Inliners International Forums General Discussion Hi Performance New Guy Here. 68 Camaro with an L6 250.

It's time to build the little 250. I posted this at camaros.net but those guys don't know engines with less than 8 pistons.

My neighbor is a medical equipment technician. He's also a car man among car guys. I've never met an artist with better abilities than him. He pretty much has a mini machine shop in his garage.

His baby is a Datsun z that has a full Ferarri 250 GT kit car body, hand built suspension that rivals many supercars, hand built interior to mimic the 250 GT, a 370z motor mated to a 6-speed manual, custom exhaust, etc, etc. It's really too much to list here without pics but suffice to say there's kit cars and there's his kit car.

In his last iteration he had a inline engine, I think a Datsun, in the car that he converted to EFI with a custom kit he created. He's no longer using it.

So I popped in his garage Friday to discuss world issues, petrol, and bonnets(since he's a Brit). I showed him a couple of my latest changes to my 68 and tossed him the keys. We went for a half-hour drive and I suppose he deemed my car worthy because he brought up his EFI kit. He knows i want to build the 6 and that I just won first at Camaro nationals for mild modified.

We started talking about the build. Turns out my car's been on his mind a bit.

He's suggesting the following to start:

Install his EFI system with a custom, hand-made polished aluminum intake, tubular header by Clifford, dual exhaust, and see how it goes. Then follow it with pulling the head, lump ports, over-sized valves, roller rockers, and a mild cam. Build it with a future turbo in mind.

For the intake we're going to weld bungs for the injectors close to the head so each injector squirts next to the cylinder instead of upstream so we don't have to deal with heating it. Use smaller runners for higher torque and velocity. Combine them to a 3 inch throttle body and pull cool air from up front by cutting a hole through the radiator support near the headlight. Toss in two O2 sensors for proper tuning.

This set up should make it easier to add a turbo or supercharger in the future.

Keep the 2-speed powerglide, swap out the diff gears and add an Eaton posi, possibly make a new driveshaft for weight, and go from there.

We're thinking we'll make it a mix of old and new using the original drive train but highly modified.

Does anyone have better suggestions? Going for a highly unique build just because, well, we can.

We can fab up just about anything so I'm not looking for kits or expensive aftermarket systems.

Does he know what "siamese port" is?

Get rid of the powerglide, unless you want it to be slow?

Having an original powerglide trans is nothing to brag about, it's something you should hide & burry it & put it to rest & out of it's misery. IMO.

Sorry for the rant, I just really dislike the PG trans, especially for a day to day street car in a low powered 6 cyl car.

A PG trans has there niche & can be a great trans for certain applications.

Good luck on your build!

The one thing I liked about my moms 73 Nova 250 & a PG trans, is that you could push start a PG tans equipped engine, but you need to be above about 20 MPH.

Not sure if you guys knew this?

MBHD

There is another option that at the end of the day will give you a 275/290 HP engine in bone stock configuration and will be less money overall than moding the 250. Be aware that the intake ports on the 250 make it hard to get a good tune with EFI unless you run TBI. Tell your buddy they are like a mini head.

www.carcraft.com/techarticles/ccrp_1108_turbocharged_vortec_inline_six/

www.vortec4200.com

Add a turbo to the stock 4200 engine and you have a 400HP engine at 8# of boost.

2005 4200 engines are going for about $1200 complete with everything to do the swap.

Whats needed besides what you get from the wreckers is:

modified oil pan or a rear sump oil pan < ~$650
modified wire harness $500
and build a set of engine mounts

What models and years are good donors for 4200 engine/transmission/ECM? I see you mention 2005 vintage above.

I would put this into a '72 Nova. Currently has stock subframe.

Chevy Trailblazer or GMC Envoy.

If you can find a bent/rolled 2WD donor - its the best way to get every thing.

i think some of you might be missing the point here...

it's the original engine and trans in car model where nearly every single inline was pulled for a v8.

i want to build the original 6 and trans.

that said does anyone see major problems with the plan? particularly mounting the injectors directly in front of the head intake ports?

You have a great plan,, good choice on the engine,,, just not the trans.

Here is mine, injector angle is incorrect, but it will work.


MBHD

You need to talk to Tom Lowe on here. The shared intake port and cam timing makes it very difficult to get a good tune with port injection. Tom has gone through the issues and can give you more guidance.

can someone tell me why there's trouble tuning the port injection set up? would a divider in the runner fix the problem?

also i ordered a set of headers from summit.

http://m.summitracing.com/parts/big-11510flt

yes i know they're for trucks and not my camaro. we'll modify them as needed.

so... what will i have to modify on them? anyone go down this road?

I modified similar (possibly exact same?) headers for my Nova. Minor cutting, tweaking, and welding to fit my Nova. Worked just fine. If you look closely, I marked the welds with a Sharpie so you can see where I sectioned them.



Then I used them for a pattern to build my own stainless headers which also work just fine but fit even better and look sharp too.

The problem is the head, not the runner. In a siamese port head you have 2 cylinders sharing 1 intake port. And because of cam timing events that cannot be corrected, it is common for one to rob fuel from the other when heavy load levels are placed on the engine. Kinda' like musical chairs except the cylinder that can get the fuel first makes the other one lean and can melt pistons and burn valves, etc...

Thats why panic asked if your friend had any knowledge of the minis, because they also have the same design issue, and anyone having tinkered with them would know that, and advise against it.

ahhh. gotcha.

it that case i have an idea.

You can divide the intake ports.
Problem when doing this mod, the intake port window is too small & really constricts the port flow.

You can widen the top of the ports like a "V" shape to try & make the port flow a little better.

MBHD

That's what my thought was.

Tore into it and I don't see how the long tube headers are going to work. They hit both the power steering pump and box and hang 6" too low. So I'm returning them...

I ordered Langdon's CI split headers instead. Still going with the same plan: Y-pipe them together and back using a single 2.5" pipe into a Flowmaster muffler, over the axle and out like stock.

I'm going to try it without doing the heat plate but if I need to I can do it using thick sheetmetal I have laying around.

Let this be a lesson to anyone else looking: the truck headers don't work on cars.

Update:

Got the Langdon headers in last night and fired it up. I'm going to go with a cheap exhaust because I plan on yanking literally everything I'm doing on this round in about a year and adding a snail to my engine bay. The more I look at things the more I realize I should go with a turbo system. They make a nifty exhaust manifold for turbo chargers for these things and though it's pricey it's the way I'll go to make it easier to install.

The plan is this: Get the exhaust put on, drive it like I stole it for a bit, next month get a 4bbl and a Clifford intake, drive it like I stole it some more, and in January pull the head (possibly the whole engine depending on what I find), get oversized valves put in, port and polish, remove .030" to up the compression a bit, lump ports and put in a cam. At that point I'm going to drive it like I stole it some more.

The following winter it'll go under the knife again for the turbo charger, Fast EFI (my original plan won't work due to the intake valve configuration), an O2 sensor to make sure I don't blowed it up real goo', and drive it like I stole it.

At some point I'll have to pull out the rear end gears and put in a posi system. Also forged pistons and rods. Crank and bearings are good for 700 hp on the stock engine according to the guys in Brazil. I don't plan on getting anywhere near that! I'm sure I'll be upgrading other things along the line as well. Maybe a TH350 or 400.

...but forget all that for now and listen to this:

https://www.youtube.com/watch?v=v03lzJ2DlF8&feature=youtu.be

eye candy:







The Langdon headers cleared pretty well. Not many real issues once I got into it. Had to trim some stuff but nothing that affects flow or durability. Overall I'm quite happy with it.

I'll know if I added any power hopefully tonight.

I'm shooting for the 400rwhp range when I'm done. I'd like to have a streetable and reliable 11 or 12 second car. Way cool with the inline 6 as well. It would make my day to pull up to the line with the 250 badge on the side and smoke a couple of 350's. Heck it might be able to do that this spring!

Question: Since I'll only be going a month or so before adding a Clifford heated intake do I really need to screw around with making a heat plate now? I'll only drive it 200 miles or so before I put in the Clifford. It's pretty warm in MD...

No, you don't need a heat plate for 200 miles in warm weather.

Truck headers can be made to work as I showed above... '72 Nova should be same fitment as 68 Camaro, I believe.

Thanks for the response. That's what I'm thinking as well.

I could have made the truck headers work but it wasn't worth the time vs the money to return them and get the Langdon's. I'm happy with the fitment of the langdons and MAN does it sound MEAN with open headers...

I was concerned about the weight but they're actually not that heavy for how thick they are. I think the shipping weight was 25 lbs vs 22 for the truck headers. Granted there will be about 1' more pipe but we're only talking a couple more pounds. I can't see why anyone wouldn't go with Langdon on this one.

I thought they always were a better option & not having to worry about header gasket leaks.

I am pretty sure you would loose a bit of power as compared to some nice tuned headers, but seems not to be worth the headache of gasket blowing out, ground clearance issues.

Something I don't think Tlowes dyno testing on the 250 engine running headers VS Langdons exhaust manifolds were a complete test.

When the 250 was running on the dyno & Langdons manifolds were on at the time & a Fluid damper, I believe the tests were inconclusive because I believe the Fluid damper was failing and @ the time it finally failed during this particular test.

A.F.A.I.K., he never did retest the Langdons manifolds with a good running damper installed.

When an engine has a damper that is not working as it should, it will absolutely kill the power output.

I struggled for a long time running stock dampers, the engines, would never turn high RPM, (meaning above about 5500 approx)
I later used a standard 8" SBC damper then all the sudden the engine would rev past 5500 RPM quicker, & make power to 6500 RPM. Really smoothed out the engine vibes I could actually feel.
When I added a Paxton supercharger it would turn 7000-7500 RPM w/the same damper.




MBHD

https://www.youtube.com/watch?v=yBFB5KvNPcE&feature=youtu.be

Much better.

Langdon headers into 2.5" dual pipes into a Y about 1' back from the bend to horizontal, along drive shaft, over the e-brake cable, into a Flowmaster series 10 muffler, over the rear axle, and dump out behind rear fender hidden away like stock.

With that kind of sound & nothing to back it up, better not rev it up @ a stop light.

Sounds good!

MBHD

It'looks do 0-60 in 8.2 minutes.

Hank,
The Gonkulator agrees with your hunch about the Langdons vs Headers -
When I Gonkulate Tom's Dyno250, with its 214-214 cam, Clifford and 390 Holley, and LumpPorts, using Headers only adds maybe 6ftlb and 5hp vs the Langdons. Really debatable if worth putting up with headers just for that.

gbauer,
Here are a few numbers to think about along the way:
When I ran my tired-250cid Nova Powerglide 3.08 on the GTECH it was very similar to your Camaro - stock 250, stock exhaust, Clifford 4bbl.
GTECH said
2.62 60ft Definitely not a traction issue....
11.42 at 61.8 1/8 mile (GTECH measured)
17.82 at 76.2 1/4 mile (Gonkulated)

The same setup only with a 292 instead of a 250 was almost a full second and over 4mph faster.

I suspect your Camaro is a bit heavier than the Nova and lacks the 4bbl (for now) but has a better exhaust (the pipes & muffler Gonkulate to a gain of 12 net hp or so) so the times will probably be similar. So counting the manifold, that's not far from your 20hp buttometer estimate!

I had a similar experience with truck headers:
* They fit the Nova, and it could even run at Daytona since they let it turn left....but not right - Pitman arm hits.
* On the 250 they just about hit the ground.
* On the 292 they give about 1.75" ground clearance, so the car would be driveable as long as you don't plan any sharp right turns or bumps. A hammer may fix that or I do plan to cut a set like the above and make them work. Lots of work though.

I can tell I need a larger intake and 4 bbl now. Also going to need head work.

At that point I think I'll be done for a bit. It needs a bit more punch but I'm not building a racecar.

I think Tom also tested the cast iron headers vs. tube headers on the 292 as well, because Tom Langdon was on hand during some of that dyno session. And he saw that in most of the street driving RPM's the cast iron Langdon's exhaust performed pretty much neck and neck with the tube headers up to a point.

Just for fun I assumed your Camaro at 250lb heavier than my Nova, so my guess is 3320lb including driver. If you can weigh the car see how that compares...

So here is what the Gonkulator thinks:
Bone stock
Torq 229 at 2500
Powr 153 at 3800
2.71
11.78 at 60.2
18.40 at 73.4

Langdons and your exhaust
Torq 234 at 2500
Powr 159 at 3900
2.66
11.52 at 61.7
17.96 at 75.8

Clifford and 390 Holley 4bbl
Torq 226 at 2800
Powr 177 at 4500
2.69
11.53 at 63.1
17.89 at 76.6
The Clifford is too big with that tall Powerglide+3.08 gear.
Not to worry, the lump port head will make up for it.
I'd be careful not to over-cam though if you are keeping the Powerglide and tall gears. Assuming you have 3.08's

I Gonkulated 1 final run adding the lump head, 9.5 compression, and a 194-204-112-.464-.490 cam.
Torq 259 at 3400
Powr 228 at 5200
2.62
11.00 at 68.3
16.87 at 82.7
Finally in the 16s!
Back in the 60s there were big-block cars in the 16s at 80 & change (and powerglide GTO's in the 15s for that matter!)
Not much will help that 60ft given all the tall gears but the small cam means it will still be a good cruiser and good on gas too. Good enough til the turbo arrives.

Hold it, just one second.
I thought you said it was a toss up between the Offy & Clifford intake manifolds.

I have always stated the Clifford is has huge runners & port velocity is low, which translates to a soggy bottom end.
Drivability is affected, carb signal is poor with the Clifford.

I also stated, if your engine & car/vehicle are properly set-up correctly, the Clifford will & does make more power over the Offy.

The Offy is hard to beat on the street.

My tests between the two manifolds were only done on a 250 sized engine like your testing.

Deucecoupe, what do you think how a stock 194 C.I. engine would perform w/a Clifford?

I know you said w/your tests, there was really not a clear winner between the manifolds, but now it seems you do favor the Offy?
"The Clifford is too big "
I would like to hear your opinion of why it is too big, if both manifolds performed the same basically w/your testing.

Not starting anything here, just would like to hear what you have to say about both manifolds, since your testing was more relevant than mine was 20-30 years ago.

Testing the manifolds in a real car that runs & drives is what tells most of the story about how they perform IMO.

Thank you

MBHD

Hank,
Indeed, at the level where I said "too big", this combo does in fact favor the Offy intake. Here is the same Camaro, all stock 250 except for manifold/exhaust and OFFY intake, 390 Holley
Torq 231 at 2800 +5 vs Clifford
Powr 174 at 4300 -3 vs Clifford
2.66
11.44 at 63.0 .09 sec win for Offy
17.78 at 76.9 .11 sec win for Offy
So the Offy wins by maybe a carlength.
That's consistent with what you have said though not by much.
As you may recall, I was in fact surprised when the Clifford actually "won" a couple of the 60ft times vs the Offy - the Gonkulator wont catch everything, some of it is just engines/intakes/carbs, maybe even jetting, that "like" each other a little better.

I too would pick the Offy at this level - stock cam, tall gears, etc. But even then, if it was a $40 Clifford vs a $200 Offy I'd buy the Clifford (for a warm climate that is). Gbauer had just mentioned plans for the Clifford so that's what I ran.

I am wondering how is the 68 Camaro almost 1second faster then me bone stock when I have a turbo 350 and he has a powerglide? Do you have the68 engine rated at gross hp and me at net hp? Do my bumpers slow me down that much? Please don't think that I am complaining , I think that the Gonkulator is great thing. If possible please explain. Thanks in advance, Jay 6155

Interesting...

Might reconsider the offy now...

On the camaros.net forums we were discussing 4 bbl vs 2 bbl for this build and it sounds like the 2 bbl might be better.

Would 2 1 bbl carbs actually be the way to go instead? Using an offy vs 4 bbl with a clifford? Or a single 2 bbl on an offy? If I go there can I later add an EFI system?

You guys have gone down this road many, many times. I'm new here. Ultimate goal is 300+ hp using a turbo and efi.

Gbauer,
Without careful study, as I concluded way back, for a mild build I'd grab either Clifford or Offy, if you can get a swap meet deal on one or the other. As Hank said the hotter the build, and the steeper the gears, favors the Clifford, tall gears and mild build or small inches favor the Offy.

I'm not a turbo guy, maybe Hank or Tom or others can comment but my guess would be that with the turbo, you will have plenty of air to fill that big Clifford so that might even be better.

The only 2bbl carbs I like are if theyre progressive. The biggest progressive available afaik is the Pinto Weber carb, about 200cfm at 1.5" Hg which is marginal even for a stock 250cid. So the next common stop is the 390cfm Holley 4bbl. You can always adapt either 4bbl intake down to a 2bbl if you want to try it but I don't see any reason.

Some of the Falcon Six Ford guys run a 2bbl sideways just because a 4bbl wont FIT, so that's a different reason.

I.M.O.,For great throttle response it's hard to beat a 2BBL carb.

That being said, they will not provide enough airflow like a single 4 BBL carb can give.
The GM dual jet carbs are OK, but even the larger dual jet seemed to not provide enough air.

I ran a 350 CFM Holley, that was definitely too small & I never tried a 500 CFM Holley 2 bbl. Anyone here has?

I seem to have better luck when I used 4 bbl carbs that were smaller than 650 CFM.
4BBL carbs that were in the 400-500 CFM seemed to have worked best for me.

After trying the Offy & Clifford & several carbs, trying for the best combo.
I tried Quardrajets, 4bbl 750,650 600 Holleys, 350 CFM 2 BBL, small & large GM dual jet carbs, 400,500,625 AFB & AVS carbs, I even tried a Thermoquad (just to try) ALSO known as a Thermobog
I finally switched to 3, 48 MM side draft Weber DCOE's.
You would not need 48 MM carbs.
They are pricey, takes time & parts to tune correctly, but the side draft were by far the best carb combo I ever ran.

I think,(but have not tried it) using a Offy intake with 2, 2 bbl carbs would work really good.

Just my opinion.

MBHD

Just curious if you ever weighed your 78 Nova?
I know a 78 Camaro is really heavy. My friends SBC 77 Camaro weighed 3825 w/A/C removed. That was with light weight Weld wheels, 15X8 rear & 15X3.5" in the front.

MBHD

The only 2bbl carbs I like are if theyre progressive. The biggest progressive available afaik is the Pinto Weber carb, about 200cfm at 1.5" Hg which is marginal even for a stock 250cid. So the next common stop is the 390cfm Holley 4bbl. You can always adapt either 4bbl intake down to a 2bbl if you want to try it but I don't see any reason.

Holley also made a progressive 2b carb in a 350 & 500 cfm. I have one of the 350 cfm. carbs. But you will pay dearly for them when you can find them.

J78,
Good question-
It looks like a matter of things stacking up:
* I have your weight down as 3310, almost 300lb heavier than the 68 Camaro.
* Your T350 helps, but you also have a taller rear - and the T350 does draw a little more power than the Glide.
* The engine is down maybe 15-20ftlb across the board, a matter of smog tuning mostly.
That pretty much does it.

I am pretty sure your doors have reinforcement panels inside the door.

A corrugated metal like a ruffles potatoes chip.

All those "safety" features really add up the weight.

I weighed my Camaro one time with this combo, not much gas, no rear seat, My friends light Weld wheels, http://www.bing.com/images/search?q=weld...selectedIndex=0 front & rear sway bars, disc brakes in front.
It weighed in at 3000 even LBS.

MBHD

Does this mean that my nova looks fat?LOL. Honestly all those little things must add up. The 3310 is without me (235) and my grandson (100) added to the car when we ran it against the stopwatch. Also true, I have 2.73 gears and probably those door beams. The integrated cam has a little more exhaust lift and duration and my stock pipe is 2 1/4vs 2 inch, any small gains there were probably lost due to the drop in compression compared to the stock 68 specs. How much faster would that camaro be both stock and with the cast iron headers if a th350 with a stock type converter replaced the powerglide? I would think also about a second. Jay 6155

It (the Camaro) would probably be .5 faster in the 1/4 mile w/a TH350 trans.

MBHD