Similar builds

[plovett]

I spent way too much time trying to find the article but failed, but either HotRod or Car Craft did exactly what's being posed here years ago, they built two big block chevies with big bore/short stroke and small bore/long stroke and compared them, all else being equal.  I recall them being surprisingly similar.  Sorry, it's from vague memory but I recall being very surprised how close they were.  I do recall the peak RPMs shifted around, as you'd expect, but the numbers were similar. 

I do NOT recall if they optimized the big bore setup to use bigger valves, which is central to the debate. 
 

I am pretty sure I can find that article in my magazine collection.  It was a Freiburger deal and pretty good as I remember.  Of course it can be picked apart like anything.  I'll look for it this weekend.

I found the article.  Hot Rod June 2005. Same exact heads on both combinations as far as I can tell.  AFR 335's on both.  So that question is not answered.  I think they did that on purpose.  It seems the the idea was to test bore/stroke and rod/stroke ratio exclusively.  Maybe they could have a different head on the big bore combo to take advantage of that extra real estate.  Of course there are thousands of different ways to run a test.  This is how they did it and I think it is pretty good.   Better than I could do for sure.

The small bore combo was 4.28"x4.25" with a 6.535" rod.  The big bore combo was 4.56"x3.766" with a 6.135" rod.  The rod lengths seem counterintuitive, but they were trying to keep the rod/stroke ratio similar.

They also ran two cams on either combo with different compression ratios.  The small cam was a 218/224, .510"/510", 110LSA hydraulic roller.  The big cam was a 253/260, .734"/.732", 111 LSA solid roller cam.

The compression ratios were 9.039:1 (small bore) and 9.076:1 (big bore) on the small cam combo.  The compression ratios were 10.83:1 (small bore) and 10.87:1 (big bore) on the big cam combo.  They used a 0.125" thick head gasket on the small cam combo and a 0.040" thick head gasket on the big cam combo. 

So there are 4 total combinations here:

1) Small cam small bore/long stroke
547hp peak@5300 rpm/ (455hp avg) / 592lb/ft peak@3500-3600 rpm/ (551 lb/ft avg)

2) Small cam big bore/short stroke
549hp peak @5400-5500 rpm/ (455hp avg)/ 589lb/ft peak@3600-4000 rpm)@ (550 lb/ft avg)

3) Big cam small bore/long stroke
717hp peak@6600 rpm/ (578hp avg) / 643lb/ft peak@4600 and 5500 rpm/ (612 lb/ft avg)

4) Big cam big bore/short stroke
727hp peak @6300 rpm/ (576hp avg)/ 636lb/ft peak@5400-5500 rpm (609 lb/ft avg)

paulie

Oh yeah, the small cam combo used an Edelbrock RPM intake and the big cam combo used a Weiand Team G intake, both with a 975 cfm Race Demon carb.  2" headers and 18" extensions on both.  Small cam combo used Flowmaster mufflers.  Big cam combo used no mufflers as far as I can tell.

edit:  oops.  corrected the rod lengths.

[chilly460]

Thanks, that’s the one I recalled, didn’t remember it had two cam comparisons.  So basically follows what many here said, little difference between the two, big bore helps a wee bit either from the unshrouding or the reduced friction with a short stroke. 

Imagine the reputation of 427 vs 428 had much less to do with bore/stroke and everything to do with solid cams in 427s, and people comparing that to sluggish passenger car 428s

[Hipopinto]

Ok

So again guys from what I’m reading on this thread

The engine dosent “know” anything about bore and stroke it’s the heads feeding the gulps of air it’s drawing in

Clearly that longer stroke engines will have advantages where shorter stroke engines will have others but output of each should be comparable

This question may be suited for another topic all together but I’m going to ask it here

Do Different camshafts perform “better” with Different strokes?

For instance a comp 270S fits a 331-427 and every thing in between but will it act differently with large bores and short strokes or smaller bores and long strokes

I’m just trying to understand as much as I can

Too often I’m explained things by people that should be listening

Thanks guys
Dave

[blykins]

Ok

So again guys from what I’m reading on this thread

The engine dosent “know” anything about bore and stroke it’s the heads feeding the gulps of air it’s drawing in

Clearly that longer stroke engines will have advantages where shorter stroke engines will have others but output of each should be comparable

This question may be suited for another topic all together but I’m going to ask it here

Do Different camshafts perform “better” with Different strokes?

For instance a comp 270S fits a 331-427 and every thing in between but will it act differently with large bores and short strokes or smaller bores and long strokes

I’m just trying to understand as much as I can

Too often I’m explained things by people that should be listening

Thanks guys
Dave

You're correct. 

A Comp 270S will physically fit into any FE block, but a camshaft has to be chosen to work with the specific displacement you have.   To dumb it down, the job of the cam is to fill the cylinders.  If you increase the displacement, the cam can't do its job anymore because the cylinders have more volume. 

The cam that's needed depends on a lot of variables.  I know that most cam catalogs will say "331-428, 2500-5500 powerband, choppy idle" or similar, but the truth is that a cam company can't list how that particular camshaft would work in every single combination of displacement/cylinder head/intake/etc. out there. 

For instance, if you stuck that 270S cam in a 352, it would sound pretty thumpy and would make horsepower higher in the rpm range than if you put it in a 428.  In the 428, it would sound a lot milder and the peak hp rpm would be much lower. 

Coincidentally, how well the heads work plays a big role in it as well.  If you have a poor flowing head, it makes it harder for the cam to do its job.  A well flowing head makes it much easier, and you will see peak hp rpms go up, as well as peak hp when you keep the same cam and add a good head.

[blykins]

I spent way too much time trying to find the article but failed, but either HotRod or Car Craft did exactly what's being posed here years ago, they built two big block chevies with big bore/short stroke and small bore/long stroke and compared them, all else being equal.  I recall them being surprisingly similar.  Sorry, it's from vague memory but I recall being very surprised how close they were.  I do recall the peak RPMs shifted around, as you'd expect, but the numbers were similar. 

I do NOT recall if they optimized the big bore setup to use bigger valves, which is central to the debate. 
 

I am pretty sure I can find that article in my magazine collection.  It was a Freiburger deal and pretty good as I remember.  Of course it can be picked apart like anything.  I'll look for it this weekend.

I found the article.  Hot Rod June 2005. Same exact heads on both combinations as far as I can tell.  AFR 335's on both.  So that question is not answered.  I think they did that on purpose.  It seems the the idea was to test bore/stroke and rod/stroke ratio exclusively.  Maybe they could have a different head on the big bore combo to take advantage of that extra real estate.  Of course there are thousands of different ways to run a test.  This is how they did it and I think it is pretty good.   Better than I could do for sure.

The small bore combo was 4.28"x4.25" with a 6.535" rod.  The big bore combo was 4.56"x3.766" with a 6.135" rod.  The rod lengths seem counterintuitive, but they were trying to keep the rod/stroke ratio similar.

They also ran two cams on either combo with different compression ratios.  The small cam was a 218/224, .510"/510", 110LSA hydraulic roller.  The big cam was a 253/260, .734"/.732", 111 LSA solid roller cam.

The compression ratios were 9.039:1 (small bore) and 9.076:1 (big bore) on the small cam combo.  The compression ratios were 10.83:1 (small bore) and 10.87:1 (big bore) on the big cam combo.  They used a 0.125" thick head gasket on the small cam combo and a 0.040" thick head gasket on the big cam combo. 

So there are 4 total combinations here:

1) Small cam small bore/long stroke
547hp peak@5300 rpm/ (455hp avg) / 592lb/ft peak@3500-3600 rpm/ (551 lb/ft avg)

2) Small cam big bore/short stroke
549hp peak @5400-5500 rpm/ (455hp avg)/ 589lb/ft peak@3600-4000 rpm)@ (550 lb/ft avg)

3) Big cam small bore/long stroke
717hp peak@6600 rpm/ (578hp avg) / 643lb/ft peak@4600 and 5500 rpm/ (612 lb/ft avg)

4) Big cam big bore/short stroke
727hp peak @6300 rpm/ (576hp avg)/ 636lb/ft peak@5400-5500 rpm (609 lb/ft avg)

paulie

Oh yeah, the small cam combo used an Edelbrock RPM intake and the big cam combo used a Weiand Team G intake, both with a 975 cfm Race Demon carb.  2" headers and 18" extensions on both.  Small cam combo used Flowmaster mufflers.  Big cam combo used no mufflers as far as I can tell.

edit:  oops.  corrected the rod lengths.

Pretty neat test and a lot of work.

EDITED....didn't realize you meant the intakes were different per cam, not per engine.  My bad.

[blykins]

Imagine the reputation of 427 vs 428 had much less to do with bore/stroke and everything to do with solid cams in 427s, and people comparing that to sluggish passenger car 428s

That's my guess. 

The 4.125 x 4 combo in a SBF and SBC is a very potent combination.  Why would it be any different for an FE?  Obviously the rotating assembly is a lot heavier in an FE than a SBF, but the combo still works.  There were 428's in Super Stock that were zinging up over 8000 on a regular basis.

[plovett]

I spent way too much time trying to find the article but failed, but either HotRod or Car Craft did exactly what's being posed here years ago, they built two big block chevies with big bore/short stroke and small bore/long stroke and compared them, all else being equal.  I recall them being surprisingly similar.  Sorry, it's from vague memory but I recall being very surprised how close they were.  I do recall the peak RPMs shifted around, as you'd expect, but the numbers were similar. 

I do NOT recall if they optimized the big bore setup to use bigger valves, which is central to the debate. 
 

I am pretty sure I can find that article in my magazine collection.  It was a Freiburger deal and pretty good as I remember.  Of course it can be picked apart like anything.  I'll look for it this weekend.

I found the article.  Hot Rod June 2005. Same exact heads on both combinations as far as I can tell.  AFR 335's on both.  So that question is not answered.  I think they did that on purpose.  It seems the the idea was to test bore/stroke and rod/stroke ratio exclusively.  Maybe they could have a different head on the big bore combo to take advantage of that extra real estate.  Of course there are thousands of different ways to run a test.  This is how they did it and I think it is pretty good.   Better than I could do for sure.

The small bore combo was 4.28"x4.25" with a 6.535" rod.  The big bore combo was 4.56"x3.766" with a 6.135" rod.  The rod lengths seem counterintuitive, but they were trying to keep the rod/stroke ratio similar.

They also ran two cams on either combo with different compression ratios.  The small cam was a 218/224, .510"/510", 110LSA hydraulic roller.  The big cam was a 253/260, .734"/.732", 111 LSA solid roller cam.

The compression ratios were 9.039:1 (small bore) and 9.076:1 (big bore) on the small cam combo.  The compression ratios were 10.83:1 (small bore) and 10.87:1 (big bore) on the big cam combo.  They used a 0.125" thick head gasket on the small cam combo and a 0.040" thick head gasket on the big cam combo. 

So there are 4 total combinations here:

1) Small cam small bore/long stroke
547hp peak@5300 rpm/ (455hp avg) / 592lb/ft peak@3500-3600 rpm/ (551 lb/ft avg)

2) Small cam big bore/short stroke
549hp peak @5400-5500 rpm/ (455hp avg)/ 589lb/ft peak@3600-4000 rpm)@ (550 lb/ft avg)

3) Big cam small bore/long stroke
717hp peak@6600 rpm/ (578hp avg) / 643lb/ft peak@4600 and 5500 rpm/ (612 lb/ft avg)

4) Big cam big bore/short stroke
727hp peak @6300 rpm/ (576hp avg)/ 636lb/ft peak@5400-5500 rpm (609 lb/ft avg)

paulie

Oh yeah, the small cam combo used an Edelbrock RPM intake and the big cam combo used a Weiand Team G intake, both with a 975 cfm Race Demon carb.  2" headers and 18" extensions on both.  Small cam combo used Flowmaster mufflers.  Big cam combo used no mufflers as far as I can tell.

edit:  oops.  corrected the rod lengths.

Pretty neat test and a lot of work.  I don't understand why they would go to the trouble of keeping everything the same, then do goofy stuff like use two completely different intakes and two grossly different head gasket thicknesses LOL

It makes sense if you think of it as two separate tests.  One test with the small cam and one test with the big cam.   They kept the intake and head gasket the same for each of the two tests.  I could've posted either just the small or the big cam combo and you would have never known.  I do think the big cam combo is probably more illustrative of what they were trying to do. But even then the small cam combo is good info, too. I'll grant you a 0.125" head gasket is always a bit goofy.

edit:  just saw your edit.  I was typing while you were posting.

[plovett]

The engine dosent “know” anything about bore and stroke it’s the heads feeding the gulps of air it’s drawing in

Clearly that longer stroke engines will have advantages where shorter stroke engines will have others but output of each should be comparable

I agree.  An engine doesn't know it's bore and stroke.  Those things can have an effect.  However the old wisdom that a long stroke engine NECESSARILY makes more torque, likes low rpm, and revs slowly, while a big bore engine NECESSARILY makes more hp, likes high rpm, and revs quick, is wrong. 

As has been said before in this thread, there are a lot more differences between a 425hp dual quad solid lifter 427 and a 345 hp passenger car 428 than just bore and stroke.  Cams, intake manifolds and carburetion, exhaust manifolds, cylinder heads, compression ratio, etc. are all different and more important in this case. Also, put the 428 in a heavy well optioned car with an stock automatic and the 3.25 gears and compare it to a (427 powered) lower optioned car with a 4 speed and 4.11 gears.   Add all that up and yes, that big bore short stroke 427 will rev a lot faster and make more top end hp than that small bore long stroke 428.

paulie

[plovett]

Do Different camshafts perform “better” with Different strokes?

Another thing they did in the Hot Rod article was vary the valve lash on the big cam combination, since it was a solid cam.  They found the big bore combo liked 0.012"/0.026" lash on the intake and exhaust.  The small bore combo liked 0.018"/0.024" lash. 

The tighter intake lash equates to about 3 degrees more duration @0.050" according to the article.  It equates to about 4-1/2 degrees @ 0.020", 5 degrees @ 0.015", and 6 degrees @0.006". 

I would have thought the small bore combo might like more duration and/or overlap because of the overlap period in the cylinder.  If the small bore is slightly shrouding the valves, especially at the intake opening, I would have thought it might want to open a little sooner?  But this says no.

paulie

[67xr7cat]

Many 427 cobra actually came with a 428. Believe it was Shelby who said you could not tell the difference until you got over 80 mph.

Most 68 Cougar GTE came with a 427 rated at 390 hp. Later it was replaced with a 428 CJ. CJ had same heads, bigger carb, better exh. Manifolds, and intake. Rated at 335 hp.  Really was faster than the 427. Ford was going to go with the 427, but the 428cj won out as it was cheaper.

427 was the basis of Fords race program. 428 just a hopped up street engine. Today all you need is a 390 stroked to 445ci tfs heads and a hydraulic roller easy reliable 500 hp. Street engine.

And I am building a 427... Because it is a 427 even knowing all need is a 390 stroker. So short answer to original question Ford answered that in 1968 when it ditched the 427 for the 428cj. It all comes down to application.

[frnkeore]

Regarding the BBC testing, it really can't be directly compared to any in line valve engine. the canted valve mitigate the shrouding issue.

For example, the first Boss 302's and Boss 351's, had 2.25 intakes and I think 1.73 exhaust. You can't physically put that valve combo in a 4" bore, with inline valves. That totals 3.98, only leaving less that .007 between any surface and no tolerance for error and heavy shrouding. But, those heads flowed a LOT of air, with there canted valves. TO much and were scaled back to 2.19, the next year. Even that was to much, but for high rpm, in that size CI. But, that's beside the point.

[plovett]

Regarding the BBC testing, it really can't be directly compared to any in line valve engine. the canted valve mitigate the shrouding issue.

For example, the first Boss 302's and Boss 351's, had 2.25 intakes and I think 1.73 exhaust. You can't physically put that valve combo in a 4" bore, with inline valves. That totals 3.98, only leaving less that .007 between any surface and no tolerance for error and heavy shrouding. But, those heads flowed a LOT of air, with there canted valves. TO much and were scaled back to 2.19, the next year. Even that was to much, but for high rpm, in that size CI. But, that's beside the point.

Actually canted valves get shrouded, too.  I remember seeing a flow test with the same BBC head on 396 size bore and a 427/454 size bore and it was significant. 

[blykins]

Regarding the BBC testing, it really can't be directly compared to any in line valve engine. the canted valve mitigate the shrouding issue.

For example, the first Boss 302's and Boss 351's, had 2.25 intakes and I think 1.73 exhaust. You can't physically put that valve combo in a 4" bore, with inline valves. That totals 3.98, only leaving less that .007 between any surface and no tolerance for error and heavy shrouding. But, those heads flowed a LOT of air, with there canted valves. TO much and were scaled back to 2.19, the next year. Even that was to much, but for high rpm, in that size CI. But, that's beside the point.

Actually canted valves get shrouded, too.  I remember seeing a flow test with the same BBC head on 396 size bore and a 427/454 size bore and it was significant.

That is correct.  It works the same for canted valve heads as it does for inline. 

The data you posted was on point.  Nice to see those average horsepower and torque figures within 3 numbers of each other.  Reasonably within any tolerance of dyno repeatability. 

[Joe-JDC]

Actually '69 Boss 302 had 2.230" intake valve and 1.711" exhaust valves, and were too large, went to 2.190" in '70, and the Cleveland used the same 2.190" intake valve size.  Joe-JDC

[Gaugster]

Many 427 cobra actually came with a 428. Believe it was Shelby who said you could not tell the difference until you got over 80 mph.

Most 68 Cougar GTE came with a 427 rated at 390 hp. Later it was replaced with a 428 CJ. CJ had same heads, bigger carb, better exh. Manifolds, and intake. Rated at 335 hp.  Really was faster than the 427. Ford was going to go with the 427, but the 428cj won out as it was cheaper.

427 was the basis of Fords race program. 428 just a hopped up street engine. Today all you need is a 390 stroked to 445ci tfs heads and a hydraulic roller easy reliable 500 hp. Street engine.

And I am building a 427... Because it is a 427 even knowing all need is a 390 stroker. So short answer to original question Ford answered that in 1968 when it ditched the 427 for the 428cj. It all comes down to application.

Agreed. While I can't back up what Shelby may or may not have said the 427 platform was not as cost effective. It could have been overall molding yield or perhaps the post cast milling operations that I've read about. Either way the GTE 427 Cougar is rare. I couldn't afford one if they dredged it out of a river bed.