1973 340 budget build.

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trigger_andy

trigger_andy

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Hey all,

so I have a '73 340 that was gonna get a budget build on but for one reason or another the builder has only got as far as boring it out 20th so I now have it home with me and plan on doing the build myself.

So I have a fresh 20th over block, a Competition Cams 274H Xtreme Energy Cam and matching lifters. ( I still need to get a set of the recommended springs) Its not decked or anything like that.

I had a Mellings High Volume Oil Pump but Im not sure if its fitted or missing as yet.

Although I have the smaller 1.88" Intake Valves 587 heads the engine builder asked me to get stainless 2.02" & 1.60" Valves as I was gonna be getting a set of 2.02" Heads from him but thats now fallen through. Would it make sense to have 2.02" Intakes cut into my 587's? (Im in Scotland by the way)

Anyone have any recommendations on what pistons I should get? Ideally as Ive paid for it to be on a 20th over bore I'd like to keep it there but if I have to go to 30th over then so be it, I already have the 20th over Piston Rings too. Keith Black ones (recommended anyway) The Crank and Con Rods I have been told are in good shape and the crank just needs a polish maybe a light grind. As this is an externally balanced engine Im really unsure how I would go about balancing the rotating assy? Or is there pistons out there that would match the weight of what I already have? Ideally I'd like to bump the CR up to 1970 standards and not keep it on the lame '73 low comp.

I realise this will all cost money but I can break it up into stages to spread the cost. So all suggestions welcome. )
 
are you married to the 340?

chances are you can sell that and use the money you get for it to buy a 360 and be cubes and money ahead
 
While there are better qualified members than me Ill post what I now. You didnt state your goal. But by the term "budget" Im thinking you want a punchy gutsy reliable engine with as many as the oem parts from this engine reused as is possible. You already have a cam. You also want the compression of a 1968-1971 340. So you want a zero deck piston which KB and another company (Sealed Power) both have in an affordable cast construction. Make sure your cam will work with a zero deck- (Higher compression) piston. Comp Cams has a line of cams that are meant to work with a low static compression engine and if you run this cam with a zero deck piston you may have unusably high cyl psi. Your block is bored .020 over? Is this a size a replacement piston is available in?? Your heads- a 1.88 intake valve will be fine in a mild application. Sure the 2.02 will make more power up top BUT you must pay to punch out/ enlargen head for 2.02 valve. Then the machinist should run a cutter into the bowl and elargen it as well. Then new seat ground in. Many have done it but do you want to spend the $$? The 1.88 size valve is not a hinderance on a MILD 340.
 
diymirage said:
are you married to the 340?

chances are you can sell that and use the money you get for it to buy a 360 and be cubes and money ahead
Click to expand...

I’m willing to bet 360’s are not plentiful at all where he is in Scotland UK
 
trigger_andy said:
Hey all,

so I have a '73 340 that was gonna get a budget build on but for one reason or another the builder has only got as far as boring it out 20th so I now have it home with me and plan on doing the build myself.

So I have a fresh 20th over block, a Competition Cams 274H Xtreme Energy Cam and matching lifters. ( I still need to get a set of the recommended springs) Its not decked or anything like that.

I had a Mellings High Volume Oil Pump but Im not sure if its fitted or missing as yet.

Although I have the smaller 1.88" Intake Valves 587 heads the engine builder asked me to get stainless 2.02" & 1.60" Valves as I was gonna be getting a set of 2.02" Heads from him but thats now fallen through. Would it make sense to have 2.02" Intakes cut into my 587's? (Im in Scotland by the way)

Anyone have any recommendations on what pistons I should get? Ideally as Ive paid for it to be on a 20th over bore I'd like to keep it there but if I have to go to 30th over then so be it, I already have the 20th over Piston Rings too. Keith Black ones (recommended anyway) The Crank and Con Rods I have been told are in good shape and the crank just needs a polish maybe a light grind. As this is an externally balanced engine Im really unsure how I would go about balancing the rotating assy? Or is there pistons out there that would match the weight of what I already have? Ideally I'd like to bump the CR up to 1970 standards and not keep it on the lame '73 low comp.

I realise this will all cost money but I can break it up into stages to spread the cost. So all suggestions welcome. )
Click to expand...
I like these KB slugs for street/street strip duty;
Keith Black KB Performance Piston and Ring Kits KB243KTM-030
I didn’t see them in a .020 overbore size.
Your machinist should ether be able to do the balance job himself or send it out to a place that does this job specifically.

Your machinist, more than likely stopped at .020 because he will want to custom fit each piston to each cylinder hole. This is a must do for forged slugs. My machinist will be super careful and do it with Hyper slugs as well.

Is the car an automatic transmission?
If so, I would certainly without a doubt have the engine balanced internally.
If it is a manual transmission, the flywheel needs to be changed.
A new damper upfront should be on the list of parts to purchase new.

Adding 2.02 valves is fine, though if you do not open the bowls underneath the valve, I’d call it a waste of time and effort. I suggest a porting or the bowl area with the 2.02 valves added.

Once I have a plan in my head, l start from the top of the engine and work down. Finishing the block last. So when the block is done, everything gets put together on it and then I install and run it.

Make a plan and stick to it because changing the plan is expensive as heck!
 
Use the KB pistons just follow the instructions related to the ring gap....top ring needs larger gap
 
Michael Harrington said:
While there are better qualified members than me Ill post what I now. You didnt state your goal. But by the term "budget" Im thinking you want a punchy gutsy reliable engine with as many as the oem parts from this engine reused as is possible. You already have a cam. You also want the compression of a 1968-1971 340. So you want a zero deck piston which KB and another company (Sealed Power) both have in an affordable cast construction. Make sure your cam will work with a zero deck- (Higher compression) piston. Comp Cams has a line of cams that are meant to work with a low static compression engine and if you run this cam with a zero deck piston you may have unusably high cyl psi. Your block is bored .020 over? Is this a size a replacement piston is available in?? Your heads- a 1.88 intake valve will be fine in a mild application. Sure the 2.02 will make more power up top BUT you must pay to punch out/ enlargen head for 2.02 valve. Then the machinist should run a cutter into the bowl and elargen it as well. Then new seat ground in. Many have done it but do you want to spend the $$? The 1.88 size valve is not a hinderance on a MILD 340.
Click to expand...

Thanks for the reply. :)

Yes, your spot on with what you interpret my 'budget build' to be. :)

Here's the Cam in question; COMP Cams Xtreme Energy Camshafts 20-224-4 I have no idea how to check if that takes a zero deck piston? I had a look but could not see anything. This is a 340/360 Cam though, but I dont think that really tells me anything? The below quote is from a UK based American Engine builder though, so I think I should be ok?

We dyno tested this cam on a high compression 360 we built, with modified heads it gave 381bhp @ 5500rpm and 413 lb ft of torque at 4500'. Idled happily at 750 rpm. Excellent cam.

Yes, there is replacement .20 over pistons. The main reason he went .20 pistons out there. The main reason the Builder went to this first cut was he said there was factory .20 forged Pistons in this size for the 340 from factory, unusual and only in the 340. He had a Crank, Rods and a these forged .20 pistons ready to drop into my 340 but things went wobbly with him so I no longer have these as an option.

These pistons are .20; Keith Black KB Performance Pistons SKB243L-020
Im hoping they are the the same as the link Rumblefish360 linked to but in .20 and not .30?

With the above cam and Pistons would my Budget Build still be considered a mild 340? I really dont know? But I have the Stainless Valves now and would like to use them. Ive Ported two sets of 587's now and kinda have the hang of it to the point I'd have them where I wanted them within a week. Lots of Grinding and lots of Polishing. Id have the Valve Guides milled out and Brass incerts installed so as to be sure there was no slop in there. Id enlarge the bowl myslef so all the Machine Shop would have to do was grind from 1.88" to 2.02" and install the brass guides. I have no idea How much that will cost yet?
 
rumblefish360 said:
I like these KB slugs for street/street strip duty;
Keith Black KB Performance Piston and Ring Kits KB243KTM-030
I didn’t see them in a .020 overbore size.
Your machinist should ether be able to do the balance job himself or send it out to a place that does this job specifically.

Your machinist, more than likely stopped at .020 because he will want to custom fit each piston to each cylinder hole. This is a must do for forged slugs. My machinist will be super careful and do it with Hyper slugs as well.

Is the car an automatic transmission?
If so, I would certainly without a doubt have the engine balanced internally.
If it is a manual transmission, the flywheel needs to be changed.
A new damper upfront should be on the list of parts to purchase new.

Adding 2.02 valves is fine, though if you do not open the bowls underneath the valve, I’d call it a waste of time and effort. I suggest a porting or the bowl area with the 2.02 valves added.

Once I have a plan in my head, l start from the top of the engine and work down. Finishing the block last. So when the block is done, everything gets put together on it and then I install and run it.

Make a plan and stick to it because changing the plan is expensive as heck!
Click to expand...

Thanks again. :D


Heres the .20 KB Pistons I found earlier. Do you think they are the same as the ones you spotted at .30 over?
Keith Black KB Performance Pistons SKB243L-020

I mentioned to Michael just now that the builder had a set of oem forged .20 pistons for me, but Im not getting them now. :( So Im hoping I can user the KB ones in my link above? Any idea of the CR Id get with them?

I intend on using the 340 behind my Australian Borg Warner 4 speed, which I have a Flywheel for. I might get a '73 340 Flywheel though? I'll need to see if it will work with the Borg Warner.

I might have a new damper, I'll check, if not it looks in very good condition. Its a 340 'cast' Damper anyway. Are these as likely to explode with age?

I do plan on sticking to one plan and building from there. I guess I should start porting the Heads now then whilst I save for the correct Pistons.
 
trigger_andy said:
Thanks again. :D


Heres the .20 KB Pistons I found earlier. Do you think they are the same as the ones you spotted at .30 over?
Keith Black KB Performance Pistons SKB243L-020
Click to expand...
Yes
I mentioned to Michael just now that the builder had a set of oem forged .20 pistons for me, but Im not getting them now. :( So Im hoping I can user the KB ones in my link above? Any idea of the CR Id get with them?
Click to expand...
There are on line calculators to figure this out. Try Wallaceracing.com, you'll need head gasket information as well as where the piston sits in the cylinder. Zero deck or the amount above/below the deck.
I might have a new damper, I'll check, if not it looks in very good condition. Its a 340 'cast' Damper anyway. Are these as likely to explode with age?
Click to expand...
They don't explode, they separate. The rubber between the two rings rots away.
I guess I should start porting the Heads now then whilst I save for the correct Pistons.
Click to expand...
Port the heads after the valve job and valve size is selected.
 
I would go with these Speed-Pro Forged Pistons L2316F30 They are very close to stock piston weight but will give you 9.5 maybe 10 to 1. Plus you can run stock ring gaps. The KB pistons are nice but for a street budget build they would not be my first choice.
 
rumblefish360 said:
Your machinist, more than likely stopped at .020 because he will want to custom fit each piston to each cylinder hole. This is a must do for forged slugs. My machinist will be super careful and do it with Hyper slugs as well.
Click to expand...
And like he said. You need the pistons to finish the bore job. You may end up at 0.30 over.
 
trigger_andy said:
Here's the Cam in question; COMP Cams Xtreme Energy Camshafts 20-224-4 I have no idea how to check if that takes a zero deck piston? I had a look but could not see anything. This is a 340/360 Cam though, but I dont think that really tells me anything? The below quote is from a UK based American Engine builder though, so I think I should be ok?
Click to expand...
Once the engine is assembled and the pushrod length checker is in, you will use clay ontop of the piston and see if there is an issue.
Correct, it doesn't tell you anything except that 340/360 is a small block like the 318/273.
I think you'll be OK as well.

We dyno tested this cam on a high compression 360 we built, with modified heads it gave 381bhp @ 5500rpm and 413 lb ft of torque at 4500'. Idled happily at 750 rpm. Excellent cam.

These pistons are .20; Keith Black KB Performance Pistons SKB243L-020
Im hoping they are the the same as the link Rumblefish360 linked to but in .20 and not .30?
Click to expand...

Nice dyno results.
Those are the slugs!

With the above cam and Pistons would my Budget Build still be considered a mild 340?
Click to expand...
YUP! Though mild is a point of view, a lot depending on where you been, what you have to start with and where you end up.
 
Hellrats said:
And like he said. You need the pistons to finish the bore job. You may end up at 0.30 over.
Click to expand...

Hey, he was quite adamant 20th was the size he went to 1, The bores needed the minimal of work. 2,so get more sizes out of it later in life, 3, he had Chrysler 20th over forged pistons and it made sense to use them.

Im a total novice and cant offer an opinion further than what I was told.
 
rumblefish360 said:
Yes

There are on line calculators to figure this out. Try Wallaceracing.com, you'll need head gasket information as well as where the piston sits in the cylinder. Zero deck or the amount above/below the deck.

They don't explode, they separate. The rubber between the two rings rots away.

Port the heads after the valve job and valve size is selected.
Click to expand...

I need to learn how to multi-quote. :D Thnak you again for the info. :)

Ok, so CR will be a thing I'll not know for quite a while then.

I thought Id port before the Valve before the seat grinding incase I knick the fresh seats? Is that a bad idea?

Andy
 
Hellrats said:
I would go with these Speed-Pro Forged Pistons L2316F30 They are very close to stock piston weight but will give you 9.5 maybe 10 to 1. Plus you can run stock ring gaps. The KB pistons are nice but for a street budget build they would not be my first choice.
Click to expand...


Ohhh, they are nice! Id have to go up to 30th though and thats adding cost I could do without. The Speed-Pro's are $300 and the KB are $500 at 20th and I already have the rings. Could I get the bores taken out another 10th and new rings for another $200? I doubt it, but I can check. Seriously worth looking into though.
 
I'm running a set in a 360 right now. Great street pistons for the price. Checked eBay as well. Sometimes you can find them for even less.
 
Hellrats said:
I'm running a set in a 360 right now. Great street pistons for the price. Checked eBay as well. Sometimes you can find them for even less.
Click to expand...

Great tip! I'll do that now I have an actual part to search for. :) WHat spec is your 360? What HP are you making?
 
trigger_andy said:
I need to learn how to multi-quote.
Click to expand...

To multi quote, I highlight the quote tag at the end of the quoted message and copy it. Notice that the bottom quote tag has an additional character in it. “/“ Remove that “/“ to begin the quote, leave it in to end the quote.

Ok, so CR will be a thing I'll not know for quite a while then.
Click to expand...
Once you know where the piston sits in the bore, add the head gasket thickness, cylinder head cc ....

I thought Id port before the Valve before the seat grinding incase I knick the fresh seats? Is that a bad idea?
Click to expand...
Yes, it’s backwards. Seats and valves installed first. Then remove and port. I forget the percentage of bowl opening you want. It is a percentage of the valve size.
 
I want to build this engine myself, I want to and have a good Small Block Mopar book to follow but I've never build an engine before and Im wondering if its too much for me? Well, not since I was an Apprentice Mechanic but Ive been in the Oil Service Industry for the last 20 years.

This quote got me wondering;

Your machinist, more than likely stopped at .020 because he will want to custom fit each piston to each cylinder hole. This is a must do for forged slugs. My machinist will be super careful and do it with Hyper slugs as well.

If I buy .20 Forged Pistons then how does one custom fit each piston to each Cylinder Bore? If this is nessesery I think I might have to farm the work out again. :(
 
so did your machinist do a finish hone with a torqueplate
or just a rough bore that has to be finished once you get the pistons
 
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