Engine Rebuilding

Even if you have noplans to modify your truck, sooner or later you will have to face some major engin rebuilding work. If you -like me- a bit more pushy and play with bolt on mods it will surely come sooner than later. I'm aware of this fact and already started to collect the information required to do a rebuilding/bluprinting on my little 4.3. * There are at least three ways to choose from.

• Doing a so called 'rebuild kit' based rebuilding. Definately the cheapest way to go, but IMO the least realible too. You'll also have to find a good mechanics, because there is no way to properly do all the tasks on your backyard.
• Buy a built engine from an aftermarket supplier. Mccoy has a full range of engines to choose from. It's definately reliable, but expensive too. Especially if you live on the other side of the ocean.
One more remark here. GM just discontinued our engine, so you can't buy a replacement engine from GM anymore. Don't be sad! According to a bunch of people it was trash anyway.
• Building an engine from carefully collected internals. This will be my way. As in the first case a good mechanics will need here too. One advice here. Try to find the mechanics first, before you start to order parts. For example in Hungary, there is no one who could balance a V6 or V8 engine, as far as I know. This means, that I've to buy a balanced package, or at least a balanced crank from someone who can make it balanced for me if I provide the required bob weights. Also beware that our engines are externaly balanced, so you have to count with the torsional damper too.

* I've to mention that I wouldn't choose the 3rd way if some people already didn't do the try-and-error type of pioneer work before me. Thanks guys! I really apreciate all the information and help which I can get from the SyTy list and the BB. * Heads
The stock LB4 heads are really not a big deal. If you open up your engine you shouldn't waste any time with them. They are prone to detonation and they flow around 165CFM. So as you might already guess I plan to replace my heads with something more powerfull. There are a few wyas to go again.

• L35 heads from 94-95'. They flow better, and a direct bolt on. Most yunkyard carries them on a reasonable price, but sometimes there are some new sets on Ebay too.
• 96' and up Vortec heads. They less prone to detonation than the stockers and L35s, flow better, but not a simple bolt on.
• There are a few aftermarket heads as well. ATR, KB. They are quite expensive aluminium heads and I'm quite sure that they can't beat a mildly ported Vortec.
• On the high end there are some heads some choose from, but this is quite blurry fo me. Brodix intake and Pontiac heads is one, but such a buildup would require a lot of money and lot customiztion work too.

* I'm still not sure which head I gonna use, the L35's or the Vortecs. Anyway I started to collect all the casting numbers which I could find.

Stock head (LB4) #10144103, 8 deg top angle cut

92'& 93' L35's #10238181, #10077626, #14099064, & #10240209 8 degree top angle

94' & 95' L35's #10238181 & #10240209 30 degree top angle cut

96' L35's (Vortec) #10235772 30 degree top angle cut, heart shape chamber, different bolt pattern




If you are hunting for 94'-95' heads you should looking for press-in rocker studs versus screw-in rocker studs. If you wanna get that 100% protection you can convert them to screw-in studs using some kind of aftermarket studs from Comp Cams, Crane or ARP. 7/16" should be fine, but 3/8" can work to, but check the diameter of your press-in studs before. You also go with factory screw-in studs too, but pls be aware that there were a so called non-adjustable screw-in studs with M10x1.5 on the head's side and M8x1 on the studs' side. You can't use these studs with anything else then the factory type stamped rockers. If you wanna go roller rockers with these studs, get 3/8" (M10x1.5 base) conversion studs from Crane (#99148-2, you need six of them, very pricey) or convert the head to 7/16" studs. *
Speaking of heads, I should say some words about valve covers too. If you find the stock valve covers or the plastic ones with "Vortec" on them ugly then there is a nice cover too use from Edelbrok. It's #4252. Also Mike Lee has a sheet metal center bolt valve cover for our application, but it's a bit pricey.



Valvetrain
We are using hydraulic lifters, with 1.5:1 rocker arm ratio. Our valve lash is one turn down from zero lash on both side. The valve spring free length is 2.03" while the pressure is 76-84lbs (1.70") closed and 194-206lbs open (1.25"). The installed height is 1-23/32". Not to much information on aftermarket parts yet here. Will do some more leg work on it. * Cam
Our stock lobe lift is 0.357" on the intake and 0.390" on the exhaust side. If you are replacing heads/turbo it definitely calls for a more aggressive cam. There are some guys who have experienced good results with Comp Cams 09-412-8 (260 intake duration) and 09-422-8 (270 intake duration). Both cams have lift around 0.500. Pls note that for a different cam you will need to change you timing chip wise for sure. * Headers
Not so much choices here. Stainless steel headers from ATR which could work with the stock turbo and with the PTE setup as well, or KB headers, which will require to reclocking the turbo and won't work with the PTE or stock downpipe. I prefer ATR, but neither of them is cheap. Rick at RK Kustom carries them around $1000. If you want to go with the KB setup for some reason Mike at Atomic Rooster Autosports is the guy to talk to. He can give you an alternative to the 2.5" KB downpipe which is not available any more. *



The coating of the headers is a usual topic amongst SyTy guys, however I can't see the ultimate solution. The headers have to whit stand some serious heat, 1700F at some places, so most of the cheaper stuff will come off very soon. Swain Technology could be one of the candidates, ceramic coating could be the other. The good thing with Swain's black satin, that you can do it yourself after made the headers sandblastedand cleaned. * There are a few guys who made some custom headers, if you really good in welding you could try. I'm a mechanical engineer and my father have been dealing with welding machines in all his life, but I don't dare to give it a try. * Pistons
The stock pistons are Hypereutectic ones (caster with a lot of silicon). The bore is 4.00, the stroke is 3.48. Compression ratio is 8.35:1. If you want to rebuild your engine the only way to go is with forged pistons. There are quite a few tried up configuration. The vendors who you can choose from:

• TRW #LF2441, the heaviest and cheapest
• JE #131636, the lightest and most expensive
• SRP #139632, the golden middle

All of the are .030. One thought here. The weight difference is around 100g between the lightest and heaviest. The lightest is not necessary the best in my case. I don't want to build an "all out effort" monster, but a reliable street performer. The heavier pistons have more mass in them so hopefully they will last longer. Also a note that SRP and JE are different products of the same brand. * I'd go with the TRW's at this point of time. Might change in the future. As the thing progress I gonna gather some more information on them and finally I'll do my own measuring too. One remark. You don't want to go more than .030 over with a stock block. * Rods
Not too much information here so far. Several people had luck with Eagle ESP H-Beam rod #CRS570063D. It's center to center length is 5.700" and ~669g. Will do some more searching here too. * Crank
Not too much things to do here. There are 9s time slips with the stock crank. One thing you can do is to make nitrated it for example. There are talks about a forged crank, but it's not a reality AFAIS. * Block
Again, not to much to do here. Stock block can take me as far as I wanna go. The only thing could be to convert it to four bolts main caps. However if for some reason you are looking for a new block you would find usefull the below table. One reason could be that a lot of 4.3 factory blocks are core shifted, which makes them weaker and might make overboring impossible. These blocks avaiable from GM directly. The aluminum blocks are really nice, but don't forgett that they will require aluminum heads as well, which won't fit the stock intake so you will need something different. *

Chevrolet V6-90 Degree Quick Reference Chart
Part Number	10185051	10134371	10134351	14011069
Block Material	Cast Iron	A356-T6 Aluminum	A356-T6 Aluminum	A356-T6 Aluminum
Cylinder Wall Type	Siamesed	Siamesed	Siamesed	Siamesed
Cylinder Deck Height	9.025	9.025	9.025	9.025
Cylinder Bore Range	4.000-4.180"	4.125"	4.125"	4.000"
No. Bearing Cap Bolts	4	4	4	4
Cap Bolt Orientation	Splayed	Splayed (20 deg.)	Splayed (20 deg.)	Splayed
Bearing Cap Type	Steel	8620 Steel	4.000"
No. Bearing Cap Bolts	4	4	4	4
Cap Bolt Orientation	Splayed	Splayed (20 deg.)	Splayed (20 deg.)	Splayed
Bearing Cap Type	Steel	8620 Steel	8620 Steel	Steel
Crankshaft Journal Dia.	2.45"	2.45"	2.65"	2.45"
Oil Sump Type	wet	dry	dry	wet
Crankshaft Seal Type	2 piece	2 piece	2 piece	2 piece
Design Max. Stroke	4.00"	4.00"	4.00"	4.00"
Weight (lbs. - bare)	163	78	78	78
Intended Usage	Professional Comp.	Professional Comp.	Professional Comp.	Amateur Comp.
Non-Standard Parts Required		No mechanical fuel pump boss	No mechanical fuel pump boss

* As you can see the middle two aluminum blocks have dry oil sump setup, so it will need some fabrication. I personally don't know any truck with such a block yet. The last aluminum block could be nice, but you can't bore it over according to the specs. I'd go with the bow tie iron block. A few trucks running this block already with great results. An other and less expensive solution could be to get a block from the yunkyard. There are at least three different 4.3 blocks, which I know about. The stock SyTy block is the VIN code 'Z' block and it's virtually the same as the block of that era (91-93'). The SyTy block has modular iron 2 bolts main caps, but it could be found in other blocks (HD, marine) too. The later L35, VIN code 'W' blocks are using a balance shaft above the camshaft in order to achieve smoother idle, but this makes that blocks weaker too. You can easily identify a balance shaft block, because their timing chain cover is different. A third block is the freshest LF6, VIN code 'X' block, which has a balance shaft as well, but the block itself is different from the above two, it has rounded cylinder case. So if you are looking for a production block, hunt down a 'Z' block. The 8th character of the VIN should be 'Z'. If the block is not in a truck, you could find the VIN stamped on the driver side on the block too. * As far as main caps. If you plan to go over 600 PS, or just have the money and wanna play it safe, convert the block to 4 bolts mains. The GM billet steel 4 bolts caps for SBC will work for us. An other root could be using Milodon caps if you have the bucks. A final remark that a couple of guys only convert to billet steel 2 bolts caps, and a couple of other only convert the center caps, not the front or rear. Either way you should find a good mechanics, who can do the conversion. * Please note that the above recommendations based only on my experience, so they could be wrong. *