New life for an old 340 (stock stroke)

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hard to tell without knowing which comp shelf gind
unfortunately nothing shorter than the XE275HL available off the shelf from comp
using a universal pattern costs torque
try Lunati- Hughes
I have some cutters for the Serdi that go way down the bowl so just a little blend is needed at the bottom
otherwise it's a lot of work
I do have some x and j heads with hard exhaust seats and bronze guides-
I lost my storage and "gave them away" (essentially on consignment)but I can get a pair back if anyone needs a set
I could not make a profit on them once the Edelbrocks came out- but they need work out of the box too-
Took them to the Mopar swap meet- brought them home
not enough matching number guys around that I could find
for a new build there are better choices like the late model heads for Iron, the EQ's etc
Me- I would not use an early stock 360 head on anything but a restore these days
 
113 lobe separation Good Lawd. I'm assuming this was a use the parts that were already in hand thing, or is there a reason for the wide LSA?
 
skrews said:
113 lobe separation Good Lawd. I'm assuming this was a use the parts that were already in hand thing, or is there a reason for the wide LSA?
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Parts already on hand. I also wanted the late intake closing so this builds steam in the upper rpms, it also helps stave off detonation with the crap chambered heads. J.Rob
 
RAMM said:
Parts already on hand. I also wanted the late intake closing so this builds steam in the upper rpms, it also helps stave off detonation with the crap chambered heads. J.Rob
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O

If you didn’t already have the cam how much different would you spec one for this build?
 
Got one similar I was going to put together. 70 340 block, .030, Trw stock replacement pistons, stock steel crank and rods, X heads and a old purple stripe cam .557 lift. Going to try to clean up the heads myself, 60 cc combustion chambers already. Would like to have the pistons lightened, think they are at 960 grams each now. Just a bunch of parts I have laying around. Also got another 340 block that must be final honed to .060, could use that also, but figured pistons would be custom. Thought it would make a decent street engine cheap.
 
RAMM said:
Good question! No idea, I didn't burn a single brain cell thinking about it. Not going to either because that tends to cost me $$$$. J.Rob
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There I thought this was some secret custom grind you were sharing with us... I was getting ready to order a replica
 
I used the XE294H. Pistons were the TRW/factory type forged, IIRC they were around .010 above deck. It was really snappy - shredding the Hoosier QTPs - but a lot of that had to do with the 8" custom convertor. It was a flash stall of 4K, but even below the stall it was pulling hard. IMO it needed a bit more carb (had a 4150 750cfm) and a lot more tuning. But it would pull hard past 6800 in 3rd. The owner was less than gifted in regard to tuning and setup and the rest of the car was a mess so I'm sure there was more in the package.
 
RAMM said:
Parts already on hand. I also wanted the late intake closing so this builds steam in the upper rpms, it also helps stave off detonation with the crap chambered heads. J.Rob
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...One of the reasons I like a couple of Crane grinds with 112 LSAs.
 
Some progress:
Gave the mains a lick in the line hone, did the math to determine target deck height. Had to take .0035" from drivers side and exactly .023" on passenger side to put the stock stroke, 6.123" rod with JE 1.804" CHT piston @ 0 deck. Passenger side deck height started @ 9.606" IIRC. Mains were also .0015"-.002" under the minimum. J.Rob

340ch100.jpg
 
After the decking it was on to cylinder honing. Torque plate installed and bores measured 4.098-4.099" . Got lucky here as I was able to straighten the taper and out of round the torque plate caused and still hit the 4.100" dimension. When the pistons come in I will measure the skirts and verify the clearance is correct . J.Rob

340torqueplate.jpg


340linehone.jpg


340deck.jpg
 
Will this thing run on Canadian pump gas ?
 
RAMM said:
I dont see why not. That's the plan anyways. 10.5 comp shouldn't require anything more, should it? J.Rob
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My gapless ring 340 is around 9.6 and it will give the odd rattle on pump...but that might be the extra oil it's burning.

I'm going to put new pistons in it this fall and will most likely go with flat tops like the one you used, I'm going to order a cam around the same size as the one you are running and throw it back on the dyno...I'm really interested in how close it these engines will be as they will be almost identical.
 
67autocross said:
My gapless ring 340 is around 9.6 and it will give the odd rattle on pump...but that might be the extra oil it's burning.

I'm going to put new pistons in it this fall and will most likely go with flat tops like the one you used, I'm going to order a cam around the same size as the one you are running and throw it back on the dyno...I'm really interested in how close it these engines will be as they will be almost identical.
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Oil consumption will absolutely cause detonation tendencies to increase exponentially--Ditch the gapless tops -use conventional and maybe you can reuse the pistons. J.Rob
 
RAMM said:
Some progress:
Gave the mains a lick in the line hone, did the math to determine target deck height. Had to take .0035" from drivers side and exactly .023" on passenger side to put the stock stroke, 6.123" rod with JE 1.804" CHT piston @ 0 deck. Passenger side deck height started @ 9.606" IIRC. Mains were also .0015"-.002" under the minimum. J.Rob

View attachment 1715192009
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How are you going to get 10.5:1 at a zero deck with those heads unless you deck the hell out of them?
 
Probably have to cut heads 50 -60 thousandths to get 60 cc. I've milled pass car heads down to 55 cc a few times, had to mill intake a like amount of course.
 
RAMM said:
Had to take .0035" from drivers side and exactly .023" on passenger side to put the stock stroke, 6.123" rod with JE 1.804" CHT piston @ 0 deck. Passenger side deck height started @ 9.606" IIRC.
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Say again? That's a big difference. Was the original crank bore also off towards the driver's side?
 
skrews said:
Probably have to cut heads 50 -60 thousandths to get 60 cc. I've milled pass car heads down to 55 cc a few times, had to mill intake a like amount of course.
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Yep last J heads I cut to 59 ccs was .050" removed. Those had flat faced valves. Notice the calc says 10.75, I will cut .045"-.050" and if it winds up @ 10.3 so be it. J.Rob
 
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