LS (LM7) Cylinder head on an Iron Duke (Page 1/3)
Slammed AUG 24, 12:54 PM
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).]

dobey AUG 24, 03:24 PM
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.
edfiero AUG 24, 03:28 PM
I love Duke projects, but wouldn't an SD4 head be less work?
dobey AUG 24, 03:37 PM

quote
Originally posted by edfiero:

I love Duke projects, but wouldn't an SD4 head be less work?



Are SD4 heads basically free now?
Slammed AUG 24, 03:57 PM

quote
Originally posted by dobey:

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).]

Slammed AUG 24, 04:02 PM

quote
Originally posted by dobey:

Are SD4 heads basically free now?



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).]

fieroguru AUG 24, 07:44 PM
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.
Slammed AUG 24, 09:58 PM
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).]

2fiero2 AUG 24, 10:25 PM
Check out Nick Arias Jr. He has been using V8 heads on in-line 4 cylinder blocks.

[This message has been edited by 2fiero2 (edited 08-24-2016).]

Slammed AUG 24, 10:46 PM
I'm familiar with his products. If I wanted to spend $3k on a bare block I'd consider it.