam specs of the cam you are looking at but I have built and driven a good few 383s, and for different uses. What I have figured out with the experience is that street 383s like around 222-232 degrees of duration at .050 (keeping in mind 9.5:1CR, mild heads, dual plane intake)
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Old 01-09-2013, 12:09 PM
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So its been a while but I'm still searching...looking for some 190cc heads with 76cc combustion chamber bc i want to run flat top pistons...however I can only find 76cc combustion chambers on heads that are maybe 170cc or lower?? Do heads exist that are 190cc with 76cc comb. chamb.? and where are they?
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Old 01-09-2013, 12:18 PM
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afr dart edelbrock and almost all the others have 76 cc chamber heads,just ask them
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Old 01-09-2013, 02:05 PM
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Quote:
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afr dart edelbrock and almost all the others have 76 cc chamber heads,just ask them
thanks for the quick reply vinnie
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Old 01-09-2013, 02:24 PM
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Quote:
Originally Posted by vinniekq2 View Post
If you used a 4.56 gear and built an engine that makes power to 6400 rpm and used a 28.5 tall tire...That car could go 120 mph at redline and at 2700 rpm(using .68 O/drive) would be cruising over 70 mph. That an extreme scenario in my opinion. like tech says thats an 11 second car that can cruise to the track.If it spends a lot of time on the track,then buy a trailer for race days,long walk home if something breaks

I know all about this, at first I used a well built 700r4 with it's 3.06 first gear and a set of 4.10 gears which comes out to a drive ratio of 12.55, if you compair this to a th350 and it's 2.52 first gear it would be the same as running a 4.95-5.00 rear gear with a th350, then the 700r4 has a 1.63 second gear which is about the equivilent of running a th350 (1.52 2nd) with a 4.56 rear gear.

this was all in a high 11 sec car, I enjoyed the o/d if I was driving on the highway (which was rare) but I didnt enjoy trying to make it hook. My 60ft times were too inconsistant because I had the hardest time finding that happy medium on take off. Not to mention that 1st gear felt like a "granny" gear. I have since swaped out to a th350 and now have 4.56 rear gears.
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Old 01-09-2013, 02:33 PM
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Okay this thread is tripping me out, I see posts I made months ago, that are in the mix of posts that I have made today. They aren't even in order. Anyone else notice this. Then it gives a date back in November for the some of the posts that I have made today.
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Old 01-09-2013, 02:41 PM
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Personally I dont think that I would go after a 76cc combustion chamber head to make up what ever CR I was tring to achive. I would be affraid that it would be too large of an area to maintain a good "burn" or quench pad area. I would not go any larger than a set of 72cc heads. If you where to use a 72cc head and a flat top piston then you would end up with 10.2:1 compression which on a motor with alm heads is easily run off of pump gas, heck my 11.2:1 CR motor can and has run on pump gas.

Dont let a good quality dished piston fool you, they have D dished pistons now, they are not like the old O oval dished pistons that had horrible quench pads. the D dished pistons are shaped so that they keep the same style quench pad as a flat top. I had 18cc dished pistons and made just over 500hp on pump gas with them, these are the same ones that I have in my gargae that still look brand new.
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Old 01-09-2013, 03:53 PM
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Personally I dont think that I would go after a 76cc combustion chamber head to make up what ever CR I was tring to achive. I would be affraid that it would be too large of an area to maintain a good "burn" or quench pad area. I would not go any larger than a set of 72cc heads. If you where to use a 72cc head and a flat top piston then you would end up with 10.2:1 compression which on a motor with alm heads is easily run off of pump gas, heck my 11.2:1 CR motor can and has run on pump gas.

Dont let a good quality dished piston fool you, they have D dished pistons now, they are not like the old O oval dished pistons that had horrible quench pads. the D dished pistons are shaped so that they keep the same style quench pad as a flat top. I had 18cc dished pistons and made just over 500hp on pump gas with them, these are the same ones that I have in my gargae that still look brand new.
Thanks I'll keep this in mind, some of the combos I've seen use the 18cc dished so I might end up going that way
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