racers, need some advice please

[benno440]

Gents,

I got a customer/friend he has a VC valiant that is street/strip car. It has a 318 (mild) in it at the moment and he is building a 360 (mild drag motor) for it. currently it runs 14 sec quarters flat. running the 904 auto (is that correct?)
He wants me to build him a set of tuned length stainless headers for it and a full exhaust system with dynomax ultra flo's and also cutouts just past the headers.

he wants these to run well on the 318 but also work for the 360 once it is built.

it is currently also running a edelbrock rpm intake and 600cfm edelbrock, but he is keen to change intake and carb, he mainly wants to see what he can get out of the 318 before he puts the 360 in.

My questions are:

What size tubes would work best for the headers to make the 318 open up and breath and then work awesome for the 360 once it is built. the build is more focused for the 360 but that motor wont be ready for another year or so and wants a good system for the 318 now, he is dead set on a tuned length of stainless headers so this has to work.

and what size exhaust system? I was thinking around 1 7/8 for headers and a 2.5 or 3" exhaust???

Also he was thinking about getting a set of edelbrock heads for the 318 and then later using them on the 360 is this doable? he wants good compression, but does not know anything about the 318, but surely it is not stock as it revs upto 6500rpm and runs a 14 flat in a 3500lb car on street tyres and a non lock diff.

let me know what you think?

 

[cbodybob]

I have a 318 powerd drag car. I'm pretty sure my headers are the standard 1 5/8 size. You can get bigger tubes, however they will have fit issues & likely will loose some lower end torque. The 2 1/2 pipes work well. Especially with headers. Eddy heads will work on either engine. I think I would wait till the 360 is ready before I get the heads. I have not run Eddy heads on my 318 because I just felt there was not enough cubes to show a good cost to performance benefit. Also you may have to notch the bore of the 318 due to the big valves. If its a street & strip car. If you get close to 400 HP out of that 360 you probably will want to swap to a A-727 tranny. I have built several mild 318's just simple bolt on's. Eddy dual plane, 600 carb, regular size headers, 2 1/2 pipes, cheap parts store turbo mufs, mild street cams. Good gears (3.55 to 3.91) and the little 318 make a darn nice street car engine on a very reasonable budget. A lot of this stuff can be bough at swap meets cheap.

 

[benno440]

these header tubes will be running up and through the inner fenders. thanks for the info, much appreciated. I want to build these headers so they work well on the 360 as well, that's why I was thinking 1 3/4 maybe, whats next size down? 1 1/2?

 

[rumblefish360]

The Edelbrock heads on a 318 do not need a notch. They will clear.
The header size best suited for a 14 second 318 would be 1-5/8.
For a semi serious 360, the same size would suite though you could step up to a 1-3/4 for a beastly engine.

1-1/2, pipe size for searching for mileage. Enhanced engine efficiency.
1-5/8, typical header size seen. Good to very good power.
1-3/4, excellent max street effort, medium strip power
1-7/8, starting strip effort size. Very good power ability
(you should be going really fast with these.)
Larger than 1-7/8, IE; 2 inch primary pipe, I'd recommend them being on;
1. A all out strip 360. 2+ HP per cube.
2. A stroked small block seeking a some high power levels of approx. 2 HP per cube at a min.
Larger primary pipe size is available.

A lot of header pipe primary size selection will have to do with the engines power output. How serious will the engine be? Is it a strip only car? How much street if not strip only? What is the intended power output?

Exhaust pipe is also a HP dependent issue. While larger is better you can go to far. The loss of torque can be noticed if you go to large. The car will slow down.

To cover the question generally, the 318 can use a 2-1/2 & the 360 can go to 3 inch considering the idea of it being a strip car is forth coming. If it is to be on the street more often, 2-1/2 will cover 400+ HP.

The choice of going to a 3 inch system becomes a catch 22. Again, what are we doing with it and is the driver OK with the sound level?

The 904 trans can be built up to meet the power requirements of a 9 sec. car. This has been done since the 70's. It should not be an issue, just cost money. The 904 uses a little less HP to drive the car foward than a 727 and weighs less.

What is the intended goal of the engine/car in terms of the 1/4 mile time slip?

 

[benno440]

owner was hoping for around 400hp once the 360 is in, probably wants to see around 12 sec qtrs. in full steel body car.
but wants the current 318 to run better but also have this system work well on the 360 when its done.
I think I will stick with 2.5" exhaust, as he also wants cutouts just past the collector flange to open her up at the drags.
unsure between 1 1/2 to 1 3/4

 

[sleepar]

1 5/8... 727.... use 6077 edelbrock heads 63cc for compassion... there's a ton on this for a bodys only....

compression ... sp.ckr

 

[benno440]

does this motor need some compassion? haha. Hughes engines, reckons we will lose power if going to edelbrock heads as we think it still has stock pistons, and that will drop the compression and the cylinders will bleed off more pressure. might sae the heads for the 360 and keep using the iron heads on the 318, what do you reckon?

will the 1 5/8 primaries be too small for a built 360?

 

[sleepar]

Kb 167 +5 hypers brings them out of the hole and they have a forged set

- - - Updated - - -

I would build the 360 and leave the teen alone... 1 5/8 is fat for a small block... go bigger and your int the inner fenders and down like side pipes...

 

[benno440]

that is the way we are building them, they are going through the fenders and down into the wheel well. so still 1 5/8? wont that be small for a 360?

 

[rumblefish360]

It is more of a horse power level thing. While the 1-5/8 will allow for good power, the 1-3/4 will allow more. Depending on the power of the engine, the header size goes up.
IIRC, did I read the owner wants 12's from the 360?
If so, the 1-5/8 will do fine. Mid 12's in A body requires approx. 400+HP.
If it is strictly a drag car, the same engine will run high 11's.
A fine example of this is the 380/360 MP create engine OOTB in Dusters running these numbers.

At Raceway park, Englishtown N.J., I have had the pleasure of talking with a good number of MoPar drivers in this exact combo.
OOTB 360/380 is a high to mid 12 second car in a fully dressed A body while high to mid 11's have been seen when there stripped down.

The faster cars ran bigger headers to maximize top end power.

 

[Budnicks]

I would think a 1.750" {1-3/4"} tube would be fine for the combo {outside diameter tube sizes},
depending on what type of collectors {collector selection can/will change flow & RPM ranges, where the power is made}
& what length header tubes are, you end up using, all can/will effect tubing sizes needed also,
longer tubes will generally make or torque, than a shorter bigger tube header, that's better for RPM...
1-3/4" is a good all around header tube size, for hopped up 360 or the little more radical 318ci too,
as long as the tube lengths aren't too long & loose allot of velocity/stalled air...

I ran 1.625" {1-5/8"} to 1.750" {1-3/4"} home built stepped headers
{24" tubes IIRC (don't quote me), with 4-2-1 Flowmaster 1-7/8" ID X 3" Scavenger series collectors, had to spread the 1-3/4" tubes to fit 1-7/8" (1.875") ID collectors}
On my old 99 Dakota 2wd 5.2ltr {R/T clone},
with ported 5.9ltr/360ci MP 2.02 Magnum R/T cast iron heads,
{IMHFO I think that the increased cylinder-head flow, of almost any aftermarket/better & higher flowing cylinder heads in either alum or cast iron, would have way outweighed the slight compression loss, because of slightly larger combustion chambers}
{mine were 60cc IIRC, combustion chambers} 0.040" Felpro Permatorque head gaskets,
I used the same headers on a 4" stroke X std. bore 9.5:1 pistons with valve relieves,
1.7:1 Harlan Sharpe rockers, MP Magnum R/T hyd. roller camshaft 272*/278* @ 0.467"/0.482" w-1.6:1 std. rockers {0.496"/0.512" gross lift w-1.7:1 HS roller rockers}, w-factory Magnum hyd. roller lifters,
Holley 52MM Hi-Flow TB & larger Hi Flow Venom injectors, on a 390ci {5.2ltr./318ci base} it ran very well...
I got it down into 11's {with 275 drag radials w-3.91:1 gears}, I think it had more in it too,
it was my Daily Driver, so I didn't want to push it too hard...

It's more than tube size...

good luck, have fun, keep us posted

 

[Cranky]

Got a converter behind the teen? What gear in the rear? If it's spooling 6400, it'll love a set of deep gears....and I would go with the 1 3/4 tubes too especially if it's turning more than 6k.