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Old 06-04-2005, 05:12 PM
ramcharger_440 ramcharger_440 is offline
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Default Dilemma on 360 build help please

I picked up a 1972 360 that will not need to be bored at all and still looks and measures new. In fact, the cross hatching from being honed is still pretty much still there.

I am building a 3300 lb street car with automatic. I will be using a 8 3/4" rear and am still looking for the chunk. I have a 3.23 open chunk and a 4.86 sure grip. One is too high and the other too low. This will be driven several times weekly and occasionally at the track, maybe a couple times a year.

I will use the 360 I purchased and have my choice of magnum heads (rebuilt on hand, not ported) or the J heads with 1.88 valves that were on the engine. Intake shoice will be limited to what I already have, a Weiand Stealth and a Strip Dominator. My deck height is 9.611 and I would prefer to stay away from the machine shop if possible. This is definitely a budget build.

My question is what pistons and cam would you run and why? Also looking for input on preferred rear gear ratio. I am leaning towards 3.91.

I am will to mix fuel if necessary but would prefer to run on the 93 octane avalable locally at the pump. One of the options I am considering is to use the magnum heads with a .020 gasket and KB 107 pistons. This would put my quench distance at .043 but the compression would be about 10.4.
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Old 06-04-2005, 07:07 PM
451Mopar 451Mopar is offline
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If you are not going to bore and hone the block, then why put new pistons in it? The cost of the new pistons and rings (and pressing the pistons on/off the rods) will be way more expensive than the machine work to bore and hone the block, so why not have the block machined to fit the new pistons correctly? The rebuild will make more power and last longer.

If your going to go cheap, keep the stock pistons and I'll make you a deal on an offset ground 360 crank (3.60" stroke vs 3.58" stock) that I have sitting in my trailer. It will only help raise compression about 0.2:1, but it already ground, polished, and comes with main and rod bearings. $100 plus shipping (or pick it up here in Denver CO.)
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Old 06-04-2005, 07:32 PM
ramcharger_440 ramcharger_440 is offline
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Yes, I am definitely budget conscience on this one.

I don't consider there to be a need to bore, only hone. There is absolutely no taper and the bore is easily within specs.

The reason for the piston change is to increase compression. I dont think a couple tenths will be enough. These pistons are .108 in the hole and are dished. One person stated that the piston dish is 9cc's. I am sure the compression ratio is in the low 8's if not high 7's. I would like at least a 9.4 compression ratio.
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Old 06-04-2005, 09:41 PM
Walkercolt Walkercolt is offline
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I'm sorry to tell you, you can't build as cheap as you'd like. The block needs to be decked to be square and to zero-deck your chosen pistons(like Kieth Blacks or my preference Diamond Racing). You probably need to bore the cylinders to make sure they are 90* to each others, even though the cross-hatch is showing. You didn't mention your tranny, so I'm guessing a 727, so a 3.91 rear would be a decent compromise. I'd use the Magnum heads and pay to have them "Stage1" ported, about $400 worth. I'd also use gapless rings. Last months' MOPAR MUSCLE had a great 360 build-up story: "365CID-465HP". Follow their "precription" and you can have a great motor. If you want track HP, you're gonna have to spend the money, otherwise you may have a great "warm" street engine. I'm guessing this is going in a Dart/Valient "A" body. Speed costs $$$: How fast can you afford to go?
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Old 06-04-2005, 11:02 PM
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dwc43 dwc43 is offline
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Quote:
Originally Posted by ramcharger_440
Yes, I am definitely budget conscience on this one.

I don't consider there to be a need to bore, only hone. There is absolutely no taper and the bore is easily within specs.

The reason for the piston change is to increase compression. I dont think a couple tenths will be enough. These pistons are .108 in the hole and are dished. One person stated that the piston dish is 9cc's. I am sure the compression ratio is in the low 8's if not high 7's. I would like at least a 9.4 compression ratio.

You wont have a problem making great power even with your budget with a 360. We get way over 400 and still streetable in our race cars. Get a set of KB pisons. With J or X heads milled .030and on a .030 over bore and .030 we get around 10.7:1 measured. You want to go X or J heads and have the 2.02 valves installed and back cut. The mags will gost you more money in valve train issuses and don't make the power you need. Get a dual pattern cam with more duration and/or lift on the exhaust side of the cam. Makes the heads work better. 1 5/8 stepped to 1 3/4 for our headers and make sure to add an X pipe into the mix for a big gain in hp and torque. I'd use the stealth for more low end if you need it. Make sure to get a good thermoquad carb. It will give the best thottle response. If you need some more help send me a PM and I'll show you some cheap tricks to make more power on stock builds. I'd also look for a 3.91 or 4.10 gear. Get your tranny parts from TCI at www.tciauto.com They have the best stuff for your tranny. And don't go too big on the cam or you will need a converter too.
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Old 06-05-2005, 02:28 AM
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LA360Dart LA360Dart is offline
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Default If it was my 360

Hi ramcharger440;

The 360 needs more compression the stock compression ratio is like you said 8:1 at best. Get the bores measured and see of a hone will clean them up, if they will then just swap in std bore aftermarket pistons like 107KB or CP114HP Speedpro's. The 360 needs more compression to make real Hp. A change to a better piston with some real compression. Will go a long way to make some real power. Try to keep compression at around 9.5 to 1 as gasoline is not what it once was, 91 in calif 93 everywhere else...

Please do not be afraid of magnum heads they produce more torque and offer many advantages over LA castings. Better balance on intake to exhaust on flow, better combustion chambers only 60cc's (will help compression) only need 34* total timing and are more resistant to detonation. The 153cc for the runners is a little smaller that X or J heads (166cc's) but velocity is better so cylinder filling is better at low speed and won't stall at top end of valve lift...

The valve train issues are minor, you need to run AMC type of lifter (2011 industry number) and push rods that oil like a chevy/ford (length needs to be checked) the stock rockers (magnum 1.6) are fine for everyday use and occasional drag use. The cam can then be a single pattern (no more than 230 @ .050) as cylinder heads don't have the poor exhaust flow of X or J heads. Header standard LA 1 5/8th's that fit your chassis. On the intake Mopar M1 dual plane or Edelbrock Airgap or Crosswind. Carburetor TQ or Demon 625 vacumm scondary will work well. e-mail me if any questions you might want answered on valve train issues. By the way the valve train parts don't know their not on a ford or chevy...


The gears for the 8 3/4 depending on tire size 235/60X15 try 3.55 if 275/60X15 then 3.91. If going to be driven around 3.55's are better for cruz'n but if leaning more to drag racing then 3.91's...


Denny
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Old 06-05-2005, 01:22 PM
Dart 65 Dart 65 is offline
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For gear ratios, I don't think I'd want much more than a 3.55 gear for the street. 3.91 might be a bit steep. If you're doing this on the cheap, stick with the stock pistons. You want to stay away from machine shops, but to make the power you need, you're being unrealistic. You can mill your heads a bit and go with a better cam, something in the 270/270 advertised range to make up for the dished pistons. I'd also strongly recommend a three angle valve job and 2.02" intake valves. The stock 1.5 rockers will be fine for what you're doing, and I personally prefer the shaft-mounted rockers for their maintainence-free performance. Port matching your intake and header/manifold will also be beneficial.
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