What is the max lift you can run with that 4 inch stroke and those Icon pistons? Did you check for piston clearance?
348 - 440 stroker build
- Thread starter cruzin
- Start date
AK-Guy
Well Known Member
I don't know what Cruzin did with his build, but I have a .639 lift. I had my machine shop grind additional "pockets/notches" in the existing notches to get the lift past the .550 limitation on the existing block. After temporarily putting the heads on the engine, I hand cranked the assembly with modeling clay on the pistons to make sure there was no contact with the pistons.
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How about exhaust valve to cylinder clearance?
AK-Guy
Well Known Member
The pockets shown above were ground .150 which would allow up to a .700 lift on the exhaust (.550 + .150 = .700). As an additional step, I put testing springs on one of my heads when I did my temp assembly and checked the clearance to the block (check springs were on a different cylinder than ones with modeling clay on the piston).
I've heard about the .550 limit before but I thought that was only associated with Edelbrock heads. That's not a universal rule of thumb for all 348's is it? I was thinking that only applied to certain head combinations. 
Checking for clearance and checking for max lift are different. You didn't check for max lift, just for clearance in general? I have the exact same set up as you but I was dumb enough to button the motor up before I checked for max lift. NOW I'll probably take the top end back off just so I can know unless you can still do that with your project. I'll have to go back but I can't remember if you have already buttoned yours up as well. Since Walden helped with the design of the pistons (I'm told by ICON) and has since passed on, there is no one who knows how much lift these stroker pistons will allow for specifically. Unless someone else on here has that information. Thanks again guys for the continued help.
I know for a fact that with a .617 lift the exhaust valve will contact the cylinder using 690 heads.
I may be wrong but max lift as far as the pistons go won't occur until the piston is over 1/3 down in the bore.The valve to cylinder wall is the main concern on these engines.KB;'s,regardless of the "line' are very generous with their valve reliefs.
AK-Guy
Well Known Member
I was very careful and did lots of checking before final assembly of the heads to the engine. To clarify a little bit more, I checked the clearances at max lift on the intake and exhaust with the rockers, cam, lifters, heads installed without the head gasket and the head just snugged up to the block. Clay on the pistons told me I would have no problems with the valve 'tapping' the piston. With the exhaust valve at max lift and a test spring, I had .032 clearance between the top of the valve and the rocker (solid lifters) with the valve pushed all the way down into cylinder. Considering I used a .042 head gasket on final assembly, that gives me about .075 clearance between the valve and cylinder wall. This is a little long winded, but I hope it makes sense. Oh, these engines are too rare and too expensive to just throw together and hope your machine shop ground everything as asked. Measure twice and cut once - motto.
In a 409 yes but I'm thinking that would be less in a 348 simply because the cylinder wall is closer in a 348. Anyone know for sure?
agree and my post to Dave about 348's having smaller cylinder walls than 409 applies to that equation. (I'm running Dave's old 690's on my 348 stroker build) I'm going to have to pull the top end off and double check because my lift will come out right at 550. Better safe than sorry and I can then share with everyone on the specs for future builds.
cruzin
Well Known Member
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You can see the cut in previus pics, this block is cut for 0,700 lift, pistons clear a bit over 0,600. Its a 0951 Comp cam so it will be no problem here. But if we go on higher lift in the future the block is ready.
AK-Guy
Well Known Member
If I may make a suggestion, before re-opening the engine, think about trying this (if you have solid lifters):
1. put some oil in a cylinder or 2 and then apply air to the cylinder via the spark plug during the compression stroke (to hold the exhaust valve)
2. swap the existing spring with a test spring (test springs will hold the valve, but can easily be pushed down)
3. rotate your engine until the exhaust lobe on the cam for this cylinder is at its highest point.
- you can put a dial gauge on the push rod to see when it peaks
4. with the exhaust lobe at its highest point on the cylinder with the test springs, but a feeler gauge between
the tip of the rocker and top of the valve while pushing the valve down into the cylinder
- the valve will bottom out on the side of the cylinder wall
5. check the clearance. IF it is still really close (can't get any feeler gauges between rocker and valve), tear into engine.
this procedure may save re-torquing bolts for the intake, heads and resetting you valve lash. I say all this because you have a head gasket that is probably .042 or larger and depending on which rockers you used (1.7, 1.72, 1.8) your lift may or may not be .550 giving you plenty of clearance between your valve and cylinder. Just suggesting to save time and money.
64 you don't necessarily have to remove the heads just yet.Remove an exhaust rocker,turn the piston down ,and use a spring compressor to depress the valve.Use a dial indicater and measure how far down the valve goes before hitting anything.If it clears your lift demensions by .070 then you're good.
AK-Guy
Well Known Member
Don, I have 600# springs when open, so depressing those are not a simple task, but your suggesting is a lot quicker. I likey.
Yes,but he'd better not have much over 300 with the cam that he has 
or he'll be tearing down the whole soggy mess to replace the cam that he just killed. I wouldn't run over 280 at the nose myself.A simple lever type compressor,like you'd use if changing the valve seals on the car should work here.
or he'll be tearing down the whole soggy mess to replace the cam that he just killed. I wouldn't run over 280 at the nose myself.A simple lever type compressor,like you'd use if changing the valve seals on the car should work here.
Ok ok, settle down boys! There isn't any reason to get excited. 
One thing I have going for me is I'm a sticker for details and have a few years under my belt fixing things. The 5 basic steps noted above will be a basic starting point because its the easiest way without making more work for myself. My rockers are 1.8 and as calculated I am literally at 550 lift. I plan to switch the cam on this motor after a period of running it because I want to get a feel for the difference in performance. I have several cars and enough parts to make them all W powered. Anyway, I just acquired the ability to measure my spring rates so I'll be doing some double checking while I have the new springs out. Keep in mind Comp Cams tried to get me to buy springs that clearly were not going to work with the 951 grind on my 348 stroker build. They had no idea what they were talking about and my concerns were confirmed through two machine shops here. Essentially I made the mistake of not measuring this before hand but I was getting excited to finish. I'll figure it out and report back on a new thread soon enough.
One thing I have going for me is I'm a sticker for details and have a few years under my belt fixing things. The 5 basic steps noted above will be a basic starting point because its the easiest way without making more work for myself. My rockers are 1.8 and as calculated I am literally at 550 lift. I plan to switch the cam on this motor after a period of running it because I want to get a feel for the difference in performance. I have several cars and enough parts to make them all W powered. Anyway, I just acquired the ability to measure my spring rates so I'll be doing some double checking while I have the new springs out. Keep in mind Comp Cams tried to get me to buy springs that clearly were not going to work with the 951 grind on my 348 stroker build. They had no idea what they were talking about and my concerns were confirmed through two machine shops here. Essentially I made the mistake of not measuring this before hand but I was getting excited to finish. I'll figure it out and report back on a new thread soon enough.
I'll be sure with any future builds to seriously consider cutting the block further. I'd like to get into the 620 range with a solid lifter later but we will see. The 951 cams have all of the right numbers for a great street cam with a trip to the track every now and then but ultimately I plan on spending a bunch of time at the track. My wagon may get the 951 cam treatment in my stroker build for the spirited family adventures that await!