Help me build my 360!

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RDJ

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OK, where to start. I haven't ever gone to this extent on an engine. I've had them apart, but never to the point where I removed the pistons/crank and replaced them.

I have an 85 (84?) 360. I want to build a nice street engine that will be bracket racing on occasion. Needs to run on pump gas, the best we have around here is 91 octane. It has dished pistons that seem to be low in the block (see pics). Probably not much compression there. To get into the 12's would be nice, but not an absolute necessity if it will make it a temperamental street driver. I don't plan to use the heads that were on the engine.

My tentative plans so far. Take the block to a machine shop, get it hot tanked, check for cracks, bored (maybe .030 over?) and have them replace the cam bearings and freeze plugs, and some off the deck (not sure how much). Get the KB 107 pistons and have the shop balance out the crank with the pistons, harmonic balancer, and B&M flex plate.

I have a set of Magnum heads, but I would prefer to use LA heads. My other choices are a set of 915 iron heads with some pocket porting, all assembled with 2.02 and 1.6 valves and springs that can go up to .550 lift for $800. Don't know the flow, but they say they are good up to 400 hp.

I could get some Edelbrock heads, but I would certainly prefer not to spend that much. Maybe I should use the magnum heads. Isn't there some issues about the 1.6 rockers and too much lift for moderate cams with these heads. Also, I'm afraid I will get them to the machine shop and find they are cracked. Although, they look to be in great shape.

I have some TTI headers already. Will probably get an Edelbrock Performer RPM intake? I have a converter that is rated at 2600. That could change if needed though.

No idea what cam, but obviously depends on the compression ratio. Carb?? I prefer the Edelbrocks to the Holleys, but am open to suggestions.

I should probably get the heads before I tell the machine shop how much to deck the block? I don't know much about this. Advice is welcome.

About the harmonic balancer. Do I need a new one? It looks like the rubber is coming out of it in between. I looked at Summit, do I need an external or neutral balanced? Here is a pic of the one I took off of my engine. Should I post other pics of my block? Obviously this is a huge part of my car, and I want to do it right the first time.

balance2.jpg


balance1.jpg


360-1.jpg


360block1.jpg
 
you could have the engine internally balanced and get a neutral balncer and flexplate....

but if you are on budget...stay with the external balance and flexplate... mallory metal get costly .....

you could ask the machine shop for a quote to internal balance verus external and see how that works out....if the money saved will pay for other things.

pistons are a very good choice...
as far as carb i would use a holley but that is my choice...
cam....look at the comp or lunati 904 lifter cams...

heads wise....might want to take a look at the engine quest magnums with LA bolt pattern....also Indy and RHS have a new cast iron head out...
 
i have an originally externally balanced 340 (72-73) that i had converted to internally balanced because it was easier. It only cost me 200 to have it balanced internally. I was having a heck of a time finding a flywheel that would have kept it externally balanced because it was only a 1.5-2 yr production flywheel.
It also depends on the Bob weight. The weight of all the components mine was really light so he only had to take out metal from the front and back of the crank.
 
Just a suggestion. I wouldn't pay somebody to install the freeze plugs. It's too easy to do. I'd also replace the damper.
 
For freeze plugs just get a large socket or wooden dowel that fits into the outer edge and tap them in with a mallet / dead head. Make sure to put silicon on the outside of the plugs. Also make sure they are all the way seated if they stick out i guess they have a better chance of popping out when it heats up and cools down.
I was nervous about getting it right but my machine shop guy said he doesn't install them unless he is building the engine. My neighbor owns a porche repair business and he showed me how to do it. Super easy and simple just make sure they are all the way seated and you shouldn't have any problems.
 
Magnum heads, aftermarket magnum replacements or closed chamber aftermarket performance heads are the way to go. You can run much higher compression and not have issues with detonation that you would with LA heads. I run 89 in my 10.6:1 magnum headed LA 360 and have used 87 in a pinch.

With the KB107's you will want to machine the block to get them zero to the deck. On my 360 it took about 0.020" to square and zero deck the KB107's.

I would use a modern fast ramp cam or a roller if you can afford it. I am running a Comp XE268H cam but some similar from the Lunati VooDoo line or Hughes will do the job. The XE268H is a great street cam pulls hard from 1500 rpm to 6000+, may not get you to the 12's but it will be awful close.

I performance dual plane intake like a Performer RPM, RPM Air Gap or a CrossWind will be ideal.
 
This thread has opened up some questions for me. Please forgive my ignorance, I have no experience in going this far with an engine.

1) Is my current harmonic balancer is an external or internal balanced?

2) I thought to have an internally balanced 360 was very expensive (Mallory metal?) to do the balancing. Is this incorrect? To have an internally balanced 360, can I just get a neutral balanced crank, harmonic balancer, and flex plate? Use the stock rods and the KB 107 pistons? Can the stock crank be used to make an internally balanced engine?

3) I see that the 4.00” stroke cranks really aren’t much more than the 3.58” stroke cranks. Can I use my stock rods with some sort of shorter pistons to make a stroker? Are the 4.00” stroke cranks harder to make internally balanced?

4) What are the purpose of undersize main and rod bearings? (I saw those choices when looking at the price of bearings). Are rod and main bearings hard to install?

5) I was under the impression that when using iron heads, you didn’t want to make the CR much more that 9.5:1, or you couldn’t use pump gas. Apparently the iron magnum heads can take more compression and still use pump gas.

6) Am I over my head with this project? I think I can do this, but I want to do it right the first time.

7) How much can you deck the block before the intake manifold has a hard time sealing?
 
1. External, look at the outer ring there is an area visable in the picture that that is not relieved, this is the extra metal for the external balancing.

2. It is expensive for the mallory metal and the actuall balancing processs gets more expensive when they have to add metal verse remove metal. Unless you plan to be turning in excess of 6000 rpm all the time its not worth the expense or effort to internally balance.

3. Yes you can use stock rods with the stroker crank but Scat and Eagle both sell I-beam rods that are stronger than stock and cost the same or less than having stock rods reconditioned with new bolts. Yes you will need pistons with a shorter compression height for a stroker motor.

4. If there are any gouges or scouring of the main or rod journels you have to have the crank machined to remove them. To make up for the reduction in juournal diameter they sell bearings that are under size. Same idea as going over size on the piston. The bearings are easy to install, just press into place with your fingers but you need to be able to measure the clearance, that is what plastigauge is for. It is a small piece of pastic strip that when clamped between the bearing and the journal will smear out. The width of the smear is compared to a chart to determine the clearance.

5. 9.5:1 is a safe bet for an open chamber LA head but closed chamber heads that are set up with a tight quench (the space between the flat surface of the head over the piston and the top of the piston) of around 0.040" generates a lot of turbulence in the chamber near TDC which is good for preventing detonation. The effect can be created with domed pistons and an open chamber head but to get the the right clearance the pistons need to be machined to the contour of the head. The closed chamber and flat top is just a better way to do it.

6. get your self a book on rebuilding mopar small blocks and read it. It will give most all the info you will need to know.

7. Not sure
 
If you want to make any kind of good compression those stock pistons have to go..if you go with a 4" stroker crank thats fine but a good set of stroker pistons are going to cost $500-$600,something to think about..i'll tell you what i did on my most recent build...

'77 360 block bored 30 over and decked
stock stroke crank nothing but a polishing
set of Eagle sir rods
set of speedpro pistons with valve reliefs(bought these at summit for $289 with the rings included)
this combo is still externally balanced with the b&m flexplate..
Lunati "voodoo" .513/.533 cam
Edelbrock heads(but if you don't have the money i'm sure a set of j,x's properly preped will work fine..
Air gap intake,if you already have the rpm thats an excellent manifold also..this combo has gone 11.79 in my duster this is just an example of what you can do....
 
I have basically a .040" over stock 360 short block, complete with the 8:1 pistons...I just added some Magnum heads with R/T Springs, Summit K6901 cam, edelbrock air gap intake, and a milodon windage tray and oil pan. It runs pretty good...Not sure if it would run 12's though.

I can tell its low compression because it will still run good with the timing advanced so far the starter can't turn it over for a hot re-start...and thats on 89.
 
Thanks for the helpful posts and great information! Stroked340 you mentioned you used the stock crankl, but new rods. Do most folks get new rods when doing this?
 
RDJ said:
Thanks for the helpful posts and great information! Stroked340 you mentioned you used the stock crankl, but new rods. Do most folks get new rods when doing this?
Click to expand...

I like to,because for the price it'll cost to have the stock ones resized with new rod bolts(i highly recommend)..you can buy a "new" set of Eagle or Scat and they'll work just fine for your application..
 
I've decided to not try to cut too many corners on the bottom end. To make a good foundation for the engine will pay off in the end. I figured I might as well get a new crank, since I am getting new rods anyway, and they are only an extra $250. I thought I might as well get a whole rotating assembly. I found these. They include all the rings, crank, bearings, rods, etc. Plus, they are internally balanced. Plus, they are all balanced as a package. The machine shop was going to charge me $210 to balance my assembly, so I don't need to pay for that. I need a new damper anyway, so I could buy a neutral balanced one, and now I don't need to buy a B&M flex plate. However, I would like an informed opinion on something like this.

One other thing, one of the sets is for a 4.00" stroke. It is only $230 more than the 3.58" stroke. Seems pretty reasonable for 40+ more cubes. Plus it has forged pistons. I called SCAT yesterday to make sure it is an internally balanced set, and he said that it is. Use a neutral damper and flex plate.

Anyway, these are them

3.58 stroke, comes with the KB107 pistons $1,114

http://store.summitracing.com/partdetail.asp?part=SCA-1-98101BI&autoview=sku

4.00 stroke, $1,345

http://store.summitracing.com/partdetail.asp?part=SCA-1-98112BI&autoview=sku

Has anybody used one of these?

Are there any potential problems or issues going with the 4.00" stroke kit?

Thanks!
 
I've been thinking of doing the same type of thing with my 360. The cost difference to build a 408 is really not that much. My main holdup is that I need to open up the motor I have so I'll know what kind of shape my bores are in (Plus find the money!). Have you checked what your compression ratio will be with the 408 kit? I think you'll still need to get the assembly balanced. There are some similar kits for sale on eBay for about the same money. One seller offers balancing for an extra $130.

I can't get a link to work but the item number is 270340180945


I asked about the balancing & this is what they told me.....

"Yes, the balance is a computer balance on a HINES computer, the balances are within 1 gram."


I've never had an engine balanced before. Does this sound like it would be a good enough balance job?
 
If you look at the kits on Summit, some are balanced, some are not. When I called SCAT to talk about it. he said that (if you chose a "balanced/yes" kit) it comes balanced and is basically a bolt in. I would probably still have the machine shop who is preparing my block check it.
 
'64 Cuda said:
Have you checked what your compression ratio will be with the 408 kit?
Click to expand...

Good question. I know to get the true compression, you have to measure the volume of your compression chamber and cylinder.

But would anybody have an estimate of compression if you have a stroker, with a flat top piston (two relief valves), zero deck, 0.040 head gasket, and Edelbrock heads? Will this combo normally run on pump gas?
 
My 416 with flat tops at zero deck running Edelbrocks was 10.9 to 1 compression..
 
stroked 340 said:
My 416 with flat tops at zero deck running Edelbrocks was 10.9 to 1 compression..
Click to expand...

I've got Edelbrock heads too, 60779's. Has anybody cc'd a set to see what the true chamber volume is? I know they say it's 63cc. but I've heard that's not necessarily what they are.
 
'64 Cuda said:
I've got Edelbrock heads too, 60779's. Has anybody cc'd a set to see what the true chamber volume is? I know they say it's 63cc. but I've heard that's not necessarily what they are.
Click to expand...

I had mine cc'd when i bought them and they were not a true 65cc...they are now...
 
stroked 340 said:
If you want to make any kind of good compression those stock pistons have to go..if you go with a 4" stroker crank thats fine but a good set of stroker pistons are going to cost $500-$600,something to think about..i'll tell you what i did on my most recent build...

'77 360 block bored 30 over and decked
stock stroke crank nothing but a polishing
set of Eagle sir rods
set of speedpro pistons with valve reliefs(bought these at summit for $289 with the rings included)
this combo is still externally balanced with the b&m flexplate..
Lunati "voodoo" .513/.533 cam
Edelbrock heads(but if you don't have the money i'm sure a set of j,x's properly preped will work fine..
Air gap intake,if you already have the rpm thats an excellent manifold also..this combo has gone 11.79 in my duster this is just an example of what you can do....
Click to expand...

I'm curious what rear end ratio and stall on your converter? Thanks for the help!
 
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