need the opinions of a few 340 guys

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71gtdart

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long story short, I have one heck of a nice duster sitting in the shop without an engine. I started the 340 build and quit on it to finish up my Dart race car about 2 years ago.

well, now that its done I am going back to the duster. I have kinda changed plans for the car, so a change in direction may be needed on the engine. heres what it has so far.

1968 340 thats bored .030 over
rotating assembly is balanced
Speed Pro forged flat top pistons (coated)
Hughs Whiplash cam
stock rods and stock forged crank
Comp double row timing set
Melling HV oil pump
mopar performance windage tray

thats where its at at the moment.

now the kicker. I told the machine shop that I wanted it at zero deck height. when I went to pick it all up the guy told me that the block was so far out that he really had to cut it to get the deck square. he said the pistons may be out of the hole a little. no big deal, I thought. I will just make it up on the head gasket, and I have open chamber J heads anyway. If I have to mix a little race fuel in then its fine.

I put it together and find that this baby is rocking with a set of pistons that are .021'' out of the hole!!!!!!!

I would like to keep this thing around 10.5-1 compression. I can have the pistons fly cut if I need to or use head gasket thickness.

on with the questions

I now would like to do more of a street strip build that will see 70% street. I know I need to change to a different cam. I have a set of J heads with 1.88 intake valves that I have not taken to the shop yet. I would like for the car to be streetable and run low 8's to high 7's in the eighth mile. I'm having my 727 built, and the car has a Powertrax locker with 3.91 gears.

from where the engine is at now where would you guys go with it from here and what parts/work do you think it will take for my power goals. I have a lot of experience with big block combos and stroked small blocks. not so much with stock stroke smallys.

thanks to all in advance.
 
The early 340s all had a positive deck height stock. It's perfectly normal.
 
Block if fine use the better felpro 1213 ?? I think head gaskets that compress to .038 or so. Stick some 2.02 valves in the J's and do a fair amount of bowl and port work. Air gap, ld340, or maybe a torker II intake with a 750 holley should work.
 
You will be fine.

Ok

With your piston sticking up .021", you have a negative 4.5 cc

You will need a total of 74.3 cc for clearance volume.

Clearance volume is the; Volume of the piston + volume of the head gasket + volume of the combustion chamber.

For a .040" fel pro head gasket the volume is 8.5 cc.
volume above the piston is - 4.5 cc (because it sticks up)

Now you subtract.

74.3 cc + 4.5 cc - 8.5 cc = 70.3 cc


So if you use a Fel-Pro .040" head gasket with a volume of 8.5 cc, you will need your heads to have a 70.3 cc combustion chamber to reach 10.5 compression.

Most 340/360 heads start at 72 cc. You need 70.3 cc for your compression. So if your heads are "stock/never decked" at 72 cc, you will want the head guy to mill them down to 70.3 cc, or take 1.7 cc out with milling your heads to get 10.5 compression.

Have your heads cc'ed to see where they are at. Your target is 70.3 for 10.5 compression and a .040" Fel-Pro head gasket.
 
most agree that for the street about 9.5 is ideal,which is probably what you have now
 
9.5:1 is plenty to run 7/8 in the 1/8. stick with the 1.88 for port velocity, bowl blend, cc head, and select cam (approx [email protected]) and head gasket to achieve 8.2 dynamic comp ratio. good converter with the 3.91 and you have a drivable street/strip car.
 
stick with the 1.88 for port velocity, bowl blend, cc head,
Click to expand...

i dont agree. i'd put zero money into the old heads... get some eddie rpm's have a shop check all the clearances. go zoom. pep boys carries those heads. they have different models, i think the standard 340 model has 65cc chambers. but a machine shop could get it all set for you , flycutting pistons or whatever to get your comp ratio correct.

lose pounds + better flow = win

if you have real big dollars you can get mopar W series heads they have iron and aluminum but you are talkin' bucks there

no way in hell i'd spend a bunch of good dollars on 1.88 j heads. if you were building a factory original show car maybe
 
i was just gonna use the J heads cause i had them. I normally use the RHS Indy iron heads.
 
Sounds like you already have a drag car and are looking for a quick street/strip for fun. Nothing wrong with j heads. A good valve job, backcut intake valves, replace exhaust guides costs 300 where I'm from. eddys are$$ and not needed for what your looking to do IMO.
 
I'd use what you have - keep tabs on the chamber size and I'd upgrade to 2.02/1.60s. To help with chamber volume go with stock tulips. I personally want lower static with open chamber iron. I'd keep the chambers big and run a thicker (Victor stock types are a little thicker - around .053 - than Felpros IIRC). You have no quench so just build lower static and then put a street-type cam in it.
 
thanks for all the opinions so far guys.

little update.

I just spoke with Clements Racing in Spartanburg SC. if you are familiar with Nascar then you may know his son Jeremy Clements who drives in the Nationwide series.

they told me for around $800-$1,000 I could get the following:

heads cleaned
checked for cracks
guides
do the valves and seats
a nice amount of bowl work
and have my springs installed and ready to bolt on.


I thought that was a fair deal for what I would be getting. however, what do you guys think? I'm not sure that for the money I can get a better head with better performance.

thoughts?
 
Well it's not an out of line price, if there is a fair amount of bowl work. Keep in mind most guys are not going to run a set of Eddy's or any other head without a checkup, I here the Eddy's need a fair amount of touch up work out of the box.
 
EL5DEMON340 said:
Well it's not an out of line price, if there is a fair amount of bowl work. Keep in mind most guys are not going to run a set of Eddy's or any other head without a checkup, I here the Eddy's need a fair amount of touch up work out of the box.
Click to expand...


I've always heard that as well.

have heard about valve guides seizing more than once on out of the box "Brocks"
 
Yup - that's what it costs. I'd also have them cut the spring seats for dual springs and cut the guides down for positive springs if that's not included. You might also want them to cc the chambers and mill the gasket surfaces. I'd expect to pay between $1200-$1400 depedning on the work and parts for a good set of non-ported iron heads.
 
60779 is the eddy closed chamber alum heads
http://www.summitracing.com/parts/edl-60779

$779.50 each so that's about $1560 for the pair

i got eddy heads for my low deck 400, only thing that needed to be done was they slightly milled the heads to make everything match up with my intake properly. and cut to fit pushrods. my block was zero decked. i guess i just was lucky, the eddy heads didnt need "rework" like everyone says.

again there is no way in hell i would have spent $1200 or $1400 for reworked ported bowl blended whatever iron heads instead of $1500 for what i got.

MAYBE if they were raised port iron heads which would outflow the eddies. then it would be worth it, if you can get your hands on a set of W2's. but then you will need matching valve train hardware, intake, headers, etc.
 
mderoy340 said:
Sounds like you already have a drag car and are looking for a quick street/strip for fun. Nothing wrong with j heads. A good valve job, backcut intake valves, replace exhaust guides costs 300 where I'm from. eddys are$$ and not needed for what your looking to do IMO.
Click to expand...

moper said:
I'd use what you have - keep tabs on the chamber size and I'd upgrade to 2.02/1.60s. To help with chamber volume go with stock tulips. I personally want lower static with open chamber iron. I'd keep the chambers big and run a thicker (Victor stock types are a little thicker - around .053 - than Felpros IIRC). You have no quench so just build lower static and then put a street-type cam in it.
Click to expand...


moper said:
Yup - that's what it costs. I'd also have them cut the spring seats for dual springs and cut the guides down for positive springs if that's not included. You might also want them to cc the chambers and mill the gasket surfaces. I'd expect to pay between $1200-$1400 depedning on the work and parts for a good set of non-ported iron heads.
Click to expand...

As has been said before .021" out of the block is not that much. Seems like my 340 was .016-.018 out of the block, and that was a stock block and heads. compression came out to 9.40:1 so if your heads are NOT shaved your only a couple thou (.002) higher. I don't thing you will hit 10.0:1 compression and if you live above sea level, probably wont have any octane issue.

At a 4400 foot race track with the timing at 36* and a 100* day. It would start to ping as i crossed the finish line. (a gallon of 110 racing fuel, mix to a 1/4 tank of 91 fix that problem)

Cam selection has as much to do with it running on 91 octane(in my area) as the compression you build into it!

Mine has a MP .474/280 cam in it. If i had to build this combo over it would have a modern day cam similar to the MP or a higher stall converter to take advantage of the combo i have.
 
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