567trishop
Active Member
Edelbrock say that their heads used on 348 engines with valve lifts up to .550" only. Can you put bigger lift cams in and what would you have to do , thanks
348 with edelbrock heads, value lift
- Thread starter 567trishop
- Start date
I believe that the .550" max lift for the 348 has to do with valve interference with the piston or block. The heads, as delivered from Edelbrock, will handle a .600" lift. The valve spring spec's as delivered from Edelbrock are as follows:
Installed height 1.885
Seat pressure 115# @ 1.90"
Open Pressure 280# @ 1.40"
Coil Bind @ 1.160"
The spring spec'c listed above are Edelbrock's Numbers. I checked my heads and they checked out almost dead-on with the listed spec's. These springs should be adequate for most flat tappet cams that will be used for street/strip use. Roller cams will usually require a different spring/retainer package.
Since I will be running a hydraulic roller cam with .628" lift, I changed out the springs and retainers to be comparable with the cam mfg's recomendations.
Barry
Installed height 1.885
Seat pressure 115# @ 1.90"
Open Pressure 280# @ 1.40"
Coil Bind @ 1.160"
The spring spec'c listed above are Edelbrock's Numbers. I checked my heads and they checked out almost dead-on with the listed spec's. These springs should be adequate for most flat tappet cams that will be used for street/strip use. Roller cams will usually require a different spring/retainer package.
Since I will be running a hydraulic roller cam with .628" lift, I changed out the springs and retainers to be comparable with the cam mfg's recomendations.
Barry
Look on the other end.....
While coil bind and seat pressure are a concern....be certain to check the valve pistion clearance and MOST importainly the exhaust valve/cylinder wall clearance. The heads you reference have larger valves....your cylinder bore is smaller. You might have to grind a relief into the top of the cylinder.....the same type of thing that has to be done when insalling a higher lift roller in a 409. Your project is interesting. I suspect you are in to some additional work....but the results might be well worth the effort.
As Russ says, the ex. valve to cyl clearance is the main issue. Isky makes a cutter that makes the job of notching the cyl simple. About $150. The 2.19 int. valves will clear the bore but valve reliefs in the piston must accomodate the valve size. Then it is always important to ensure valve to piston clearance. When using aftermarket pistons, the relief depth can be ordered to provide good vp clearance. If using the stock cast pistons, you will have to mark, measure and enlarge reliefs. An oxymoron, why go to high lift cam and use cast pistons? There is a magazine artlicle about the cyl notch modification by Joe Jill which has pictures of the process. Afraid I don't remeber the name of the mag. The 348-4 in. stroke engine he built. Had really good numbers. So, bottom line, the 348 can use the Edelbrock heads with high lift cam, if you consider all the proper steps to get proper clearance.
:There was a pretty good article in the Jan 09 issue of HotRod deluxe Magazine, entitled Prehistoric Rat. They built a 348 with "eddy" heads used an isky valve notching tool and claim .700 inch exchaust lift with no issues. Motor made 520 hp @ 6000 with a tq peak of 489 @ 5100.
For a back issue you can log onto www.primediabackissues.com , or they pop up on ebay now and then. $6 bucks + $3 shipping.
Tim
Oxy Clean?????
oxymoron......I wanted to use that word....but was afraid of it. There's a lot of oxymorons down here in the Ozarks!
oxymoron......I wanted to use that word....but was afraid of it. There's a lot of oxymorons down here in the Ozarks!
567trishop
Active Member
Thanks guys, I have order the heads, ross pistions at 8.5 to 1 eagle rods, 4' inch stroke crank, roller valve gear, but not the cam. This motor will be supercharged at 10% under. I just wasn't sure about the cam. I will get the parts in 4 weeks.
Just my opinion.......... make sure you calculate the compression by CC'ing the chamber....... if they are off the shelf Ross pistons with a 4" stroke you may have a lot more....... Whoever you are buying from should know that but unless the supplier has done it be sure and check before you do the final assembly.
Dave
Dave