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Discussion Starter · #1 ·
I finally finished my 2.9L Junkyard Dog engine project a couple of weeks ago and after a couple of hard weeks racing at the track she is still running strong. This combo is a bit unorthodox but for the small cash outlay I couldn't resist trying it.Basically ,it was assembled using some old parts that had some flaws in them(thus the name junkyard dog) The block is a 75 280 which I had previously broken two cranks in due to some wild speedshifting overrevs at the the local racetrack(Lift when you shift the crank you save may be your own!!!) Anyway, it had some main bearing cap walk from the stress created from the broken cranks and had a loose fitting #5 main bearing cap. The diesel crank I used had a very small crack(discovered under magnafluxing) on a previously damaged #2 rod journal(a rod had broken due to no oil lubrication caused by a clogged oil hole in the crank journal from the previous owner not changing the oil) and its questionable lifespan was the reason for trying this cheap engine project. I used the old 280 pistons and rods but balanced them perfectly using a very expensive digital weight scale at work which measures down to .1 gram. The factory did a horrible job balancing these pistons and rods with the lightest being 1445.1 grams and the heaviest 1448.8. I suspect that is the reason I broke the two previous crankshafts because ideally they should be at least within 1 gram of each other. Anyway I balanced each rod and piston assembly to 1445 grams and the benefit of doing this is quite evident as the engine revs extremely smooth all the way to 6700 RPM. I also shaved the pistons .015,which was done before the afforementioned balancing, by hand on 100 grit sandpaper, although this was'nt really necessary as .035 is the required minimum piston to head tolerance and I now have .055 piston to head clearance.Unfortunately, I did'nt find out Fel pro made a $25 .020 copper head shim until after I had alreasdy shaved the pistons. I used two std. head gaskets and a .020 copper head gasket shim from Fel Pro to keep the pistons from hitting the previously .070 shaved N42 head. The resulting compression ratio was about 10.1:1. So far I love the TORQUE this engine makes, it is a real stormer at low rpm. The engine pulls to 6700 RPM, but the power at that RPM does not seem to match my old stock block 280. So far my trap speed and time in the 1/8 mile is about 2 MPH and 3 tenths slower due to the lower rev capabilities of the stroker motor,the lack of speedshifting and the fact I am having to shift into 4th gear at the lights instead of crossing the line in 3rd. If my open diff with Nitto street drags would hook off the line instead of spinning I feel that I could easily match my old times just from the improved 60 ft. times ,but as it is I cannot use all the TORQUE this engine makes without just sitting and spinning. So far I have put about 800 miles on the engine and it has used no oil at all ,even though nothing was done to prep the cylinders and I used the old rings as well. The bottom line so far on the engine is this ...huge torque increase down low but similiar horsepower figures up top. One thing is for sure though, the added torque makes for a much more drivable car and you don't have to rev the motor and dump the clutch if you want fast acceleration off the line when running on the street and you dont need to downshift when accelerating on the freeway. So far, believe it or not ,my gas mileage is actually a little better than I was getting with my old stock 280 block. I am getting about 22.3 MPG with the new engine combo. I will keep you all posted on the engines progress and will hopefully improve my times with some different tranny gearing by swapping input shafts back to allow me to cross the 1/8 mile finish line in 3rd instead of 4th gear. Well, I'm off to the track tonight for some bracket racing. Hopefully I can improve on last weeks 8.85 @ 78.8 Mph(for reference a stock 99 SS Z28 Camaro only runs about 9.1-9.2 in the 1/8 mile) and whoop up on some stangs and camaros. Later, norm
 

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<b>RE: The 2.9 L Junkyard Dog Lives!!</b>

Norm...

Sure sounds good... let me know how ya did at the races. Thanks for all of the details, it helps me understand what's happening under the hood. If you get time, also list size and tire types used.

Thanks
 

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Discussion Starter · #3 ·
Tonights track times posted aove

I got her to run a 8.65 at 80.611 MPH so far.Hoping to go back next week and improve a little more!!
 

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Discussion Starter · #4 ·
Tonights track times posted aove

I got the dog to run a 8.65 at 80.611 MPH so far.Hoping to go back next week and improve a little more!!
 
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