318 build for retro race car

[genepewl]

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A little background
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My '72 Duster 318/904 is mostly original and the numbers match. I want to keep it that way. It's a base model, and I mean BASE: no a/c, manual drum brakes, manual steering, 904 trans, and 2.73 gears. HOWEVER, the end goal is to build an unsuspecting period correct race car using as much original Mopar stuff as possible. Not a drag car, but a track car of sorts. Something that will straighten the curves and flatten the hills when I'm not getting the groceries or picking up my kids. I may even make up a fake driver and history just for funsies. I think that would be better than "Yeah, a guy named Ernie in South Dakota bought it new and owned it for 40 years until his doctor told him he couldn't drive anymore." There will be a disclaimer that it's a fabrication.

Anyhow, it ran okay, though it had a ticking noise since I bought it. Seafoam helped some, but the ticking never completely went away. It got worse after being parked for a month over this summer while out of town. Terrified, yet thoroughly excited to satiate curiosity, I pulled the motor to replace the oil pump (per a friend's recommendation). A flag was raised when I noticed the exhaust valves were coated in white build up. I showed pictures to my car club (Middle Georgia Mopar Club) and it was recommended that I pull the heads and have them worked. Okay. No biggie. I removed the intake and found 5 or 6 lifters that were stuck. Not too big of a deal. Then I pulled off the heads and found a nice, tall ridge at the top of the cylinders and pistons covered in flaking carbon.

The further I dug, the more I found. By the time I got to a bare block I found stuck lifters, two leaking freeze plugs (one rear was rusted through but was plugged with muck), worn cylinders, really dirty valves and seats, failing cam bearings, failing crank bearings, a broken motor mount, and the exhaust pipe was half smashed behind the driver side manifold. So yeah... it's time!

I've read some 400hp 318 articles and decided that I could be happy with ~300 streetable ponies. I think my decisions will get me close and give me the option to make more without removing the entire engine again.

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Parts
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Here's what I have so far:
-Block bored .030 over
-Unmolested LD4B
-Unported 302 heads with stock valves I believe. (Scored from the machinist. He said they've been sitting around for months and wanted his work paid for. Don't welsh on your bills!)
-Sealed Power rebuild kit with pistons
-COMP Cams XE256H cam kit with timing chain, springs, etc
-Stock 318 exhaust manifolds (For now)
-Accel electronic ignition conversion (It went in right after I bought the car. I love it!)

Yet to be acquired:
-600-ish cfm carb (end goal would be vintage and Mopar correct, but whatever works for now)
-Non-obnoxious dual exhaust. Flowmasters? (Pipe size and muffler suggestions are welcome)
-Air cleaner assembly (I'll use a cheapie until I find what I want)

Possibles:
-Bowl work the 302 heads
-Port match intake to heads
-Headers (suggestions welcome)
-Viscous fan (thoughts?)

Considerations:
-The original pistons were 0.080-0.085 down the hole. I'll measure with the new pistons when I get them installed. It should have around 9:1 compression with the 302 heads. I'll attempt to cc the heads when I get them.
-I believe the ignition coil is original. It seems to be in working order.
-The 302 heads were forged in 85. I realize they don't exactly fit into the "retro race car" theme, but they were cheaper than having the originals worked over and I saved money on compression raising pistons. I'll figure something out later.
-The trans is bone stock original.
-I realize I have highway gears. I don't plan on racing it... too much!

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Questions
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According to CamQuest (I know... optimistic) I'll get close to 300hp. How accurate is this? I'd greatly appreciate real world numbers from anyone with a similar setup or a desktop dyno run.

If I don't acquire a 4bbl carb, how well will the 2bbl Carter BBD run on the LD4B with an adapter? I know there will be a performance hit, but how much? This is more of a curiosity than anything.

What size are the intake and exhaust ports on the 302 heads? I've yet to pick up block and the heads so I can't measure. My stock 318 head intake ports are 1.8" tall and 0.9" wide, but the LD4B is right at 2"x1". I don't really have a problem getting them gasket matched, though I'd like to avoid the cost if possible. And more likely than not, if they go to the porter, I'll go further than simple gasket matching.

Are there exhaust manifolds that flow better than stock 318 and don't cost $300+ for a set? 360 exhaust manifolds, perhaps? I haven't been able to find any flow numbers or port dimensions. I know headers would be best for performance, but they're loud, hot, and tend to rust.

Will the stock torque converter suffice with this engine? If so, should I change the fluid in the tc? It has the drain plug so it would be super easy. If not, what is a budget friendly tc?

Is balancing important for a street motor? The new pistons (with pins) are 749g, except for one 750g and one 747g. A 3 gram difference should good, right? I weighed the rods, too, but I didn't write down numbers. I remember a difference of maybe 10 grams between the extremes. One was heavy and looked like the pin end hadn't been ground. There's, like, 3/16" more material than the others. I'll weigh the rods and post numbers if balancing is super important.

I had the original small radiator re-cored earlier this year and I'd like to keep it in use. I seriously doubt I'll be winding the engine beyond 4k for extended periods. Will this radiator be okay for my purposes?

Have I missed or overlooked anything?

Anything else?

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Upcoming
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This engine should come together over an upcoming weekend with the help and expertise of a fellow club member. He's one of the "why not a 360?" types. I'll try take pics of the process for club purposes, but I'll post them here as well.

There's a car show coming up in early December that had a dyno last year. If everything comes together and is confidently tuned then I'll run it and post numbers for all to enjoy.

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Thanks!
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Whew! That took a while to type. I hope I didn't leave anything out. Thanks for taking the time and reading my post. I haven't posted much, but I read lots of stuff on FABO. I'd also like to thank everyone for being a member of this great forum and sharing your knowledge. It's incredibly helpful for new guys like me.

 

[RustyRatRod]

Are you related to greymouser7?

I see you're in Warner Robins. I'm in Jones County. Probably goin to Reeves Monday to pick up an intake.

 

[genepewl]

Ha ha. Derailed with the first response. Love it! To my knowledge I'm not related to anyone on this forum or in this state. So I highly doubt it.

Reeves quoted $4k-5k for an engine rebuild when we first moved here last year. I've not heard good things about them from my car club. "Sub par" and "expensive" are terms often used to describe them.

I took my stuff to Hill Automotive Machining in Fort Valley. Harvey is a really nice guy that's been doing machine work for decades. He loves how Mopar guys know exactly what they want. Less work for him, I suppose. He said something along the lines of "Ford and Chevy guys drop off their stuff and say '500hp please!'" and leave the decision making to him.

 

[DaveBonds]

I'm guessing you'll be right at 280hp 300tq or so with that combo, but that's a big if, with the pistons you choose.

What is the compression distance on the pistons you have? Do you know what they are?

I'm running a 318 with those heads, .030", cam has lower duration than yours, high ramp and just under 500" lift. I'm guessing this engine is pushing 260? Maybe more, with about 300tq, from the high lift and velocity, same intake, even. I'm running Keith Black pistons, 5cc valve relief, 9.8:1 static, but I'm in Denver, so it's closer to 9.1:1 static with the air density. I haven't checked cyl pressure yet, but I'm guessing 150ish. It has .039" quench with a compression distance of .012" from TDC with those pistons. The 904's that I have, have bowled valve faces, .010" deck for square and a .5cc chamfer around all of the hard edges to help quench and keep my CC's at 62, when I lost a bit from milling. I'm also running 3° adv on the cam

Don't bother with a BBD or any small CFM 2bbl. That engine will suffocate.

I am running a Street Demon (Modern day Carter Thermo-Quad look-a-like) with its new idle bleed position design and it is a very nice carb. Technically a 3bbl, bolts right on the LD4B. I down jetted the carb and when I was playing with my hand over the air horn, I still think it needs more fuel. It stopped climbing in RPM around 4400 until I put my hand over the air horn. It likes the fuel. Once I get it back together, I'm playing with bigger jets.

I didn't gasket match anything yet, although I haven't seen how off it is with a pair of actual 318 intake gaskets. I was running 340/360 intake gaskets until I just took it apart for some repair work and bought a set of Fel-Pro 1243's with the 273/318 runner size intake.

If I do gasket match, it will be to the correct size gasket. If you go big (340/360 runner gasket size), you can kill the idea behind those 302 head ports and the LD4B and slow the velocity down at the gasket.

I don't think you'll have to trim the valve guides with that cam. It looks like a 340 cam, only more friendly for the street with split duration. Good choice.

The car that the 318 is in right now, has a 904 and stock converter with 3.23's. I'm building an 833 O/D with a low first for the street, so I don't need a converter. You should probably go with something in the 2500 range, with some 3.23's. That engine will like a little RPM, even though it will have torque, the cam will want to put it into afterburner takeoff at around 3K and I'm guessing you'll have an engine that you'll want to shift around 5500.

I'm running dodge truck 360 exhaust manifolds, with a little bit of clearance work done to the ears and around the lower edge, to clear the power steering box. I didn't need to do anything to the heads to get them to clear, but I've been told that the 302 heads need a notch at the rear, if you use the driver's side 318 manifold or a 340 manifold that rises up on that side. I can see that the corner could cause some clearance.

Be sure to check exhaust manifold fit while it's on the stand and be sure you're getting at least 1/8" around the outlet, from the head at the back, there, on the left head.

I like the truck manifolds, because they are bigger than the 318, have a bigger outlet and don't nuke spark plug wires on the driver's side, but if I were trying to get more out of it and keep my power steering and stay off of speed bumps and out of gutters, I'd skip the headers and get a set of 340 manifolds, with the proper inner heat shield for the driver's side, to keep from nuking wires.

I put the ignition coil on the firewall, just behind where it sits, to get it off of my LD4B.

The offset bracket works really well, just underneath the heater hose outlets on the firewall, where there is a step in the metal.

I can dig up pics of the manifolds and everything else if you're interested in what I did. The last server I had everything uploaded got greedy, deleted everything I had up and wants to sell me online photo hosting, so I have to get everything up on photobucket from my CPU.

 

[moper]

The short, short version - get the compression to 9.5:1, run one step larger in the camshaft, have the heads port matched to the intake, and I'd run either Magnum truck manifolds or the 68-71 340 ones. Most powerful 318 builds rely on headers - you gotta get the air out and the logs can't do it.
As far as your questions:
According to CamQuest (I know... optimistic) I'll get close to 300hp. How accurate is this? I don't see it happening.

If I don't acquire a 4bbl carb, how well will the 2bbl Carter BBD run on the LD4B with an adapter? I know there will be a performance hit, but how much? This is more of a curiosity than anything. It will suck - get a 4bbl of around 600cfm. Expect to have to tune it.

What size are the intake and exhaust ports on the 302 heads? The mismatch is bad - you will need to port match the heads to the 340/360 sized intake port.
Are there exhaust manifolds that flow better than stock 318 and don't cost $300+ for a set? 360 exhaust manifolds, perhaps? I haven't been able to find any flow numbers or port dimensions. I know headers would be best for performance, but they're loud, hot, and tend to rust. Magnum V8 manifolds or the early 340s - your only options really.

Will the stock torque converter suffice with this engine? If so, should I change the fluid in the tc? It has the drain plug so it would be super easy. If not, what is a budget friendly tc? The 262 will work fine with the stock convertor. Completely draining is good - but wait until the car is back in and running before you change the fluid. That way nothing is dry for the cam break in.

Is balancing important for a street motor? The new pistons (with pins) are 749g, except for one 750g and one 747g. A 3 gram difference should good, right? I weighed the rods, too, but I didn't write down numbers. I remember a difference of maybe 10 grams between the extremes. One was heavy and looked like the pin end hadn't been ground. There's, like, 3/16" more material than the others. I'll weigh the rods and post numbers if balancing is super important. You're way off. The pistons have to be weight matched - less than 1g is acceptible IMO. The smal ends of the rods have to be weight matched. Then the big ends need to be weight matched. The total weight of the rod means nothing as far as balancing goes. The problem with replacing pistons is the crank is already weighted for the factory stuff. You are replacing them with lighter pistons - so now the crank will be heavy. While some circle track engines are set up this way (know as overbalanced) it is not the way to properly balance and will create bad harmonics that can damage things or at minimum rob power. Have the assembly correctly professional balanced.

 

[RustyRatRod]

Ha ha. Derailed with the first response. Love it! To my knowledge I'm not related to anyone on this forum or in this state. So I highly doubt it.

Reeves quoted $4k-5k for an engine rebuild when we first moved here last year. I've not heard good things about them from my car club. "Sub par" and "expensive" are terms often used to describe them.

I took my stuff to Hill Automotive Machining in Fort Valley. Harvey is a really nice guy that's been doing machine work for decades. He loves how Mopar guys know exactly what they want. Less work for him, I suppose. He said something along the lines of "Ford and Chevy guys drop off their stuff and say '500hp please!'" and leave the decision making to him.

Well, I was "your car club" from it's inception for about 10 years. "Sub par" would be a good term some people would use to describe them. At any rate, I've used Reeves a very long time and never had any trouble. Heard good things about Hill's. Just never used him. I know he was out of business for a while. Glad to see he's back up and running.

And I wasn't trying to derail. I was letting you know I would be in your area tomorrow. Would be good to meet another FABO member and make a new friend.

 

[rumblefish360]

Start with the book, how to hot rod my small block MoPar and the MoPar engines book. Finish reading the books and THEN come back and ask questions.