WizardBlack

Ah very good then!

Oh, you are right. Hmm, I guess I should have taken it from the chamber cc's? Anyone know if ten thou off the N47 head will cause piston to chamber or piston to valve issues?

Caveat Emptor, my friend. There's a reason it's spoken in Latin; it's one of the oldest rules everyone eventually learns. Hope everything goes well.

Actually if someone can check my math, I think I have done it. Taking the info off of the L calculator, I have: Volumes at BDC: 458.83 - cylinder sweep 10.9 - Piston Dish 6.1 - Gasket (Fel-Pro) 44.6 - Chamber ________ 520.43 cc's total Volumbes at TDC: All less cylinder sweep ________ 61.60 cc's total Compression with an L28 N42/N47 with Fel-Pro gasket comes out to 8.45:1. Now, with the skim of the head, ASSUMING the removed area is the same diameter as the bore and ASSUMING I didn't get into any reduced cross section of the N47 head (I don't believe so), I have: .010 inches removed, or .0254 cm. Area is 58.09 cm^2 for stock bore L28. Volume removed: 1.48 cc. New chamber cc = 44.6-1.48 = 43.12 cc. Recalculating gives me a compression ratio of 8.63:1. I likey. Assuming no piston-to-valve and I did everything right. Does this sound reasonable? Is my cam timing gonna be totally borked? I am not sure I could convert .010" reduction in height to angular retard of the cam sprocket without getting back into some college books. As an aside, decking the block dropped compression from 8.45 to 8.42.

I had the head decked to clean it up.

OK, I have an N42/N47 (dished piston) setup that has been turbo'ed. I noticed a blowout on the HG and the engine had been weeping coolant out the passenger side of the head gasket as some people had noticed. I decided to use a Fel-Pro gasket to give myself an "out" for detonation and pick up the compression a bit. For this weekend car, I suspect I will use leaded race fuel blended with premium anyways. Likewise, I had the head taken to a performance machine shop and told them to deck it until straight (one thousandth at a time). It came back requiring .010" decking to get straight. How can I calculate my new compression ratio? The L-series calculator does not provide for decking the head or block. I did search but evidently haven't hit upon it. Stock indicates 8.29:1 and the Fel-Pro raises it slightly to 8.47:1.

I can't give you all the resulting issues from doing so (I am sure the machinists will answer shortly), but the quick answer is it isn't a good idea. I have never seen such a substantial mismatch. I used a Fel-Pro gasket. They can be had in a day or two from many auto parts store chains. What are you doing with the engine?

Gah, I didn't say anything against your tuner. Just was posting as "a followup for everyone" that it makes a good example of diagnosing turbo tunes.

Just a followup for everyone. Any tuner who "knows his !$%@" should know that not enough timing is the first issue to look at with high EGT's on a turbo car. It sounds like it just needed a tweak. Good to hear it's getting ironed out. EGT gauges are popular for mildly tuned modern EFI cars as the EGT's will change (go up) when the ECU pulls timing due to detonation.

Yeah, most cars with short, open exhaust and turbo sound like a tractor at idle unless you have some wicked headwork. Beware the heat transferring to your fender. I, too, am curious about how it sounds.

They're going to tell you to do some searching; a lot of this has been covered. You have lots of options; you just need to know what they are and how they work. No one is going to make a list for ya, etc. Welcome to the forums. I'd personally recommend you go to a standalone since the stock EFI systems are durable but really only suitable for very near to stock.

Definitely get the AFR's above 10.5:1. Below that becomes a concern for the engine. It can wash the oil off of the cylinder walls and damage them. The excess fuel can also make it's way into the oil and thin it out for the rest of the engine, too. Likewise, you can start to experience spark blowout. It will feel like someone is randomly bumping the brake pedal while you are at full boost. At 7 psi you can easily be up in the 12's. Just because it's boost doesn't mean you have to be at 11.0:1. I typically tune cars so they taper from normally aspirated AFR's (13.5:1) at 0 psi relative down to the richest you go (say, 11.5:1; it varies with the engine) at about half of full boost. Running 11.5:1 at 1 psi is just wasted fuel and power. It doesn't need that much fuel to avoid detonation and keep the chambers cool. Get it to taper smoothly and you'll have better spool and partial boost power.

I have a question to further the specific exhaust lip you referred to. As you follow into the port from the steel exhaust valve seat, you have a short ring of aluminum that is smaller in diameter (the area that should be opened up) and just after that, it opens up substantially in diameter for the start of the steel exhaust liner. The steel liner is larger in diameter than the steel seat. The port floor can be worked to provide even laminar flow from the seat, past the ~3mm section of aluminum and onto the start of the liner. The walls and ceiling cannot. Should the aluminum section be opened up to the diameter of the inner diameter of the valve seat or should it actually be tapered open further (toward the starting diameter of the liner)? If you get past the very start of the liner (say, the first 8mm), it narrows in diameter somewhat (to maybe a bit larger than the seat diameter). I just figured on opening the aluminum section to a straight diameter and let it line up with the diameter of the liner further in. Am I explaining myself very well? LOL.

Ugh, yeah, I was just trying not to fall into the "while I'm in there" syndrome. Hasn't worked so far.

No, I am referring to the Fel-Pro seals for the Datsun L. The ones included in a typical HG kit.

Since this is a sticky on valve stem seals, has anyone confirmed that a .490/.480 Isky regrind will be OK with Isky springs/retainers on the Fel-Pro stem seals?

Just to update this thread, MSA's '83-only cams are indeed for hydro lifters.

Ya, I'd go for the white tails.

I am not an expert on the factory EFI, but I'd say you're either going to be spot on while at full boost or spot on for drivability, but not both. Megasquirt.

That works fine until you have a pretty engine you don't want messed up. I have pulled lots of engines and I almost always use a trans to engine bolt for a solid mounting spot. Up front, either a solid accessory mount bolt or (for the L28 specifically) the fuel pump bolt hole works great.

While in the process of tearing my L apart for the first time and poking about, I noticed that the coolant and oil passages in the timing cover have some pretty wicked casting flash or sprue in them. The outlet channel from the water pump to the block has quite a bit that could be smoothed down. Some of the lips were almost a 1/4" step. There was also a slight ridge in the ~75* angle that was machined for either the oil feed or return from the oil pump (didn't bother to check which). A good 15 minutes with a slight grinding tool and some hand work with a file, etc. seemed to smoothe everything quite a bit. I know it isn't going to be a major impact, but I thought while I was in there... Any comments?

LOL, I knew someone would come on and nit pick. Yeah, in a racing car, sure. Not for anything he's bound to do.

If you want plug n play then you are pretty much going to be paying someone else to do the "cutting" for you.

Just about anything will burn out if it's leaking. As in, the flanges are warped, etc. If exhaust can get around it from the very beginning, it doesn't stand much of a chance. Make sure both sides are totally flat. Custom made exhaust flanges get warped pretty easily during welding. This will lead to leaks and blown out flange gaskets.

Ditto. If you want to change tails, look for another old school tail light design. If you really must. Don't put modern tails on the 'ole lady. That's like suggesting DD breast implants on.... ah nevermind. Not going there.