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Old 04-21-2004, 10:12 AM
Thom Laybourne's Avatar
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The 305

Boy have we beat this horse to death. But I have decided to build one for my self and see just what it can do. It will be put in my 55 PU for a while and then moved to my son's boat. I checked all the back posts and I could not find anything on the roller rocker ratio. 1.5 verse 1.6. I am changing the studs to 7/16. I am also looking at using the aluminum rollers. I figure every once counts. I need understanding on the ad/disad on the ratios. I am going to use ISKY cam and hydraulic roller lifters. Oh, I AM also going to do some porting and polishing. Thoughts?

hr41pearl

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Old 04-21-2004, 10:43 AM
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While you already know that a 305 is less than optimum for building power compared to a 350 or larger engine it still has great potential. A 305 can be made to produce good torque and power depending on the combo you choose.

You didn't say which heads you are running, early ones like my 78 305 had won't make much power because they have small valves and intake runners, they are also prone to cracking valve guides.

Going to a higher rocker ratio is an option you can take if you want to increase the lift of your current cam while maintaining the same duration figures. More lift will produce more power without moving the power band up the rpm scale(in theory).

Since the engine is intended for truck or marine use you want an RV or torquer cam. If you decide to go for the roller rockers with the higher ratio make sure you check for proper clearance at the valve keeper/valve guide to avoid bottoming. A properly chosen cam shouldn't need 1.6 rockers but it's really up to you as the engine builder. The power freed up from roller tip rockers is marginal.

I mulled over re-building my tired 305 vs a 350 build and decided it wasn't that much more to build a cheap 383 since my 305 needed machine work on the block and heads.

I have about $1400.00 into my 383 build up and that includes buying a re-machined block, new gm cylinder heads($300.00) from a buddy who pulled them off a crate motor for bigger heads and the stroker kit from Powerhouse.

You might want to re-think your build up since a re-buildable core is around $150.00 regardless of displacement. If your 305 needs machine work you will be spending "350" money to build a 305.

The cost of a good set of roller tip aluminum rockers would buy your 350 core.
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Old 04-21-2004, 11:19 AM
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Quantity

Well the good part is that I have five of these things sitting in the storage shed. I took two apart last evening and they look to have about 20k-30K on them. As of this moment, I am planning to use the stock heads with a little porting and polishing. I will check with ISKY or CRANE on the cam/rocker issue. As for rollers. They release 65-70 ft lbs of torque at a small cost.

hr41pearl
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Old 04-21-2004, 11:43 AM
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65-70 ft lbs gain with rollers rockers??? What is the source of this info?
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Old 04-21-2004, 01:02 PM
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65-70 ft-lbs is the torque spec on the studs, not the improvement in power!



K
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Old 04-21-2004, 01:11 PM
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You won't even need that with a littlle locktight.
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Old 04-21-2004, 01:31 PM
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Torque

Attach a TORQUE wrench to the front of you motor. With the plugs removed crank turn the motor over using the TORQUE wrench. It should be around 150 FT LBS. Now install rollers. Do the same thing. Guess what> 70-80 Ft Lbs to rotate the same motor. That is on a 383. The numbers will vary based on the engine size. But I have always called that number TORQUE. Maybe I am using the wrong phrase.. Don't think so.

hr41pearl
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Old 04-21-2004, 01:46 PM
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Re: Torque

Quote:
Originally posted by Thom Laybourne
Attach a TORQUE wrench to the front of you motor. With the plugs removed crank turn the motor over using the TORQUE wrench. It should be around 150 FT LBS. Now install rollers. Do the same thing. Guess what> 70-80 Ft Lbs to rotate the same motor. That is on a 383. The numbers will vary based on the engine size. But I have always called that number TORQUE. Maybe I am using the wrong phrase.. Don't think so.

hr41pearl
By that theory if you could find something that gave you an additional "70-80 ft/lbs of torque" you should be able to turn the engine with your bare hands then.
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Old 04-21-2004, 01:47 PM
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That may be true Thom, but real world dyno testing on a running engine reveals a marginal gain in engine output, maybe 2 horsepower.
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Old 04-21-2004, 01:58 PM
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Re: Re: Torque

Quote:
Originally posted by buckethead1
By that theory if you could find something that gave you an additional "70-80 ft/lbs of torque" you should be able to turn the engine with your bare hands then.
Yeah but two things are different when the motor is turning itself over. First you have a steady, heavy flow of oil going on to the rockers and the moving valve train is giving the cam some slack at certain points. Second, physics states that friction gliding is a different coefficient than friction static, so if the rocker is already moving, its going to take less power to keep it moving.

K
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Old 04-21-2004, 02:23 PM
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Physics 101

Yup, I remember "objects in motion tend to stay in motion", "objects at rest tend to stay at rest". And I do agree that my formula is not that scientific. But if I am accelerating down the strip, I am "object at rest tending to stay at rest" because I am always trying to increase my speed. I also understand that dun shows us that as rpm increases torque decreases (after about 3800). So, yes I agree that after I get this thing moving down the strip torque will become less a factor and will not be sustained. But the premise is still that the roller system provides a very nice torque return for the investment. Also, remember we are only discussing ONE of the advantages of rollers. Anyone care about oil temp? Anyone care about MPG? Anyone care about water temp? Anyone care about valve ware?

hr41pearl

http://www.airflowresearch.com/dyno/chevy_dyno.htm

This article seems to support 20HP and 20 ft lbs across the entire RPM range.

Last edited by Thom Laybourne; 04-21-2004 at 02:58 PM.
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Old 04-21-2004, 03:05 PM
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That article references a roller cam not roller rockers.
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Old 04-21-2004, 03:17 PM
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wow

so if i get a full rolloer valve train i would be able to turn my engine over with one hand as per what you are saying lol yea rollors may help redce some resistance but it sounds like you are sold on them so buy them and try them. make a run with them and with out them and prove us all wrong. but make sure you do the rollors at nigh in the cold dense air and thr stockers in the early after noon when the air is warm and less dens so you see more of a significant gain to prove every one wrong.
buy them you are sold to the horsepower you will build....
Jesse
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Old 04-21-2004, 03:26 PM
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My mistake?

I guess I presumed one used a ROLLER CAM with roller lifters and rockers. I guess I presumed that one could also use roller lifters and rockers with a standard cam. I wonder if you can run non rollers on a roller cam? Or, are you saying that the lift on the cam is greater and that is the cause of the increase?

hr41pearl

Jesse. Not sold about HP, but rather the torque. Which would you rather have? 100 HP or 100 FT LBS Torgue?
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Old 04-21-2004, 03:38 PM
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Re: My mistake?

Quote:
Originally posted by Thom Laybourne
I guess I presumed one used a ROLLER CAM with roller lifters and rockers. I guess I presumed that one could also use roller lifters and rockers with a standard cam. I wonder if you can run non rollers on a roller cam? Or, are you saying that the lift on the cam is greater and that is the cause of the increase?

hr41pearl

Jesse. Not sold about HP, but rather the torque. Which would you rather have? 100 HP or 100 FT LBS Torgue?

... uhhh, i don't think you'll ever get to choose. THey are mathematical derivatives of one another.

K
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