Marko's GTD (I think) 40
- Thread starter Marko Stefanac
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Mike Pass
Supporter
As a point of reference.
A 351 Windsor stroked to 427 with ally heads, mild cam, 750 cfm Holley and Victor Junior inlet manifold on the dyno drew a maximum of 638cfm.
A 347 Windsor with high lift road cam, Edelbrock Performer RPM heads, RPM Air Gap inlet, 650cfm Holley did 420hp and 430 ft lbs torque with 300 ft lbs at 2,000rpm.
Also remember that these engines are externally balanced as standard and achieve balance by having an out of balance crank damper and flywheel/flex plate. However some of the stroker kits are made to be balanced internally and use a neutral balance flywheel and damper. The advantage is that with the external balance engine the internal out of balance is giving the main bearings quite a hard time as the out of balance crank spins. The internal balance engines just seem to run sweeter.
Cheers
Mike
A 351 Windsor stroked to 427 with ally heads, mild cam, 750 cfm Holley and Victor Junior inlet manifold on the dyno drew a maximum of 638cfm.
A 347 Windsor with high lift road cam, Edelbrock Performer RPM heads, RPM Air Gap inlet, 650cfm Holley did 420hp and 430 ft lbs torque with 300 ft lbs at 2,000rpm.
Also remember that these engines are externally balanced as standard and achieve balance by having an out of balance crank damper and flywheel/flex plate. However some of the stroker kits are made to be balanced internally and use a neutral balance flywheel and damper. The advantage is that with the external balance engine the internal out of balance is giving the main bearings quite a hard time as the out of balance crank spins. The internal balance engines just seem to run sweeter.
Cheers
Mike
Only that it's a vacuum secondary rather than double pumper. The VS will certainly be better for gas mileage but as for performance, it will depend on intake manifold and cam and that will depend on your usage. Street or track? If it's going to be 80% street then you go one way, more track than street, you go the other. A compromise will hurt both styles.
It's a lot of carb and one I've used a lot.It will certainly flow the numbers for your stroker but for ultimate performance I would have preferred a double pumper, as you can tweak the performance.. .Don't even think about trying to convert it. Ain't going to happen..
It's a lot of carb and one I've used a lot.It will certainly flow the numbers for your stroker but for ultimate performance I would have preferred a double pumper, as you can tweak the performance.. .Don't even think about trying to convert it. Ain't going to happen..
All this carb stuff is very confusing. I must read up thoroughly about this subject. I found a Holley 4150 (Holley 4150 750CFM Competition Drag Racing Double Pumper Carburetor | eBay). From what I understand it's the type of carb you guys are referring to - double pumper. I then realized there are multiple versions of the 4150. Boosters, accelerator pumps, linkages, jets... As I said, very confusing indeed. Also, the guy mentions doing a lot of work to it, half of what I can't understand. However, I do understand that it's a racing carb built with performance in mind and that's exactly what I want. After all, I wouldn't be building a GT40 if I wanted to think about fuel consumption.
Keith, the 420hp (flywheel i presume) and 430 ft lbs of torque is more than I was aiming for, and more is always better. If I get these numbers from my engine I'd be more than happy. Even more impressive is 300 ft lbs at such low rpm. Goes to show that it's an "elastic" engine fit for street use.
Cheers,
Marko
Keith, the 420hp (flywheel i presume) and 430 ft lbs of torque is more than I was aiming for, and more is always better. If I get these numbers from my engine I'd be more than happy. Even more impressive is 300 ft lbs at such low rpm. Goes to show that it's an "elastic" engine fit for street use.
Cheers,
Marko
Mike Pass
Supporter
Holley carbs have a List Number stamped into the choke tower. This can be checked against a chart of the many different types here.....
http://documents.holley.com/techlibrary_carb_numerical_listing.pdf
Eg. A 650cfm double pumper will have a List Number of 4777
There are basically two types of 4 barrel Holleys, the vacuum secondary type 4160 and the double pumper type 4150.
When you operate the throttle the primary butterflies open first and then the secondaries. In the double pumpers the secondaries are mechanically opened by a link rod. In the vacuum secondary type the secondary butterflies are opened by a vacuum system which senses the vacuum in the inlet manifold. When the vacuum is at the set level a diaphragm opens the secondaries. In other words with the double pumper type you decide by opening the throttle more when the secondaries open. In the vac secondary type the carb decides on the basis of the inlet vacuum when they open. The double pumper type is therefore more responsive.
The double pumper are called that because these carbs have an enrichment device to fill in the lean condition when the throttle is snapped open. There is a plastic cam which operates a diaphragm which pumps a squirt of fuel staight into the venturi of the carb. The vac secondary type has a pump on the primary side only. The double pumper has them on both primary and secondary sides and hence the name double pumper. The name double pumper is generally applied to carbs which have mechanically operated secondaries.
As a new 650cfm double pumper is about £500 new the economic way is to get a used one off Ebay and then strip it, check it out and rebuild it. Holley sell Trick Kits which contain most if not all of the bits you need for this. A good idea is to use the Holley blue gaskets which are provided in the kits which will allow the carb to come apart in the future without tearing. As long as the castings are good and the throttle spindles too worn they rebuild easily.
Cheers
Mike
http://documents.holley.com/techlibrary_carb_numerical_listing.pdf
Eg. A 650cfm double pumper will have a List Number of 4777
There are basically two types of 4 barrel Holleys, the vacuum secondary type 4160 and the double pumper type 4150.
When you operate the throttle the primary butterflies open first and then the secondaries. In the double pumpers the secondaries are mechanically opened by a link rod. In the vacuum secondary type the secondary butterflies are opened by a vacuum system which senses the vacuum in the inlet manifold. When the vacuum is at the set level a diaphragm opens the secondaries. In other words with the double pumper type you decide by opening the throttle more when the secondaries open. In the vac secondary type the carb decides on the basis of the inlet vacuum when they open. The double pumper type is therefore more responsive.
The double pumper are called that because these carbs have an enrichment device to fill in the lean condition when the throttle is snapped open. There is a plastic cam which operates a diaphragm which pumps a squirt of fuel staight into the venturi of the carb. The vac secondary type has a pump on the primary side only. The double pumper has them on both primary and secondary sides and hence the name double pumper. The name double pumper is generally applied to carbs which have mechanically operated secondaries.
As a new 650cfm double pumper is about £500 new the economic way is to get a used one off Ebay and then strip it, check it out and rebuild it. Holley sell Trick Kits which contain most if not all of the bits you need for this. A good idea is to use the Holley blue gaskets which are provided in the kits which will allow the carb to come apart in the future without tearing. As long as the castings are good and the throttle spindles too worn they rebuild easily.
Cheers
Mike
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Also, I believe there may be some quality issues with the newer carbs because Holley went into Admin and their production suffered somewhat. An early US manufactured one would be best although they may have been made in Mexico thinking about it...
It's been a long time! I am a big fan of the Holley. Seriously more bang for the buck only drawback being it doesn't have the eye candy appeal of the stack/weber set ups. Never-the-less, I think they're actually easier to tune & engineer for cold air induction and don't have the liability of all that weight up top where you don't need it..
And of course, more HP. What's not to like?
It's been a long time! I am a big fan of the Holley. Seriously more bang for the buck only drawback being it doesn't have the eye candy appeal of the stack/weber set ups. Never-the-less, I think they're actually easier to tune & engineer for cold air induction and don't have the liability of all that weight up top where you don't need it..
And of course, more HP. What's not to like?
Howard Jones
Supporter
If you know enough about tuning Holley's that you would never have asked questions on this forum then go ahead and buy a used modified carb. On the other hand if you are learning as I am then NEVER start with a modified carb. Many things done to tune a Holley for a race car involve drilling out fuel passages or putting small holes in the throttle plates for example. These kind of things can not be undone without buying new parts.
The best advice I can give you is use a new from Holley 650 or 750 if you want to and start with a baseline that is fully documented . ALL NEW PIECES OUT OF THE BOX! Buy the way the 750DP from Holley are really close out of the box. Just set float levels and idle and drive the car. I have one on my 360ish HP 302 and it runs really well.
Get a carb with a choke if you are going to use the car on the street.
This is what I have but the 650s are very similar.
https://www.holley.com/products/fue...le_pumper/classic_double_pumper/parts/0-4779C
Holley 4150 Carburetors 0-4779C - Free Shipping on Orders Over $99 at Summit Racing
The best advice I can give you is use a new from Holley 650 or 750 if you want to and start with a baseline that is fully documented . ALL NEW PIECES OUT OF THE BOX! Buy the way the 750DP from Holley are really close out of the box. Just set float levels and idle and drive the car. I have one on my 360ish HP 302 and it runs really well.
Get a carb with a choke if you are going to use the car on the street.
This is what I have but the 650s are very similar.
https://www.holley.com/products/fue...le_pumper/classic_double_pumper/parts/0-4779C
Holley 4150 Carburetors 0-4779C - Free Shipping on Orders Over $99 at Summit Racing
It's always been the same since I was importing parts in the '70's. Change the dollar signs to pounds and you're in the ballpark. Only 'results' I ever had was bringing manifolds and carbs back as carry on luggage! We always had a good game at places like JFK where the customs guys would guess the part from the x-ray image. I was amazed by how knowledgeable they were about some quite obscure tuning stuff..
First of all, thanks for all the replies. Means a lot to get a few good pointers from people who know what they're talking about.
Now, I found a few Summit videos on Youtube with a guy explaining carbs and how to tune them and make em work properly. I found them very interesting and I think the guy does a very good job at explaining things. I only watched one video but I'll try to go through the rest tonight.
I got the part about mechanical and vacuum secondaries from that video and I was wondering if I got that right, so thanks for confirming that Mike. Things are getting a bit clearer.
I will stick with an unmodified Holley as Keith and Howard suggest. Found a few used 650s and 750s double pumpers on German Ebay for as low as 40 euro. I'll get one of those for starters, take it apart, try to rebuild it and learn a bunch about it in the process. Best education you can get is to tackle something yourself. If things get good money-wise I can always go for a new one later on in the build.
One more question though and this one is about the intake. The Brodix heads I have coming have the intake port area of roughly 2.8 square inches and the Edelbrock Air Gap which you guys suggested has only about 2.0 square inches. Is what is referred to as the intake port on the manifold actually the port that has the carb attached to it or the ports that get attached to the heads?
Thanks a bunch once again for the the help I'm getting here.
P.S. That's a good story Keith. I started laughing alone in the room, almost woke up the kids
Cheers,
Marko
Now, I found a few Summit videos on Youtube with a guy explaining carbs and how to tune them and make em work properly. I found them very interesting and I think the guy does a very good job at explaining things. I only watched one video but I'll try to go through the rest tonight.
I got the part about mechanical and vacuum secondaries from that video and I was wondering if I got that right, so thanks for confirming that Mike. Things are getting a bit clearer.
I will stick with an unmodified Holley as Keith and Howard suggest. Found a few used 650s and 750s double pumpers on German Ebay for as low as 40 euro. I'll get one of those for starters, take it apart, try to rebuild it and learn a bunch about it in the process. Best education you can get is to tackle something yourself. If things get good money-wise I can always go for a new one later on in the build.
One more question though and this one is about the intake. The Brodix heads I have coming have the intake port area of roughly 2.8 square inches and the Edelbrock Air Gap which you guys suggested has only about 2.0 square inches. Is what is referred to as the intake port on the manifold actually the port that has the carb attached to it or the ports that get attached to the heads?
Thanks a bunch once again for the the help I'm getting here.
P.S. That's a good story Keith. I started laughing alone in the room, almost woke up the kids
Cheers,
Marko
Howard Jones
Supporter
Usually intake port references for an intake manifold means the size and shape of the opening on the head face of the intake. On a head it usually means the same matching opening on the head with the intake valve down at the bottom of it. If documents talk about volumes then they are in reference to the intake or exhaust port runner total volume.
A bit of advice. Call Brodix help line and tell them which head you have and make sure the intake manifold you want to use will match up to it. Brodix makes some very good stuff but some of their heads can only be used with their intake manifold.
You are probably OK but make sure before you buy pieces. While you are at it get gasket part numbers from them. They will usually give you a Felpro reference.
A bit of advice. Call Brodix help line and tell them which head you have and make sure the intake manifold you want to use will match up to it. Brodix makes some very good stuff but some of their heads can only be used with their intake manifold.
You are probably OK but make sure before you buy pieces. While you are at it get gasket part numbers from them. They will usually give you a Felpro reference.
I'll ring them up Howard thanks. I'll wait until the heads arrive first though so that I have them in front of me before I make a $2 per min phone calls
So if I got this correctly, the intake port dimensions on the manifold are 1.90" by 1.05" and intake port dimensions on the heads are 2.15'' by 1.30'' which means that the airflow is actually getting restricted by the manifold right? Not only that but since there is a sudden increase in port size there is bound to be swirling because of the low pressure area at the beginning of the head intake ports just as the airflow exits the intake manifold and enters the head and this can't be good for the airflow. Can be ports on the manifold be machined to match the head port size? Is there enough meat in them to do that?
Cheers,
Marko
So if I got this correctly, the intake port dimensions on the manifold are 1.90" by 1.05" and intake port dimensions on the heads are 2.15'' by 1.30'' which means that the airflow is actually getting restricted by the manifold right? Not only that but since there is a sudden increase in port size there is bound to be swirling because of the low pressure area at the beginning of the head intake ports just as the airflow exits the intake manifold and enters the head and this can't be good for the airflow. Can be ports on the manifold be machined to match the head port size? Is there enough meat in them to do that?
Cheers,
Marko
Measure the head port area where it necks down adjacent to the pushrods to get a more correct measurement, inlet manifold ports should be slightly smaller in width/height to create an anti reversion step and ensure any misalignment between head/manifold does not create a 'step' for the incoming gases to climb over on the way in- does not really matter if they get impeded during the reversion process of trying to get back out.
Hi Jac,
Thanks for the reply. I'll measure the ports as soon as my heads arrive, but I think the manufacturer specs should be correct. What you're saying makes sense. There will be 1/8'' "edge" if you will, protruding outwards as the manifold port "becomes" the head intake port. That isn't a lot, only 3 mm or so each side, but in relations to the head port size the "edge" area adds up to roughly 30% of the total area of the head intake port and I can think of much better ways to use up those 30%.
Cheers,
Marko
Thanks for the reply. I'll measure the ports as soon as my heads arrive, but I think the manufacturer specs should be correct. What you're saying makes sense. There will be 1/8'' "edge" if you will, protruding outwards as the manifold port "becomes" the head intake port. That isn't a lot, only 3 mm or so each side, but in relations to the head port size the "edge" area adds up to roughly 30% of the total area of the head intake port and I can think of much better ways to use up those 30%.
Cheers,
Marko
Hi guys,
Received the heads today. They seem to be very well made. However, there are a few casting leftovers on some of the edges and I'll have to get that thoroughly cleaned off before mounting them. Some of them I can take off with my fingers. Don't want that crap flying into the cylinders.
Finally bringing the 40 home on Monday along with its engine and some tools I bought. Leased a nice workshop for it and some other projects I have so I will have plenty of room to work with.
Here are a few photos of the heads. Training my kids to be petrolheads from early age
Cheers,
Marko
Received the heads today. They seem to be very well made. However, there are a few casting leftovers on some of the edges and I'll have to get that thoroughly cleaned off before mounting them. Some of them I can take off with my fingers. Don't want that crap flying into the cylinders.
Finally bringing the 40 home on Monday along with its engine and some tools I bought. Leased a nice workshop for it and some other projects I have so I will have plenty of room to work with.
Here are a few photos of the heads. Training my kids to be petrolheads from early age
Cheers,
Marko
Attachments
Btw if anyone's on a lookout for 48 IDAs here a link
Weber 48 ida carburettors x4 | eBay
Apparently one is faulty but for 700 pounds I still think it's quite a deal.
Weber 48 ida carburettors x4 | eBay
Apparently one is faulty but for 700 pounds I still think it's quite a deal.
Hi all,
Getting settled in the new workshop. Got the Granada bits bead blasted and primed and the parts keep stacking up
Been busy the last few days with sorting out the loading deck of my van. The 40 and the engine are going on there Monday.
Cheers,
Marko
Getting settled in the new workshop. Got the Granada bits bead blasted and primed and the parts keep stacking up
Been busy the last few days with sorting out the loading deck of my van. The 40 and the engine are going on there Monday.
Cheers,
Marko
