Author Topic: 340 Info and Advice (Read 2278 times)

gs69350 · « **on:** October 21, 2009 - 12:18:22 PM »

Hello all,

I've answered an ad on Craigslist, now I find myself working on a 340 project. I've got the experience (education too) to handle the job, however I'd like to find some more detailed info on these beastly little engines...

Here's what my goal is:

72 340 from a duster going in a duster w/ 727 and 3.55 rear.

Going for 9.5:1 to 10:1 compression, mild street cam with good vacuum, stock internals, unported "J" heads with 2.02" valves.

I'm taking the block down to the machine shop today to get it cleaned up and mic'd. It looks like it won't need any boring but I want to be sure before I order pistons...

As far as pistons go, I'm thinking a cast-replacement flat top w/ valve reliefs. Anyone have any recommendations? Keith Black vs, JE, vs

How about forged vs. hypers...

Camshaft... this is where I need the most help... I'm looking for a cam thats better than stock but has very very good manners... I want at least 15" of vacuum at idle... Doesn't need to pull past 5500. I'm thinking somewhere in the .470-.480 range w/ short duration. but I really don't know what these engines respond to. please help!

Also, if anyone could point me to a resource with tolerances/clearances (OEM and/or currently generally accepted as better) for bearings/ring gap, piston, etc etc...

Anything thats generally known in the 340 mopar community I need to know before I start buying parts and putting things together??

Thanks in advance!

Dan

moper · « **Reply #1 on:** October 21, 2009 - 01:13:34 PM »

I like hypereutectics for mild builds like this. Neil (CP) doesnt...lol. They make one that is basically a lightweight performance 340 piston similar to the battleship heavy TRW forged flat tops in shape but lighter. That lighter will be better in internally balancing the cast crank 340. These types of pistons are the only way to get decent compression from a 340 with factory iron heads. Have the heads redone by a competant shop. I'd run a cam around 230�@.050 and a static around 9.8:1. Too much more and a smaller cam will have detonation issues. As far as specs... you should talk about that with your machinist as that will get into a "too many cooks" deal very quickly.

Chryco Psycho · « **Reply #2 on:** October 21, 2009 - 01:14:12 PM »

Welcome

IMO I would just spend the extra for a forged piston , , fi you want more out of the engine later it will not require rebuilding later , the extra cost will be around the cost of a gasket set nevermind the extra machine work . JE , Diamond , Ross & Wiseco all make top quality Mopar pistons .
The best cams I have found are the Lunati VooDoo series & the Engle grinds But Engle sold out so I have not been using them since they did as I have clue if the quality is as good . The 60401 or the 60402 lunati VooDoo grind shoul meet your needs exactly if you want a hyd grind , if you want a solid grind there are some other Lunati grinds I can direct you too .
A bit of port work around the valve guides can really help the heads as well as port matching .
the performer RPM Air gap is a great intake for the small block

gs69350 · « **Reply #3 on:** October 21, 2009 - 10:20:58 PM »

Thanks for the replies..

I feel shame for admitting this, but since I am just the idea man/wrench and not the money man my choices are somewhat limited... The machine work is being done by the local Napa... The shop seems well equipped and is larger than I thought it would be, but I have no personal knowledge or references of their quality.. I can only hope that the machinist is worth his beans... In the past, when I was working in a resto shop and built a few engines, I would gather all my info ahead of time and tell the machine shop what I wanted, then double check the work when I got the parts back... But that was years ago and I no longer have my measuring equipment...

We dropped the block off today for clean up and inspection (he's going to measure the bores for taper/out of round/all that good stuff, magnaflux the block and check the mains for straightness)... Once we have his report (in a week /sigh) we'll get the parts on order.

This build is supposed to be the last for this car, at least while this guy owns it. He's got a 2nd Duster that he plans to go nuts on.

Only reason I hesitate on Forged is that I have no personal experience with them, but understand they make quite a racket while the engine is warming up do to increased tolerances with the cyl wall... Since this isn't a race application nor a super-hipo build, forged is not necessary and the less non-cool engine noises it makes, the better..

I'll lookup the Lunati cams tonight, thanks for the tip.

He's decided against porting, but I may be able to talk him into a simple portmatch/cleanup. As of right now its going to have a stock iron 4bbl intake. I'm going to try and change his mind on that.

Assuming the heads have never been milled and we went with Hyper flat tops with valve relifes, and a standard issue fel pro head gasket, any educated guess on the comp ratio? The goal is between 9.5 to 10:1. Would it be worth it or necessary to have the heads decked .010"?

Thanks, and probably more questions to come... I'll see about posting picks as the build progresses.

moper · « **Reply #4 on:** October 22, 2009 - 09:31:48 AM »

The shop means little really. A good machinist will do excellent work anyway. If they are to be assembling the engine you may want to verify they are familiar with hypereutectic pistons. They should be... but some require special ring gaps when it gets assembled. Also, if you have the option you may want to have them blueprint the engine. It costs more but it's worth it. As far as compression, depending on the work and the gasket, it shoudl end up around 9.8:1.

Chryco Psycho · « **Reply #5 on:** October 22, 2009 - 11:07:05 AM »

most Mopar blocks are overly tall so you need to check the deck height to make sure you are making the compression you want , properly cleranced the forged piston are not noisy even when cold
the stock intake is actually a good piece , a lot of the alum intakes are not better

gs69350 · « **Reply #6 on:** October 22, 2009 - 07:29:03 PM »

After doing some research, I think I am going to go with the Keith Black KB243 Hypereutectic pistons with only cleanup passes on the deck and heads. There's just no reason to justify forged for this application. From all I read, the Hypers should give the performance, reliability and last a long time without causing extra wear to the bores or rings.

I was playing with an old copy of Dyno2000 that I have.. I plugged in the Lunati 60402 and it came in way lower than expected, but I think thats because of the odd valve event timings their website showed. It came in around 250 horse peak at 4500 rpm, the Comp 270H came in at 330 horse peak at 5200 rpm. I'm going to chock it up to the software... For now its still in the running and high on the list.

Can anyone recommend a source for buying these parts at a good deal? I've been looking at Summitracing but I don't know if there's a better source for Mopar go fast goodies.

Thanks,

Dan

Chryco Psycho · « **Reply #7 on:** October 23, 2009 - 04:49:22 AM »

I can tell you positively the Lunati makes more power then the Comp grind
Summit or Jegs would be the first places I would price , of course being in Canaduh I source stuff differently

Author Topic: 340 Info and Advice (Read 2278 times)

gs69350

340 Info and Advice

moper

Re: 340 Info and Advice

Chryco Psycho

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gs69350

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moper

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Chryco Psycho

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gs69350

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Chryco Psycho

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