360 Advice Needed - Autocross / Street Engine Build

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Kicker92 said:
I've been running similar numbers in CamQuest, and it looks like in these flow rates, the manifolds are costing like 40-50 lb*ft across most the rpm range.

@ AutoXcuda, how do you have any ground clearance left with it low and the headers underneath? Even the TTI's look like they hang down low compared to the rest of the car.

Shortie headers with a factory looking heat shield may be my next best option.
Again, it doesn't need to be OEM mopar, but my goal is that is look like it "could" have come from a factory like that.
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A bit of a different type sleeper build... :)
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TTI long tubes only hang down about 3/8" more compared to Doug's long tubes, which are about as tight to the car as they can be. The Doug's only hang down a bit less than 3/8" more compared to the TTI shorties. I was surprised that the shorty headers weren't a larger improvement in ground clearance, but they weren't. I think the TTI long tubes would only be about 5/8" or so lower than the TTI shorties, less than 3/4" for sure. I mean, that's not nothing, but, unless your car is absolutely slammed on the ground you probably don't need it. Here's a write up of the TTI shorty install I did, and why I switched back to the Doug's. My "new" '74 Duster- or why I need a project like a hole in the head

The other thing is, unless you have really short tires, you run out of suspension travel before the clearance on the exhaust becomes a real problem. I run 1.12" torsion bars on my car with tubular QA1 LCA's that added a bit of travel before they hit the bumpstops, and then lowered the car until it occasionally hits my low profile polyurethane bumpstops on the street. And my header flanges are still almost 4" off the ground, which is plenty even on the street. I ran my Challenger around for awhile at only 3.5" to the flanges, but that required some creative parking lot exercises when speed bumps were involved. I raised it back up to 3.75" to the flanges and it was fine. The other thing is that with the 25.6" tall tires I run and the amount of suspension travel I still have left the tops of the tires get VERY close the the inner fenders at full compression. I'd have to raise the inner fenders to go much lower than I am with the tire heights I have, when I measured from the spindle to the inner fender at full compression I only came up with 13", so, with a 26" tall tire I would be close to interference at full compression.

I know autoxcuda was running tires that were like 24" tall, so his car is really low, so if he can get away with it almost anyone can. Probably a pain for a daily driver like mine, but for a car that sees more track than street it would be fine.
 
We blended the edge of the spark plug thread. You can see it to left-side plug hole in first picture.

Note the actual bore is scribed unto the head by bolting them up to the bare block. Then you blend the side of the chamber to side of bore so there is not a tiny shelf there to shroud intake/exhaust flow and potential hot spot.

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Bowl porting. Those points and edges between the cast and machined were blended. These are in process pics. :

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Exhaust:

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Head runners:

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Intake:

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Kicker92 said:
A bit of a different type sleeper build...
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I respect that. That's totally cool.

If you're willing to make a custom heat shield then think real seriously about custom headers - even with shorties. This way you can make them real performance pieces and fit your car specificly. In terms of performance, this means good match to the ports at the tops, the right size primary and then possibly a step up, and a nicely merged collector if there is room. By that I mean that the tubes taper together at a nice angle, not the high dollar fancy merges. If the primaries are pinched together in the center as Headers By Ed recommends, a bonus is little less space taken up.

The Magnum Muscle cam looked more promising to than the others. See what you come up with compression and octane after you've confirmed the head cc's. Maybe a different cam will work better with the limited octane fuel.

As far as your autocross goals, you can compete at least some modern stuff with just the basics - some oil control in the pan, springs, front sway bar , decent shocks, and of course a sticky tire. As you probably know, even within SCCA, competion within a class will vary from region to region.
Street Prepared: Softest PAX, but if there are competitors with National level cars (and skills) in the region, its another ball of wax. Besides, the aluminum heads don't count as 'bolt on' modification, so nix that.
Street Mod: You can easily fit in. This was a fun class around here for a while. Then it got really tough to keep up with - in fact I couldn't, although always finished decent. Regionally now its not as competitive or as populated. I still run here when I show up and always do moderately well.
C Prepared: You could fit in here too. Some of us call cars like ours CP lite 'cause they're no where nearly as developed as Sandburg's 'cuda never mind Meier's and Stagnaro's cars. Again depends on local interest. Philly region rarely has any CP cars. In NNJ, before the advent of SM, we had a great group CP (lites).
CAM: Check this out for a possibility. The rules are evolving, as are the cars.
There also may be various vintage and 'street tire' classes offered. Since you're going to bigger diameter wheels, you could run those 200 TW tires. I took a look and was not impressed with the low temperature limitations and high cost (compared to R-comps).

But do have something in mind so you can have some fun competition.
 
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Thanks for all the porting pics, I have a flame shaped carbide burr on the way.

Haven't cc'd the heads yet, but did trade some other parts for a set of full length headers... :)
Once the engine is in I'll figure out heat shielding and how to make them look right. I expect to do a bunch of work on the collector area to get them tucked up tight and a small skidplate for the speedbumps.

They'll probably be about 3" off the ground at ride height...
 
One issues I've been having is getting the valve stems thorough the guides.
Seems to keepers have mushroomed the stems a bit and those guides seem very, very tight.
Filed / sanded one pair a to get them out.

The port shapes seem good, edelbrocks factory goes a little heavy on the grinding on the short turn, but can't reverse that now so will work with it.
Looks like the pushrod holes and the center head bolts are going to need brass sleeves to get a straighter shot on the intake though!
 
Post up your source for the tubes please.
 
Cool man, thanks.

I also wondered where I could get aluminum cylindrical slugs like Hughes uses to plug the pushrod hole entirely.

Anybody have a clue on that one?
 
I don’t know off hand what the pushrod hole size is on the Edelbrock head but below are 2 examples of cost for the sizes listed.

7/16 x 4 foot is $10.88
3/8 x 4 foot is $6.72

Thanks Mike!
 
Kicker92 said:
Looks like the pushrod holes and the center head bolts are going to need brass sleeves to get a straighter shot on the intake though!
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Mmmmm....so you are gonna put brass sleeves in the head bolts holes? Seems like a lot of work for a few more HP...though it might pull half a car length on someone on a long straight; that can be big.
I just never been exposed to that idea.... Any problems in the relative expansion coefficients and the head clamping?
 
Not the head bolt but the pushrod tubes for porting purposes.
 
Got some rough work done on one chamber and intake port. Will do a bit more cleanup then see what I'm at for cc's.

A couple pics:
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I don't have one of those fancy 5-axis cnc's, but I do have a wood router and the ability to 3d print jigs.
This one gives me a reference plane at 18° to match the valve angle:
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Also made one for flush cutting the intake ports:
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Started with a 3/4" bit with bottom bearing, finished the lower pass with a flame shaped double cut burr mounted in the router.
I'm about an inch into the port so far, and will do the rest by hand once a 6" long carbide comes in the mail.

Just barely broke through the pushrod hole on the left.

I wanted some good reference lines to do the hand work from, so trying to start with the jigs to make each port & chamber match...
A bit of a different approach that some, perhaps we can call it "hybrid" porting? :)


Ryan
 
Measured just under 70cc in the chamber, that puts the CR @ 10.2:1 and the DCR at about 8.2:1
 
Indeed. As to why, I do t know why you would want to bush the bolt holes. I need a head infront of me.
 
I would get some 68-70 340 HP ex manifolds or some '92/early '93 magnum ex manis (they have ~2&5/16" outlets). the 360 ones are extremely restricted (check the outlet dia & you will see). I would keep (or get) the right cam & use octane booster as needed (add some in & proportion the % down to meet what the eng wants), no pinging allowed EVER.
 
Definitely sleeves for the pushrod tubes, broke through already. They really choke off the intake window.

The head bolts I'm not sure, the lump is further into the port, and in widens out at that point already.
Might just blend and hopefully not break through the casting there.

Will take some pics tonight on the intake runners to explain, but really it's the same goal as Hughes, ProComp, and others do with the CNC porting, just on a $50 budget. :)
 
Hit a bit of a snag while porting, my 5" carbide burr got a vibration, then exploded into several pieces.
Never had that happen before, scared the crap out of me. Got luck though, only one small cut from it on the arm.

I'm calling it quits for the night... :(
 
Got some work done, chambers all cut to 70cc's with a decent quench still:
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