L24 Rebuild -Again!

[Diseazd]

Looks great Steve......

[Chickenman]

Your notches in the block look pretty deep........does the top ring fall short of the notches ATDC?

Yes, they're definitely very deep and also too long ( circumference around the bore ). It just takes a slight bit of bore notching to un-shroud the Intake Valve and too provide clearance for high lift cams. Always do the minimum notching necessary in the bore.

 

Excessive bore notching reduces CR ( can be as much as half a point ), reduces combustion quench ( not a good thing ) and creates a " Dead Zone " pocket for unburned combustion gases to collect. Bad spot to get carbon buildup and possibly cause detonation.

 

And you never want the notch extending into the ring seat area. If that happens, go to a bigger over bore and hope you can salvage the block.

[madkaw]

Richard,

your warnings are well noted. That's why I stated my disclaimer-. I really didn't exhibit any symptoms that I can say was directly caused by heavy notching. I fully intend to recheck that my top ring clears the notching as stated earlier.

It is a bit of an old hot rodders trick to help make the engine breathe better, but like you said, it could cause dead spots for carbon build up. I don't believe I lost much compression, but we actually figured it in to my 9.5:1 CR. Didn't have issue with detonation either, but my engine didn't have a ton of miles.

I didn't like the carbon build up I had, but this engine has been thru tuning hell with SU's and then triples.

The length of the notch is following the HG, nothing more. I understand that it is waaayyy more than enough to just clearance a valve, but there was more to the notch than that. 

[madkaw]

Well today was notch checking day-and they were all fine. My main concern was verifying that the notch did not extend into the ring area.

The notches actually cleared more than what I thought they would.

I verified by installing piston with top ring and using permanent marker around the bore. I ran the piston up and down in the bore until the top ring wore the marker off and that gave me a line of reference.

I also checked my oil clearances using plastic gauge and they were in tolerance. 

 

Next issue is rings. My rings do not fit my bores. The gaps are excessive. I actually have two sets of NEW rings and both sets show excessive end gap. I have seen as much as .027 on the top ring. I have had discussions with the machinist and without going thru the whole conversation I have decided to take my block and pistons to someone else for a second opinion. I believe the machinist went to far overbore to fix scratches that his machine put in the bore. I don't have exact dimensions but it sounded that he went to the limit of the tolerance. The only way to be sure is to take it somewhere else.

If this is the case, I might just move on to my L28. Or my other option is to pull my numbers matching block out and work it.  

[siteunseen]

That sucks.  Maybe it'll be okay but the 2.8 wouldn't bother you would it? 

[siteunseen]

Well here I am again reading the intakes need notching. Which is it?

[EuroDat]

Well here I am again reading the intakes need notching. Which is it?

The exhaust increased size when they went to the L26 (33 to 35mm). The inlets increased size (42 to 44mm) when they went to the L28 with the bigger bore diameter.

Edit: You would think the inlets would be the problem, but I have since read the exhaust are the problem with a high lift cam.

Chas

Edited February 22, 2015 by EuroDat

[siteunseen]

Well my larger exhaust valves hit on 2.4 block. The intakes barely squeeze by. Maybe I'll do both but that would make my combustion area bigger resulting in less compression, know?

Edited February 22, 2015 by siteunseen

[madkaw]

Cliff,

If I were to do it all over again on a L24, I probably notch both sides but stay on the conservative side. You wouldn't loose much compression, and what you lost there you would probably gain in flow. Google bore reliefs for valves and you will see it has been done before on other engines.

 

 

Maybe my pistons will be up for sale after all is said and done Cliff if you haven't bought any yet. I want to move on to the L28, but really wanted to dyno my L24 with the triples. So I might pull the other l24 out of the shed if need be.

 

I just pulled apart my L28 and the crank and pistons look great. It had another 100K left in her easy. Looks like a hone, rings and bearings!

[siteunseen]

I figured out the other day while cleaning up my mess in the garage and stuffing another motor in there that I have a ready to go .030" over bored F54.  It came with that persimmons and white 240 I bought.  It was a guys project, he needed some money and sold it.  It's got new dished pistons though so I'm going to get some flat ITMs and put a P79 that I have and do that build Dizeased does.  

 

I want to keep my orange car on the safe side and dependable.  It's going to have the E31 that was part of the guys project and a medium cam, slightly notched block for the bigger valves.

 

That's the plan. 

[madkaw]

Haven't got a lot done, but have made some progress. After deciding .030 over rings weren't going to cut it, I have ordered .040 over rings. Maybe not the conventional way of doing this, but I guess going to the next size ring will still fit correctly as far as being concentric and allow a tighter gap. After taking many measurements it seems that these pistons (sealed power I believe) are big as far as being .030 over. The piston skirt measures right about .030 over not leaving hardly any clearance. Getting the clearance plus adding a fresh hone added to the bore size enough that rings came up a bit short. If the pistons weren't so new I would be getting .040 over set, but I am taking the cheap route. Money will be spent when the L28 comes into play. This block is all about learning and experimenting.

My Isky cam arrived and looks pretty! Still not sure on the rockers. i told the machinist we would swipe the Delta regrinds and see how that turns out. He is still doing valves. Probably going to shoot for 40cc chambers at this point. 

[madkaw]

Well I changed my other mind again.  I decided that I wasn't going to settle with the L24 block the way it was(to far over bore/sloppy), so I broke out my original l24 out of the shed and dropped it off at a different machinist. I handed him my pistons and told him to fit the bores to the pistons. He called the other day and talked numbers again and said the boring had started. This should allow me to use my(expensive) .030 rings and a chance to redo my bore notching.

No cylinder head done yet. My machinist-soon to be ex machinist, send the rocker to the wrong address and that caused a big delay. I sent them to Rocker arms USA in CA. Going to compare them with the ones I got from Delta. I am pushing the machinist to have the head done first of May-we'll see.

At the same time I am cleaning up my zx block. When I pick up the l24 I am going to drop the L28 for tank and magna-flux. After seeing the flat tops clean up like new, I am guessing the bores will take a deglaze and be done. I am excited that this will be a cheap fast short block for whatever head I use. trying to get a MN47 for this block to make a real performance l28.