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Roller Rocker Arms

Old 02-05-2008, 05:23 PM
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Hi

I have a 502 EFI from 1995 with EMI Thunder Exhaust and a Smal EFI Upgrade.
Iīm thinking about the 1.8 Ratio Roller Rocker Arm, but i donīt know does it make sence ore not. I have with the EFI upgrade a adjustable Fuel pressure, Aircleaner and EFI Programm from Tyler Crokett Marine (works good)
In the last 3 Boats i had always Roller Rockers but never alone, always with High Performance cm, intake, carb....
Will the 1.8 Roller Rockers alone make the Boat faster, i have 4700-4800 Rpm at the moment with 67-69 Mls ( 28 Scarab Excel)
Someone wrote he had always 200-300 RPM more could it be ?
Iīll be thankfull for any experiences

Hans

please donīt look at my english
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Old 02-05-2008, 07:42 PM
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Hans,

The difference between a stock 1.7 rocker that comes on your 502 and a 1.8 is about 6% lift. I dont know what the specs of your cam is, but using .500 lift as an example , you would see .530 lift if you were to switch to 1.8 rockers. I would be mildly concerned with the ECU mapping that Tyler Crocket did. I am sure he set it up very conservatively ( on the rich side ) but I would ask him what the extra lift may do to the fuel curve. I dont imagine it would change dramatically, but better to be safe. I also dont see you gaining much speed, 200-300 rpm, I dont think so. If you do go for a roller set up, I would suggest using Comp Cams Pro Magnums and avoid aluminum Crane Golds. Just my opinion..
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Old 02-05-2008, 08:23 PM
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From cranecams

Advantages of Higher Rocker Arm Ratios

Since the introduction of our ?Quick-Lift? rocker arm geometry, many pundits have debated the benefits of using higher ratio rockers as a means of increasing valve lift. Most of these debates have taken place on Internet websites where ?everyone is an expert,? but there is no way to validate their credentials. Some of these people seem to think it is ?unnatural? to use a rocker ratio higher than stock. They argue that if you want more lift, design it into the cam lobe. This argument has some merit to it as long as you have a big enough cam basecircle to begin with. However, on some special ?stroker? grinds with small basecircles; increasing valve lift with a lobe change is not practical, as the basecircle gets so small that the strength of the camshaft (as well as resistance to torsional twist) is compromised.

Increasing rocker ratio as a means of increasing valve lift has several advantages; not the least of which is that it is unnecessary to remove the camshaft in order to reap the advantages of increased lift. Of even more importance, however, is the fact that when the lobe is changed to increase valve lift, everything else in the valve train changes in terns of acceleration and velocity (this includes lifters, pushrods, and the valve/valvespring assembly). This increases the operating stresses (due to the inertia of the mass of the components) imposed on the valvespring. Achieving increased lift by changing the rocker ratio does not change the acceleration and velocity of two very heavy components; the lifter and the pushrod. They continue to operate under the same conditions as the lower lift provided by lower ratio rockers. Only the valve/valvespring assembly increases in acceleration and velocity. This means that the valve spring has much less work to do controlling the valvetrain. Additionally, the extra leverage afforded by the increased rocker ratio allows the use of lower seat pressures to control the lifter as it returns to the basecircle and to control hydraulic pump-up of the lifter?s inner plunger. These advantages are significant and evident in the dyno testing we have done.

Certainly, you must be careful anytime valve lift is increased. Factors such as piston-to-valve clearance, retainer-to-seal clearance, spring seat and open pressures, and spring coil bind must be considered; but these are all issues that must be checked no matter how valve lift is increased. All of our testing at Crane has shown that increasing valve lift by changing rocker ratio (especially with any of our ?Quick-Lift? rocker arms) is a very convenient and reliable way to increase the power level of an engine without changing the RPM band in which the power is made. For additional information on our ?Quick-Lift? rocker arm geometry, please check our website at www.cranecams.com.
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Old 02-07-2008, 03:11 PM
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Hi,

All internal parts are Stock.
The programming and fuelpressure is realy on the rich side. I can smell it at the exhaust gases and the backside off the boat is more black ( witch was at absolutly non time before)
This engin runs realy wunderfull and iīm just looking for the 70mi. With a Cam i will lose some of itīs convinience and i have to remove the Motor out of the Boat and open it what is not my concern.
I think i will try the 1.8 and maybe get nothing but hope for 1-2 mi.

Thanks

Hans
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Old 02-11-2008, 03:05 PM
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Hi,

second question
My Motor is from 1995 502 EFI.
Have they all the non adjustable Rocker Arms or are they different older/ newer Models. i have a manuel from 1999 Generation 6 looks like they all have the non adjustable. In a older Big Block book all have the adjustable Rockers. But there are no 502īs in this Book.
Iīve never opened this engin before and i have no number at the moment because itīs covered for winter.
Does anybody know which Rockers are in this motor an which Generation it is ?

Thanks

Hans
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Old 02-11-2008, 09:06 PM
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That should be a Gen 5 engine and it will have the non-adjustable valve train. You just need to get some rocker studs to make it adjustable.

ARP part number 135-7102 for the rocker studs.
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Old 02-12-2008, 05:21 PM
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Hi

I donīt find any 1.8 Comp cam pro Magnums Rocker arms for Big Block donīt they produce them ? Donīt find Crane in 1.8 also only 1.73
Is Harland Sharp a good Brand ? they have 1.8 Roller rockers for "Chevy" big block for 7/16" Studs.
The 1.8 ratio seems to be difficould to find the right thing, there are not so many offers to choose from

Thanks

Hans
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Old 02-12-2008, 09:04 PM
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Harland Sharp is also a top quality brand.
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Old 02-13-2008, 04:24 PM
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Thanks for all this info

Hans
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Old 02-14-2008, 05:53 AM
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I've used the 1.8 roller rockers on a single engine Baja a while back. It was a bone stock brand new 454 Magnum (365 hp) at the time I had also installed a pair of Fast Glass stainless risers. No increase in top end but pulled harder out of the hole and a bit more mid range.
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