Engine question

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mopar_t

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I'm getting ready to freshen up the 340 in my dart and have a few questions. First it's a stock bore and stroke. I plan on installing a set of Edelbrock Performer RPM cylinder heads pn.60779 Comp cams pn.CL20-672-4 .508 inch lift cam. and a Weiand Stealth intake. My question is what carburetor (brand and cfm) would be best for this set-up, and is this going to be a solid set-up? I'm running 391 gears and plan on having fun on the street and occasional track time.
 
mopar_t said:
I'm getting ready to freshen up the 340 in my dart and have a few questions. First it's a stock bore and stroke. I plan on installing a set of Edelbrock Performer RPM cylinder heads pn.60779 Comp cams pn.CL20-672-4 .508 inch lift cam. and a Weiand Stealth intake. My question is what carburetor (brand and cfm) would be best for this set-up, and is this going to be a solid set-up? I'm running 391 gears and plan on having fun on the street and occasional track time.
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Any 4-bbl, cuz at 292/299/108 and 3.91s, you'll be either; spinning, or on the primaries, or shutting down early for the speed limit; most of the time. Heck you could run a 2bbl on the street just fine.Unless you are running a 2200TC, that ain't gonna work so good.
 
I see 'stock bore and stroke'. Just make sure these are not original or original-like pistons. Those stick typically .018" ABOVE the block deck at TDC, and with a standard Felpro kit heads gasket, those pistons will end up being .030" or so from the bottom of the closed section of the head chambers; that is too close, and may well eventually end up with some piston-to-head contact, especially with engine wear, which allows the pistons to rock a bit more in the bores.

Compression would end up around 10:1 and DCR at 8 with that cam, depending on the exact pistons being used.
 
nm9stheham said:
I see 'stock bore and stroke'. Just make sure these are not original or original-like pistons. Those stick typically .018" ABOVE the block deck at TDC, and with a standard Felpro kit heads gasket, those pistons will end up being .030" or so from the bottom of the closed section of the head chambers; that is too close, and may well eventually end up with some piston-to-head contact, especially with engine wear, which allows the pistons to rock a bit more in the bores.

Compression would end up around 10:1 and DCR at 8 with that cam, depending on the exact pistons being used.
Click to expand...


.030 is not a problem.
 
nm9stheham said:
I see 'stock bore and stroke'. Just make sure these are not original or original-like pistons. Those stick typically .018" ABOVE the block deck at TDC, and with a standard Felpro kit heads gasket, those pistons will end up being .030" or so from the bottom of the closed section of the head chambers; that is too close, and may well eventually end up with some piston-to-head contact, especially with engine wear, which allows the pistons to rock a bit more in the bores.
Compression would end up around 10:1 and DCR at 8 with that cam, depending on the exact pistons being used.
Click to expand...

You could be right.
I have been running the KB107s, stock rods, and aluminum Eddies since the beginning, 1999.
I initially ran a zero-deck and .028Q for the first season, until I had enough of the 292/108 cam. At teardown that winter,(yr 2000) I found the gasket crawling into the valley, but there was no evidence of any piston to head contact.
I installed a 223/230/110 cam and swapped to the .039 FelPros for a Q of .039. That was my forever-combo; I thought.
Then about 3.5 years later that 223cam went flat.
I replaced it with one-size bigger a 230/237/110 cam and trimmed the decks another bit (cuz they were not square enough the first time)and ended up at .034Q;(I think that spec was plus/minus .0015). I also opened up the skirt gap to .003 at this time , cuz I had been having issues with hot-starting, running at 205*F.Then I re-installed the by-now well-used FelPros. And that is how it has remained ever since.
Up here those FelPros are close to $100 a pair delivered. Being a broke-azz-Dad of three teenage kids at the time,I decided to reuse them to see what would happen. I mean, I was freshening the engine every winter anyway.Those FelPros kept going and going and going.... they have been very good to me,lol. Worth every penny I paid for them,lol.

So bottom line is .034 has been working for me since about year 2004; and .028 worked for at least one summer on a fresh build. It might have been good longer, with the better gaskets; but I wasna gonna use .028s again.
But you may be right.
I was more concerned about valve to piston contact. Running .579 exhaust lift into the KB factory eyebrows,with the 237exhaust duration cam, and hitting 7000 on a regular basis. I measured it but have forgotten the clearance. It would seem that the oem pockets are deep enough,lol.
IIRC all of these combos have run right around 185psi cylinder pressure, on the very same MacTools gauge.
Between the tight-enough-for-me quench and aluminum heads, she has always run on 87E10 without complaint.
That's my tight-Q story
 
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MOPAROFFICIAL said:
.030 is not a problem.
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My concerns with .030" for this particular situation are:
  • If the bores are stock and worn, and allow the pistons to rock some.
  • Deck height variations and other tolerances like rods and crank pins might pop 1-2 pistons out more than .018"
I don't know how closely all of this will be checked in this build.
 
do double check the quench, there are thicker gaskets or shims if you have less than .030 check all four corners
still a much better choice than an open chamber head
have someone check the concentricity on those heads and the guides
but they have been better lately
 
nm9stheham said:
I see 'stock bore and stroke'. Just make sure these are not original or original-like pistons. Those stick typically .018" ABOVE the block deck at TDC, and with a standard Felpro kit heads gasket, those pistons will end up being .030" or so from the bottom of the closed section of the head chambers; that is too close, and may well eventually end up with some piston-to-head contact, especially with engine wear, which allows the pistons to rock a bit more in the bores.

Compression would end up around 10:1 and DCR at 8 with that cam, depending on the exact pistons being used.
Click to expand...
I'm fairly certain the bottom end is factory. Felpro says the headgasket is between .047 and .057 inch thick out of the package. What rocker arms and pushrods should I be using?
 
stock rockers are fine with correct length pushrods
273 adjustable are better- different pushrods
find out if the cam is on a stock base circle
if you are thinking roller tip rockers do a search and read the 4 articles on the B3 website

.010 variation in the thickness tell fel pro they have to do better best to measure a used one or did they change materiel
 
AJ/FormS said:
Any 4-bbl, cuz at 292/299/108 and 3.91s, you'll be either; spinning, or on the primaries, or shutting down early for the speed limit; most of the time. Heck you could run a 2bbl on the street just fine.Unless you are running a 2200TC, that ain't gonna work so good.
Click to expand...
Oh my! What a crap post
 
Wyrmrider said:
stock rockers are fine with correct length pushrods
273 adjustable are better- different pushrods
find out if the cam is on a stock base circle
if you are thinking roller tip rockers do a search and read the 4 articles on the B3 website

.010 variation in the thickness tell fel pro they have to do better best to measure a used one or did they change materiel
Click to expand...

The cam is a Comp Cam CL20-672-4. The heads, cam and intake I'm getting a good deal on. That's why I'm asking these questions. The cam is new in the box. The heads only have a couple hundred miles on them. I'm just wanting to be sure this will work and be a solid reliable set up.
 
Well that is the whole point of discussing the piston=to head clearance. If the Felpro gasket ends up being .047" and the pistons are ALL .018" above deck, then you would have .031" clearance between pistons and heads. BUUT:
  • You have an old engine, and with wear, then pistons may stick up higher and now you have reduced clearance.
  • Not all rods are the correct length, and if 1 or more are long then that is also reduces piston to valve clearance
Clearances like .031" are OK IF everything is well set up and each dimension measured. MoparOfficial puts everything accurately to the proper dimensions. You don't have new parts and I'm going to guess that none of these things have been accurately measured. In that case, no way can I recommend that you use run anything like this tight piston-to-head clearance. IMHO, a KNOWN thicker had gasket in the .055" to .060" thick range is needed to put these heads on this old short block. Assuming it has the stock early 340 pistons.

What year 340 is this?

BTW, how well is this engine running now? Have you done a compression check on it? The reason to ask is that this is a pretty big cam, that is only gonna run at high RPM's......

Also, is the original torque converter in the car?
 
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