Ron this is only a 383 cu. in. motor. Does your math still apply? Maybe fuel injection would be better. Does that get around some of these issues?
I took the plunge!!!
- Thread starter Dlampe
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Ron Earp
Admin
I think so Dean. The issue is that 48mm IDA/IDFs only handle 44mm chokes without special work to them. 44mm chokes are too small for 7000+RPM on a 351 inch motor, much less a larger motor as you have. Sure, it'll still run, but your hp peak will not be at the higher RPM nor as high as it should be. Smaller motors, like the 289/302s will rev well in the higher RPMs ranges with the webers and make power as a couple of users has shown with dyno plots/numbers. The venturi size doesn't limit them.
The math still applies with the EFI stacks (with some fudge factor since the equations were developed with webers in mind, not smooth EFI stacks), but the thing is the EFI stacks are much larger than webers in general. 50mm, 55mm, 60mm, and larger are available and as many who have used them on larger motors don't impede flow.
I remember being at Knott's one year and looking at some Cobra's with webers. One motor was a little 289 with 48mm IDAs (don't know the choke size) and the other was a BB 460 with 48mm IDA. I remember talking to the BB fellow about the carbs and couldn't quite figure out how that was going to work with both owners claiming 6000+ RPM capacity, although I didn't really give it a lot of thought at the time. The big block with 48mm IDAs and 44mm chokes (unless otherwise re-worked) would probably peak out at 4800-5000 RPM.
It is hard to beat a single plane 4bbl manifold for the upper RPM ranges, but they just don't look cool. I'm using one of the Funnelweb intakes that have gotten very good reviews from users over the more standard Victor Jr.
The math still applies with the EFI stacks (with some fudge factor since the equations were developed with webers in mind, not smooth EFI stacks), but the thing is the EFI stacks are much larger than webers in general. 50mm, 55mm, 60mm, and larger are available and as many who have used them on larger motors don't impede flow.
I remember being at Knott's one year and looking at some Cobra's with webers. One motor was a little 289 with 48mm IDAs (don't know the choke size) and the other was a BB 460 with 48mm IDA. I remember talking to the BB fellow about the carbs and couldn't quite figure out how that was going to work with both owners claiming 6000+ RPM capacity, although I didn't really give it a lot of thought at the time. The big block with 48mm IDAs and 44mm chokes (unless otherwise re-worked) would probably peak out at 4800-5000 RPM.
It is hard to beat a single plane 4bbl manifold for the upper RPM ranges, but they just don't look cool. I'm using one of the Funnelweb intakes that have gotten very good reviews from users over the more standard Victor Jr.
Dean, is that a 302 or 351 based block? Does the aluminum block give you ability to put in larger bores in the 302? I like the 348 configuration,with short stroke and large bores as opposed to the 347 with the opposite configuration. It would seem to be able to sustain higher rpm. The EFI stacks will set you back an additional 2-3 grand over webers and 4-5 over a holley setup as you probably know. chuck
Pat Buckley
GT40s Supporter
Having just done a dry sump on my Kirkham I can say with a fair amount of confidence that I would never attempt it on my GT40......there is hardly enough room for the existing componentryas it is.
Now if I was paying some race mechanics the big bucks it would be a different story.
The Webers do look cool. To me though, cool is something that works without requiring Luigi to be on call....or $700 worth of dyno time and jets to get to work right.
One more thing, the next time I talk to someone who has installed EFI and who hasn't gone through a bunch of brain damage trying to get it to work properly will be the first time.
Now if I was paying some race mechanics the big bucks it would be a different story.
The Webers do look cool. To me though, cool is something that works without requiring Luigi to be on call....or $700 worth of dyno time and jets to get to work right.
One more thing, the next time I talk to someone who has installed EFI and who hasn't gone through a bunch of brain damage trying to get it to work properly will be the first time.
The block I am considering is a 8.7 deck. The 302 is 8.2 and the windsor is 9.5. The bore is a 4.125 which is a big bore. The EFI is probably out for the simple fact that it is so expensive. Is there a valid argument in that the throttle response is much better than a 4 barrel? It sure seems like the last 1500 rpm's in the range is VERY expensive!
Lynn Larsen
Lynn Larsen
Dean,
A question you need to ask yourself at this point, and you need to be brutally honest with yourself in the answer, is, "why do I need the engine to turn ≥ 8K rpm?" If the need is testosterone based, then go for it if you have the bucks. If the reason is more pragmatic: my ZF has a final ratio of X:1 and I will require ≥ 8K rpm to achieve N mph; then that is cool, but you are limiting yourself to a single variable.
So, really the issue is with the costs of the cars speed over say 165mph. Keep in mind though that there are two variable that can be manipulated to get to the speed range being sought: engine rpm and gearing. Either way getting over 165 mph gets expensive. But, if your engine has the grunt (500-600HP) at a cheaper 7-7.5 K rpm (and will probably have more longevity as well) you may actually be cheaper to look at gearing. Although, I think that this RPM will yield > 200mph with either a ZF 5 DS 25 or a Porsche G50/50 with stock gearing. (By my calculations my R302 iron block based engine with a target redline of 7200rpm, calculated to produce right at 500HP, attached to my G50/50 should have numbers almost identical to the new Ford GT: top end ~212mph.)
With the weight of your alloy engine (that's what I'd have if I had the $$) and the kinds of power you can very safely get out of it at < 8K rpm, acceleration is NOT going to be an issue. But there is another issue that you will need to address if you plan to take the car to speeds over 165-170mph: aerodynamics. The plain GT40 Mk I body shape and some playing around with different front and rear ride heights does good up to ~170mph. It may not take off like the Mercedes at Nurburgring after that, but it can become a very light, twitchy handful. Those early GT40 drivers at Le Mans and other high speed tracks had to have had a wheelbarrow to carry their testicles around in. Things like chin splitters, adjustable spoilers and diffusers need to be seriously looked at and fitted.
OK, there are a LOT of issues to consider when preparring a car to go VERY fast. Once you've looked at all of them and their costs, one must ask himself, "Realistically, how many opportunities will I have to attain the kinds of speeds this car is going to be capable of?" If you are aware of a racing series whose rules will allow this car to compete and you plan to compete regularly, the answer may be "often enough to make it worthwhile." If you have sponsors who are forking over baskets full of money, the answer may be, "I have to do EVERYTHING I can to win!" For the vast majority of us, the answer is not often enough to justify the costs.
The initial enthusiasm for this hobby/past time/profession, what ever it is for a given individual, makes it VERY easy for ones head to overload ones ass. But, if you ask yourself all of the right questions and the honest answers are the right ones, Katie bar the door and go for it full on, balls to the wall just because you can! We'll all be glad to share the ride, help you when we can and gain some real and vicarious enjoyment along with you!
Regards and Good Luck,
Lynn
A question you need to ask yourself at this point, and you need to be brutally honest with yourself in the answer, is, "why do I need the engine to turn ≥ 8K rpm?" If the need is testosterone based, then go for it if you have the bucks. If the reason is more pragmatic: my ZF has a final ratio of X:1 and I will require ≥ 8K rpm to achieve N mph; then that is cool, but you are limiting yourself to a single variable.
So, really the issue is with the costs of the cars speed over say 165mph. Keep in mind though that there are two variable that can be manipulated to get to the speed range being sought: engine rpm and gearing. Either way getting over 165 mph gets expensive. But, if your engine has the grunt (500-600HP) at a cheaper 7-7.5 K rpm (and will probably have more longevity as well) you may actually be cheaper to look at gearing. Although, I think that this RPM will yield > 200mph with either a ZF 5 DS 25 or a Porsche G50/50 with stock gearing. (By my calculations my R302 iron block based engine with a target redline of 7200rpm, calculated to produce right at 500HP, attached to my G50/50 should have numbers almost identical to the new Ford GT: top end ~212mph.)
With the weight of your alloy engine (that's what I'd have if I had the $$) and the kinds of power you can very safely get out of it at < 8K rpm, acceleration is NOT going to be an issue. But there is another issue that you will need to address if you plan to take the car to speeds over 165-170mph: aerodynamics. The plain GT40 Mk I body shape and some playing around with different front and rear ride heights does good up to ~170mph. It may not take off like the Mercedes at Nurburgring after that, but it can become a very light, twitchy handful. Those early GT40 drivers at Le Mans and other high speed tracks had to have had a wheelbarrow to carry their testicles around in. Things like chin splitters, adjustable spoilers and diffusers need to be seriously looked at and fitted.
OK, there are a LOT of issues to consider when preparring a car to go VERY fast. Once you've looked at all of them and their costs, one must ask himself, "Realistically, how many opportunities will I have to attain the kinds of speeds this car is going to be capable of?" If you are aware of a racing series whose rules will allow this car to compete and you plan to compete regularly, the answer may be "often enough to make it worthwhile." If you have sponsors who are forking over baskets full of money, the answer may be, "I have to do EVERYTHING I can to win!" For the vast majority of us, the answer is not often enough to justify the costs.
The initial enthusiasm for this hobby/past time/profession, what ever it is for a given individual, makes it VERY easy for ones head to overload ones ass. But, if you ask yourself all of the right questions and the honest answers are the right ones, Katie bar the door and go for it full on, balls to the wall just because you can! We'll all be glad to share the ride, help you when we can and gain some real and vicarious enjoyment along with you!
Regards and Good Luck,
Lynn
Thanks for the reality check. You are right. I can see maybe 165 at mid Ohio or Road America but most tracks run out of straight away before I can turn the bigger numbers. I think I am going to run the webers and just shift earlier! I really don't think I will need more than 7000 rpm and that is just because I like the sound of the engine at high RPM's. The truth is I could easily shift at 6000 and have all the power I need. I like the aluminum block because of the weight savings thats about it. I think a good shock upgrade would probably effect my lap times more than the higher RPM's. Thanks for the help.
Paul Thompson 'Hooligan'
Admin
Hi Dean -
Congratulations on your RCR purchase - Fran certainly seems to have put together a great package and re your motor - forget the 8000rpm requirement unless you have deep pockets and don't mind regular stipdowns/checks/rebuilds. Someone once said to me "the life of a reasonable crank, is directly proportional to the rpms it spins - at 5000rpm it will last years, at 6000rpm - months, at 7000rpm days and at 8000rpm - hours!" - not entirely sure how true that is today but the idea must still be true..
In Roy Smart's lightweight Mk1 GTD, we used to use an A4 steel block (302/4.030) with 4-bolt mains, which with appropriate cam and rocker assy would easily and regularly pull hard to 8000rpm although it was 'soft' below 4000rpm and at 6000 to 6500 'all hell would break loose' - not an easy car to drive on sprints and hill climbs. (it did sound awesome though!) -
This we replaced with an all alloy 'Joe Fontana' 302 (Clevor) that was then bored +0.125" and stroked 0.25" giving approx 347ci. This was a beast! - it didn't rev as easily as the smaller 302, although we think that was due to the injectors running out of time, but hell it had some torque! It would pull hard from about 2000rpm and was awesome out of slow hairpins on hillclimbs. This combination won 9 events the following year when it was always placed either 1st or 2nd at each event entered and subsequently ran an 11.83s (max 132MPH) quarter at the Brighton speed trials.
True there were occasions where it would have been useful to rev higher than about the 6200/6400 rpm we were using, but larger injectors sorted that. For me, the increase in cubic capacity was well worth the effort and the top speeds at Goodwood were similar with either engine, except the 302 would scream in 4th and the 347 would match or slightly better it in 5th and you did'nt feel like you were 'wringing its neck!'.
Getting back to the 'throttle sizing' issue, it was and still is fitted with 58mm? bore items and they work well.
Congratulations on your RCR purchase - Fran certainly seems to have put together a great package and re your motor - forget the 8000rpm requirement unless you have deep pockets and don't mind regular stipdowns/checks/rebuilds. Someone once said to me "the life of a reasonable crank, is directly proportional to the rpms it spins - at 5000rpm it will last years, at 6000rpm - months, at 7000rpm days and at 8000rpm - hours!" - not entirely sure how true that is today but the idea must still be true..
In Roy Smart's lightweight Mk1 GTD, we used to use an A4 steel block (302/4.030) with 4-bolt mains, which with appropriate cam and rocker assy would easily and regularly pull hard to 8000rpm although it was 'soft' below 4000rpm and at 6000 to 6500 'all hell would break loose' - not an easy car to drive on sprints and hill climbs. (it did sound awesome though!) -
This we replaced with an all alloy 'Joe Fontana' 302 (Clevor) that was then bored +0.125" and stroked 0.25" giving approx 347ci. This was a beast! - it didn't rev as easily as the smaller 302, although we think that was due to the injectors running out of time, but hell it had some torque! It would pull hard from about 2000rpm and was awesome out of slow hairpins on hillclimbs. This combination won 9 events the following year when it was always placed either 1st or 2nd at each event entered and subsequently ran an 11.83s (max 132MPH) quarter at the Brighton speed trials.
True there were occasions where it would have been useful to rev higher than about the 6200/6400 rpm we were using, but larger injectors sorted that. For me, the increase in cubic capacity was well worth the effort and the top speeds at Goodwood were similar with either engine, except the 302 would scream in 4th and the 347 would match or slightly better it in 5th and you did'nt feel like you were 'wringing its neck!'.
Getting back to the 'throttle sizing' issue, it was and still is fitted with 58mm? bore items and they work well.
Attachments
Jim Rosenthal
Supporter
Just curious....what is the benefit of an alloy-block engine over an iron-block SBF other than the weight reduction? I had the impression that SBFs were light enough in their iron-block version that you didn't get a large weight saving by going to an aluminum block, but I don't know the numbers and would like to. Is the difference that great? or is it other issues such as cooling, durability, etc?
Don't beat me too hard, I'm just asking....I went with an iron block because I wanted a 1960s era engine...alloy blocks weren't around then. And yes it cost less.
Gearing/RPMs: we limited my 302 to 6500 revs. Rough math indicates ETS of 165 mph with 4.22 ring and pinion, .7:1 fifth gear, and normal tire sizes on 15" rims. We'll see. Not sure I'm that brave.....
Don't beat me too hard, I'm just asking....I went with an iron block because I wanted a 1960s era engine...alloy blocks weren't around then. And yes it cost less.
Gearing/RPMs: we limited my 302 to 6500 revs. Rough math indicates ETS of 165 mph with 4.22 ring and pinion, .7:1 fifth gear, and normal tire sizes on 15" rims. We'll see. Not sure I'm that brave.....
<Cut from another thread, bare block only>
Dart Aluminum Block 8.2" deck 83 lbs
Dart Iron Block 8.2" deck 160 lbs
M-6010-F302 SVO Aluminum 8.2 deck block 92 Lbs
Dart Aluminum Block 9.5" deck 93lbs
Dart Iron Block 9.5" deck 195 lbs
So yes you can save a good amount of weight with the alloy block, just have to pay for it
Sandy
Dart Aluminum Block 8.2" deck 83 lbs
Dart Iron Block 8.2" deck 160 lbs
M-6010-F302 SVO Aluminum 8.2 deck block 92 Lbs
Dart Aluminum Block 9.5" deck 93lbs
Dart Iron Block 9.5" deck 195 lbs
So yes you can save a good amount of weight with the alloy block, just have to pay for it
Sandy
Paul Thompson 'Hooligan'
Admin
Hi Jimbo
Roy went to an alloy block as the car had been specifically built light with competition in mind. Lightweight chassis, bodypanels, leaving off what was not required (aircon/heater/carpets etc) - using a compact battery, single fuel tank and for a time, drilling/machining holes anywhere Roy considered weight could be save without affecting safety/performance. Other than that - no reason I can think of, the lighter the rest of the car, the better the gains to be had by using an lightweight block.
Can't remember the weight, but I could easily pick up bare block and carry one handed. The numbers have been previously posted by others more knowledgeable on the subject and a search should turn them up.
(As Sandy has already done above - )
Roy went to an alloy block as the car had been specifically built light with competition in mind. Lightweight chassis, bodypanels, leaving off what was not required (aircon/heater/carpets etc) - using a compact battery, single fuel tank and for a time, drilling/machining holes anywhere Roy considered weight could be save without affecting safety/performance. Other than that - no reason I can think of, the lighter the rest of the car, the better the gains to be had by using an lightweight block.
Can't remember the weight, but I could easily pick up bare block and carry one handed. The numbers have been previously posted by others more knowledgeable on the subject and a search should turn them up.
(As Sandy has already done above -
)Lynn Larsen
Lynn Larsen
Dean,
The one other notable advantage of aluminum is the heat transfer properties which is one of the reasons there have been aluminum heads for a while: move the heat away from the valve faces/seats.
Regards,
Lynn
The one other notable advantage of aluminum is the heat transfer properties which is one of the reasons there have been aluminum heads for a while: move the heat away from the valve faces/seats.
Regards,
Lynn
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