Due to popular request, I will start a new message thread and use it to show "step-by-step" assembly of an iron block Slant Six.
It was suggested that this thread be locked in order to keep the assembly process as concise as possible. Question, comments and discussions are welcome but they will need to be posted on a different thread. We will use the "separate the Twins" thread for the comments and discussions.

As most know, this project was started with 2 cast iron engines, one nicknamed "Guzzi" and the one to be assembled here, nicknamed "Raquel". See this link for details on the Guzzi engine assembly and car.

So here we go....

With any engine build-up, you need to have a "vision" or end result in mind and then build a plan to get that. My goal with this engine is to have a race SL6 that makes 225 to 250 HP, is strong and assemble it using many of the parts I have on hand. Oh... I want to be able to spray the engine with a 100 HP shot of N2O and have it live... pass after pass, race after race.

So I start with looking over 3 used engine blocks, all of them the 5 freeze plug type, 2 of them the "BH" blocks with the extra ribs.

IMPORTANT: Before you dis-assemble the short block(s), Measure the piston deck height and make note of what it is. (I engrave the numbers onto the block) See if there is any difference between the deck height of piston #1 and #6. This will show you block deck taper that can be machined out when (if) you surface the block's deck. (you should have the deck resurfaced)
Take the time to do this measurement now because this is a measurment you will need in order to do accurate compression ratio calculations. I have "kicked" myself many times for being in a hurry and breaking down a core engine, just to have to 'mock it up' (re-install the crank and 2 pistons) in order to take these measurments.

See this link for more info on SL6 engine block selection and prep.

I abandoned one of the blocks because of some visual casting defects and acid cleaned the other 2 as outlined in the article



Now I have 2 clean & visually identical engine blocks. I weighed them both and found 1 of them to be heaver so I moved forward with that one thinking it will be the stronger block of the 2.

Note: I will be using some "file photos" as well as references to articles already posted.
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Here is a list of things you can do to get your engine block ready to go to the machine shop: (more details in the block article listed above)

-Water jacket cleaning with acid.
-Deburr all casting flash and sharp edges.
-Drill & tap the boss at the rear of the oil gallery for an extra gauge.
-Round the edges where the oil gallery enters into the oil pump mounting pad.
-Drill thru the main oil feed holes, mains to oil gallery
-Drill a drain hole in the lifter galley so oil drains onto the fuel pump arm & cam lobe.
-Inspect and Re-chase all threaded holes
-Deburr and round the edges where the water enters the block.
-Check & grind extra pushrod clearance to the side of the head / block.
-Tap a hole for a temp gauge bung.
-Tap the holes and install plugs into the extra holes on the top deck.
-Cut-off the block's fixturing "lumps", front & rear, driver's side of block.







Do all your cutting, drilling and grinding before sending the block out for machining. That way, all the dust and chips can be cleaned-off by the shop, after they have completed the needed machine work and do their final wash.

If you plan to do any block filling, you will need to do that before sending the block out for cylinder boring or main line align honing machine work. I always torque down the main caps prior to adding block filler.
Raquel got 1 1/2 inches of block filler added to the bottom of the water jacket in order to help stabilize the bores and to fill-in all the "peaks & valleys" you find on the floor of the water jacket.
DD

You will need a set of pistons before you send your block out for machining.
It is sad to say that the availability of good quality forged pistons for the SL6 is not good these days. Custom made pistons and "old stock" sets are the only options for forged / high compression SL6 pistons.

Here is some basic piston info:
6.7 rod 225 piston compression height is 1.760 (flat top)
7.0 rod (long rod) 225 compression height is 1.500 to 1.590 range, depending on desired C/R and any piston dish.
The factory piston pin diameter is .900 - .901, depending on press fit or floating pins. The pin diameter can be changed with some additional machine work but doing so removes material from the already thin walls of the "small end" of the connection rod.

Standard SL6 bore size is 3.400 with common oversize to .060 and even .080 if you look hard. Most Sl6 blocks can be bored to 3.500+ (.100 oversize) which opens-up the piston selection.

Buy your pistons early... they are the first new part you will need so have them "on hand" before starting on the block work. I have learned this the hard way so these days I am always looking (and buying) SL6 piston sets way ahead of needing them.



Go to This Thread to post questions or comments.
DD

It is good to fit-check the head you plan to use, to the empty block and inspect the alignment of the combustion chambers to the bores.
You may want to wait on making any "fine" adjustments if the block's deck will be resurfaced. (the block should be resurfaced)
The head location pins in the top of the block will need to be pulled-out in order for the machine shop to do the resurfacing so you want to wait until that is done before reworking the pins / head holes to get things centered.

I checked 2 different heads on Raquel's block, one head is unmilled and the other is already milled .100 and has oversize valves in it.
Here are some photos on how the head aligned to the bores. Some adjusting of the pins is in my future:

There were some questions on ways to correct the placement of the cylinder head to the block's bores so I am posting some info here.
As noted, any locating dowel pins changes should be done after the block deck has been resurfaced.

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Take some measurements and then shift the head's location on the block.
4 ways to do this:
-Make some off-set dowel pins. (a "dab" of braze and a lathe)
-Grind "oval" the the holes in the head, drawing arrow on parts helps.
-Grind / file flats on the side of the pins to allow the needed shift.
-Drill out the location holes in the head and install some off-set cam bushings.





I find that you can only get the chambers "pretty close" and then you will have to scribe and grind-off the remaining exposed edges.
So this adjustment is a two step process. First center the valves over the chambers and then grind-out sharp edges and shrouding that remains.
Pay closer attention to the valve placements, rather then the overlapping / exposed edges you see.

Once you get the position set, punch, grind or engrave some 'witness marks' so you can return the head to that placement once the pistons are installed.

So your block is prepaired and you have a set of pistons... it is time to send the block off to the machine shop.

The shop I use "knows the drill" because I usually bring them a block, a set of pistons, a old cam and my hone plate (torque plate) with instructions to do the following: (in this order)
-"Hot tank" the block.
-Surface the block's deck .XXX amount, angle adjust if needed.
-Install torque plate and bore / hone to match pistons.
-Install a new set of cam bearing.
-Jet wash and plastic bag the block so it is ready for painting. (please, no greasy finger prints)

Be sure the main caps are with the block.

Parts I do not give the shop:
-Rear main seal cap and special bolts. (aluminum melts in their hot tank)
-The main oil gallery plugs. (I will "mis-place" those myself, thank-you)
-Oil pick-up tube. (the shop likes to throw those away and say "buy a new one" when they are not available)



Questions the shop will ask you:
-How much should we take off the block's deck surface?
-What type of rings are you running? (cast, moly, chrome?)
-How much piston to bore clearance do you want?

The answers to these questions relate to the parts you have and your "pre-check" measurement results, so do your homework so you do not have to guess.

Now that the block is off getting machined, you can focus your efforts on all the other parts that you will need to have ready for the engine assembly.

You will need these parts:
-Crankshaft (use a 1968 or newer "big pilot" crank if possible)
-Reconditioned connecting rods
-Rebuilt cylinder head
-Camshaft
-Timing gear and chain set
I will review each one of these areas to show part selection and prep.
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The plan is to make some big HP with this engine so I want a strong crankshaft, basically a forged steel crank with-out deep holes drilled into it for balancing.

Spent a few weeks looking at a lot of different cranks before finding one we liked. We did basic deburring, oil hole reaming and "banana grooves" before sending the crank off to a different shop for shot peen, grinding and rebalancing.





A close look at a forged steel SL6 crank shows a lot of "hanging burrs" and rough / sharp edges... you should remove / grind those spots smooth. The crank rotates clockwise when looking at it from the front so run you hand over the leading edges of the journals and counter weights... think about how the leading edges will cut thru the oil mist.

The oil cross holes in the crank can have bad, chewed-up finishes so a quick pass thru those holes with a reamer or oversized drill will remove any high spots and take-out "baked-on" deposits.
Shinny and smooth is what you want to see inside those oil passages.

The most important spot to rework on a crankshaft is where the oil cross holes enter the journal surface. A nice smooth radius is ideal for getting good oil flow out of the feed hole and into the bearing clearances. Getting a nicely blended edge is easier said then done, seeing that the angle of the cross holes produces an oval shaped exit. I use a number of different size "ball bur" cutters, followed by a small dremel stone to carefully blend the oil hole to journal surface edges. The photo above actually shows white dust left by the small grinding stone. Also shown is one of the "banana grooves" we added to this crank. These grooves are made with a "wizzer wheel" and a steady hand and help deposit the in-coming oil across the entire bearing surface. Note that the grooves are ground at a 45 degree angle so the "load point" of the bearing never "sees" much of the groove at any given moment. Banana grooving is not needed for most engine builds, simple radius work gets you the most "bang for the buck".
All this crankshaft prep work must be done before the crank is reground.

Another good crankshaft option that I have use in the past is to simply buy a crank kit that comes with a reground crank and bearings, ready to install. Doing this does not allow you to do any of the prep work as outlined above... except for may-be removing any obvious "pigtail" burrs that you may spot. If you do any additional grinding work to an already ground crank, wrap some electrical tape around the journals before starting to drill and grind.

The key to getting a nice set of factory connecting rods is to sort through a bunch of them and pick the best ones.
The areas I look at are:
-Centerness of the piston pin hole. (the "small end")
-The amount of material along the beam. (rib or an indent?)
-The amount of material on the end bosses. (the balancing pads)
-Thin wall section(s) around the cap. (the "big end")

Con rods that have had bearing failures and overheated - discolored should be discarded. Rods with thin wall sections should be set aside for a lower horsepower, mild engine build-up.

I like to use rods that have a thick, protruding parting line "rib" instead of an indentation along the parting line. I also like the rods that have short balance pads, where the extra material, on each end of the con rod, has been machined away to get the needed weight. Rods that weigh the same but have short balance pads, have more material in the important places.





Carefully weigh the rods that "look good" and see if you can find 7 or 8 rods that are with-in a few grams of each other. (I have seen as much as a 20 gram difference) I do some basic deburring work to those rods. If the piston pin will float in the small end, I drill an oil feed hole.



Do another weight check after the rough deburring / drilling is done. Check the weights of both ends and write your finding right on the rod. (dis-reguard the mounted piston)



Find the lightest ends and start cutting / grinding to get all the other rod ends to match. Also do any beam edge rounding or polishing work before finalizing the weights. When you are finished, all the rods should have the same total weight and the "1/2 & 1/2" weight of all the ends should also be the same.

If you have new con rod bolts, now is the time to install them. Always check to be sure the new bolt heads clear the bolt head cut-out on the rod and sit flush on the surface. (some clearance grinding may-be needed to allow the bolt head to sit flush)

Once the rods are ready, send them to a qualified shop for reconditioning/re-sizing.

You should do the following to the pistons:
-Deburr and round any sharp corners
-Make sure there is some form of wrist pin oiling
-Balance the pistons so they all weigh the same.

Other optional work:
-Cut valve notches or add a dish
-Coat the piston skirts with an anti friction coating.
-Coat the piston top to a thermal barrier coating

A common problem I see with SL6 pistons is worn or seized-up piston pins so you want to be sure the pins get a lot of oil. The best way to do this is to have a hole that leads from the oil ring groove, down into the pin bores. Many high quality pistons come with this type of pin oiling, (forced oiling) lower priced pistons have oil holes or grooves to let the splashed oil into the surfaces. The forced pin oiling feature can be added to pistons with some careful hole drilling.





The most common piston top machine work is the addition of valve clearance notches which are usually needed for "zero deck" or near zero deck engines, combined with an aggressive cam. (deeply milled block & head 225. "long rod" 225 and 170 "low block" engines usually need valve notches when an HP cam is used)

Static compression ratio adjustment and setting-up quench / squash zones is another reason for doing piston top machining. As a rule, the piston top thickness should never be less then .200 in thickness but more is better, especially with high compression, turbo or N2O use.





After all machining and deburring work is completed, the pistons can be balanced using a gram scale. Find the lightest piston and remove material from the heaver pistons so all the units are of equal weight. Do the same with the piston pins, weighing and grinding-off material until they are all equal in weight. Combine the two parts as a last weight check and fine-tune the weights as needed.





I got lucky with this engine by having a "swap meet" set of high compression Venolia pistons to work with. I gave these pistons the treatment listed above and also had the pins TiNi coated. (titanium Nitride) This special coating will allow us to float the pin right on the forged steel connecting rod surface with-out gulling.



This set of pistons also got the special coatings listed above. The coatings are sprayed-on then baked at 400 degrees. (file photo)



Once all the parts are "done"... assemble the pistons to the con rods. Use a little assembly lube on the pins so they do not gull during the first few moments of running.

The block came back from the machine shop and the first thing to do is get it painted. That is right... if the shop followed your instructions, the block is now spotless so get some paint on it before getting fingerprints and assembly lube all over the thing.

Just when I think I am ready to start the final assembly, I do more checking and grinding on the block.

This additional grinding work is based on fit checking a different cylinder head with more unshrouding around the valves and a thicker surface. (not milled more then .020)

The head to block alignment was checked using a special, large bore head gasket and some relief grinding was done on the upper edge of the cylinder bores, next to the intake valves.





During this "last" mock-up and grind session, the pushrod clearance areas were also rechecked, this time, using a set of 1.6 rocker arms as our guide, some additional metal came-off the block and head in order to allow room for the more aggressive rocker arm ratio.



So now we have "triple checked" all the parts and have fresh grinding dust all over the engine block. Time for a good soap & water final wash... with a compressed air "blow-dry" afterwards.



Comments Thread - Click Here

The first part to install is the cam, not the crankshaft.
It is a lot easier to get the cam in first and to do some basic checking, without having to work around the crankshaft.

The first thing I do to the cam is check the rocker arm oil feed cross hole in the rear journal, an old rear cam bearing will show you any mis-alignment problem(s).



The cam I am using had just a little mis-match, which we fixed with a small edge break, on both holes.



Wash / blow-off the dust, add some assembly lube to the cam journals only (not the lobes) and in goes the cam to check the gear mesh with the oil pump. I stick a head bolt into the front of the cam to help hold onto the piece as it goes in. It is easy to hold both ends of the cam when the crank is not in your way!



OK, part #2 for installation, the oil pump. Place a small dab of fine valve lapping compound onto the oil pump's drive gear and install it with-out the gasket, using 2 bolts to hold it in place. Spin the cam around a few times and look to see if the lapping compound is getting distributed over the mating cam gear. I have an old cam gear with a knob on it, just to make this job easy.





Remove the oil pump, clean off the gear and inspect the mesh pattern, it should be even and well-centered on the gear.



We have a nice gear mesh pattern with this combination of parts so use these photos as a "it's good" reference.



Pull out the cam, clean the lapping compound out of the gear (toothbrush and carb cleaner) apply assembly lube on the journals and cam lobes, the re-install the cam. Clean your oil pump gear while you are doing the cam gear, you do not want to forget to clean it, then install the pump with lapping grit still on the gear.



I leave the oil pump off for now, (you will see why) and move onto installing the crank.

Before installing the crank i check the fit of the rear main seal using a fixture I made-up.



I also check the seal halves to the crank surface to see if the seal's lip compresses evenly.



The rubber lip seal type, main seal, fit-in and matched-up well so that is what we will use in this engine. We installed all the upper main bearing and the rear seal.



I was reminded on how the factory supplied a stream of oil to the timing chain & gears... they put a small chamfer along the parting edge of the upper main bearing shell to allow pressurized oil to squirt-out and onto the chain. Replacement main bearing sets do not have this chamfer so we added one.





This is a fast way to get oil out to the chain & gears. The other way we have done this is by drilling a hole in the front oil gallery plug but doing that takes a little more time and lay-out effort.



Set the crank in and torque it down. You may want to check the first journal for proper oil clearance by using some plasty-gauge.



Once you have the mains torqued to spec, you can install the rear main seal cap. I off-set the seal halves slightly and use some sealer along the joint.

This is the point where you confirm all your mesurments and see if the "combo" of parts is going to work as planned.
Seeing that this engine is using oversize pistons and a reground crankshaft, this is the moment when all the actual parts will bolt together for the first time. (pistons will not fit into the block until it is bored-out)



I install the #1 piston, with-out the ring pack and proceed with measuring the engine's deck height, check for true TDC and degree-in the cam. This is important to do now and it is much easier with one "ringless" piston installed.





The deck height on Raquel is at -.012 so that is good.
The Isky cam we installed in the engine... not so good, it checked out at 268 duration, .460 lift which is too mild for the high compression, o/s valve head(s) I want to run. (one head has chambers at 48cc, the other is at 40cc)

Soooo.... out come all the extra cams and the binder full of cam cards for review. I also called Tom at Erson and ordered a special 290 / 280 grind cam that is my "plan B".... I am running out of time if this engine goes to Vegas.
DD

We did a lot of cam checking yesterday and all the good race cams are currently "hiding" inside various assembled engines. It is not a good time to break down one of these motors just to dig-out the cam so we decided to install the most aggressive cam in the "available" stack and adjust the final compression ratio to match that.

The "winner" is a reverse, dual pattern cam that was ground with a few other cores, back in 1998 by a now out of business grinder, called 'Cal Cams". I have run some of the other profiles from that group with good results but these are not full race grinds.

The intake lobe is one that Cal Cams had, 270 degrees on .480 lift, the exhaust lobe is a Crane, 264 degree, .460 lift. The reason this cam keeps getting passed-up, it is ground on a wide lobe center which measures at 111 degrees. I could never figure-out if the grander was "shooting for a 110 or 112 L/C but it ended-up at 111. Basically, this cam does not have a lot of overlap, only 44 degrees at lash.

Anyway.... we need to get this engine assembled so we will use that cam for now. All the basic degree work was done and we advance the cam 2 degrees to account for some future chain slack.



We had a new JP Performance all steel, multi-keyed, roller chain and sprocket timing set that we used. I am always impressed with the quality of these sets.





I have found that the bottom gear on these is tight on the crank snout so we sand the bore out, go at it as hard as possible, sand for a long time and it ends-up 'about right' on the press-fit.



The top gear gets a quick flat sand on the back surface just to knock down some high spots. That surface has a spiral cut oil groove on it that makes the high spots, a few passes on the long sanding board makes the surface flat and smooth.



Heat the bottom gear to 400 degrees and it will slide right onto the crank, give it a few taps to be sure it seats. (I love our garage toaster oven, it is a "well used" tool)



I find the new JP set seems to be a little tight in the chain when installed for the first time. I have gone back into engines with these sets and the chain tension was perfect after a short amount of running so do not worry if a new one seems a little tight upon installation.



STOP!!.... you forgot something, and it is really important.
Double & triple check that you have installed the front oil gallery pipe plug into the block. If you leave this out, the engine will not get oil pressure. I usually do install these plugs right after the final soap and water cleaning and actually did install the rear gallery plug. (yes, there is one at the rear also)
At that point, I saw that my shop had not installed a rear cam bearing plug. I dug-out and installed the cam bearing plug and moved-onto another task... forgetting about the front gallery plug... my bad.



Note how this "BH" engine block has a dime-size impression casted-in, next to the front cam bearing. This prevents oil from building-up behind the cam gear and pushing the cam assembly forward, and off the fixed positioned oil pump and distributor drive gears. Other blocks have a small groove machined-in and that groove is not large enough. When I use the machined groove blocks, we drill an extra hole through the face of the cam gear to allow the excess oil to escape out from behind. Photo #2