So I’m an idiot young kid that thought I could buy some cheap after market heads for my 96 bronco 351w. I purchased the Edelbrock 5025 Heads. I sat on these way too long before installing them and now I cannot return them. I found out very quickly when trying to install them, my stock Hydraulic roller cam is not compatible with these heads and my stock rocker arms are not compatible. I’ve seen very little information on trying to adapt a new valve train to these heads probably because it’s not normally worth it. Looking at buying COMP CAMS STUD MOUNT HIGH ENERGY ROCKER ARMS-1.6 RATIO 3/8" pn# cca-1704316. My understanding that I’m possibly going to run into clearance issues with the stock valve covers, which then runs into the stock intake on the passenger side. Seems like I need some sort of spacer and tall covers. Picking valve springs seems to be my bigger issue. I’m having trouble figuring out my spring diameter if it needs to be 1.46. The Edelbrock heads have an installed spring height of 1.800”. Im assuming I need to match the install height and diameter of the Edelbrock heads. Now for the spring rate I’m assuming I need to be close to my stock spring seat lbs and open.

Now I’m having trouble figuring out what I need for that and would greatly appreciate the help. It’s my understanding that my push rods should be ordered after I install my new springs and rockers and measure.

 

welcome to this site, welcome to the very costly been there done that club. yes i to have been there ,

sadly many fail people fail to properly read about the heads,in the summit site the edelbrock in the listings all the way in the notes at the listing bottom do state what the heads are good for, you needed the 60255 heads which are for the roller cam engines
notes on the 5025 heads states( Notes:
Designed for use with hydraulic flat tappet camshafts with less than .550 in. lift. Requires use of hardened pushrods. Part number EDL-9680 head bolt bushing kit required for use with 7/16 in. head bolts. The valve and seat combination used in these heads is not recommended for use with a hydraulic or mechanical roller camshafts.)

good luck man

 

You can get a spacer from Jomar very inexpensively to raise the intake plenum so that it will clear the valve cover. Piecing the valvetrain together is no big deal once you decide on what rocker arm to use. The pushrod is the last component to get so that you can buy whatever length you need to tie it all together.

 

I see this but I'm not sure how this could be a real concern with the factory roller cam which only produces 0.450" lift with 1.6 rockers and has very mild ramp rates. I bet the concern is that many high performance aftermarket roller cams require valve springs with very high seat pressure and spring rates, but those aren't required with the OEM roller cam. FWIW ford used the same valve springs in both flat tappet and roller 5.0 motors, and the specs were something like 85lbs closed seat pressure and 225lbs open. Those springs were only just enough to prevent valve float at street rpms(4500rpm or less), so it wouldn't hurt to use a little more spring to cover a future cam upgrade, but you don't need to go too crazy. I bet the springs supplied with the fully assembled version of these heads exceed the oem spring spec.

 

Dave, would you have any input for valve springs? The “Edelbrock performers” list an install height of 1.800” at 150lbs I’m assuming this is where I need to be I can’t seem to find a 1.46” spring that matches this. Would a spring with a different install height work with the correct seat lbs?

 

Do you think the 125lbs seat pressure from the pre installed springs would be too much stress on the stock cam shaft?

 

It won't hurt the camshaft it's billet steel, if you have springs on the heads already use them.

 

Thank you, as much as I read the Flat tappet cams where supposedly needed to be paired with valve springs with less pressure and roller cams would need a higher spring rate. After comparing different spring rates and doing some math it didn’t make sense why I would need a higher spring rate with my cam. If the stock rate was lower than then the Edelbrock heads factory installed valve springs.

 

I don't think that the additional loads will give you any trouble. They will increase the bleed rate on the lifters somewhat but if they're good quality they should still be able to run quietly.

 

The stiffer spring rates for roller cams is because the roller lifters are heavier than flat tappet lifters. As Conanski said, use what came with those heads. My concern is what EFI system you have on this now. Is it Mass-Air or Speed density ? Speed Density mat be unable to handle the increased flow those heads deliver.

 

'96 Bronco should be OBD2 mass air.