Marko's GTD (I think) 40

[Marko S.]

Hi guys. Been planning a lot the last couple of days, buying tools and whatnot, building stands. Also spoke with both Darren from GT-Forte and Andy from Tornado and I'm preparing some orders. Ordered some aluminium heads for my 302 as well from the UK.

I'm talking to some people about tires and I would appreciate someone's opinion. I have a few choices:

1) 4x BFG 295/50 R15, used, 7mm thread, on Mopar steel rims (which I could use for my New Yorker) - 800 euro
2) 2x BFG 295/50 R15, new - 600 euro
3) 2x Avon CR7ZZ 295/50 R15, new - 840 euro
4) 4x Avon CR7ZZ 215/60 R15, used for 30 mins on track, 5mm thread - 400 euro
5) Toyo Road Pro 215/60 R15, used 7mm thread - 40 euro

Any thoughts? I'm leaning towards new Avons for the rear and used Toyos for the front. Anyone had any experience with these Toyos?

Cheers,
Marko

 

[Geert-Jan]

I think you mean Avon CR6ZZ (never heard of CR7ZZ!?)

The Avon are in my opinion the best choice!

 

[Marko S.]

It was late when I posted that Yes, the CR6ZZ. I was thinking about that today and having a low grip tire at the front could cause a car to understeer too much maybe. I now think that I'll go with four new Avons and be done with it. Thanks for the input Geert.

Damnit why aren't I filthy rich and not having to worry about prices...

 

[Marko S.]

It's been a sad day yesterday. Lost auction on quad 44 IDFs complete with intake manifold. Went for $1.325,00. Peanuts. They were used but in good working order.

Other than that I'm waiting on some lifters and a cam to arrive. It's a Compcams Thumpr cam with huge overlaps that proved to be the way to go on a higher CR engines. Also gives the engine that sweet rough idle which we all love so much.

In the meantime I'm trying to secure a suitable working area. Found a nice workshop for rent, I'll probably be taking that and bringing the car over sometimes next week or the week after.

Regards,
Marko

 

[Keith]

It was late when I posted that Yes, the CR6ZZ. I was thinking about that today and having a low grip tire at the front could cause a car to understeer too much maybe. I now think that I'll go with four new Avons and be done with it. Thanks for the input Geert.

Damnit why aren't I filthy rich and not having to worry about prices...

Hey Marko, you now have a GT40, you'll never be rich :laugh:

 

[Marko S.]

Haha Keith, well said. I was on a brink of personal bankruptcy before buying the 40 with all the other money pit cars I'm working on. This one may well finish me off. But what the hell, what better car to cause my downfall than the 40, right?

 

[Mike Pass]

A high overlap cam and Webers may not be a happy combination. The quad Weber set up has one inlet tract for each cylinder and with high overlap cams the carb ventures do not get a good signal and this may cause poor low speed running. On a race track this is not a big problem as the engine runs at high rpm all the time but on the road and in stop start traffic is a real pain. If you are mainly running on the road a mild cam works well as these engines have lots of useable torque. Remember torque gives acceleration and power gives top speed.
Cheers
Mike

 

[Marko S.]

Hi Mike,

This is the way I see it, and please bare in mind I'm not an engine builder so I might be wrong.

A high overlap cam provides better scavenging since the exhaust valves are open at the same time as intake valves therefore providing a "cleaner" mixture. On the other hand, high overlap also means a richer mixture since the carbs don't "register" the up stroke as soon as it happens so the mixture goes back in the carbs and draws a bit more fuel as it is coming back. This, as you said, is good for overall performance gains but hurts low rpm behavior of the engine.

I was reading a lot about 40s the last few days and decided I'll try to build something as close as I can to a Gulf GT40. I think that the Gulf, as well as other track cars, uses this combo, so I wanted to build an engine that somewhat resembles that of a Gulf GT40.

If I'm off the track here please lemme know. I appreciate your input.

Cheers,
Marko

 

[Mike Pass]

Hi Marko,
Building an engine for racing which will only see high rpm is very different from building an engine for the road. A cam with lots of overlap will indeed give lots of power at high rpm but it will not run well at low rpm because both valves are open at the same time so the carbs do not get a good flow which is needed to make the carb mix fuel and air properly. This low speed poor running with Webers is made worse as there is a single intake to draw from rather than a plenum with a big reservoir of mixture. High overlap cams produce a "cammy" engine which fluffs a lot and the suddenly comes "on cam". The more overlap the higher the rpm that this happens. This is not nice on the road where you want a the engine to pull strongly from low rpm and run smoothly at low rpm and small throttle openings. This is why you need to decide what you want the engine to do before you spec it up. A friend of mine had a race cam in his 302 on Webers which he used for hill climbs and sprints. It would only pull strongly over 4,500rpm. It did not perform well on hillclimbs as it did not get going until the engine was at high revs. My car with a low overlap cam but good lift would easily out drag it. He changed out the race cam and was instantly much quicker because he now had really good torque all the way through the rev range.
The big overlap cam only scavenges well at high rpm because it relies on the momentum of the incoming mixture to flush out the burnt gas. At low rpm the incoming mixture is too slow to do this and the burnt gas can be pushed back up the inlet and the engine does not run well.
Cheers
Mike

 

[Marko S.]

Hi Mike,

Thanks for clearing that up, I understand what you're saying.

Correct me if I'm wrong, but another factor that has an impact on the usability of this setup must be the gear ratios right? If the ratios are short, then while upshifting the rpms only drop by a small amount, thus keeping the engine in the sweet spot where there is enough momentum to clear the cylinders of any remaining burnt mixture and also enough negative pressure to suck the fresh mixture inside the cylinders. This of course only applies to the engine that's being revved. I'm asking this because I'm going for the 01E gearbox and by what I read the ratios on those are pretty short.

However, I never thought that this cam would be useless below 4,500 rpm. I thought 3,000 or maybe 3,500 rpm would be the point at which it starts to "work". This is not good news. I now have to decide between getting another cam or getting some Edelbrocks or something with a large plenum on the manifold. What would you suggest?

By the way, this cam has 0,512 intake lift and 0,489 exhaust lift.

Cheers,
Marko

 

[Keith]

The absolute best bang for the buck on a traditional American V8 for performance and drive-ability is the good old 650 Holley double pumper on a medium/high rise single plane manifold. It'll most likely make more power and torque than Webers too..Just bolt on and go.

Best intake manifold I ever used was the Victor Junior..

You could get into your more exotic intakes down the road apiece. The point about the camshaft is, you'll never be able to stretch the rpms out on a public road, otherwise you'd be doing 150 mph everywhere and zero to shit yourself in 5 seconds..

 

[Mike Pass]

On a street 302 the Edelbrock Performer RPM Air Gap is hard to beat as it is dual plane which are good at lower rpms. For a bigger motor or very good heads the Victor Junior as suggested by Keith is very good but it has big ports and is single plane so needs good airflow to keep up the gas speed. Also Keith's suggested 650cfm holley double pumper will do the job very nicely. Ebay usually has a few examples for sale. I have bought them for between £30 and £120 depending on condition. The tunnel ram and sheet metal intakes are really race only.
Remember also that most GT40 replicas weigh just over a ton so tend to have a fairly good power/weight ratio.
Cheers
Mike

 

[Peter G-Pete Fritsche]

It's been a sad day yesterday. Lost auction on quad 44 IDFs complete with intake manifold. Went for $1.325,00. Peanuts. They were used but in good working order.

Beware of cheap knockoffs out of china:thumbsdown: - you will have always problems with them. They end up cheap on ebay.

 

[Marko S.]

Hi guys,

Thanks for all the input.

Pete, I noticed a whole bunch of knockoffs and I steer clear of those. Chinese crap on a car of this caliber is simply out of the question. Thanks for the heads up though!

Mike, Keith, I'll go with what you suggested. I had a read up on some intakes and carbs and Air-gap plus 650 Holley seems to be a combo everyone is happy with. As Keith says, I can always go ballistic once the car is done and I get bored with this setup.

My only concern now, and you may have some insight on this, is will I get enough flow from that carb and intake for the 210cc 60cc Brodix heads I got. If I understand the basic fluid mechanics properly (and I really hope I do since I'm studying to be an aircraft engineer), the larger the cross section diameter (of the intake port on the heads) is, the lower the velocity is which in turn hurts high rpm performance since more burnt fuel stays trapped in the cylinders. Furthermore, the lower the velocity is, the less mixture goes into the cylinders thus reducing overall performance. Could this be the case where Air-gap is the choke point and perhaps I should be looking at Victor Jr.? Bear in mind also that I'm increasing the displacement to 347 so there's additional room to fill.

P.S. I truly hope I got this right otherwise I wasted tons of money on education for nothing.

Cheers,
Marko

 

[Keith]

I'm not an expert here but I would have thought a 650 would be right in the ballpark for a 302. I ran a 750 dp on a Victor Jnr on a 5.8 litre 550 BP SBC Chevy turning 7,500 rpm in drag and road racing without any issues. You can 'blueprint' a standard 650 to flow a whole lot more than stock too. They are a great all round carb. As Mike says, stick with a dual plane for better lowdown grunt and just match the ports using the intake gasket as a guide. I don't think you'll notice the difference on the street, and eventually you'll be good to go once you upgrade your intake system with that lottery win you've got coming, because you'll already have good heads!

What's the intake valve size?

 

[Marko S.]

Keith, the intake valves are 2.02'' and exhaust 1.60''.

I already very much need that lottery win. I haven't even started on the 40 and I'm thinking about selling off my 300C to finance the project. If you have a good number picking system lemme know

 

[Keith]

They are 'big heads' for a mild 302 aren't they? How did you manage to acquire those? Don't get me wrong - they'll give you a lot of flexibility later on if say, you go for a stoker or a screamer. Great heads - I ran a pair myself.

I still think the 650 will be in the ball park though, especially if you can get it flowed. There are some good books on Holleys and if you are an aspiring engineer, I cannot see a difficulty with you being able to blueprint it yourself..

Of course, you might even find a 700 or 750 on Evilbay although they are rarer.

The main thing is, providing it is in good refurbished condition a Holley DP is as simple to run as just bolting it on and firing it up...:thumbsup:


Sorry, just seen you are now building a stroker. You're moving fast man! Thing is it won't be a Rev monster so velocity will be a concern but you are moving towards a single plane application with more cubes...

 

[Peter G-Pete Fritsche]

Just a word Marko, you can spent a bunch of money on a small block and you don't get the results what you want.
Experimenting with an US V8 in Europe is very expensive - especially when you blow the engine up.

That said, did you ever looked at a complete crate engine - like this one here...

Ford 302 330 HP Turn Key Crate Engine High Performance Balancedbest Street 3471 | eBay

Add everything up at your engine build, don't forget the small things like the crankshaft bolt for the harmonic balancer ($20), gaskets and so forth. You will soon discover which makes more sense.

These engines are broken in, tuned and ready to drop in. ------ THEN you can play.

I understand your desire to build that engine - but you are on a budget and getting parts cheap, with free shipping it's for you impossible.

Just think about it.......

 

[Peter G-Pete Fritsche]

BTW:

Check this out too...
1964 Shelby Cobra 289FIA


https://www.youtube.com/watch?v=3yVnNpSnL0U

 

[Marko S.]

Hi Pete,

I was considering taking the route you mention. However, I had a 302 laying around and I had plans on fitting it inside a 67 New Yorker. However, once I bought the 40 I decided to keep the 302 and buy a 440 for it. The 302 I'm putting together was fully rebuilt before I bought it. The guy put some $2.500 into it. It seemed a shame to just leave it aside since I knew it was a healthy engine so I decided to go this way. In the end it will probably cost me about the same getting the crate engine or getting this engine to the 350 hp mark that I'm planning for. But this way I get some oil on my hands which I've always been fond of plus I'll learn stuff since I never built an engine this way before.

That's a nice looking Cobra. Really nice. Very neat and tidy. You can never tell from the video but it seems as it goes like stink too

Keith, I was reading up a lot on those and people say that AFR is just slightly better, if at all. I wanted to go for some bigger heads. It gives me room to play with the engine in future. I think they should be good for 500 hp at least.

I got them from a guy in the UK, off Ebay. 570 pounds fully assembled including shipping which I think is a good price considering they're within EU so I avoid all customs fees.

I also did some researching (read scrolling through Ebay) regarding carbs and came up with this:

Rebuilt Holley Carb 750 CFM for Big Block V8 Air Filter and Fuel Line Ford Cobra | eBay

Any thoughts? I don't think 750cfm would be an overkill considering the heads and the stroking. Plus, the guy is also in the UK so again, no customs and I get an air filter assembly and fuel lines as well. Maybe you heard about this guy, does he do good work?

Regarding the stroker kit I found a complete set including rings, bearings, flex plate and damper with cast crank and rods and forged Wiseco pistons for under $1,000. Haven't ordered yet since I don't have the engine with me yet and I need to check the teeth on the flex plate first.

Cheers,
Marko