[manchildau65]

Originally Posted by Greg T

Using Edelbrock's tech support is like having the 6 year old neighbor kid perform brain surgery.

True... my assumption is that they will re-read everything that is already stated in the manual.

So if I change out the valve springs to match what is recommended, what's the harm with running the different rocker ratios? I'm currently at 1.5 intake and 1.6 exhaust...

[cobalt327]

Originally Posted by manchildau65

I'll try and get through to their tech department today to see what their reasoning is. My assumption is that if the statement is true, then the lobes aren't case hardened deep enough to accept the force of the double springs.

The Summit 1107 cam you said you had in another thread is almost identical to the Eddy RPM cam you want to change to. Advance the Summit cam 4º and it'll pick up the bottom a little. Changing an entirely different grind w/less duration and overlap would be a better choice IMO.


Edelbrock Cam #7102

ENGINE: CHEVY 283-400 V8
RPM RANGE: 1500-6500

Duration at 0.006" Lift: Intake: 308° Exhaust: 318°
Duration at 0.050" Lift: Intake: 234° Exhaust: 244°
Lift at Cam: Intake: 0.325" Exhaust: 0.340"
Lift at Valve: Intake: 0.488" Exhaust: 0.510"
Timing at 0.050" lift: Open Close
Intake: 10° BTDC 44° ABDC
Exhaust: 59° BBDC 5° ATDC
Centerlines: Lobe Separation - 112° Intake Centerline - 107°

Note: Use only stock ratio rocker arms.

CAUTION: Use Edelbrock Performer-Link Timing Chain and Gear Set #7800 or Accu-Drive gear drive #7890. Do not use late model timing chain and gear sets that are designed for emission-controlled engines. These timing sets are machined in a retarded position and are not recommended for this camshaft installation. Edelbrock Timing Sets feature three keyways for specified timing selection. Use "0" position for most applications.

Do not use dual valve springs.Use only recommended Edelbrock Sure Seat. Valve Springs #5703. Use stock ratio rocker arms only.


Summit Cam #1107

Cam Style: Hydraulic flat tappet
Basic Operating RPM Range: 3,000-6,500
Intake Duration at 050 inch Lift: 234
Exhaust Duration at 050 inch Lift: 244
Duration at 050 inch Lift: 234 int./244 exh.
Advertised Intake Duration: 292
Advertised Exhaust Duration: 302
Advertised Duration: 292 int./302 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.488 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.510 in.
Valve Lift with Factory Rocker Arm Ratio: 0.488 int./0.510 exh. lift
Lobe Separation (degrees): 114


The double spring warning is for the tyros out there who would throw a set of 150 lb seat pressure springs and expect the cam to break in w/o issue- obviously the cam doesn't give a whit about the spring being a single, dual or triple- as long as the pressures are within the range of what the cam needs to keep the lifters in contact w/the lobes, and not so high as to cause the cam/lifter to gall and/or have the lubrication fail. Had nada to do w/the heat treat.

Using a 1.6 rocker arm isn't recommended for much the same reason- an experienced engine builder knows it's better to spec the cam for a 1.5 ratio rocker from the get-go, instead of buying a cam w/specs that require a 1.6 rocker to get the lift that's needed. Inexperienced builders will often make mistakes that cause coil bind or other things that cause the cam to fail. It's easier for Eddy to just say "Don't do it!", than to try to explain how to do it RIGHT. Less returned cams that way.

[manchildau65]

Cobalt327, excellent reply! Thank you for the response.

I have zero complaints with the performance of the engine and thoroughly enjoy the hp I get at the top end but don't feel it is a good fit for my application. This engine would be amazing in a car but my K30 with 38's (4.56 gears and SM465) doesn't have the low RPM grunt I'd like. Is there a cam out there that provides similar top end hp but provides low end grunt?

I'm probably asking for the unachievable (best of both worlds)...

Sounds like i should replace the 1.6 with 1.5 rockers; I didn't have a reason for running the different ratio other than I already had them. Will this make a noticeable difference in performance?

[cobalt327]

Originally Posted by manchildau65

Cobalt327, excellent reply! Thank you for the response.

I have zero complaints with the performance of the engine and thoroughly enjoy the hp I get at the top end but don't feel it is a good fit for my application. This engine would be amazing in a car but my K30 with 38's (4.56 gears and SM465) doesn't have the low RPM grunt I'd like. Is there a cam out there that provides similar top end hp but provides low end grunt?

I'm probably asking for the unachievable (best of both worlds)...

Sounds like i should replace the 1.6 with 1.5 rockers; I didn't have a reason for running the different ratio other than I already had them. Will this make a noticeable difference in performance?

As a rule, I don't pick cams. But take a look at the Summit 1105. Run the 1.6 rockers on the intake side, you'll have 0.496" lift on the intake using your 1.6 rockers.

[F-BIRD'88]

With the gear- tires you got and the heavy application, you need a way smaller cam for more low end grunt.

The edelbrock rpm cam and the summit 1107 are near identical other than the LSA. 112vs 114. Its the same cam.

You need a cam with around 218 to 222@.050"

Use Isky cam number #201271 270 mega cam. 270 270-221-221 .465 .465 108lsa.

Use the 1.6 rockers on the intake side.

It is highly recomended with using "dual springs" on a flat tappet cam that you remove the inner spring for the inital run in to let the cam break in.

Then when its all broke in, reinstall the inner springs.

Seat pressure should not exceed 135psi. open pressure should not exceeed
360psi. Its up to you to check and verify your spring presssure.

remove a spring and check it. Some of the dual spring combos are more for street roller cam and have excessive open presssure for a flat tappet cam.

use an oil additive like Moly slip or ZDDP or a oil that contains a good dose of these anti wear additive.

This isky cam will have a good bit more low end grunt yet still power to 6000+rpm.
Degree it in on a 104 intake C/L for best results.

The cam you have now and the RPM cam don't make power below 3000 rpm and are not a good "truck cam"

You don;t have near enough gear ratio. big cams want to rev and need the right gears. The heavier the vehicle, the more critical.

You need 5.57:1 or 5.86:1 ++ gears in your monster tire truck to best use the Performer RPM cam or the summit cam you got now. (3000++ cruising rpm at 60MPH).
You can improve what you got now by changing the gears and recurving the distributor for more initial timing. A stock distributor curve will not work well.

[manchildau65]

Thanks for the info guys, I will take a look at the cams you are recommending and will check the spring pressure prior to install.

I'm currently running an MSD Distributor with the MSD 6AL controller box. I haven't messed with the distributor b/c everything works great throughout the entire power band... just doesn't have the low power grunt I'm looking for in the truck.

I hope I'm not painting the wrong picture with the current set-up, I can light up the 38's pretty easy as long as I'm ~4k RPM or higher. I just feel like I'm driving a 2 stroke!

The SM465 and 4.56 gears net me around 3k RPMs at 65-70 mph...