Pete this is a good discussion,

I agree with you with the Rectangular port heads, but lets face it chevy did that for drag racing purposes. I never planned on rectangular port heads for the reason you cited. I autocross mine occasionally, plan on doing it more, and your hard off and on the throttle all the time so port velocity is extremely important. In all actuality my step-fathers 86 TPI engine is better at this bottom end torque stuff then my LS-4 is now, of course as far as midrange torque and hp the rat walks all over it, but it's hard to get enough of a run between cones to really take advantage of it. Same scenario as you mentioned with the SB having more torque up to 3800 then the BB came on real strong in the torque department ending up 50lb/ft more at one point. Again this is probably all in the head design and the reason why GM went to the peanut ports on the trucks to make better low end torque. I can see your point with large diplacement smallblocks having some advantage in recipricating weight, and if they can make up the flow difference of the BB's canted valve heads then it should be the more powerfull engine. It would be kinda like comparing 440 mopars, to 426 Hemi's. The Hemi has the superior head design but given equal flow rates (eg. a little work on the 440 heads or aftermarket 440 heads) there isn't any real advantage everything else being equal. Same Idea, the hotter 440's tend to stay right with the 426's until the RPM got way up there and the 426's were able to take full advantage of their heads.

:cheers:
Pat Kunz

 

Cappy,

your not happy with high 11's :confused: out of a 415 with a street car. I know mine can't get anywhere near that, mid 13's would be my best educated guess along with some other drag racing friends of mine who also run vettes. Actually mid 12's is my final goal, but I'm wanting to build a very well rounded car that I can autocross, drag race, and take on long trips if needed and still looks fairly stock, and do all equally well. Obviously it won't be the best at any one of those but it should be able to hold it's own. Actually a smallblock car would have fit in my goals a little better, but the Rat has some advantages of getting the power levels I want fairly easily, although it does handicap me on weight and car balance and gas mileage. As I said in my other post, if you can get the same airflow out of a smallblock chevy head as the big block chevy head and you have the same displacement, you have an advantage with the smallblock.

:cheers:
Pat Kunz

 

I'm very happy with the performance of the Bill Mitchell SB 415ci engine.....I have the best of both....SB with big block numbers.....and performance levels approaching or exceeding cars with BB.
I'm just curious about quarter mile times and MPH.....since most of the BB cars seem to promote the BB as the answer to performance. I've not seen any big block C-3 quarter mile times or MPH posted......providing these numbers would help me make a choice for my next project.....Should I buy the new GM 572 Rat or go for the Bill Mitchell 427 Small Block......The Bill Mitchell 427 Racing engine is putting out 675 HP with 685 lbs of torque.....
This is axle twisting numbers that should place my car some where in the low 9's or high 8's.....if I could ever find a good solid axle set up, roll cage, and not loose my nerve or need for speed. :seeya Cappy

 

Great discussion, I learned a lot from it. This is the type of post that many of us desire, THANK-YOU all I and I know that many others have gained much valuable insight from you. :cheers: :cheers: :cheers:

 

Here's the parts list I made for my engine, it's missing prices for a few parts but the total is about right...for 1999!

http://temp.corvetteforum.net/c3/427...partslist.html

 

No times as of yet for my car, I'll let you know this Summer. There is a guy with a '69 427 at the track that runs in the "Stock" class. The class limits the car to the original engine (only up to .040+ bore), heads, cam, carb, transmission, and rear end. You are allowed to port and polish heads and intake, run headers, jet up the carb. He has been holding the state and national reccord for the past several years.

He's running a TH350 and limited to 10.5 slicks. The car runs consistant 10.7's at the track. Pretty inpressive considering it's mostly stock and only been "tweaked".
:cheers:


[Modified by Corey 68, 12:07 PM 2/27/2003]

 

Cappy, I think your choice between the 572 and 427SB would come down to weight and longevity. Obviously the 427SB is going to weigh less and given about equal power outputs will be faster due to weight alone, but I believe there is going to be a drawback here. Obviously that 572 isn't going to be working as hard as that 427. Given equal VE's, the larger engine needs to spin less rpm to make the same power so It should be easier on parts. Now you can argue the recipricating mass on the 427 is going to be a lot lighter to offset this but then again your talking a very long stroke on a 427 SB which tends to stress connecting rods much more then a shorter stroke engine. Also your talking a lot more power potential out of the 572. For example lets say the 427 makes 675hp at a 95% VE, given the same 95% VE on the 572 would put it at 903hp! As you can see a 572 probably isn't working that hard to make 700 hp.

:cheers:
Pat Kunz

 

73 LS-4,
Your info is fine and dandy with me.....Thanks You.....however I would sure like to see some quarter mile performance numbers from BB C-3 owners here on the forum.....Not what my friend's car or my dad's car or some dragster out on the strip numbers.
Do these blocks get low ET high MPH in a C-3 without blowers, NOS, superchargers, etc. through the quarter mile?
I'd like to see some of the C-3 numbers using these big blocks.
:seeya Cappy

 

Cappy, You may want to ask this over on the C2 board, i know there are a few of the guys over there that run some pretty big hitters. Most of us over here are running pretty mild to stock BB's, especially those of us with #'s matching engines still in the car, although there are a few exceptions. I thought there was someone on the C2 board that was running a pretty healthy 500+ BB that was normally aspirated. Gdaina (sp?) I think has a 530 or so NA BB on this board but I don't know if he has any numbers. Actually I'm kinda curious myself now, I'll post here and on the C2 board (we are running the same suspensioon so all should be relevant) as for 1/4 mile times and engine setups. I'll think you'll find the trap speeds to be a little higher then expected for the ET's, becouse most of the big blocks higher breathing characteristics on the top end.

:cheers:
Pat Kunz

 

The only issue I have with Bill Mitchell 427 Racing engine is it doesn't run on pump gas, last time I checked his racing engines had pretty high CR.

 

That's still some nice HP and TQ numbers for a normally aspirated engine :eek:
If I get off the fence and go to the "Dark Side"...this will be the engine I'll run. :seeya Cappy

 

Cappy:
I'm running a 468 big block. I ran 12.40 @ 116mph that is with VERY little tuning (i.e. I have never hooked a timing light up to it). I also ran that time with 3.36 gears, 4 speed manual transmission AND 215/70/15 radial TAs (come on, that has to be somewhat impressive). My setup is not even radical. My heads were purchased for $450, they came pocket ported and with larger valves. My compression ratio is a modest 10.5:1 and my cam is a solid flat tappet with lift at .595"/.595". I'm putting slicks on this spring and will easily hit 11s....I'm also going to be fine tuning it this spring (finally).

My point is my motor is a VERY modest setup, in fact some small blocks have a cam with more lift than I. With my tuning I hope to get my MPH up to around 118-119MPH. That just goes to show you how well BBC heads flow. My heads are from 1966 for god sake :) and yes they were purchased for $450. The head design of the big block is by far it's biggest asset. It's known as a semi-hemi head (porcipine head) with it's staggered and splayed valves. When the head was designed....the ports were designed first, to get the best flow numbers with little restriction...then the valves were added at angles to avoid the intake/exhaust ports. The small block head was designed the other way around with the valves side by side and the ports built around the valves.

I like small blocks, don't get me wrong but I just love big blocks more after experiencing the brute torque. As Cory said, I'd like to see you find a small block with 357cc intake runners, 118cc combustion chambers, 2.30/1.88 valves :). I do like small blocks though, I don't want anyone to think I'm anti-small block.

 

Biggest "small block" I've seen is a 488 ci in. It was a Rocket block. Cost was 30,000 big ones. Power was over 1000 HP. Guy had very deep pockets and very big (well you know). Custom everything. 415 is a great combo without pushing to many limits.

 

I always look at this in relation to the HP/$$ ratio, and in that regard the big inch small blocks and normal 454ish big blocks just don't compare. Why would you compare a high dollar, custom small block to a production based, iron head big block? You can build a BB 540+ for the exact same cost as a 427 small block, and make WAY more power. I'm not trying to say that the big small blocks don't have their place, I've owned a 406 and it was a nice engine, but if ETs are your goal the BB will get you there easier and cheaper. If you're buying an aftermarket based engine for a shark (and you have a budget), the BBC is the only way to fly. :yesnod:

 

Isn't this fun???

This one never ends. I love small blocks too, have owned many, and had my hands full several times trying to get in front of them. But usually it was a case of nitrous being involved. Sometimes them spraying and me not, other times both of us spraying. Once power adders(nitrous, blowers, turbos) are introduced to a small block with a good set of heads, the advantages of the big block go away quick. They become very similar. You can just keep adding more as long as it stays together.

But on the street, I like big blocks because the power is always there. No need to drop a gear and scream it. Just nail it and go.

And there is no doubt that a 500 hp small block can have pretty decent and similar maners to a 500 hp bigblock. Maybe a little more radical, but nothing crazy. 550...yeah, that's Ok too.

Once you get into that 600hp+ range, a small block gets pretty hairy. Yes it can be done, but the cost starts becoming outrageous.

My 427 was a nice oval port street roller motor in it's last detuned street version(423 RWHP). It could idle all day and took 1000 mile weekend trips. It was no where near radical, but had a torque curve that was unreal..just never stopped pulling. Loved it and it would run 11.20's/123 anywhere, capped up with 2.5" pipes, points ignition, 3.36 gears, pump gas on 10x26" slicks. 11.70's on 255/60 BFG street radials. It's only downfall getting into the 10's was me trying to walk it out to save the rear axle parts. It was basically all stock and never pulled more than a low 1.70 60' time launching at 1500 rpm and then rolling into it after you got moving.

My 540 in it's first version made 732 HP on pump gas. This was a very mild bolt together deal with good, but stock Brodix unported or CNC'd heads. Using same carb and intake from 427 and pump gas and points again. I really think there was more in it, but we only made a few pulls to make sure it got over 700. It later made 615 RWHP on the chassis dyno with some tuning and proceeded to spit rear axle chunks on every light launch at the track. Working on that!

It's being put into "Phase2" now, and I thoroughly expect over 800 HP in the new set up. It will still be able to cruise around and take 1000 mile trips on pump gas. And the goal is to run a 9.99 after driving in and bolting on slicks with no bottle.

I've personally seen quite a few 9 second IRS Vette's, some with small blocks with power adders and some with N/A bigblocks. There are even some 8.80 IRS cars out there.

It all comes down to what you like, but to get the performance numbers you guys are talking about, it's going to take big $$, or a load of N2O and a lot of luck!

Making the power isn't too hard....putting it to the ground and making a pass is where it really gets tough!

And I always like to end these deals with one last thing....

"Small Blocks are OK if your Mommy won't let you play with Big Blocks"!!

JIM ;)

 

Pat,
Thanks for the reply....
I noticed some of our guys with C-3 Big Blocks have started another thread with times and MPH.... I'll stick with Bill Mitchell Small Block 454 ci ...I'm sure it'll produce some respectable power....I just received my copy of Chevy High Performance and they have a good article about World 454 SB engine....Looks like Bill Mitchell and the gang are busy making 454 ci to round out the 415 ci and 427 ci Small Block crate engines.....Hmmmm Cappy like the looks of things to come. Thanks again guys for posting your times and MPH....
:seeya Cappy