Tracking a SPF

Does anyone here track their SPF. If so is the rear spolier plate really helpful or is it more cosmetic. At what speeds would it help.

What type of wheels and tires do you run. Anybody use hoosiers on 17 in rims. What about avon bias plys on 15 in rims.

Shocks, and changes tot he stock setup, anybody run adjustables.

As to motors, leaning towards a aluminum 302 with 3.25 crank and 4.125 bore with solids. Anypone have any experience witht his type of setup.

I am hoping for a motor that is really a sweet rever, some people say any type of stroke makes weird harmonics. The idea is to have a 20% street time 80% tracktime car. Some say just to go with an iron block 302 as you can then historic race(which probaly wont do for a few years if ever, or maybe 1 race per year now), but to get the power then you need race gas only. Or am I over thinking.

The idea of a 302 based motor is light weigt(I come from a lotus) and I hear the 351 based 427's kill halfshafts and other bits on track.
 

Larry L.

Lifetime Supporter
I have been told by 3-4 'big name' pro shops that after market alum blocks (not factory blocks) are really a no-no for the street. Reasons: (1) the constant heat, cool, heat, cool, partial heat, completely cool, hot to partial cool and back to hot again, etc., etc. over time (they all said that means within 5K miles or so) will cause the cyl bores to 'go oval on ya'...and the mill will start blowing oil past the rings. Why? Because after market blocks don't have the extra 'webbing'/'stiffening' that the factory blocks do, they're just made thicker...and they tend to twist/warp/distort because of it; (2) Alum blocks create more engine compartment heat than an iron block due to more rapid heat dissipation...& therefore more heat transfer to the pass. compt (and wherever else!), and, (3) an all alum engine will make and 'broadcast' more internal engine noise when running. An iron block doesn't let as much internal noise 'escape', if you will.

EXCEPTION to #1: If an engine is used for racing/track 'only', then the engine is most often run to 'full hot' and kept there for the race/track session duration, then shut off and cooled all the way down to cold before it's started and run again. THAT kind of heat cycling tends to have less negative effect.

As I said, everyone I talked to told me the same things.

So, maybe since you're going to be on a track 80% of the time the above won't really matter. ;):chug:
 
Sean,
I've done some track days with my MkII 427 Windsor. I run Nitto NT-01's on 17" rims. The Nittos aren't bad, but Hoosier R6's are probably better. Stiffer springs and adjustable shocks would also help. With the stock set up the car rolls more than the Lotus Europa track car I have. I haven't changed mine because I primarily use the 40 for street use. Also you'll definitely need harder brake pads. Wilwood B pads are up to the task, but Olthoff uses a Performance Friction alternative. If you're really into track days you could go to 6 pot Wilwoods with 17" wheels. I have no idea about the spoiler. As small as it is it probably provides little downforce. With the 427 power needs to be squeezed on exiting corners to avoid oversteer. I have not had halfshaft or other mechanical problems with the 427. Use Schnorr washers and red Loctite on the CV bolts and adjust rear wheel bearings often with track use.
 
Last edited:
Sean, one thought here....you mentioned historic racing...I'm not sure where you're located but here in the Pacific Northwest it won't make any difference if you have an iron block or aluminum because a non-original car won't qualify regardless. In other words, if the car isn't an original GT40 then it's not racing in historic racing out here.

I like the sound of your free rev'ing engine - revs over cubic inches has appeal from more than one perspective.

Good luck!
 

Howard Jones

Supporter
My GT40 has a 2.5 inch plate all the way across the spoiler. At >110-120MPH it adds enough rear grip to cause the car to push just a bit. < 80mph and the car will slightly oversteer. It works but in only fast corners. I think it also adds a bit of grip at the beginning of a very high speed brake zone but goes away pretty quickly as the car slows to under 80 or so.

Alum engine block? they weigh about 60- 70 pounds less than a iron block and cost a couple of thou more. I think you can find a hell of a lot more performance for the money than saving 70 pounds.

MUST FOR TRACK....... LSD......... I like my Quaife..........best money I ever spent and works like frigin magic! The car feels like it has a hundred less HP it has so much more grip under power.

Nice mild pump gas 331 with 400hp, best Grbx you can afford with a TBD, really good sorted out brakes, and tires. R6 Hoosiers are the best unless you want to spend $$$$$$$$$$$$$$ on real race rubber.
 

Attachments

Last edited:
My GT40 has a 2.5 inch plate all the way across the spoiler. At >110-120MPH it adds enough rear grip to cause the car to push just a bit. < 80mph and the car will slightly oversteer. It works but in only fast corners. I think it also adds a bit of grip at the beginning of a very high speed brake zone but goes away pretty quickly as the car slows to under 80 or so.

Alum engine block? they weigh about 60- 70 pounds less than a iron block and cost a couple of thou more. I think you can find a hell of a lot more performance for the money than saving 70 pounds.

MUST FOR TRACK....... LSD......... I like my Quaife..........best money I ever spent and works like frigin magic! The car feels like it has a hundred less HP it has so much more grip under power.

Nice mild pump gas 331 with 400hp, best Grbx you can afford with a TBD, really good sorted out brakes, and tires. R6 Hoosiers are the best unless you want to spend $$$$$$$$$$$$$$ on real race rubber.
So you are running hydraulics then.? Thanks for the advice on the lsd. Are your Hoosiers on the 15 inch rims? What woud constitute "real race rubber" IAgree too much motor does not make snse on the track, however for the street accleration makes things live. So its a balance.
 

Howard Jones

Supporter
Yes I have a 300HP at the wheels 302 that has hyd rollers. My SLC has R6's and what I mean by real race rubber is Daytona prototype slicks or some other pure race slicks that would last about a weekend on the street, if that long, before you poked a hole in them.

As far as wheel sizes go 15 are really not doable anymore unless you buy some sort of historic race tire, avons ($$$$$$$$$$$$$), or shitty street tires. I have 17's on my GT40 and with 245.40.17 F and 315.35.17 R. I run street tires but there are R6's in those sizes as well as several other good Z rated summer only max performance tires in several 17 inch sizes.
 
Last edited:

Ron Earp

Admin
Hoosier offers the R6 in 225-50-15 that is great for the front, and a 275-50-15 that will work well on the rear. It may not be as wide as what you might want for appearances, but they'll offer performance exceeding the historic tires or high performance street tires. The R6s are DOT approved but don't really pass the smell test for street legal.
 

Howard Jones

Supporter
Ron, I stand corrected. I did think that there must be some 15 inch hoosiers but I've become so tired of looking for 15 inch tires that I have simply given up. Then there's the brake fit issue. Again, you can fit pretty good brakes into a 15 inch wheel but it SO much less hassle to start with a 17 that I can't see the point, especially for a open track car.

Class racing that has wheel and tire requirements or a desire to replicate the look of period correct GT40 tire sizes of course might lead to using 15 inch tires but other than that I just don't see the reason to do so.
 

Kelly

Lifetime Supporter
I have been told by 3-4 'big name' pro shops that after market alum blocks (not factory blocks) are really a no-no for the street. Reasons: (1) the constant heat, cool, heat, cool, partial heat, completely cool, hot to partial cool and back to hot again, etc., etc. over time (they all said that means within 5K miles or so) will cause the cyl bores to 'go oval on ya'...and the mill will start blowing oil past the rings. Why? Because after market blocks don't have the extra 'webbing'/'stiffening' that the factory blocks do, they're just made thicker...and they tend to twist/warp/distort because of it; (2) Alum blocks create more engine compartment heat than an iron block due to more rapid heat dissipation...& therefore more heat transfer to the pass. compt (and wherever else!), and, (3) an all alum engine will make and 'broadcast' more internal engine noise when running. An iron block doesn't let as much internal noise 'escape', if you will.
EXCEPTION to #1: If an engine is used for racing/track 'only', then the engine is most often run to 'full hot' and kept there for the race/track session duration, then shut off and cooled all the way down to cold before it's started and run again. THAT kind of heat cycling tends to have less negative effect.

As I said, everyone I talked to told me the same things.

So, maybe since you're going to be on a track 80% of the time the above won't really matter.
The thread is mostly a wheel tire thread but since the OP does pose the engine question…..

As far as the argument against aluminum blocks on the street, I just can’t follow that logic at all. Some of the greatest automotive engineers in the world disagree with the premise because just about every modern street sportscar has aluminum block and heads. The comment that aftermarket aluminum blocks don’t have extra webbing/stiffening (let’s call it features that promote more structural integrity), is just not the case. It’s the other way around and that’s why there is an aftermarket and why they exist. Cylinders going oval in alloy blocks? IMO, bore distortion is no more or less an issue in either material. An engine block is a strange shape that doesn’t heat or cool evenly, nor does it displace under stress evenly. This is a phenomena rooted in the geometry of what it takes to package a piston/cyl reciprocating internal combustion engine not material choice.


Aluminum is about one third the weight of iron but also exhibits about one third the elastic modulus. Modern aluminum alloys have strengths that often approach or even exceed iron. The fact that it is a far better thermal conductor than iron is a huge advantage for an engine designer because it means you can manage engine heat much more effectively than iron. Today, it really is a superior material choice for an engine block over iron. The block just needs to be properly designed. As far as the use of aluminum alloy and engines go, some of the biggest issues arise from mixing aluminum and iron/steel components because of the difference in coefficient of thermal expansion between the two materials. Iron can have better attenuation of harmonics because of its mechanical properties compared to highly tempered aluminum alloys particularly in highly stressed assemblies.

The most inconvenient reality of an all aluminum street engine comes with solid valve train. If you calculate the difference in growth from hot to cold cycle between aluminum and steel over the pushrod length (assuming we’re talking pushrod engines here), you’ll find it to be most inconvenient in maintaining the hot lash you prefer and will find yourself dangerously tight at cold. This means either be conservative on your hot lash target or take great care in bringing your engine to temp before running it hard or you’ll bend pushrods and suffer a potentially worse aftermath. It used to be common for racers to have oil heaters and manual drive there dry sump systems to preheat their pushrod alloy engines prior to starting. Street cars typically have hydraulic lifters and in many cases today, aren’t pushrod engines so the subject becomes moot. There are similar discussions on thermal growth and corresponding accommodations necessary in alloy engines for crank, cam, and bearing clearance.

The change in thermal growth can be a problem for sealing surfaces between dissimilar materials too. Even so, people run aluminum heads on iron blocks forevermore and manage just fine even though the head gasket must be compliant enough to accommodate movement between the two parts. Bottom line, at like power levels, it’s possible to build a lighter alloy engine than iron. If this is an 80% track car as stated, you can’t be fast if you can’t be light.
Without engine accessories, I’ve found a reliable (this is a relative term) 500-600 HP 427 CI street engine is possible in the range of 400 lbs. I’m a Ford guy, but if you doubt any of the above just look into a modern LS7. They are a very impressive example of aluminum (and a dry-sump version to-boot) of a street engine in the above weight and power level and there are many-many of them running on the street today.

Best,
K
 

Alan Watkins

Lifetime Supporter
As far as the argument against aluminum blocks on the street, I just can’t follow that logic at all. Some of the greatest automotive engineers in the world disagree with the premise because just about every modern street sportscar has aluminum block and heads.
Kelly --

The argument isn't that aluminum is not a suitable block material per se. The argument is that it does not work well to take a block originally designed to work as cast iron and simply duplicate it in aluminum. Olthoff as well made that argument to me when I was choosing my block.
 

Ron Earp

Admin
Class racing that has wheel and tire requirements or a desire to replicate the look of period correct GT40 tire sizes of course might lead to using 15 inch tires but other than that I just don't see the reason to do so.
Me neither. The only reason I know anything about 15" wheels and tires is because I have to use them on my Mustang SCCA race car. There is only one advantage to a 15" wheel/tire over a 17" wheel/tire, providing you can get the sizes you want, and that is weight. And that's little consolation.
 

Larry L.

Lifetime Supporter
Kelly --

The argument isn't that aluminum is not a suitable block material per se. The argument is that it does not work well to take a block originally designed to work as cast iron and simply duplicate it in aluminum. Olthoff as well made that argument to me when I was choosing my block.

Mr. Olthoff is one of the people to whom I referred in post #2 above.
 
The thread is mostly a wheel tire thread but since the OP does pose the engine question…..

As far as the argument against aluminum blocks on the street, I just can’t follow that logic at all. Some of the greatest automotive engineers in the world disagree with the premise because just about every modern street sportscar has aluminum block and heads. The comment that aftermarket aluminum blocks don’t have extra webbing/stiffening (let’s call it features that promote more structural integrity), is just not the case. It’s the other way around and that’s why there is an aftermarket and why they exist. Cylinders going oval in alloy blocks? IMO, bore distortion is no more or less an issue in either material. An engine block is a strange shape that doesn’t heat or cool evenly, nor does it displace under stress evenly. This is a phenomena rooted in the geometry of what it takes to package a piston/cyl reciprocating internal combustion engine not material choice.


Aluminum is about one third the weight of iron but also exhibits about one third the elastic modulus. Modern aluminum alloys have strengths that often approach or even exceed iron. The fact that it is a far better thermal conductor than iron is a huge advantage for an engine designer because it means you can manage engine heat much more effectively than iron. Today, it really is a superior material choice for an engine block over iron. The block just needs to be properly designed. As far as the use of aluminum alloy and engines go, some of the biggest issues arise from mixing aluminum and iron/steel components because of the difference in coefficient of thermal expansion between the two materials. Iron can have better attenuation of harmonics because of its mechanical properties compared to highly tempered aluminum alloys particularly in highly stressed assemblies.

The most inconvenient reality of an all aluminum street engine comes with solid valve train. If you calculate the difference in growth from hot to cold cycle between aluminum and steel over the pushrod length (assuming we’re talking pushrod engines here), you’ll find it to be most inconvenient in maintaining the hot lash you prefer and will find yourself dangerously tight at cold. This means either be conservative on your hot lash target or take great care in bringing your engine to temp before running it hard or you’ll bend pushrods and suffer a potentially worse aftermath. It used to be common for racers to have oil heaters and manual drive there dry sump systems to preheat their pushrod alloy engines prior to starting. Street cars typically have hydraulic lifters and in many cases today, aren’t pushrod engines so the subject becomes moot. There are similar discussions on thermal growth and corresponding accommodations necessary in alloy engines for crank, cam, and bearing clearance.

The change in thermal growth can be a problem for sealing surfaces between dissimilar materials too. Even so, people run aluminum heads on iron blocks forevermore and manage just fine even though the head gasket must be compliant enough to accommodate movement between the two parts. Bottom line, at like power levels, it’s possible to build a lighter alloy engine than iron. If this is an 80% track car as stated, you can’t be fast if you can’t be light.
Without engine accessories, I’ve found a reliable (this is a relative term) 500-600 HP 427 CI street engine is possible in the range of 400 lbs. I’m a Ford guy, but if you doubt any of the above just look into a modern LS7. They are a very impressive example of aluminum (and a dry-sump version to-boot) of a street engine in the above weight and power level and there are many-many of them running on the street today.

Best,
K
kelly so if I understand correctly and aluminum block and solid lifters is not an ideal way to go, due to valve lash ussues with thermal growth of block and heads exceeding pushrod growth. So if its solid stick with an iron block and aluminum heads..
 

Kelly

Lifetime Supporter
Kelly --The argument isn't that aluminum is not a suitable block material per se. The argument is that it does not work well to take a block originally designed to work as cast iron and simply duplicate it in aluminum. Olthoff as well made that argument to me when I was choosing my block.

Not sure where you’re coming from there Alan. There was no reference whatsoever in this post to aluminum blocks being made in the image of iron blocks of course until you raised it. If there are aftermarket alloy blocks that are merely reproductions of an OE iron block in aluminum they are the exception not the norm. There are some very good aftermarket aluminum blocks and the world is a much bigger place than just viewed through the lens of Ford engines.


If you read the post I responded to it was casting all aftermarket blocks in the same light and suggesting they all were a “no-no” on the street. Your premise is not the basis to which I responded. I’m not interested in debating the merits of a specific brand aluminum block but anyone who thinks there is something wrong with aluminum blocks in general for street use is simply misinformed. Whether or not it’s value for money and there is better bang for the buck in lap time as Howard pointed out is a comment that certainly has merit.


kelly so if I understand correctly and aluminum block and solid lifters is not an ideal way to go, due to valve lash ussues with thermal growth of block and heads exceeding pushrod growth. So if its solid stick with an iron block and aluminum heads..

To be clear, in alloy blocks/heads push rod engines, the block grows more than push rods as the engine heats so hot lash is more than cold which is always true even in iron engines but more so in the case of alloy. The difference in thermal expansion between aluminum and steels/iron can be 3 to 5 micro strain (5x10 minus 6th power) per degree F. So for 200 temp rise degrees (hey I live in the Midwest so 30-230 F is real for me) it could produce .009” inch difference in hot/cold lash over a 9” pushrod. In practice I’ve found it to be .004-.006” but that can be a big deal if you were trying to run your lash that tight and then find yourself with little to no lash cold.


I run solids in my aluminum block pushrod street engines. I just wouldn’t run my lash a tight on that combo as I would iron. Doesn’t bother me and can be corrected with cam specs but bouncing your lifters cant. I’m just saying you need to be aware of it and consider how often to you want to mess with your valve train in a street car versus a track car. If you drive the car 2-5k mile/yr on the street it’s not much of an issue if you have moderate spring loads and lift for solids. It’s less so of an issue with an iron block and tight lash but the fact is, running solids just requires more attention and maintenance. Is that less than ideal. –To each his own.


If you want low maintenance and decent street performance run a hydro roller and the whole discussion is moot. If it’s really a track car and you’re going to spin it, it calls for solid because you likely won’t be able to control the oil and have stable valve train in a hydraulic valve train in hard high rpm track driving.


-My 2 cents
 
So 2k per year, say 1500 of which is on track with soilds and shaft rockers should last the year between adjustments then?

There is always a time at the beginning ont he season and end when I have the day to mess witht he car, in between its gotta be as simple as fuids and pad changes.
 

Jack Houpe

GT40s Supporter
I really can't understand why the corvettes with aluminum LS motors are holding up so well, it just amazes me, also the 5.4 in the ford GT. Just lucky I guess. :)
 
The vettes though are not DOHC. They are however hydraulics and the z06 have a 7100 redline. Which is interesting because a SBF is limited to 6500 with hydraulics.
The z06 also have Titanium conrods and valves and a 1.51 to rod ratio.
Was at the track last week and two vettes dropped valves.

The ford GT is of course a completly different story as it a modern non pushrod motor.
 
Top