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Critique my 340 build please ........ #101515
08/08/08 02:59 PM 08/08/08 02:59 PM
Joined: Mar 2003
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North Florida
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RebelDart Offline OP
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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.
Re: Critique my 340 build please ........ [Re: RebelDart] #101516
08/08/08 03:11 PM 08/08/08 03:11 PM
Joined: Jan 2003
Posts: 8,128
New Mexico
UCUDANT Offline
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New Mexico
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
Re: Critique my 340 build please ........ [Re: RebelDart] #101517
08/08/08 03:17 PM 08/08/08 03:17 PM
Joined: Aug 2007
Posts: 74
Haysville, Kansas
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rdrmod6 Offline
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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.
Re: Critique my 340 build please ........ [Re: rdrmod6] #101518
08/08/08 03:22 PM 08/08/08 03:22 PM
Joined: Mar 2003
Posts: 756
North Florida
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RebelDart Offline OP
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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 (?)
Re: Critique my 340 build please ........ [Re: RebelDart] #101519
08/08/08 03:31 PM 08/08/08 03:31 PM
Joined: Feb 2004
Posts: 4,501
Gainesville,FL
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goldmember Offline
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Gainesville,FL
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?

Last edited by goldmember; 08/08/08 03:36 PM.
Re: Critique my 340 build please ........ [Re: goldmember] #101520
08/08/08 03:36 PM 08/08/08 03:36 PM
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North Florida
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RebelDart Offline OP
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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).
Re: Critique my 340 build please ........ [Re: RebelDart] #101521
08/08/08 03:38 PM 08/08/08 03:38 PM
Joined: Feb 2004
Posts: 4,501
Gainesville,FL
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goldmember Offline
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Are you going to assemble it yourself?
Re: Critique my 340 build please ........ [Re: goldmember] #101522
08/08/08 03:47 PM 08/08/08 03:47 PM
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Posts: 756
North Florida
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RebelDart Offline OP
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If I can get up the nerve , I'd like to
Re: Critique my 340 build please ........ [Re: RebelDart] #101523
08/08/08 03:48 PM 08/08/08 03:48 PM
Joined: Mar 2003
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North Florida
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RebelDart Offline OP
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Or I can bring to G'ville and you can evaluate in person !
Re: Critique my 340 build please ........ [Re: RebelDart] #101524
08/08/08 05:22 PM 08/08/08 05:22 PM
Joined: Jan 2003
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Bethel Ct
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AdamR Offline
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Like said, Check the piston to head clearance. Its to tight. Compression could be better but could be worse. It should run hard.
Re: Critique my 340 build please ........ [Re: RebelDart] #101525
08/08/08 05:22 PM 08/08/08 05:22 PM
Joined: Aug 2004
Posts: 3,333
MARYLAND
69Cuda340S Offline
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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.
Re: Critique my 340 build please ........ [Re: 69Cuda340S] #101526
08/08/08 05:26 PM 08/08/08 05:26 PM
Joined: Jan 2003
Posts: 8,128
New Mexico
UCUDANT Offline
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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
Re: Critique my 340 build please ........ [Re: RebelDart] #101527
08/08/08 07:01 PM 08/08/08 07:01 PM
Joined: Jan 2003
Posts: 8,144
Arkansas
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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.

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Re: Critique my 340 build please ........ [Re: RebelDart] #101528
08/08/08 07:23 PM 08/08/08 07:23 PM
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Ottawa, ontario
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dd340 Offline
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you might need more cam for mid to low 12's
Re: Critique my 340 build please ........ [Re: RebelDart] #101529
08/08/08 07:52 PM 08/08/08 07:52 PM
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Lincoln Nebraska
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RapidRobert Offline
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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.

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Re: Critique my 340 build please ........ [Re: UCUDANT] #101530
08/08/08 08:26 PM 08/08/08 08:26 PM
Joined: Apr 2007
Posts: 4,233
petaluma,ca. u.s.a.
west Offline
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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.
Re: Critique my 340 build please ........ [Re: west] #101531
08/08/08 09:42 PM 08/08/08 09:42 PM
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North Florida
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RebelDart Offline OP
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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.
Re: Critique my 340 build please ........ [Re: 340727dart] #101532
08/08/08 09:56 PM 08/08/08 09:56 PM
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Posts: 756
North Florida
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RebelDart Offline OP
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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.

Last edited by RebelDart; 08/08/08 10:48 PM.
Re: Critique my 340 build please ........ [Re: RebelDart] #101533
08/08/08 11:50 PM 08/08/08 11:50 PM
Joined: Jul 2007
Posts: 161
New Zealand
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dart6 Offline
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i get 9.362 cr with 4.070 bore and .039 gasket
Re: Critique my 340 build please ........ [Re: RebelDart] #101534
08/09/08 12:17 AM 08/09/08 12:17 AM
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Lincoln Nebraska
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RapidRobert Offline
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[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?

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