1984 iron duke build (rebuild now) (Page 1/3)
cartercarbaficionado SEP 06, 05:56 AM
so uhh turns out our knocking 100 dollar engine I procured was very built. .125 overbore, short stroke crank, olds 324 rods and a reground cam with 110 pound springs (feels like it at least.) with comp cam timing gear and lifters and a larger than stock tbi
I only tore this iron duke down to save the head and block for anyone who needed it but now I'm probably gonna rebuild it since it just needs lifters and bearings done plus checking for a cracked block or head since oil isn't supposed to be diarrhea green. also if my flexplate reusable? im iffy aboutit but my spare is just gone




Dennis LaGrua SEP 06, 09:00 AM
Looks like you stumbled onto something good but I believe that a .125 overbore is beyond what is recommended on the Duke engine. If the engine had a knock then it would be good to mic all the crankshaft journals. About 15 years back Dawn and Neil Kline built a similar performance Duke and they said it ran well. IIRC, they used a cam and small block pistons and rods. If you want to be on the path to 125HP check out Ira Crummy's web pages here:
Performance Duke Pages

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 09-06-2024).]

cartercarbaficionado SEP 06, 11:13 AM
it was making more than 125. it snapped every bolt in the flywheel with little effort. and based on how far apart i have the 50k mile automatic with the ecu I pulled from the csr it was in(finally found the mileage on the reg from 93 when it was parked due to a blown engine since I had to buy a cheap cluster off ebay for it) it was well on its way to exploding that as well. it was definitely as quick as a 2.8 v6 with how fast it was getting to 60. (8 seconds which is scary fast for an all original 84) the head has been ported quite far and the exhaust path was chamfered for more flow into the valve.
I will be likely sending the crank off to be checked for roundness (or throw it in my buddies lathe with a micrometer on it) and definitely gonna get the rods checked throughly. nothing was spun or even that scratched up so I think it had just enough lube to save it
cartercarbaficionado SEP 06, 11:22 AM

quote
Originally posted by Dennis LaGrua:

Looks like you stumbled onto something good but I believe that a .125 overbore is beyond what is recommended on the Duke engine. If the engine had a knock then it would be good to mic all the crankshaft journals. About 15 years back Dawn and Neil Kline built a similar performance Duke and they said it ran well. IIRC, they used a cam and small block pistons and rods. If you want to be on the path to 125HP check out Ira Crummy's web pages here:
Performance Duke Pages


also that's exactly what these pistons are. they are overbored small block chevy pistons someone made fit. I might have to bore out further and sleeve the block with a fire ring for a bit more strength. also just kind of concerned the block has cracked under a cylinder bore but I haven't cleaned it up yet
82-T/A [At Work] SEP 06, 01:43 PM
Honestly, it doesn't even look like there's a ridge there. I'd get the crank checked out to make sure it's in spec (unless you can properly measure it with a caliper), and if everything checks out... I'd just throw in some new bearings and put it all back together. The flywheel looks fine, but you'll want to get some ARP studs. Those flywheel bolts should not have sheered like that. My guess is that they didn't torque them down properly and / or they didn't use thread locker on them either.

That's pretty bad-ass though.
richard in nc SEP 06, 06:23 PM
[QUOTE]Originally posted by cartercarbaficionado:

so uhh turns out our knocking 100 dollar engine I procured was very built. .125 overbore, short stroke crank,
so you are saying they went for LESS cubic inches?
cartercarbaficionado SEP 06, 08:46 PM

quote
Originally posted by 82-T/A [At Work]:

Honestly, it doesn't even look like there's a ridge there. I'd get the crank checked out to make sure it's in spec (unless you can properly measure it with a caliper), and if everything checks out... I'd just throw in some new bearings and put it all back together. The flywheel looks fine, but you'll want to get some ARP studs. Those flywheel bolts should not have sheered like that. My guess is that they didn't torque them down properly and / or they didn't use thread locker on them either.

That's pretty bad-ass though.


it's looking like we got this just out of cam break in. also I torqued those bolts to spec amd it definitely broke them since there was little bits in the crank. otherwise everything is still checking out
cartercarbaficionado SEP 06, 08:50 PM

quote
Originally posted by richard in nc:

[QUOTE]Originally posted by cartercarbaficionado:

so uhh turns out our knocking 100 dollar engine I procured was very built. .125 overbore, short stroke crank,
so you are saying they went for LESS cubic inches?


with the overbore and longer rods this is now a 0 deck block. (pistons are actually like .005 below deck but close enough) so it's an attempt with the longer rods to get more rpm by making it more of a square motor and that worked very well considering it would rev to 6k.
I'm not honestly sure why they spent so much time and money on this engine considering each bit is worth over 500 on its own. but definitely something went wrong with its oiling system
armos SEP 07, 03:45 AM
FWIW, there is an obscure brand of high-zinc oil (Brad Penn) that is dyed green. Small chance that could be what you found in it.
Dennis LaGrua SEP 07, 04:58 AM

quote
Originally posted by cartercarbaficionado:

it was making more than 125. it snapped every bolt in the flywheel with little effort. and based on how far apart i have the 50k mile automatic with the ecu I pulled from the csr it was in(finally found the mileage on the reg from 93 when it was parked due to a blown engine since I had to buy a cheap cluster off ebay for it) it was well on its way to exploding that as well. it was definitely as quick as a 2.8 v6 with how fast it was getting to 60. (8 seconds which is scary fast for an all original 84) the head has been ported quite far and the exhaust path was chamfered for more flow into the valve.
I will be likely sending the crank off to be checked for roundness (or throw it in my buddies lathe with a micrometer on it) and definitely gonna get the rods checked throughly. nothing was spun or even that scratched up so I think it had just enough lube to save it



We have read claims of guys building Duke engines to 200HP . While I cannot dispute this it may be pushing the limits of the Duke crank and block. Regardless you have an very interesting project there and hope that it goes well. BTW, high ZDDP Zinc oil does help. It coats everything with a protective coating that bonds to the parts. Just be sure that no CAT is used. If you run an automatic I recommend a shift kit,

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "