340 upgrades.

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ltrripp11

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good morning all

im new to this site and have a question regarding the 340. i have a 1972 340 duster with the low compression motor. the car is a ground up resto i just purchased but the motor was left alone and just detailed becuase it ran to well. it has 85000 miles. with this milage however i would like to upgrade it at some point to match the rest of the cars newness. my question is what seems to be the best head,intake and cam option for this year motor. this will be basicly a street car to and from shows. i probably will not get into the block (good compression) and will just freshen up the top end for more grunt. at some point ill upgrade the bottom end (pistons etc) to the high compression earlier models but not yet. what package would you all suggest and why. thanks for any and all input and glad to be here.
 
I'd find something similar to the old hemi grind 274 deg .471 lift. You'll probably want to take the heads off and get the valves done and get the springs set up. You can get the heads cut .030 to bring up the compression. One caveat: A fresh valve job with old rings can make the old rings start to smoke. If you decide not to remove heads when you change the springs ( you MUST change the springs) also change the valve seals they're cheap. Change the timing chain and gears. You gotta be careful about intakes some are really tall and won't fit under the hood. A 750 Holley would sork pretty good too. The factory carbs are next to impossible to find jets for.

don
 
Id cheat. If you plan on upgrading in the future, and jus twant to cruise and have some fun for now, I'd run either the "302" later model heads, or the '68-'71 318 heads (smaller chambers). If you use the MP thin head gaskets, and the smaller chamber heads, the compression you gain will far exceed the top end power they may or may not loose. I did this on a late model 360. With the XE268 cam, 9.8:1 compression, and minor bowl work and gasket matching for the larger intake ports, it pulls quite well to 5500, idles at 800, and runs on pump gas. The 302s are the best choice IMO, as they have the unleaded seats in them. If you stay with the factory J heads, I'd run an XE262, and follow Don's ideas with regard to timing chain, springs, and seals.
 
moper
i forgot to mention the heads are marked "X". now i read that they should be j heads for this year so who knows what may have been done as far as the heads go in 34 years. given that, are the X heads worth just freshening up. i heard they flow pretty well as they are. to make things even more confusing for me i read somewhere on here that some of the X heads actually had the smaller valves versus the 2:02. is this fact or fiction. so many decisions!!! lastly what do you think about the factory intake. good or bad??
 
The "X" heads are natural 2.02/1.60 heads. They come off early 340 engines.
A '72 intake is a T-Q spreadbore intake and is a very good factory intake. I would go as far as a 280* cam which mostly come with a .480 lift. A Comp XE would be better being a split duration. (Helps with the exhaust which flows OK at best. With or without headers)
A aftermarket intake would be better for performance adding 10 - 15 HP, but thats your money to spend if you want the Aluminum.
 
As has been pointed out before, the 'J' castings for '72 had the 1.880 intake valves. If you have the 'X' castings...you would indeed have the 2.020 valves. I ran a set of those on my '72 Duster 340. All factory stock when I bought it. I changed over to a set of the 'X' heads and it ran great. If you do pull the heads do a 'bowl' port on them, mill .030, freshen up the seats, replace the seals and back cut the valves 30 degrees, inexpensive mod and worth it. You already have some good spring recommendations. Comp XE 262, or XE268 will work good as will a set of headers if that is in your budget. 3.91's , TQ and TQ manifold or the Air Gap with a Holley Vacuum sec. will work well also. Would be a good street performer with good street manners. Good luck and keep us informed as to your progress and results. Terry.
 
just wondering in doing the mods to the "j" heads alone,what kind of compression can be made? i'd like to use the comp cam XE268 as a base, in case valve clearence is an "issue" in the calculations.
 
The J heads are (mine are) 72 cc large. With a zero deck piston, the ratio works out to be 9.8-1 with a .039 head gasket. I used KB 107's @ .030. They have ample valve relief. I had a .500 lift ccam in there with booooo-koooo room.
Though this ratio is a bit high for the cam mentioned, a Fed-Mougal piston is also good being a slight below zero deck.
I *Think* it was .010 down the hole. Also has deep valve reliefs.
 
This is kind of opening a can o' worms, but this thread seems to be the place to do it.

I have an early 340. Completely dis-assembled. The heads had a valve job 25 years ago & were bagged. I have Isky adjustable rockers & a new Direct Connection (Racer Brown) P3690769 Hyd. Cam & lifters (292 deg. .510 lift don't know lobe ctrs.) that I bought close to 30 years ago. I have 1 5/8" fenderwell headers w/fairly long primaries, factory windage tray, new Ansen 1 piece bellhousing, Savage racing flywheel, Savage clutch (somewhere) hardened tip distributor drive, high vol. oil pump, Moroso deep sump chrome oil pan Don't think I'll be using this), new Direct Connection magnafluxed double row timing set, might have a set of Isky valve springs (don't remember for sure), & probably a few other things, all bought when I was younger & stupider than I am now.

My car is a 1964 Barracuda with a 3.91 sure grip 8.75 rear, factory 4 speed (Unfortunately it has a 3.09 low & that awful drop to a 1.92 2nd. I would like to put in the OD conversion that changes to a 2.66 low and a .8 something OD but that's about $2000!), & hood scoop to seal to the engine.

This car WILL ABSOLUTELY have a six pack on it. (This portion is not open to negotiation) I also plan to add a Mopar electronic ignition distributor to it.

The car will mainly be street driven, hot rodded, cruising, etc. & will have air conditioning.

Soooooooo........... What does everybody think I should do when I build this engine? What C.R? I live in the boonies & will have to run it on whatever premium swill I can find. What cam? I'm sure there are better hydraulic grinds out there now. What about my heads? Leave them as is (maybe a port match) or should I try to do something to help them run on unleaded? I'm open to just about anything, suggestions, criticism, rants, whatever.

I plan to take my time, do it right, & hopefully never have to it again.
 
72- J heads will respond the same way as Xs to good work. The work suggested is all good, I would just add that the intake face of the head may need to be milled to get an intake to fit and seal properly. Overlooking that can cost a lot of power and give you headaches later. I seriously doubt the factory chambers are 72cc. I'd guestimate closer to 74ccs, if they are indeed virgin. Also, your pistons will be way down in the bores. I'd also guestimate the true static ratio is closer to 8:1 then 9:1. Milling will get back some of this, but the only way to know for sure, is to cc your heads after the work is done, and measure the deck height, then figure the ratio out that way. I'd change the valves to 2.02s to move the seats out, but that will lead to more $$ spent if they are indeed 1.88s (which I seriously doubt). The XE268 will run quite well in it, but if you dont plan to touch much, I'd rather use the XE262 in it. I've also run the Comp Magnum 268H in one of my 340s and had excellent results. I ran it with the factory '71 Tquad intake, and a '72 Tquad carb, and 1 5/8 headers. Passed emmisions, ran pump gas for 2 years in an E body stick w/3.23s.
 
[QUOTE='64 Cuda]This is kind of opening a can o' worms, but this thread seems to be the place to do it.

I have an early 340. Completely dis-assembled. The heads had a valve job 25 years ago & were bagged. I have Isky adjustable rockers & a new Direct Connection (Racer Brown) P3690769 Hyd. Cam & lifters (292 deg. .510 lift don't know lobe ctrs.) that I bought close to 30 years ago. I have 1 5/8" fenderwell headers w/fairly long primaries, factory windage tray, new Ansen 1 piece bellhousing, Savage racing flywheel, Savage clutch (somewhere) hardened tip distributor drive, high vol. oil pump, Moroso deep sump chrome oil pan Don't think I'll be using this), new Direct Connection magnafluxed double row timing set, might have a set of Isky valve springs (don't remember for sure), & probably a few other things, all bought when I was younger & stupider than I am now.

My car is a 1964 Barracuda with a 3.91 sure grip 8.75 rear, factory 4 speed (Unfortunately it has a 3.09 low & that awful drop to a 1.92 2nd. I would like to put in the OD conversion that changes to a 2.66 low and a .8 something OD but that's about $2000!), & hood scoop to seal to the engine.

This car WILL ABSOLUTELY have a six pack on it. (This portion is not open to negotiation) I also plan to add a Mopar electronic ignition distributor to it.

The car will mainly be street driven, hot rodded, cruising, etc. & will have air conditioning.

Soooooooo........... What does everybody think I should do when I build this engine? What C.R? I live in the boonies & will have to run it on whatever premium swill I can find. What cam? I'm sure there are better hydraulic grinds out there now. What about my heads? Leave them as is (maybe a port match) or should I try to do something to help them run on unleaded? I'm open to just about anything, suggestions, criticism, rants, whatever.

I plan to take my time, do it right, & hopefully never have to it again.[/QUOTE]



A lot has changed..I'd keep the rockers, the timing set, the headers,and oiling system stuff (minus the pan). A 25 year old valve job isnt good enough for my tastes. It wont have hardened seats (the value of which is still debated, but for a pure street car, I think they need to be in them), wont have an accurate machine that did the seats, probably has knurled guides.all stuff I dont accept as good any more. The cam is a cool peice, but I dont think it's for this build. Some idea of the piston type is needed really, but I'd go conservative on a cam too. A lot of tech has changed, even in the last 8 years. heavy forged pistons dont need to be used. Balancing processes are much better, as are the machines that do the machining. Many steps that years ago were "blueprinting" steps, are now part of how the tooling does its' work. Cam science is light years ahead, especially in the "street" area. It's worth a good modern performance build, using the new parts that will work well, and not depend on 30 year old tech for the inmportant stuff.
 
7demon2 said:
so without going into the bottom end maybe 9.0 to 1 or 9.25 to 1?
Click to expand...

When you take the heads off, measure how far down the piston is in the cylinder at top dead center.
This combined with actual cyl. head cc and gasket diamentions are the numbers needed for the math on ratio.
 
rumblefish/terry

thanks for the replys. this will be down the road but at least i can get a jump on what i want to do with all the input. seeing the heads and intake are pretty respectable from ma mopar already i may just have them freshened up (especially the heads) and re-install. what do ya think about shaving the heads to bump compression??
 
Shaving the heads for rise in the comp. ratio is fine if the bottom end is up to snuff for the increased pressure. The bottom end should not have rattles and oil blowing by the rings.
You'll also need to mill the intake side of the head a bit to have it all fit.
 
[QUOTE='64 Cuda]This is kind of opening a can o' worms, but this thread seems to be the place to do it.

I have an early 340. Completely dis-assembled. The heads had a valve job 25 years ago & were bagged. I have Isky adjustable rockers & a new Direct Connection (Racer Brown) P3690769 Hyd. Cam & lifters (292 deg. .510 lift don't know lobe ctrs.) that I bought close to 30 years ago. I have 1 5/8" fenderwell headers w/fairly long primaries, factory windage tray, new Ansen 1 piece bellhousing, Savage racing flywheel, Savage clutch (somewhere) hardened tip distributor drive, high vol. oil pump, Moroso deep sump chrome oil pan Don't think I'll be using this), new Direct Connection magnafluxed double row timing set, might have a set of Isky valve springs (don't remember for sure), & probably a few other things, all bought when I was younger & stupider than I am now.

My car is a 1964 Barracuda with a 3.91 sure grip 8.75 rear, factory 4 speed (Unfortunately it has a 3.09 low & that awful drop to a 1.92 2nd. I would like to put in the OD conversion that changes to a 2.66 low and a .8 something OD but that's about $2000!), & hood scoop to seal to the engine.

This car WILL ABSOLUTELY have a six pack on it. (This portion is not open to negotiation) I also plan to add a Mopar electronic ignition distributor to it.

The car will mainly be street driven, hot rodded, cruising, etc. & will have air conditioning.

Soooooooo........... What does everybody think I should do when I build this engine? What C.R? I live in the boonies & will have to run it on whatever premium swill I can find. What cam? I'm sure there are better hydraulic grinds out there now. What about my heads? Leave them as is (maybe a port match) or should I try to do something to help them run on unleaded? I'm open to just about anything, suggestions, criticism, rants, whatever.

I plan to take my time, do it right, & hopefully never have to it again.[/QUOTE]


Okay, I brought this to the top because I've dug out some of my parts & now have a couple more questions. I looked at the heads I have. I thought they were early 340 heads but I guess I'm wrong. They have casting #3418915, which makes them early 70's 340/360 heads. I found a 360 cast in one of them, didn't check thr other. I have a picture of one below. Looks like somebody put 2.02 valves in them. I have the complete block with all it's components, disassembled. It is rusty but I don't think it's ever been bored so will probably be usable after cleaning, etc. The crank is forged & when removed from the engine it looked good. I covered the journals with grease, bagged it, made a wooden box for it & stood it on end & it has been that way since the early eighties. I also have a brand new Edelbrock 3 x 2 manifold with brand new Holley (aftermarket, side hung floats, mechanical secondaries) carbs that have never been on an engine. I also now have my choice of three transmissions, the original, a 66 dart trans (rebuilt, has slip yoke setup) & an OD 833. Probably will try to use the OD trans.

Now for the questions. What can I expect from the heads? I had them in plastic bags but the bags fell apart so they have a bit of surface rust & will need cleaned up. I will most likely have to have new guides put in (present ones have been knurled, I think) & hardened seats for unleaded gas. Any idea what this would cost? Is it worth the cost to convert them or should I sell these on eBay or something & look for some later head? I need to use the pre-Magnum heads so I can bolt up my six-pack. I think Mopar Performance sells a Magnum style head with the early manifold bolt holes. Or what about the Edelbrock heads? I'm not out for all-out performance, just cruising, dependability, & (of course) all I can get fort my money. There's a new Mopar crate engine, 410 cu in, 465 hp, 500 ft lb torque, with a complete six pack on it that I would love to use, but it costs about $10,000 & even if I sold all of the parts I have I don't think I could offset the cost enough to get it past the wife. Any thoughts or suggestions? Anybody interested in paying a bunch of money for the parts I have? :tongue10:

I'll be waiting to hear EVERYBODY'S opinions. Keep those cards & letters comin'.


:burnout:

Head pic 1.jpg
 
Those are good heads and not much rust. Have you seen some of them on E-bay? I would just keep what you have. Just get 10.5-1 pistons and if you want have the heads redone. But if they were redone and never used -even for 25 years-they should be ok. Might want to lap the valves if theres any rust on the seats. The 360 and 340 used the same heads back then. You get between $200-$400 for the heads on E-bay and could get Eddys heads new for $1300 but I would keep those heads if I was you. $10,000 for a motor is nuts-unless you have money to burn and if you did I sure would not get a Mopar factory motor. Have a good machine make it up.
 
Isn't 10.5 to one a little high for today's gas? I notice most crate motors use about 9 to one & probably have a better chamber design. Also, what about valve & seat problems with unleaded gas?
 
Yes its a little high but 10.5 was with .020 head gaskets. Today most are .040 thick and you can buy .060 thick one too. Each .020 will lower the compression about a half of point so if you use the .060 ones that give you 9.5-1 compression. It might even be ok with 10-1 but yeah thats pushing it. If the timing is back off a few degress it should be fine. The only heads you find today that are better are Eddy's or Indys heads. Those heads might be for unleaded gas, I am not sure. Think by 1972 the heads were made for unleaded gas but you could have harden seats put in I guess to be safe. You know if you are to spend money on head work maybe you should get Eddy heads. They love those 10-5 pistons cause aluminum heads knock a full point of compession down. Well not really but if 9-1 compression with iron heads are max for the type of gas being used then aluminum heads are 10-1 max for the same gas. Something about heat loss is why. Eddy heads have harden seats too. I would call or look at Indy heads, they help you out. They have everything too from 318 heads to the heads you have and also Eddy's and of course Indy's, but those are like $3000! Its www.aeroheadracing.com its a part of Indy heads company.
 
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