Bad Engines: Where are they?

[cchase]

The GM 305 is definitely quite anemic. I have read about people getting 400+ hp out of them running N/A but even that is well under 100 hp/liter.

Still a good engine though, just not a particularly mod-friendly one when the 350 was the same price and already had a huge following.

And the 5.0 only came out to bridge the gap between the 4.3 and 5.7 engines.

 

[d00df00d]

Originally Posted By: artificialist
What doesn't makes sense to me is how the VG30 Nissan engines were so tough, yet the VG33 series were a disaster.

Maybe there's a difference in internal dimensions. What is the bore and stroke of each engine?

 

[swalve]

I have to jump in and say that the Mitsu 3 liter engine is one of my favorite engines. Yeah, it's got the valve lifter guide problem and noisy lifter issues, but those are pretty darn minor. I've "known" a half dozen of them or so, and they all performed admirably. Still running one on my work car @ 210000 miles and 17 years. Knock on cast iron, still goes just as good as it did when new.

I had a Sebring coupe and my mom has a 3000 GT, and I have to hand it to Mitsu, their suspension designs are awesome. Those cars stick to the road like glue, and feel nice doing it.

 

[440Magnum]

I've gotta say I've never understood the SBC 305. All the downside of the 350 (long stroke, poor rod ratio) plus a tiny bore. I guess it did the job of moving low-cost transportation appliances around rather well, but seems to me the same job could have been done with a stout six-cylinder or the 307. The Chevy 302 was also a superb little engine, but since it was only offered in a very high state of tune (unlike the Ford 302 that ran the gamut from pickup truck tune to Boss tune) it was much more of a niche engine.

I fundamentally disagree that a 3x4 stroke/bore engine somehow cannot be a decent torque builder at low RPM. The Ford 302 proved that rather well, I'd say. And look no further than the Mopar 383 (and "smogger" 400 version of same) for another engine with a very oversquare layout that still produces scads of torque. Bore/stroke ratio is far less significant than cam, compression, valving, port design, manifold tuning, etc. when it comes to the shape of an engine's power curve.

And on the flipside, undersquare and near-square has come back in vogue since its easier to control emissions with a smaller bore and longer stroke, but manufacturers are still using undersquare engines to favor high-RPM horespower over low-end torque at times. Look at a Honda VTEC for example. Or a Ford Modular for that matter.

 

[mechanicx]

Originally Posted By: cchase
The GM 305 is definitely quite anemic. I have read about people getting 400+ hp out of them running N/A but even that is well under 100 hp/liter.


I don't consider that 80 HP/L very anemic for engines of this type. Most stock 305 were anemic by intended design application. But most srock 302's are also anemic.

Quote:
Still a good engine though, just not a particularly mod-friendly one when the 350 was the same price and already had a huge following.


That's the main thing, not too many good cylinder heads are available or pistron kits.

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And the 5.0 only came out to bridge the gap between the 4.3 and 5.7 engines.


I don't look at it that way at all really. The 305 and 4.3 were introduced at about the same time with the 305 probably first. But Chevrolet has a long history preceding this of offering smaller bore sbc, the 307 since '68 which also was ignored, the 262, 267 which was a dog and the 4.3 V6 did replace. The 305 was probably the long-lived and more used version by far. GM was considering dropping the 350 all together in the 80's except for the 'vette and maybe heavier duty trucks.

Anyway, it's more of a case that the 350 got all the attention than the 305 being so anemic by it's designed bore diameter. Plenty of other similar engines before it and after were no more oversquare yet aren't particular considered to be anemic. The '83-'84 HO wasn't bad for its time and I remember reading an article in Car and Driver back in the day where it whipped up on a 302 Mustang in a test comparison. I think this was back in '83 or '84.

 

[mechanicx]

Originally Posted By: 440Magnum
I've gotta say I've never understood the SBC 305. All the downside of the 350 (long stroke, poor rod ratio) plus a tiny bore. I guess it did the job of moving low-cost transportation appliances around rather well, but seems to me the same job could have been done with a stout six-cylinder or the 307. The Chevy 302 was also a superb little engine, but since it was only offered in a very high state of tune (unlike the Ford 302 that ran the gamut from pickup truck tune to Boss tune) it was much more of a niche engine.


There is a lots reasons why a manufature might opt to reduce the bore instead of the stroke in a production engine when the extra CID isn't desired. The straight 6 is nothing comparable to 305 and the 307 is litle better than the 305. People seem to forget that Buick 3.8 has about the same bore/stroke ratio as the 305.

Quote:
I fundamentally disagree that a 3x4 stroke/bore engine somehow cannot be a decent torque builder at low RPM. The Ford 302 proved that rather well, I'd say. And look no further than the Mopar 383 (and "smogger" 400 version of same) for another engine with a very oversquare layout that still produces scads of torque. Bore/stroke ratio is far less significant than cam, compression, valving, port design, manifold tuning, etc. when it comes to the shape of an engine's power curve.


What has the Ford 302 really proved? Most of the stock ones scarcely have valves or ports any bigger than the 305's. The Ford 302 just isn't a torguey engine IMO. I'm not arguing that the 302 doesn't work or since its received so much attention has been made into something. Sure all those things that you mention matter, but what sense does it make to have 4x3 bpre/stroke, then run short rods and small cams, ports and valves because all you are looking for is low speed torque? You can't stroke the Ford 302 much either. Anway, I think the way some people cast aspersion on the 305 are kind of ridiculous.

Quote:
And on the flipside, undersquare and near-square has come back in vogue since its easier to control emissions with a smaller bore and longer stroke, but manufacturers are still using undersquare engines to favor high-RPM horespower over low-end torque at times. Look at a Honda VTEC for example. Or a Ford Modular for that matter.



Honda's are notorious for suffering in low-speed torque. Not that Honda uses a lot of oversquare engines, but generally street engines may not make the most peak power being les oversqaure but they do run better at lower RPM generally. Very, very few street engines even in the past are as oversquare as the 302.

 

[cchase]

For sure you would know better than me about the exact history. I remember reading years ago that the 305 was the "smog motor" to offer better emissions than the 350 and more torque than the 4.3 in vehicles over a certain wheelbase. Beyond that, I don't know very much about its specific history.

All I know is that I really like the 305 in my truck. Even with 3.42 gears it tows my 3200 lb boat without a problem, I get 20-22 mpg on the highway and it seems very smooth even compared to the 350.

In my limited knowledge of this, I had always thought that long stroke/small bore was good for torque low down and that short stroke/large bore was good for hp higher up.

All in all this has turned into one of the most intellectually stimulating topics this board has had in the time I've been reading through it, even if it has gone off on a bit of a tangent.

 

[Ben99GT]

Originally Posted By: 440Magnum
I've gotta say I've never understood the SBC 305. All the downside of the 350 (long stroke, poor rod ratio) plus a tiny bore. I guess it did the job of moving low-cost transportation appliances around rather well, but seems to me the same job could have been done with a stout six-cylinder or the 307. The Chevy 302 was also a superb little engine, but since it was only offered in a very high state of tune (unlike the Ford 302 that ran the gamut from pickup truck tune to Boss tune) it was much more of a niche engine.

I fundamentally disagree that a 3x4 stroke/bore engine somehow cannot be a decent torque builder at low RPM. The Ford 302 proved that rather well, I'd say. And look no further than the Mopar 383 (and "smogger" 400 version of same) for another engine with a very oversquare layout that still produces scads of torque. Bore/stroke ratio is far less significant than cam, compression, valving, port design, manifold tuning, etc. when it comes to the shape of an engine's power curve.

And on the flipside, undersquare and near-square has come back in vogue since its easier to control emissions with a smaller bore and longer stroke, but manufacturers are still using undersquare engines to favor high-RPM horespower over low-end torque at times. Look at a Honda VTEC for example. Or a Ford Modular for that matter.



I agree with all of this 100%, spot on.

Originally Posted By: mechanicx
Honda's are notorious for suffering in low-speed torque. Not that Honda uses a lot of oversquare engines, but generally street engines may not make the most peak power being les oversqaure but they do run better at lower RPM generally. Very, very few street engines even in the past are as oversquare as the 302.


And you'll find that most low torque, high revving Honda 4 cylinders are very undersquare. The EFI 5.0, despite being oversquare, is known for its low end torque. It's their best trait in stock form.

Look at the bore and stroke of certain engines that spin north of 8000 rpm and are known for having lots up top but very little down low. Honda S2000 I4, 360 Modena V8, BMW M3 I6, all undersquare.

 

[mechanicx]

Quote:
Originally Posted By: Ben99GT

Honda's are notorious for suffering in low-speed torque. Not that Honda uses a lot of oversquare engines, but generally street engines may not make the most peak power being les oversqaure but they do run better at lower RPM generally. Very, very few street engines even in the past are as oversquare as the 302.


And you'll find that most low torque, high revving Honda 4 cylinders are very undersquare. The EFI 5.0, despite being oversquare, is known for its low end torque. It's their best trait in stock form.


But is that to say they wouldn't have less low-end torque and/or not more top end potential if they were square or more over-square? I just don't really agree that the Ford 5.0 is known for it's low-end torque versus similar designs. Like I said, the Ford 302 is crutched that way in stock form with small valves and runners and a small cam. Obviously under and over square is just part of the equation, but it was others saying that less oversquare 2V can't breath. And so I think the 305 being less over-square (not even box or under-square mind you) is just part of the equation of why it doesn't seem to breathe well.

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Look at the bore and stroke of certain engines that spin north of 8000 rpm and are known for having lots up top but very little down low. Honda S2000 I4, 360 Modena V8, BMW M3 I6, all undersquare.

I think think the orginal Honda 2.0 was slightly oversquare. I'm not sure but the Modena 360 I thought it was very oversquare and I thought the M3 made good torque, the 2.2 Honda is slightly undersquare I think that's true. But this is apple and oranges, those engines are 4 or 5V per cylinder. And no one is saying if you put too much cam timing and valve area in even an undersquare engine that it won't be a dog in the low-end. 4 and 5 valves tend to give up a little low-end torque to 2V anyway. And I'm sure you will have a fit over that general statement too.

 

[mechanicx]

Originally Posted By: cchase
For sure you would know better than me about the exact history. I remember reading years ago that the 305 was the "smog motor" to offer better emissions than the 350 and more torque than the 4.3 in vehicles over a certain wheelbase. Beyond that, I don't know very much about its specific history.

All I know is that I really like the 305 in my truck. Even with 3.42 gears it tows my 3200 lb boat without a problem, I get 20-22 mpg on the highway and it seems very smooth even compared to the 350.

In my limited knowledge of this, I had always thought that long stroke/small bore was good for torque low down and that short stroke/large bore was good for hp higher up.

All in all this has turned into one of the most intellectually stimulating topics this board has had in the time I've been reading through it, even if it has gone off on a bit of a tangent.


Yeah I agree with all that. I remember the 305's getting very good gas mileage for the time, running very smoothly. You would expect that with its smaller combustion chambers. And I also remember almost full torque available right off idle. What some might not be considering is that most of the 305's had smaller valves than the maximum possible, very small cams and restrictive intake and exhausts, and on top of all that the 305 cars typically got a very tall rear axle ratio. So maybe that is why the 305 gives such an impression of being anemic. If you ever drove an '83 or '84 HO you would not feel the engine is anemic at all. You might even conclude the the '87 350 TPI is as anemic. It is mostly in the tuning.

 

[Ben99GT]

Originally Posted By: mechanicx
I think think the orginal Honda 2.0 was slightly oversquare. I'm not sure but the Modena 360 I thought it was very oversquare and I thought the M3 made good torque, the 2.2 Honda is slightly undersquare I think that's true.


Honda S2000 2.2 (b x s) - 3.43" x 3.57"
BMW M3 e46 3.2 (b x s) - 3.43" x 3.58"

I misremembered the Ferrari bore and stroke.

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But this is apple and oranges, those engines are 4 or 5V per cylinder. And no one is saying if you put too much cam timing and valve area in even an undersquare engine that it won't be a dog in the low-end. 4 and 5 valves tend to give up a little low-end torque to 2V anyway


4V engines have better velocity characteristics and tend to produce better low end torque, with all other variables equal. My 4V 4.6 made right at 280 rwtq (281" engine) by 2200 rpm on the dyno. My buddies similarly modded 4.6 2V made ~230 rwtq at the same rpm and only did ~290 rwtq at peak (4300 rpm). The truth is head/cam/intake/compression have a much lager impact on an engine's torque curve than whether it is oversquare, square, or undersquare. One of the nastiest high rpm N/A screamers I know of is undersquare.

N/A 5.4 4V

http://www.youtube.com/watch?v=4ApIYjTpWIo
http://www.youtube.com/watch?v=8ORq_zuyzxI&NR=1
http://www.youtube.com/watch?v=ehMS3mztPwo&feature=related (blew the tires off on the dyno)

 

[mechanicx]

Well still the fact remains that if you have too much valve area and valve timing your torque curve can dip at the lower RPM. If a 4V engine has small valves and ports and little valve timing as many stock engines do then of course it can make good low RPM torq. I don't know what all was going on between those two cars, due to variable valve timing, different exhaust, compression or tune. But the point is it's not really a direct comparison of 2V vs 4V or bore/stroke ratio. Using smaller valves, ports and less valve timing is not really exploiting an engine's being oversquare.

The point is as interesting as that all is none of it really has anything to do with whether or not the 305 is so bore shrouding the valves to not be able to breathe. Or whether a 302 with bigger valves, ports, and more valve timing to make more HP than a 305 won't suffer loss of low speed torque. It is sort of all a tangent.

 

[Ben99GT]

Originally Posted By: mechanicx
Well still the fact remains that if you have too much valve area and valve timing your torque curve can dip at the lower RPM.


4Vs can get away with more total valve area because they have two smaller intake and exhaust valves which helps promote velocity.

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If a 4V engine has small valves and ports and little


The 4V has 177cc intake ports and 1.457" intake valves while the 2V has 159cc intake ports and a 1.752" intake valve.

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I don't know what all was going on between those two cars, due to variable valve timing, different exhaust, compression or tune.


Both cars tuned by the same tuner on the same dyno, both cars 4.6L, both cars stock long blocks, both cars with basically the same mods, 4V has 10.1:1 CR, 2V has 9.3:1, not nearly enough to account for the ~50 ft lb at 2200 rpm disparity. Neither car has any form of VCT or variable intake maniold. Multi-valve engines lacking low end torque is a generalization based on a misinterpretation of data.

 

[mechanicx]

Well I can't speak for what you say your tuner measured or these 2 modular engines, not really a Ford guy. But you are missing my point and misconstruing things as usual. You can go on believing valve area, port volume, bore/stroke ratio and rod ratio and especially on carbureted engines have little or no bearing on the torque curve if you want. I've seen plenty of dyno test that show it does. Valve timing and compression ratio are probably the biggest factors, but smaller bores tend to allow a little more compression and less ignition advance needed. So there's another tidbit you might want to start another debate about.

Anyway I'm not going to spend all day debating every argument or strawman that can be created.
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4Vs can get away with more total valve area because they have two smaller intake and exhaust valves which helps promote velocity.


I will give you that point. To a degree I think a $valve can promote velocity through the same size port because the valves tend to be less shrouded than some 2Vs.

 

[OVERKILL]

Originally Posted By: mechanicx

What has the Ford 302 really proved? Most of the stock ones scarcely have valves or ports any bigger than the 305's. The Ford 302 just isn't a torguey engine IMO. I'm not arguing that the 302 doesn't work or since its received so much attention has been made into something. Sure all those things that you mention matter, but what sense does it make to have 4x3 bpre/stroke, then run short rods and small cams, ports and valves because all you are looking for is low speed torque? You can't stroke the Ford 302 much either.


1987 302 (HO, SEFI):
225 HP@ 4800
300 TQ@ 3200

1987 305 (HO, TPI):
215 HP@ 4400
295 TQ@ 3200

1987 350 (TPI):
225 HP@ 4400
330 TQ@ 2800

The 302 made MORE torque than the 305, at the SAME RPM. And it managed to still make 10 more HP.

The 350 matched the HP of the 302, but at a lower RPM. And made more torque (and I would hope it would with 48 extra cubes).

The 302 had a broader power band (just looking at the numbers) and yet with all this talk about square, over-square, under-square, made MORE torque than this fabled "torque monster" 305.

The 302 can be stroked (in the stock block) to 347ci. Aftermarket blocks (like the R block I posted earlier) can be stroked beyond 360ci.

If one wants more displacement, you can then go to the 351W, which will do 427ci.

 

[Ben99GT]

Originally Posted By: mechanicx
You can go on believing valve area, port volume, bore/stroke ratio and rod ratio and especially on carbureted engines have little or no bearing on the torque curve if you want.


I don't believe that, when I say "heads", port volume and shape are two of the bigger factors I am referring to. You want an example of too much runner volume killing an engine, look no further than the 96-98 Cobra 4.6 4V. The split-port intake ports had a combined runner volume of over 230 cc, which killed low end and mid-range on those cars.

And yes, I do believe the intake manifold (primarily runner length and diameter), heads, and cam(s) specs are the primary factors determining where the engine is going to make it's power/torque. You can make undersqare engines high rpm banshees (with multi-valve heads) and oversquare engines torque monsters based on H/C/I selection. This pretty much flies in the face of the old school rules of thumb.

 

[Ben99GT]

Originally Posted By: OVERK1LL
1987 302 (HO, SEFI):
225 HP@ 4800
300 TQ@ 3200

1987 305 (HO, TPI):
215 HP@ 4400
295 TQ@ 3200


The 302 made MORE torque than the 305, at the SAME RPM. And it managed to still make 10 more HP.


Game, set, match

 

[mechanicx]

Originally Posted By: OVERK1LL
Originally Posted By: mechanicx

What has the Ford 302 really proved? Most of the stock ones scarcely have valves or ports any bigger than the 305's. The Ford 302 just isn't a torguey engine IMO. I'm not arguing that the 302 doesn't work or since its received so much attention has been made into something. Sure all those things that you mention matter, but what sense does it make to have 4x3 bpre/stroke, then run short rods and small cams, ports and valves because all you are looking for is low speed torque? You can't stroke the Ford 302 much either.


1987 302 (HO, SEFI):
225 HP@ 4800
300 TQ@ 3200

1987 305 (HO, TPI):
215 HP@ 4400
295 TQ@ 3200

1987 350 (TPI):
225 HP@ 4400
330 TQ@ 2800

The 302 made MORE torque than the 305, at the SAME RPM. And it managed to still make 10 more HP.

The 350 matched the HP of the 302, but at a lower RPM. And made more torque (and I would hope it would with 48 extra cubes).

The 302 had a broader power band (just looking at the numbers) and yet with all this talk about square, over-square, under-square, made MORE torque than this fabled "torque monster" 305.

The 302 can be stroked (in the stock block) to 347ci. Aftermarket blocks (like the R block I posted earlier) can be stroked beyond 360ci.

If one wants more displacement, you can then go to the 351W, which will do 427ci.


Or we can not compare the worst year/ratings for the Camaro engines to the best rating of the Ford Mustangs:

1991 was also the first year that Z28 Camaros equipped with the 305 TPI motor and a manual transmission had the same roller cam profile as the 350 TPI motor. Power ratings on the 350 TPI were as follows; 250 hp (186 kW) at 4400 rpm and 345 lb·ft (468 N·m) at 3200 rpm. Power rating on the 305 TPI motor were as follows; 235 hp (175 kW) at 4200 rpm and 300 lb·ft (407 N·m) @3200 rpm. Rumors say that these numbers were slightly underrated by GM, but this has not been investigated.

Keep in mind these are just factory Peak HP and Torque ratings and do not really address the overall torque curves.

For the Mustang I couldn't find good ratings handy for the '91 5.0, but seems it was overrated by then anyway as many Chevy guys and some disgruntled Mustang owners have claimed through the 90's and Fords seemed to acknowledged by '93.

Quote:
For 1987, the Mustang received E7TE heads and a more capable intake manifold. The E7 cylinder heads were sourced from the truck line after the 1986 swirl-port design demonstrated performance problems. Power ratings jumped to 225 hp (168 kW) and 300 ft·lbf (410 N·m) of torque. With the end of the run near in 1993, Ford switched to cast hypereutectic pistons for all 302 cu in (4.9 L) engines and also re-rated the 5.0 GT at 205 hp (153 kW) and 275 ft·lbf (373 N·m) of torque. This estimate was more accurate because the previous power ratings were made before the addition of the mass air flow system, a minor revision in the cam, and other various changes.



So to highlight,

1991 305 (TPI):
235 HP@ 4200
300 TQ@ 3200 (possbly underrated as GM was known to do)

1991 350 (TPI):
250 HP@ 4400
345 TQ@ 3200

1991 302 (HO, SEFI):
225 HP@ 4800
300 TQ@ 3200

Possibly overrated as has been claimed about Ford by some during the time period and perhaps closer to this:

205 HP
275 TQ

Anyway I think I'm going to drop out of this thread since the inaccurate/unfair comparisons never seem to quit coming. I'll say this though. When you see Ford guys' arguments then why they are Ford guys in the first place starts to make sense

.

 

[mechanicx]

You are missing my original point that even a 2V wedge 5L doesn't require a 4X3 bore/stroke to make decent HP. And you can't just stick any size valves and port size that such an oversquare engine will allow and not potentially make compromised in low-end torque especially with a carbed engine. Same principles apply to 4V engines.

Can you make a 4v undersquare engine rev, yes. Can you make a very oversquare engine torquey by "crutching" valve and port size, yes. And my point, can you make a slightly oversquare engine like the 305 SBC rev, yes. With engines can you have your cake and eat it too, generally no. Anyway, I think I'm done with this discussion and some people throwing everything but the kitchen sink in and jumbling the whole point with half facts and what amounts to confusion.

 

[cven]

Using factory hp ratings to make a point is funny.LOL..