Building my 72 340 and need some help

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gunmetal72

gunmetal72

Life is a dark ride
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I am going to re-build my 340 and would like some info. The engine is mostly stock except for a 650 cfm edelbrock carb and 360 "J" heads. I am not looking for crazy power, just a few more horses with a nice smooth cam lope sound, if that makes any sense.

I know there are guys here that are a lot smarter than me when it comes to mechanical so here I am asking for advice. I am unsure what kind of parts will work properly with as little hassle as possible. I have heard stories of guys having night mares when they try to fit up the alternator and power steering pump.

In a nut shell, here is what I am planning:
The engine is stock bore with lower compression pistons with a stock crank. The block is in great shape with very little wear on the cylinder walls. Was just going to clean up the block and have the crank machined. I will do the rings, rod and main bearings along with a new oil pump. All new gaskets and seals go without saying.

For the top end I want to put in new roller rockers, roller lifters, new roller cam, cam bearings and push rods. Rather than have the the old "J" heads machined I thought I would go with new aluminum heads and maybe an intake.
So here are some questions I would like some input into.
What heads, roller rockers, lifters and cam would be a good to use and should I go with an aluminum intake. Any other thoughts on what else should be changed would be welcomed. Thanks in advance for taking the time to help.,,,,,,,,,,,Dale
 
With the cam RRR mentioned, you can stick with the J heads and add stainless steel 2.92-1.60 valves. Also while getting the calves put in, have a performance valve job done and have the Comp springs installed.

The factory intake is a good intake that can be used with the cam. An aftermarket intake (& or heads) would help in power production but it is not an"Needed" part. As well with aluminum heads. The cost vs. power return may not be to your liking.

Installing a roer cam in an older engine is or can be labor intensive. (Read costly, $$$) a Byd. Cam can and will perform very well. Consider a Comp XE268H or equal from Lunati or Howard's came. A good muscle car sound idle will come from a cam cut on a 110 or a choppier sound from a 108 centerline. Regardless, an aluminum top half is an excellent upgrade and a great look. I would suggest a all Edelbrock top end.
 
I had a little bit of an issue with my Alt. installation. I took the factory metal sleeve spacers and cut them to fit. The Edelbrock head is a little longer than stock. My square back Alt. is a few paper widths away from the head. But it is away from the head.

I have noticed most "Nightmares" written about pulley alignment comes from a lack of time out into the problem and understanding how to address the issue. Sometimes it is quick, sometimes it takes all day. Parts on hand play a part in time consumed.

I also used the March serpentine pulley set up and brackets on both Alt. & the P/S pump. No REAL issues.
 
Deck height meaning how far the piston is above or below the block. This will result in different compression ratios.

I believe some 340's had their pistons above the deck resulting in the need for open chamber heads but I don't recall at this time.
 
First question: What is the intended use(s) for your car? This is the most important thing to get right, to get a good package together. Road cruiser? Just drag racing? Taxi service LOL? Pump gas only? If so, is premium OK? What transmission is in the car?

Rumblefish is spot on about the labor and cost intensive aspects of roller rockers and a roller cam and lifters. We just went through this for the roller rockers, and it is not a good thing for someone in their first engine builds; there can be a lot of fiddling and adjusting gaps and you have to do it right; you don't just slap them on. And besides, for a mild build (which this sounds like) the benefit is marginal to none.

Read up some of the threads on roller cam conversions for the problems associated with putting them in an older LA block: this is a great example of the problems there:
http://www.forabodiesonly.com/mopar/showthread.php?t=335882

Plus the roller cam conversion will cost up in the $500-$900 range, unless there are some GOOD bargain parts out there. Roller cams give a significant upgrade in cam profiles but it is a lot of cost to get there for your block. The cost is a good reason why the older flat tappet cams and lifters keep on being used.

For a good reliable engine, get the engine block to a good machine shop and have them measure and check the bores first. I'd plan on boring the block and putting in new pistons; it will be an awful waste of money and effort and time to put that kind of money into new bearings and the top end and have to tear it down again because a worn cylinder bore or 2 lets out too much blowby. It does not make sense to not od new pistons with everything else, and I would surely do that well before a roller cam or rocker upgrade for a street machine.

You won't be sorry you put money into the AL Edelbrock Performer heads or the Indy X equivalents. The improved port flow will open up the engine to a wider RPM range and significantly better torque and HP overall all. And the closed chambers raise CR and help low end torque. (Important for a road cruiser, not so much for a drag engine...) They really bring any SBM up to another level of performance. (But of course, it is not a budget upgrade!)

BTW, the Summit kit pricing is decent but you can match it or beat it by a bit with some judicious shopping, and have more chance to pick the exact parts you like.
 
When your talking about pistons get comfortable with Compression Height measurements.

A 68-71 are 1.84", 72-73 are 1.74".

If you go shopping for LA aftermarket pistons you'll find many are at 1.81" making it approximately .012" below deck allowing for a block clean up cut and the possibility of zero deck that everyone talks about.

So get out your math and 1/2 stroke, plus 6.123" rod, plus C.H. and compare to 9.60" block height. With this you can juggle gasket thickness and get involved with the quench discussion that is sure to pop up.
 
'72 340s came with 360 J heads (with 1.88 valves), pistons in the hole, my early block is external balance, and they had a 268 cam. The 340 intake is actually quite good. If you're not replacing it with an aluminum as high quality as a Performer RPM then it's not a terrible idea to continue using it.

rumblefish360 said:
I have noticed most "Nightmares" written about pulley alignment comes from a lack of time out into the problem and understanding how to address the issue. Sometimes it is quick, sometimes it takes all day. Parts on hand play a part in time consumed.
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First thing that pops into my head is if people are getting Magnum heads since it's not much more and then not knowing about the alternator bracket mods that're required. Factory and aftermarket iron Mag heads require alternator bracket mods for the old style and I can't imagine Edelbrock Mag heads would be too different.

Nobody else corrected that you meant 2.02 instead of 2.92 in your post. Simple typo, but thought it was important to mention.
 
LOL, true! Right now, there is some poor bastard looking for a 2.92 or 3.00 valve for his 360.
 
The lifter bores in my block look like they are counter-bored. I read the threads that nm9stheham sent and there was a link from those threads that shows a solution to the problem. The link below shows what I am thinking as a possible solution. I have also attached a pic of the lifter bores in my block. Any thoughts on whether this would work.

http://www.hughesengines.com/Index/...el2=Um9sbGVy&level3=SHlkcmF1bGlj&partid=26114
 

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Figure out what your budget is before you make any choices.
If you are not running headers then that plays into cam selection as well.

It comes down to how much improvement do you want and how much are you willing to spend to get it?

Compression and head flow give the greatest gains in power and compliment everything else.
 
I am looking to spend around the $5000 mark ($4000 us), I am not going use headers and I am planning to use the 650 edelbrock carb and stock ignition. I would like it to run on premium pump gas. The car is a 4 speed with power disc breaks and power steering. I really hate the noise the lifters made when it was fired up so I thought rollerizing it would take care of that and add some hp. So, nothing too crazy, just a nice solid cruiser that will set you back in the seat when the time arises.
 
340's are made to wind up. loose solid lifters and big valves. You can get a nice torquey quiet 360 magnum with your budget. Just make sure the crank will accept your 4-speed
 
Any engine of similar bore and stroke can be made a torque engine or a high revver, relatively speaking; the bore and stroke differences of the 340 versus 360 are too small to make one a revver and the other a torquer.

For the manual trans, you don't have the option to push of the torque converter stall RPM for a big cam. So if you put in too big a cam, it is gonna bog all over the place and you will have to keep it revved and slip the clutch a lot to get going. That will tend to suck for a road cruiser (Although it WILL draw attention every time you leave a stop sign LOL!) I checked the Thumpr cam and it looks too big to me for a manual trans street cruiser. And if your keep the 650 cam, then again, that points to a smaller cam and too for the stock exhaust manifolds

I would surely go to the better breathing Edelbrocks or Indy-X's to help the engine to rev some with a moderate cam, but you will lose some of the value in those heads if you don't add headers. I would put headers on a higher priority than roller rockers for sure; headers will help you all over.

Work on the higher CR to help the lower end and extend the usable bottom end RPM's, but don't go too high on the CR. With a manual trans, it is a lot easier to get caught in traffic in a higher gear for convenience in gear selection, but the lower RPM's will make it more prone to lug under acceleration and thus ping/knock/detonate more than an auto trans car. So I would be inclined to keep the DCR (dynamic compression ratio) down to the low 8 or the upper 7 range, even with AL heads. (A little less CR might be a good reason to go with the 65 cc Edelbrock heads rather than the 63 cc's but you would lose any chance for using quench.) If you are not familiar with DCR, find some articles on that and find a DCR calculator that you like and use it as part of your cam selection process.

Your budget is decent IMO, but how far you get with it depends on how much you do yourself. If you do your own final assembly, then I think you could get good headers or roller rockers with that, but not the roller cam. If you have someone else to do the assembly, the I'd forego the roller rockers too. That is just shooting off the hip for $$ estimates, so start picking parts and adding up a budget, and don't go with the cheapest parts for pistons and rockers. Don't forget things like water and oil pumps, timing chains, gaskets sets, new pushrods with the roller rocker setup or roller cam, maybe a better distributor, new block plugs, ad nauseum.

And yes, do the AL intake manifold. For an all purpose street cruising in all weather conditions, the RPM Performer would be my choice over the AirGap, just to keep the intake charge a bit warmer when you stop and start.
 
Bodyperson said:
340's are made to wind up. loose solid lifters and big valves. You can get a nice torquey quiet 360 magnum with your budget. Just make sure the crank will accept your 4-speed
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They came with hydraulic flat tappets all years, and the 360 1.88 intakes in '72. The difference in '72 and '73 between 340 and 360 heads is what the block below them had wrote on it. The '74-up 4bbl 360s used the old 340 cam, they do make the same power a couple hundred RPMs sooner though- a 360 being torquier isn't just a factor of the larger displacement: 340s aren't really more so than 318s despite the displacement difference with the same stroke. It's a minor difference but one that exists the same.

gunmetal72 said:
I am looking to spend around the $5000 mark ($4000 us), I am not going use headers and I am planning to use the 650 edelbrock carb and stock ignition. I would like it to run on premium pump gas. The car is a 4 speed with power disc breaks and power steering. I really hate the noise the lifters made when it was fired up so I thought rollerizing it would take care of that and add some hp. So, nothing too crazy, just a nice solid cruiser that will set you back in the seat when the time arises.
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340s're not bad stock with decent gears. (which they all came with) The roller conversion is expensive to do right besides just buying a roller motor- that should be worth considering but with what I've ever paid to rebuild stock heads- it'd be worth doing that and the roller conversion.
 
I did not say they were made with solid lifter cams. But they sure did like em with the x heads.

What I'm trying to convey is make use of the new technology that is cheap and readily available instead of old school way of thinking.
 
When I changed the cam in my motor, 3 years ago, I do not think I put in the proper one in. (bad advice) The car had problems, no power from a dead stop but if I brought the RPM's up to around 1500 it had no problem which I think says I should have went with a cam with better low end torque so it would not bog without having to rev it up so much.
If anyone would like to give me their thoughts on which cam would work better with a 4 speed, would be appreciated.

[ame]http://www.cranecams.com/158-159.pdf[/ame]
 
496 polara said:
The second one on the list looks good for you.
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I think that is where I would end up. But # 1 would work too, but I wish it had more lift; #1 does not seem to gain the typical benefit of a roller: more lift for a given duration. Bog? I had a cam that I had to rev to 3800 before launching with the clutch in to a race section.....LOL
 
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