Everyone's favorite thread. Wasting time and money on a duke. Factory '85 Fiero block decked .050" and bored .030" over, .100"(2.1 to 2.0 rod) under mercruiser one piece seal crank, forged 6.00" chevy I6 rods and forged pistons 18cc dish 1.280 ch. All balanced. All the machine work and assembly will be done by me. I will put up as much information as possible
rods 66000206SGL pistons 8763S-4030
The head is an 862 head from a 5.3l LM7. I chose this head because I have several and the combustion chamber is only 61cc compared to the 67 of the 241 off the LS1 and others. I'll be using a .051" mls head gasket. Right at 8.5:1
I'll also be making a main girdle and drilling out the block for 1/2" bolts. As far as fitting the head, the head bolt holes in the block will be filled, skimmed flush and re drilled to accommodate the LS bolt pattern. Water jackets are right where they need to be. The rear left corner of the block will need a small portion welded on to use the corner most bolt on the head. Depending on how thick the casting boss for the head bolts are I may need to countersink and weld in some inserts.
The head will only need a filler plate welded to it so the pushrod cavity can seal against the block and a few oil passages drilled
I don't have a pushrod # yet
I'll put up my drawings for the filler plate and guide for the deck so if anyone wants to duplicate this they can. I am also going to be building an intake manifold with MPFI that uses a Quad 4 TB.
Close enough to work.
Fresh head
Mock up head
I'm pulling the motor this weekend. I haven't been able to work for a while so I have some things I need to finish up before I can get to this but it should progress very rapidly.
[This message has been edited by Slammed (edited 09-07-2016).]
I think you meant the 241 LS1 heads for the 67cc number? The 243 are ~64cc stock.
Interesting to see how this works out though. Are you going to port and polish the head at all? What about larger valves? With a 4.060 bore, 2.100 intakes shouldn't be a problem for clearing, but I don't know if it'll help or hurt in the duke, off the top of my head.
I think you meant the 241 LS1 heads for the 67cc number? The 243 are ~64cc stock.
Interesting to see how this works out though. Are you going to port and polish the head at all? What about larger valves? With a 4.060 bore, 2.100 intakes shouldn't be a problem for clearing, but I don't know if it'll help or hurt in the duke, off the top of my head.
Yes 241s my bad. I'm going to keep the 1.89 valves that are in it. When I did the valve job I opened the throat 2.5 mm, half bullet the guides and widened the short turn but I won't do any more than that. This won't be naturally aspirated so I'm not super concerned with getting the most flow, I like the ratio a little bit better
[This message has been edited by Slammed (edited 08-25-2016).]
This. SD4 head would be easier, but they are pricey and usually found bare. And the LS heads are a better design. I'm doing all the work so this whole project will cost me less than $1k
[This message has been edited by Slammed (edited 08-24-2016).]
Interesting project... I would probably try to relocate the head bolt holes on the head to match the duke first as relocating them on the block might not hold up well long-term especially if you plan on forced induction as some point. The used heads are near free and you probably have a spare one anyway, so give it a shot and see if there is enough material to relocate the holes on the head.
There isn't unfortunately, that was my first plan. I was thinking of welding the holes up completely and steel sleeving them but it's just so much more to do and then I'd only have one head that works. Anyway, I'm going to start with this. If it doesn't work, I'm only out an hours time drilling the block and I'll mod a head. I have done some incredibly weird repairs on marine motors over the years and am very confident in my spray welding on cast iron blocks. < That's if I have to add material in the block to drill the holes
[This message has been edited by Slammed (edited 08-24-2016).]
At least 400hp. With the parts I'm using the only limiting factor would be the size of the turbo and the possibility of lifting the head with too much boost, which can be remedied in various different ways. The only factory part will be the block and I can cage the whole thing if I have to
I would love to have a 4-banger that can mount an LSx head. I bet that thing would scream! Not sure about the Duke bottom end, though. Hope it all works out for ya.
I'd like to clear up a couple things on the duke. First, I have bored I don't know how many to .060 over. You can safely go this far. The cylinder walls are not "thin" nor are the walls of the block. The bulkheads are thicker than the 4g63T, #010 350 and just .026 thinner than a ford 2.3 turbo I have here. The deck is .55" thick. Now this does not take into account the metallurgy, these are just measurements. I will be half filling the jackets with hardblok
I have never seen or spoken to any machinist that has seen a broken crank. I won't be using the stock crank because I don't need to, but the LIMA 2.3 Turbo uses a cast crank that is built exactly the same as the duke. Semi-counter weighted and those routinely are built to 300+whp. Many diesel cranks are like this because they see low revs
looks good
There
[This message has been edited by Slammed (edited 09-07-2016).]
I'm tanking the block and cutting the crank today. I've swapped around a few parts on the list because I'm going to shoot for a little more power than I previously planned. I should have put more in the title lol
But I wanted to bring it some closure. My guess is that he ran into the "Big Problem", which is the damned valve layout.
The Duke's valve pattern is I E I E E I E I, and the LM7's is I E I E I E I E. So only half of the cam lobes would be in the right place.
This can only be remedied by getting a custom camshaft made. Good luck finding a blank duke cam. So your only option is to go full on billet. Okay. Thats expensive, but whatever.
Oh wait, the Duke has the distributor gear built into the cam! Your custom billet camshaft just got 3x more expensive, because now it has to be made on a 5 axis CNC milling machine. Great.
I tried literally this exact same thing, and that's the conclusion I ended up at. Its a real shame, because everything else about the head is perfect for mating to the duke block.
Oh well. Someone will find another way...
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quote
Originally posted by Frank2:
here's the goal: Build a mid engine car 1/2 as good as a Lotus Elise at 1/10 the cost.
I have no idea what Im doing, but Im doing it.
IG: @backwards_citation
[This message has been edited by Boot (edited 03-09-2018).]
Another thing is don't drill the stock head bolt holes deeper at the three middle on tappet cover side. You get a nice water/oil mix due to breaking through in lifter area. I know this thread is dead but just another duke tip. The SD block has casting changes to accommodate deeper holes for head studs. Second block I just cut about 3.5 threads off 1/2" studs for those holes in stock block.
Originally posted by Boot: Oh wait, the Duke has the distributor gear built into the cam! Your custom billet camshaft just got 3x more expensive, because now it has to be made on a 5 axis CNC milling machine. Great.
Change to a crankshaft trigger, COP or wasted spark, problem solved.
