Moparts
Critique my 340 build please ........
Posted By: RebelDart
Critique my 340 build please ........ - 08/08/08 06:59 PM
The only machine shop in my vicinity aren't the most talkative bunch. I need some insight before we button this thing up. Any thoughts or concerns would be appreciated :
Bottom end:
68 340 .030 over
TRW L-2316 forged flat top w/ 8cc valve relief, .030 above deck (shouldn't be an issue from what I'm being told)
Stock rods w ARP's
Stock forged crank
Lunati 60403 @ .050 IN/EX: 226/234;Lift IN/EX: .494"/.513"
Worked X heads flow around 240 @ .050, 75 cc
With current head gasket I calculated 9.2:1 compression (not sure how to get more if needed)
Airgap and 670 Street Avenger
TTI headers
3500 stall
3:91 gear
Look okay ? I do have an objective eventually which would be mid-low 12's.
Thanks all.
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Posted By: UCUDANT
Re: Critique my 340 build please ........ - 08/08/08 07:11 PM
If the pistons are .030 out of the hole I think your compression might be higher than you calculated. I think a 70 340 piston was .018 out of the hole and compression is rated over 10 to 1.
How big are the relief's in those pistons? Heads might be 72cc
Posted By: rdrmod6
Re: Critique my 340 build please ........ - 08/08/08 07:17 PM
You had better check your clearance between the cylinder head and the piston. I think you might have problems at the spark plug side of the chamber, also if the chambers are stock there is an eybrow shaped part of the casting around the intake valve that protrudes into the chamber that could hit. The final check of the clearance has always been to try and turn the engine over with no head gaskets in place, then if you use a ,040 gasket you will be in the ballpark. If your pistons are .030 down in the cylinder instead of .030 out you should be fine.
Posted By: RebelDart
Re: Critique my 340 build please ........ - 08/08/08 07:22 PM
We will be checking ... pistons are .030 above. Chamber volume is 75cc. If all clears I'm happy except for compression being lower than I want (?)
Posted By: goldmember
Re: Critique my 340 build please ........ - 08/08/08 07:31 PM
Sounds like a nice streetable combo.My experience is with 360 and larger small blocks,I don't see any problem with your plan.I'd consider having the heads milled to get the compression up a bit,if the chambers are really 75cc. What machine shop are you using?
Posted By: RebelDart
Re: Critique my 340 build please ........ - 08/08/08 07:36 PM
Called Tachyon Performance - I get the sense I'm "bothering" them. Unless I'm dropping off something or picking up and handing them my Visa - you know. I'm trying to do as much myself as possible. Didn't know if I should shoot for higher compression or not for my goals - and don't know how I'd achieve with the current config (pistons out the top).
Posted By: goldmember
Re: Critique my 340 build please ........ - 08/08/08 07:38 PM
Are you going to assemble it yourself?
Posted By: RebelDart
Re: Critique my 340 build please ........ - 08/08/08 07:47 PM
If I can get up the nerve , I'd like to
Posted By: RebelDart
Re: Critique my 340 build please ........ - 08/08/08 07:48 PM
Or I can bring to G'ville and you can evaluate in person !
Posted By: AdamR
Re: Critique my 340 build please ........ - 08/08/08 09:22 PM
Like said, Check the piston to head clearance. Its to tight. Compression could be better but could be worse. It should run hard.
Posted By: 69Cuda340S
Re: Critique my 340 build please ........ - 08/08/08 09:22 PM
I would think you would want compression in the 9.5:1 range. Issue is piston to head clearance. Measure how deep the relief is in the head to get an idea of how thin a gasket you can use. Bolt it together and check piston to head clearance by removing rod cap at TDC and measuring how far up piston travels until it hits the head.
Then if that works out degree in cam and check piston to valve clearance.
Posted By: UCUDANT
Re: Critique my 340 build please ........ - 08/08/08 09:26 PM
You can use some real soft clay on the piston and cycle it with the valves/cam installed to check clearance.
I run KB 243's .019 out of the hole and some stock J heads with a 284/284 MP cam
Posted By: 340727dart
Re: Critique my 340 build please ........ - 08/08/08 11:01 PM
If you're using a head gasket with 0.039" compressed thickness, you should still have plenty of piston to head clearance with the iron heads.
IIRC, the chambers are about 0.100" or more deep.
I've got that same cam in my 340 and love it.
My pistons are 0.020" above the deck and I have plenty of piston to valve clearance. But the KB pistons have pretty generous valve reliefs.
That's the clearance you need to be concerned about.
Posted By: dd340
Re: Critique my 340 build please ........ - 08/08/08 11:23 PM
you might need more cam for mid to low 12's
Posted By: RapidRobert
Re: Critique my 340 build please ........ - 08/08/08 11:52 PM
1st need ALL measurements: piston amt in/out of hole(deck height),amt(cc's) of piston dome, cc's of valve reliefs, CC's of heads,depth of open chamber recesses. So you can machine to achieve .035-040 quench & the CR you need(& 9.2 isn't enough) which will go with determining what head gasket you need & wondering what octane FUEL will you be useing? Thats too bad they are not being customer friendly but unfortunately that is all too common. Stay with it,you want this thing right.
Posted By: west
Re: Critique my 340 build please ........ - 08/09/08 12:26 AM
Quote:
If the pistons are .030 out of the hole I think your compression might be higher than you calculated. I think a 70 340 piston was .018 out of the hole and compression is rated over 10 to 1.
How big are the relief's in those pistons? Heads might be 72cc
i'm not an engine wizzard by any means but this is what i was thinking half way throuh your post.
Posted By: RebelDart
Re: Critique my 340 build please ........ - 08/09/08 01:42 AM
I used one of the on-line calculators, pretty self explanatory - chambers cc'd by the shop @ 75cc's , valve reliefs are 7.5 cc's The calculators have a field for deck height and state to use a negative number for positive deck height, etc. I'm fairly certain I'm accurate in regards to these specs and using the calculator correctly. Any old-schoolers may have a different method.
Posted By: RebelDart
Re: Critique my 340 build please ........ - 08/09/08 01:56 AM
Quote:
If you're using a head gasket with 0.039" compressed thickness, you should still have plenty of piston to head clearance with the iron heads.
IIRC, the chambers are about 0.100" or more deep.
I've got that same cam in my 340 and love it.
My pistons are 0.020" above the deck and I have plenty of piston to valve clearance. But the KB pistons have pretty generous valve reliefs.
That's the clearance you need to be concerned about.
This is what we're supposing as well. The TRW's we're using L2316F)have a 7.5cc relief. If I have to shave - so be it, but I need the compression so not sure the best route to take.
Posted By: dart6
Re: Critique my 340 build please ........ - 08/09/08 03:50 AM
i get 9.362 cr with 4.070 bore and .039 gasket
Posted By: RapidRobert
Re: Critique my 340 build please ........ - 08/09/08 04:17 AM
[quote The TRW's we're using L2316F)have a 7.5cc relief. If I have to shave - so be it, but I need the compression so not sure the best route to take.
You will be milling the heads & probably not the dome. this calculator is very nice. http://kb-silvolite.com/calc.php?
Posted By: Prince_Valiant
Re: Critique my 340 build please ........ - 08/09/08 05:57 AM
Without getting into the specifics of your clearance or lack there-of (I think you'll be fine, with decent compression to boot), I'll comment on your overal build:
Need more cam for the head flow you've got, and you need more carb.
As it sits, it should be a good safe mid/perhaps low 13 second car...provided you have good spark/timing.
However, at first I'm a little disappointed in the flow of the "worked" heads...if it's minor work, then that's good...but if they were going through and porting the crap out of them, then I at least hope that it was on a VERY pessimistic bench. With that cam, I think you would have wanted flow in the 270-280 cfm range. With the flow you've got, I'd want at a minimum the next step up, but likely something in the 240 @ .050, .530+ lift range...or better yet, a roller cam with similar duration @ .050 as your current cam.
Also I'd want probably a good Holley 700-750 DP for the best performance at the track.
All in all, as it sits, it's a great street-strip combo, no doubt.
Posted By: 451Mopar
Re: Critique my 340 build please ........ - 08/09/08 07:05 AM
Here is the numbers I used:
Block Deck Height = 9.600"
Bore = 4.070" (0.030 over)
Stroke = 3.310"
Rod Length = 6.123"
Piston Height = 1.840" (TRW 2316)
Valve relief volume = 7.5cc (seems big, is this right?)
Est. Head Gasket Volume (0.040" thick) = 9cc
Cylinder Head Volume = 75cc
If the engine is the stock 9.60" deck height the piston should only be 0.018" above the deck, and the compression ratio calculates to 9.05:1
If the decks have been milled 0.012 to where the piston is 0.030" above deck, the compression calculates to 9.29:1
If you use a 0.020" head gasket (estimate 4.5cc) or mill the heads 0.020" the compression should be approximatly 9.76:1
I don't think the positive piston height will be a problem, but check the head chamber height to be sure. On my 360 heads the chamber was recessed 0.070"+.
The combination looks good for a dual purpose vehicle, but most likely mid to high 13's?
I don't know the cars weight, and the track altitude. Anyhow, to run 12's you will probbably need more cam and compression?
Posted By: AdamR
Re: Critique my 340 build please ........ - 08/09/08 10:55 AM
Quote:
Quote:
If the pistons are .030 out of the hole I think your compression might be higher than you calculated. I think a 70 340 piston was .018 out of the hole and compression is rated over 10 to 1.
How big are the relief's in those pistons? Heads might be 72cc
i'm not an engine wizzard by any means but this is what i was thinking half way throuh your post.
That is correct but the actual compression of a stock 340 is lower the 10:1.
Posted By: 69Cuda340S
Re: Critique my 340 build please ........ - 08/09/08 01:24 PM
Actual compression of a stock 340 ('68-'71) is around 9.5:1.
Posted By: RobX4406
Re: Critique my 340 build please ........ - 08/09/08 04:35 PM
It's a low 13's-high 12's combo if you can get it to hook. My car is similar with stock heads, less cam, and runs 102 in the 1/4.
The carb will be the choke point up top. Not near enough IMO.
Posted By: RebelDart
Re: Critique my 340 build please ........ - 08/09/08 08:01 PM
Thanks everyone ... I've got two carbs to choose from in the garage - 670 or 770 Avengers. Cam I could probably exchange at Summit for next step up Lunati (?). 68 motor with forged crank, these pistons are forged as well, i was thinking ahead as I may spray with one sole (albeit childish)purpose in mind .... beat my buddies 93 Mustang Cobra which runs 12.8's or so. I've got a point to prove (I know - grow up your pushing 50 bro' !) Anyway all the help is appreciated. Heads were not worked extensively, I got about what I paid for - I guess.
Posted By: AverageJoe
Re: Critique my 340 build please ........ - 08/10/08 01:44 PM
I believe I would step up to the 770 - or sell both for a double-pumper ! Cam - I won't suggest, if Summit will let you exchange, you'll be limited to a stock grind (which is fine for your purpose). I'd wait for others to suggest a cam ..... As far as the childish issue of wanting to one-up your buddy - isn't that what makes us tick in the first place ?
Posted By: AdamR
Re: Critique my 340 build please ........ - 08/10/08 02:29 PM
I think the 670 will be enough carb but no reason not to try the 770 if you have it also.
The cam is enough for a good low 13 second car. If you want low 12s you will need more gear and cm.
Posted By: wkroncke17
Re: Critique my 340 build please ........ - 08/10/08 03:09 PM
You have plenty of Cam,and use the 770...its way better to lean out a bigger carb than richen up a small one. My '72 Demon had a stock bottom end 360 w/MP .484/284 Cam,Holley strip dom intake,and Holley 750,3800 stall, 4:56 gear,SS springs,9x28 slicks and ran a best of 12.28 @ 108 mph. Now I did race it every weekend,so I had a lot of time to fine tune it.
Sounds like you want to be a little more streetable,so don't go crazy with the gear,3:91 sounds good,and don't be afraid to run SS springs on the street,they'll be just fine. You should be able to dip into the 12's no problem!
I don't like the way your machinist sounds,you're paying him good money for hopefully a good finished product,Don't be afraid to get info out of him.
I hope it all turns out well in the end!!
Best of luck!!
Wally.
Posted By: Prince_Valiant
Re: Critique my 340 build please ........ - 08/10/08 04:08 PM
The MP 484 cam is a bigger cam than that voodoo "268" cam by a healthy amount...even if it doesn't have the lift the the voodoo has.
241 @ .050 w/ 108 LSA for the MP vs 226 w/ 110 LSA for the voodoo...
The "voodoo" series has two cams in it's line-up, both available from summit that could do the job nicely...both MIGHT hit your goals, one certainly will.
The 60404 features 234/242 @ .050, .513/.533 lift, 110 LSA...with the mild porting, this cam stands a good chance of getting your ET goals provided the chassis is up to snuff...should be fine with your torque converter. With the aggressive ramps, it's should be comparable to the MP 284/484 cam in terms of power, but with better vacuum/idle, wider power band.
The 60405 will DEFINITELY get your goal (and perhaps more) and should have comparable if slightly better vacuum and idle to the MP 284/484 cam; but it'll make a healthy bit more power...specs are similar at 241/252 @ .050 on the split pattern cam, but with a wider 110 degree LSA (overlap is still greater due to the large exhaust duration vs the single pattern MP unit). Where this cam shines over the MP though is it's ramps...very aggressive (not the most aggressive; racer brown and hughes offer better...but the voodoo is probably the best you can exchange for at summit) featuring .533/.552. It's lift @ .300/.35/.400/.450 should all be significantly better than the MP unit as well...making the cam seem bigger w/o the all the poor idle/driveability of the MUCH bigger cams.
The caveat is, what springs are you running and are they suitable for either cam?
Posted By: AdamR
Re: Critique my 340 build please ........ - 08/10/08 04:54 PM
I would leave the combo alone and spray it with a 150 shot. If you go swapping to a bigger cam now your going to need more head work, More compression, More gearing, different valve springs, ect.
You have a real nice, strong street car right now.
Posted By: RebelDart
Re: Critique my 340 build please ........ - 08/10/08 05:21 PM
Valve springs installed -
Part Number: CCA-930-1
Number of Springs Per Valve: Dual
Outside Diameter of Outer Spring (in): 1.550 in.
Coil Bind Height (in): 1.160 in.
Damper Spring Included: Yes
Spring Rate (lbs/in): 354 lbs./in.
Inside Diameter of Outer Spring (in): 1.150 in.
Inside Diameter of Inner Spring (in): 0.795 in.
Valve Spring Style: Standard
AdamR - I'm leaning towards your suggestion - I need to run low 12's maybe a hlf dozen times, with nitrous is fine if that'll be my best chance (no shame here as the Mustang sprays as well)Already running superstock springs - 3/4 relocation kit so I'm thinking on that fatefull weekend I'll borrow the rear slicks/wheels (have a source) switch rear gear (find a used set) and use the nitrous. I beleive I could get a few low 12 runs if all plays out in my favor. After I've proven my childish point - my life can go on (set car back up for street/cruise-ins) Sound good? Also - I will have a few trips to the track to dial in before our grudge match.
Posted By: AdamR
Re: Critique my 340 build please ........ - 08/10/08 06:41 PM
With the juice you wont need anymore gear. 391s will work.
Posted By: 340727dart
Re: Critique my 340 build please ........ - 08/10/08 08:51 PM
Just curious, why did you use Comp springs with the Lunati cam?
Those springs have a 1.900" installed height.
The recommended springs are Lunati P/N 73949. Their installed height is 1.650".
Posted By: RebelDart
Re: Critique my 340 build please ........ - 08/11/08 12:59 AM
These are what the shop installed - I told them what cam I was planning on using, they said these Comp springs would be fine - charged me 90.00 parts/(mostly)labor,. Should I change 'em out ?
Posted By: goldmember
Re: Critique my 340 build please ........ - 08/11/08 01:47 AM
Since the stock installed height is MUCH shorter than 1.9" I would investigate this further. The Voodoo hyd cams are designed by a friend of mine,I'd go solid lifter cam or PM me for more info.
Posted By: 69Cuda340S
Re: Critique my 340 build please ........ - 08/11/08 01:59 AM
Posted By: goldmember
Re: Critique my 340 build please ........ - 08/11/08 02:09 AM
OK?
Posted By: 340727dart
Re: Critique my 340 build please ........ - 08/11/08 02:25 AM
Quote:
These are what the shop installed - I told them what cam I was planning on using, they said these Comp springs would be fine - charged me 90.00 parts/(mostly)labor,. Should I change 'em out ?
Let me guess, the shop you used normally does chebby engines, and they figured what works in a chebby will work in a Mopar.
I went through the same thing. I was never happy with the way the engine revved.
Even after taking the correct springs to the guy he used another spring.
I ended up putting the correct springs on the engine and it really helped.
Posted By: RebelDart
Re: Critique my 340 build please ........ - 08/11/08 01:56 PM
Quote:
Quote:
These are what the shop installed - I told them what cam I was planning on using, they said these Comp springs would be fine - charged me 90.00 parts/(mostly)labor,. Should I change 'em out ?
Let me guess, the shop you used normally does chebby engines, and they figured what works in a chebby will work in a Mopar.
I went through the same thing. I was never happy with the way the engine revved.
Even after taking the correct springs to the guy he used another spring.
I ended up putting the correct springs on the engine and it really helped.
You are correct, sir. I'd rather not shell out another 100.00 on springs ...
Posted By: Anonymous
Re: Critique my 340 build please ........ - 08/11/08 05:26 PM
Quote:
It's a low 13's-high 12's combo if you can get it to hook. My car is similar with stock heads, less cam, and runs 102 in the 1/4.
The carb will be the choke point up top. Not near enough IMO.
naw, no way 12's. the cams too small. compression too low. Need at least 9.7:1 and a good 284/484 (something around 240 @.050). mill the heads to up the compression
Posted By: AverageJoe
Re: Critique my 340 build please ........ - 08/11/08 06:34 PM
Quote:
Quote:
It's a low 13's-high 12's combo if you can get it to hook. My car is similar with stock heads, less cam, and runs 102 in the 1/4.
The carb will be the choke point up top. Not near enough IMO.
naw, no way 12's. the cams too small. compression too low. Need at least 9.7:1 and a good 284/484 (something around 240 @.050). mill the heads to up the compression
Lots of opinions here .... even if he goes with the 150 shot of nitrous ?
Posted By: RobX4406
Re: Critique my 340 build please ........ - 08/11/08 11:27 PM
Quote:
Quote:
Quote:
It's a low 13's-high 12's combo if you can get it to hook. My car is similar with stock heads, less cam, and runs 102 in the 1/4.
The carb will be the choke point up top. Not near enough IMO.
naw, no way 12's. the cams too small. compression too low. Need at least 9.7:1 and a good 284/484 (something around 240 @.050). mill the heads to up the compression
Lots of opinions here .... even if he goes with the 150 shot of nitrous ?
Tuned right that will get into the 12.90. Don't need a lot of motor to go that fast if it hooks and runs right. It might run high 11's on juice.
So I guess a 340 with 3.91's, short tires and a 214*/224* at .050 cam can't run low 13's at over 101? I clearly did something wrong. 
The listed engine is capable of about 380-400hp, maybe a smidge more, if the carb is changed to a 750 or better. That's enough HP to push a 3200-3300# car to a 13.00 or slightly better.
Don't need huge cams with lots of duration to get a car to run low 13's. He won't get near the low 12's without juice, and would need to up the cam/compression/carb/gear to get there on motor.
Posted By: AverageJoe
Re: Critique my 340 build please ........ - 08/12/08 01:18 AM
My thoughts as well