How NOT to build an economical or powerful 'teen

[Ottmundr]

I thought the 302's might be a good idea because of the small combustion chamber. Flat tops and a closed chamber has got to be better than a flat top and open chamber especially if the piston is down from tdc. Am I close? I know the valves aren't huge and the ports small but it's a teen with a small cam. Just my take.

So did I, also because if you look at the pick and pull or other junkyards, they are MUCH less than the Eddys. The Pick and Pull less than 8 miles away has them for like $50 or $60. They have a buttload of late 80's Dodge Diplomats. I was planning on heading down there when I get my tax refund.

I ain't made of money!

 

[273]

What makes the 302s crap? It was my understanding that smaller intake side increased the airflow speed, and you got better torque as a result. Just the thing I'd want on the street. Is it because they are iron instead of aluminum?

Do these 302s make me look fat? :banghead:

Your right to a point. You always want to keep the velocity high as possible but you also want to allow your engine to breathe there's always compromises to make.

Think of torque is what an engine can do in one power stroke and hp is what an engine can do in many power strokes (rpm) (work over time). That's why torque is tied to cid and VE%. VE is how much cid is being utilize per stroke. So yes small ports is gonna help the very low rpm but quickly be inefficient at higher rpm.

Don't forget 318 heads were actually designed with 273 size in mind. The 318 short block hasn't change much over the years and the hp numbers are pretty consistent even with the addition of the 302 heads it's only when they came out with the Magnum did the 318 gain some real hp.

If you look at the torque range of engines stock make about 1:1 - 1.1:1 high performance street make 1.1:1 - 1.3:1 and race engines make 1.3:1 - 1.5:1. So bigger ports carbs headers cams etc... actually make more torque than smaller but at a sacrifice to low end torque.

So unless you like stock power your gonna want to add airflow. The trick is to extend the powerband without moving it from idle. As long as you don't go to crazy with heads it gonna give you more power without loss down low.

 

[Bill Crowell]

RAMM wrote: Mopar cam flat tappet hydraulic .430" .450" 110

That is the Mopar Performance P4452759 dual pattern cam, which is the largest cam you can install in a Mopar small block and still pass California smog. (I determined this by experimentation.) This engine reminds me of a 360 I built once with the same cam in order to pass smog. You can't pass smog with pistons at zero deck; too much NOx. I'll bet the owner is smarter than you are giving him credit for. I'll bet he built the engine for a vehicle subject to the smog laws.

 

[ir3333]

Not really, I tested a 340 (344.5) on Monday with stock "X" heads very similar cam same intake and Eddy 600 carb and it made 364 hp and 403 ft/lbs. I was impressed with the torque. J.Rob

..364 hp and 403 ft./lbs on a stock 340 rebuild?

 

[RAMM]

RAMM wrote: Mopar cam flat tappet hydraulic .430" .450" 110

That is the Mopar Performance P4452759 dual pattern cam, which is the largest cam you can install in a Mopar small block and still pass California smog. (I determined this by experimentation.) This engine reminds me of a 360 I built once with the same cam in order to pass smog. You can't pass smog with pistons at zero deck; too much NOx. I'll bet the owner is smarter than you are giving him credit for. I'll bet he built the engine for a vehicle subject to the smog laws.

Well I spoke with him at length about his choices and almost all of them were "really good deals on E-bay". Also his 1980 F-Body is emissions exempt here as is anything up to 1987. On top of all this 7.5" idle vacuum ain't ever going to pass e-test. J.Rob

 

[RAMM]

..364 hp and 403 ft./lbs on a stock 340 rebuild?

Not stock but not a race build by any stretch of the imagination. KB flat-tops, some mild Comp Cam, Pro-form roller rockers, Air-Gap intake. Stock 2.02/1.60" valves with no port work. J.Rob

 

[nm9stheham]

1 Hp per cu inch is not all that bad, but it is so easy to get well past that these days, 'specially with the good heads used there. The pistons and the very low idle vacuum are my disappointments, and maybe the carb. The cam choice is another mystery; maybe it sounds 'lumpy'... Something is wrong with the oil pump relief .... should be limited at 70 or less psi.

But, if the owner is happy, that is a big deal, and if it runs clean, that is a lot more than a lot of builds can say. For a road cruiser, reliability and endurance are the main battles so in that regard is it not really a disaster IMHO..... it just missed a few chances to be better.

Wish I could see the vertical scale in the pix in post #2.

 

[rumblefish360]

Someone asked if the "302's" were junk/not worth it.
In fully ported form there very good for a iron head. I would only use them in a class of racing that said iron head only. Or a resto, but what car uses a 302 that you would want to resto? I don't know.

 

[RAMM]

Wish I could see the vertical scale in the pix in post #2.

I fixed the picture. J.Rob

 

[Hipo65]

273, My heads are stock closed chamber 1965 273 castings. Stock back cut valves & mild port work. Domed hi-po 273 pistons from kanter. It has an isky e-4 with crane iron 1.6 rockers on it & a ld4b made to fit my early heads. From 2500 to 5700 it pulls like a little freight train.Idle vac is 15-16 @ 750. Dont know power output but im sure its not far from the teen. Im sure headders would help even more but I like how stock exhaust sounds, works & fits.

 

[crackedback]

Well I spoke with him at length about his choices and almost all of them were "really good deals on E-bay". Also his 1980 F-Body is emissions exempt here as is anything up to 1987. On top of all this 7.5" idle vacuum ain't ever going to pass e-test. J.Rob

7.5" of vacuum with that camshaft? Something sure doesn't seem right. Retarded cam timing, not enough initial timing, something. WOW!!!

I thought maybe pushrods too long, but it's got adjustable rockers on it.

 

[Infecteddog]

Oddly enough he was happy with 300hp-ish. At least its going in a 3600lb F-body with 727, 2.91's--LOL. J.Rob

You can imagine it's likely a huge improvement over what's there.

Someone asked if the "302's" were junk/not worth it.
In fully ported form there very good for a iron head. I would only use them in a class of racing that said iron head only. Or a resto, but what car uses a 302 that you would want to resto? I don't know.

2 barrel cop cars are about the most notable thing. The 4bbl cop cars didn't even use them.

What makes the 302s crap? It was my understanding that smaller intake side increased the airflow speed, and you got better torque as a result. Just the thing I'd want on the street. Is it because they are iron instead of aluminum?

Do these 302s make me look fat? :banghead:

Flow. They don't have it. Yes, it's better than stock. If you've ported them the work would've been better spent porting better heads. You need more low-end torque if you're regularly towing over 5k- most people don't understand that most of the appeal they see in modern engines totally disagrees with this logic pattern.

Your right to a point. You always want to keep the velocity high as possible but you also want to allow your engine to breathe there's always compromises to make.

Don't forget 318 heads were actually designed with 273 size in mind. The 318 short block hasn't change much over the years and the hp numbers are pretty consistent even with the addition of the 302 heads it's only when they came out with the Magnum did the 318 gain some real hp.

So unless you like stock power your gonna want to add airflow. The trick is to extend the powerband without moving it from idle. As long as you don't go to crazy with heads it gonna give you more power without loss down low.

It's a very new idea that the 302s offer any kind of improvement. Whenever that idea is conveyed there's usually heavy port work involved. They are brittle small port castings without much material behind them- never meant as performance pieces, just workhorse stuff. The factory itself dropped the compression and added larger cams to improve performance on their vehicles. All those 318 4 barrels didn't have less compression than the E58s in SuperCoupes and LRE motors. Adding compression alone is not a good idea. That is not the best way to improve power and while it definitely helps as you're making other upgrades it shouldn't be the first priority.

I know you are being humorous but NO I am not saying that. Surprisingly enough the Eddy RPM Air-Gap is such a good intake even for a 318. The intake and the Pertronix distributor and carb are my favorite parts. J.Rob

I was surprised to see a very noticeable gain in a stock 340 intake over the Performer.

 

[nm9stheham]

I fixed the picture. J.Rob

Many thanks! That is very courteous of you.

Yes, going from 210 to 245 ft-lbs at 3500 RPM is a pretty significant % change (+15%).

 

[RAMM]

Many thanks! That is very courteous of you.

Yes, going from 210 to 245 ft-lbs at 3500 RPM is a pretty significant % change (+15%).

That's the HP curve youre looking at. It was pretty much +40 points in both HP and TQ everywhere. J.Rob

 

[RAMM]

I was surprised to see a very noticeable gain in a stock 340 intake over the Performer.

The Performer is not nearly as good as an RPM, let alone an RPM-Air-Gap. J.Rob

 

[RAMM]

7.5" of vacuum with that camshaft? Something sure doesn't seem right. Retarded cam timing, not enough initial timing, something. WOW!!!

I thought maybe pushrods too long, but it's got adjustable rockers on it.

Totally agree which is why I checked the pre-load hoping to find jacked up lifters from too much pre-load.

I have had more than one bad experience with Mopar Performance grind cams. I would not even raise an eyebrow if this one turned out to be improperly ground-have seen it before. J.Rob

 

[Infecteddog]

The Performer is not nearly as good as an RPM, let alone an RPM-Air-Gap. J.Rob

Yup, why I found the point relatable. Some see aluminum itself as an upgrade and worth the price of admission instead of going with a cheap stocker if a good aluminum's not in their budget or upping the expenditure and getting a better intake.

 

[crackedback]

Totally agree which is why I checked the pre-load hoping to find jacked up lifters from too much pre-load.

I have had more than one bad experience with Mopar Performance grind cams. I would not even raise an eyebrow if this one turned out to be improperly ground-have seen it before. J.Rob

Yep.

I had one, along with a garbage timing chain, was 12 or 14 degrees retarded... LOL

Cam was 8 degrees retarded after changing TC's to one that was spot on in another build. The chain was in the 4-6 range.

That's some awesome QC for you!