Worthwhile upgrades to stock '73 340?

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zig

zig

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I have a stock 73 340 on an engine stand that I am cleaning up for my 74 Duster. It hasn't been ran in about 10 years. I tore it down to the shortblock and want to get the heads redone. I've heard the larger valves make a big difference. Am I ok with having larger valves put in at the machine shop, doing some minor port and polishing and keeping the stock low compression pistons?? I am looking for a nice street car. Nothing to crazy, but want some power. I know I want a new cam also, something a notch or so above stock. Probably stock intake with some porting unless I should upgrade. Headers, dual exhaust also in the plant. I know I can just keep spending money if I want. I am debating on the pistons also, are they a good bang for the buck upgrade?? Or am I safe with the stockers and doing the heads only.. I know it is much easier to do things now while the motor is out...

Thanks for any advice...
 
Get a price for parts springs, and work first. If it is going to be too expensive, look into the RHS heads. The 73 model 340 is a little low on compression so maybe even ad in the cost of shaving a little bit on the heads to bring compression back up.
 
If the shortblock is worn as the headas are, and you put fresh heads on it, it will have issues pretty quickly in terms of oil use and ring seal issues. My advice would be to leave it alone with the exception of a better cam and timing set, and add the right matched valve springs and seals. If there is money in the budget for a rebuild, do it all properly. If not, don't spend just to spend. Clean it, cam it, paint it, add the headers and duals, and save to "do it right".
 
Good idea about shaveing the heads a bit to help with compression... I am going to start pricing out having the heads redone this week.

I didn't necassarily say they were worn out, I just want to upgrade while the motor is out of the car. Supposedly the rings, bearings and everything were replaced 5k miles prior to storage. I have debated on replacing the rings just to be safe. Everything is fairly clean, just some carbon on the valves and pistons, that I could probably clean up myself.. So are you saying that might be a good idea??

I am looking for a strong reliable 340 for the Duster...
 
I would look for a cam that can help build some compresion and leave the smaller valves in. The use of headers is a plus, but I don't know if you wanna go there. Even more so since theres only 2 I'd recomend and there a bit pricey.

Doug's headers and tti's.
 
That's another good option. Any cam you would recommend? I can always put the money I was going use for the heads and buy some good headers. I don't really have a budget, but I kind of do.. I don't want to spend a ton of money on the engine, but I am willing to spend it in the right place. I wanted to upgrade the cam anyway, so that and maybe an intake?? I can still port and polish the heads myself and just clean them up good. I think a basic valve job would be fairly cheap..
 
Another good idea upgrading the cam only. Any cam you would suggest? I am willing to spend some money if it makes sense. I might just go for the tti headers. I know they are expensive, but seems like they are real nice.. Less head work could save me some money for the headers... I think I should get the old heads at least reconditioned, I don't think it is that expensive for that...

Any other suggestions are appreciated...
 
I think there is a member on here that sells the RHS Heads with a clean up, bowls blended and 4 angle valve job for around $1300-1400. You can get a set OOTB cheaper. They are a great head, and I don't remember the guys name on this board that sells him, But I plan on buying a set through him when I get a set of new heads.
 
I think you should spend less money on the heads--keep the stock valves and just get them clean and a valve job with new valve springs..no milling either.

Those pistons need to go, they are heavy and likely worn and low on compression. Kb hypers are $250 a set at Summit, will boost the compression to 9.5 with 68cc heads. Can always mill the heads if you want more but it still is a nice increase form 8.5--if you have even that now. Plus with new rings the piston seal will be much better.

Heads always can be upgraded later on--but you might be happy enough with how it is....same with the camshaft--if it looks ok, and have a shop guy look at it, just get new lifters and a timing chain. Those 340 cams were not too bad--power and mileage wise.

Those pos pistons need to go!
 
Dodge Freak- That is actually a really good idea. I probably am better off upgrading the pistons while I can. Once the motor is in and I don't like the way it runs, then I am screwed... I can always do more to the heads later like you said or I might be happy with just cleaning them up. 9.5 would be nice for compression. I don't need anything higher. I am going to check a shop by work tomorrow and see how much head work would be. How about the bearings?? they should be ok? or is there a way to check them?
Thanks for the input
 
Bearings HAS to go. Man you spin a rod bearing if you don't replace them. Things get old and wear out. It sounds like this is how it was since 1973, that is 37 years old.

Bearings are like $50, come on. Even if you did nothing else replace those bearings. Mains last longer but gee you always replace those too. And the Cam bearings if you get the block hot tank/bake clean.

Really the rods should be rebuilt, new rod bolts, re sized but its not always needed. My 340 might see 6,500 rpm everyday, if you are a "normal driver" and think 5,500 rpm is pushing it, no need for new rod bolts, imo. Was like $200 I believe after the new bolts and them re sizing them. I got peace of mind now to take it to 7,000 but cam could be a bit hotter.

Cam is the last biggie cause its a pain to change in the car. Can be done thou, unlike changing the pistons. A balance job will be needed too.

Careful on which shop you pick. I yank my stuff out of one after hearing them run the bill up by saying "oh its like always needed" when stuff like line honing, decking came up. Before they even checked it out!

Some shops are cool and won't replace more than is needed or at least first check if its really needed.
 
pull the heads and mill them .040 each.
those need cylinder pressure BAD.

headers, performance timing curve, ld340 intake or rpm.
msd ignition & good wires.
 
Not sure if I mentioned it, but according to the previous owner everything was rebuilt 5k miles ago, but 10-12 years ago... Stock rebuild only, so new rings, bearings, and stuff. The The inside is fairly clean. The cylinders walls look in great shape. The reason for buying the engine was not to do a full rebuild. He said it ran great 10 years ago... So I kind of wanted to replace the needed parts and worthwhile upgrades. I am not in a big hurry, so I can spread things out a bit. This is a winter project to swap motors...

I am going to ask around to the "car" people I know. There are tons of shops to choose from in the metro Detroit area...
 
The fact that it was done with stock parts means it has certain limitations built in. "Doing it right" doesnt mean full rebuild. It means taking into account the whole package. As it stands now, it has very, very low compression due to piston choice, head gasket choice, and a stock valve job. You can do simple things, like adding a cam and the associated items, or you can replace the pistons which basically means going most of the way through the rebuilding process again. This is why I suggested waiting until such time as you can "do it right". For your engine, you're looking at redoing the heads or replacing with better, replacing the pistons which means at minimum re-honing and re-balancing, plus the "bolt on" stuff, torque convertor, etc.
 
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