Junk 350

General engine tech -- Drag Racing to Circle Track

Moderator: Team

KnightEngines
Guru
Guru
Posts: 1855
Joined: Fri Jan 09, 2009 8:51 pm
Location: Australia

Junk 350

Post by KnightEngines » Wed Jan 18, 2017 9:38 pm

Got a 350 in for a young bloke I've done work for in the past, it's for his dads car - it was bought as a freshly rebuilt good engine (aren't they all?).
They figured it'd be a good idea to pull it apart & check it over, that's when I got the call LOL.

The rebuild consisted of fresh bearings & a reground crank, new rings & 3 stone in a drill hone job, brown box cam, cheap timing kit & basic rollers, stock everything else.

He dropped it off & I checked it out - stock rods, not resized, stock replacement type .030" pistons, 2 bolt block with a small crack in the valley.
Old 492 heads that have been ported at some stage in their past life (porting looks decent) but have had a crappy valve job since then, has stainless valves that look ok & guides are good.

It's a rough thing, .005-.007" piston to bore clearance, valve tip heights all over the place, stock springs etc.

Plan is to avoid over capitalising on old 1/2 worn out junk & get it together on a tight budget to see him through a few years & build something nicer later.
I'll stitch up the crack, give the bores a proper cross hatch, mill it to zero deck, resize the rods & fit ARP bolts, linish the crank & throw the short motor back together.
Heads will get a decent valve job, a touch up on the porting, skim to get comp to 10:1, some new LT1 style springs & get set up properly.
Cam will be a hyd flat, likely around the 238/244 on 108 area.
Intake is a performer & carb is a 650 pumper.

looking at the heads (haven't flowed them) I'd guestimate they'll flow around 210-220cfm on the intake & 170 or so on the exhaust, MCSA at the pinch is about 1.7-1.8^"

I'm thinking this old junk can make about 350hp, car it's going in is about 2800lb with a 4000 converter & 3.7 gears - should be lively enough for a while.

Who want to take a punt on what this junk can make?

wyrmrider
Guru
Guru
Posts: 6932
Joined: Thu Jan 10, 2013 10:52 pm

Re: Junk 350

Post by wyrmrider » Wed Jan 18, 2017 10:10 pm

238 degree cam in a dad's car? 4000 converter? what's the usage what trans?
basic rollers- is this a roller cam motor?
rods out of round? how do the rod brgs look?? don't fix something that's not broke
are these "compensated" pistons how much do you have to deck the block- enough to have to also do the intake?
maybe leave the pistons down a little and use a thin gasket
timing chain?
clean the oil pump
what difference will it make to flow the heads and touch up the porting?
HD stock long slot rockers? I'd spend the porting time checking the rocker geometry and maybe some new pushrods unless the old ones are pristine or they will eat up your new rockers
were these new pistons with this rebuild or is this a refresh of a previous rebuild- hard to figure that much clearance on a fresh bore and rigid hone
if it is a refresh with that much clearance how's the taper etc?
good rings ?
I've been handed worse

Amilcar
Pro
Pro
Posts: 272
Joined: Mon Jun 20, 2011 9:32 am
Location: Brazil

Re: Junk 350

Post by Amilcar » Wed Jan 18, 2017 10:11 pm

450/470HP ?

KnightEngines
Guru
Guru
Posts: 1855
Joined: Fri Jan 09, 2009 8:51 pm
Location: Australia

Re: Junk 350

Post by KnightEngines » Wed Jan 18, 2017 10:35 pm

Car is a weekend warrior that'll see a few trips to the track, 'Dad' is a rev head & influenced the son - son now owns a 440hp 308 holden that I did for him, Dad wants some of that sh\t!

By rollers I mean rockers, unknown brand 3/8" stud rockers, they look like they'll live just fine with a hyd cam.
I'd leave the rods alone, but I can't find the courage to trust 40 year old rod bolts..........
Bearings are new - it hasn't run since the 'rebuild', they're just King stock replacement type, they'll do.
Pistons are second hand, she's done plenty of work on these pistons & bores, but they'll live 1 more time, I just have to pretend the bores are nicer.
No idea if they're compensated or not, no idea what the deck height is - I received it in bits.
If the manifold needs a skim to fit then so be it.
Timing kit is new, albeit cheap, it'll work in this one.
Porting looks decent, I'll have to blend in the new valve job & the intake short turns are a bit ordinary, worth the time to sort it, won't take long, I won't bother flowing them, if I do I'll end up doing more work.
I'm going to replace the cheap iron rings with some semi decent hastings stuff.

The aim is to get it together as something he can enjoy & get a taste for racing, if the bug bites harder I'll build him something nicer, if not it'll last quite a while as an understressed street engine.

I too have been handed worse to patch up, this one I think will turn out pretty good for a pile of 1/2 used up old crap.

wyrmrider
Guru
Guru
Posts: 6932
Joined: Thu Jan 10, 2013 10:52 pm

Re: Junk 350

Post by wyrmrider » Wed Jan 18, 2017 10:50 pm

sounds like it
studs pinned?
before you get too far on the rods check to see if they are angle cut- that's really hard on bolts too- and hard to fix
should rev like crazy with that piston clearance- got a knurler?
I'd stick a piston and rod in all four corners and measure deck height clerance- but you say this is in a basket?
was the rebuild shake and bake? or shot blasted- I know you know the places where crap hides
I usually bottom tap the mains just because the history is unknown
any hidden rust or sludge?
sps bolts are just as good and less expensive if you have a source

user-612937456

Re: Junk 350

Post by user-612937456 » Wed Jan 18, 2017 10:53 pm

I think 350 is real close if you get tune right maybe a little more torque The better way to raise the Horsepower potential is get a little more flow from those intake ports and raise the compression to 10.5-1 by cutting the heads and a steel head gasket maybe?

KnightEngines
Guru
Guru
Posts: 1855
Joined: Fri Jan 09, 2009 8:51 pm
Location: Australia

Re: Junk 350

Post by KnightEngines » Wed Jan 18, 2017 11:12 pm

Has screw in studs already, 3 different lengths LOL, I've got some spare ones that came with a set of Dart heads a while back, so I'll swap out the mismatched studs for the Dart ones.

No knurler, I've run worse than this, big skirted cast pistons, they'll be ok.
Rebuild was a backyarder, block was not tanked or anything, I'll pull the gallery plugs, tap the threads & just run it through the spray wash.
Block really looks ok, other than the little crack it's pretty clean.
Dad & son will do the dummy up to check deck height - they're hands on & will be doing assembly (Son assembled the 308 I did for him), the more they do the less I have to charge!

It'd be nice to slap a 244/250 on 107 solid cam & vic jnr intake in it, but then the cost will start to blow out into the 'overcapitalising on junk' zone, it'd need main studs, line hone, spring seats machined, double springs & new retainers, longer pushrods etc.
May as well start over if going down that path, we'll use what's there & see what happens!

I reckon it can run high 11's with the driveline it has in a car weighing around 3000lb with driver.

KnightEngines
Guru
Guru
Posts: 1855
Joined: Fri Jan 09, 2009 8:51 pm
Location: Australia

Re: Junk 350

Post by KnightEngines » Thu Jan 19, 2017 12:29 am

Looking through the Crane catalogue I found this:

294/300 adv dur
238/244 @ .050"
106 lobe centres
.502/.516" lift

They even have stock across the other side of town.

I think we have a winner, nice to see a shelf cam with close lobe centres!

pdq67
Guru
Guru
Posts: 7233
Joined: Thu Mar 04, 2010 8:05 pm

Re: Junk 350

Post by pdq67 » Thu Jan 19, 2017 12:57 am

IMHO, a 294 cam really needs 11.5 to 1 CR to run like it should! I know guys run them at 10.+, but still -----

At 10 to maybe 10.5 to 1 CR, I would go with something like an Isky 270 or 274 Mega or an old CC 270 magnum hy-cam here. His 350 will be POWERFUL!!

pdq67

KnightEngines
Guru
Guru
Posts: 1855
Joined: Fri Jan 09, 2009 8:51 pm
Location: Australia

Re: Junk 350

Post by KnightEngines » Thu Jan 19, 2017 1:18 am

Closer lobe centres help with lower compression, I'll get it to at least 10:1 - chambers are currently 62cc, pistons are 12cc, with zero deck & heads as they are it'd have about 9.8:1, around .020" off the heads will be 59cc & 10.1-10.2:1, which will be enough.
I'd love some 1.6 ratio intake rockers for it.

I put a cam very similar to that in a 355 cube holden with slightly smaller heads than this & a performer intake, had a 750 on that one tho, that was another 'spare parts' motor for a mate, bloody thing made 420hp, sounded the goods & was not at all soggy even pulling a 3000 converter & 3.08 gears in a 3700lb barge.

paulzig
Pro
Pro
Posts: 362
Joined: Sun Aug 03, 2008 6:29 am
Location: Australia

Re: Junk 350

Post by paulzig » Thu Jan 19, 2017 3:24 am

KnightEngines wrote:Looking through the Crane catalogue I found this:

294/300 adv dur
238/244 @ .050"
106 lobe centres
.502/.516" lift

They even have stock across the other side of town.

I think we have a winner, nice to see a shelf cam with close lobe centres!
Nice Tony, its gonna run like a raped ape .... 420-440HP Guess??

KnightEngines
Guru
Guru
Posts: 1855
Joined: Fri Jan 09, 2009 8:51 pm
Location: Australia

Re: Junk 350

Post by KnightEngines » Thu Jan 19, 2017 4:12 am

Nah, don't reckon it'll hit 400, got your favorite performer intake on it, with a Vic jnr it may get there.

If it turns out as good as I reckon it might I may suggest a Vic jnr & some 1.6 intake rockers as a future upgrade.

Got the heads washed & a half assed bead blast done to get rid of the 3 layers of paint, no cracks!
Couple of exhaust guides were flogged & the rest were fine, dunno why, they're all K-lined.
I popped a couple of fresh K-lines in & called em good.

Heads appear to have been ported way back in the day - they were ported with stones!
Not a big port job, but more than a pocket port & it's decent enough that I'll just fix the turns & leave it alone.

Carnut1
Guru
Guru
Posts: 3687
Joined: Tue Jun 11, 2013 6:32 pm
Location: Melbourne fl.

Re: Junk 350

Post by Carnut1 » Thu Jan 19, 2017 4:58 am

I think it will make more steam than I would want to push through cast pistons. I think it will spin until it yanks the pin out of the rods. Durability will be directly dependant on how much oil gets past the rings and into the chamber. With your porting ability I bet 15 min per port would make a nice boost in airflow and with the cams and compression you are looking at I would really be fighting for 4 hours porting work bore it and decent pistons! They won't ever need the next motor. Problem with crap builds I have done like this is the damn thing exceeded everyones expectations and the pos out lasted the truck. So never did get to build the better one. Jmo, please post before and after flows. I know, but it will help with the cam and combo selection. Thatnk, Charlie
Servedio Cylinder Head Development
631-816-4911
9:00am - 9:00pm EST

KnightEngines
Guru
Guru
Posts: 1855
Joined: Fri Jan 09, 2009 8:51 pm
Location: Australia

Re: Junk 350

Post by KnightEngines » Thu Jan 19, 2017 5:27 am

Too late for before & after, I'm just about done with the valve job!

MCSA is less than 1.8", she's gonna peak before 6500rpm, likely just over 6000, I've run cast pistons well past that with no issues!
It'll be mostly street driven, won't see beyond 5000rpm very often, so long as it survives the odd blast to 6500 & a few dozen 1/4 mile passes it'll have done it's job.

The problem you get when you start thinking too hard with this sort of build is that a rebore & fresh set of decent slugs then leads to 'well, if the pistons gotta come off the rods anyway may as well buy some cheap scats rather than resize old crap', & that leads to 'well, shit, now it's too good to not put main studs in' & the inevitable 'we've come this far & we're buying pistons & rods anyway, may as well get a 3.75" crank'
& all of a sudden you got a whole bunch of $ invested in junk that won't make much more HP coz the heads are old crap!

Nope, all junk or all good, budget ain't there for all good so all junk it is!

I know these guys, I wouldn't do this stuff for people I didn't know.
But I do love this sort of build, something very satisfying about building something better than the sum of its parts.

PS - I got a 3hr porting budget, so about 15 min per intake port, 5 min per exhaust & 5 for chambers - enough to get the turds as shiny as justifiable!

Carnut1
Guru
Guru
Posts: 3687
Joined: Tue Jun 11, 2013 6:32 pm
Location: Melbourne fl.

Re: Junk 350

Post by Carnut1 » Thu Jan 19, 2017 5:57 am

Sounds good just flow one intake and exhaust port to get an idea of where you are. It may alter your choice of cam. Thanks, Charlie
Servedio Cylinder Head Development
631-816-4911
9:00am - 9:00pm EST

Post Reply