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I have been reading thru various threads, attempting to sort out options for planning for this build, 94 vintage roller block I believe out of a Bronco. Anyways there is a fair amount of discussion about the explorer gt 40 p and non p heads and using various intakes. However I believe those options for the 302 engines do not apply to a 351 build, so what performance intakes are suggested for this one ? I do currently have a set of gt40p heads that I was planning to use, but looking at all the options .....
The factory 5.8 intake is unique and at least the lower portion is unique for all aftermarket versions including the GT40 because of the wider block. None of the upper/lower portions are interchangable meaning you can't put a stock upper on a GT40 or aftermarket lower because the port shapes, sizes, and locations are different and also because the bolts fastening the two pieces together are in different locations. So you will need a complete upper/lower combo for this motor and that is just as well because both of the stock pieces are pretty bad.
The 5.8 Lightning used the GT40 intake but Ford no longer makes it so they are hard to find and expensive when you do.
Edelbrock makes several intakes that will fit this motor including a truck specific version with twin throttlebodys, and the Performer and a Victor which use single TB uppers.
TrickFlow makes a pair of single TB intakes, one smaller and one larger.
Professional Products makes a single TB intake that is a copy of the Eddy performer and I have one of those for sale if you are interested.
The factory 5.8 intake is unique and at least the lower portion is unique for all aftermarket versions including the GT40 because of the wider block. None of the upper/lower portions are interchangable meaning you can't put a stock upper on a GT40 or aftermarket lower because the port shapes, sizes, and locations are different and also because the bolts fastening the two pieces together are in different locations. So you will need a complete upper/lower combo for this motor and that is just as well because both of the stock pieces are pretty bad.
The 5.8 Lightning used the GT40 intake but Ford no longer makes it so they are hard to find and expensive when you do.
Edelbrock makes several intakes that will fit this motor including a truck specific version with twin throttlebodys, and the Performer and a Victor which use single TB uppers.
TrickFlow makes a pair of single TB intakes, one smaller and one larger.
Professional Products makes a single TB intake that is a copy of the Eddy performer and I have one of those for sale if you are interested.
Paul:
Ok, I've tried to do some research that shows some testing on flow to show how different these other options are from the stock intake, upper and lower combinations. Also TB sizes obviously factor in. Can you point me to some further testing results ? I do not want to go crazy as I still need some decent mpg on the highway ......
I found this chart some time ago that shows a lot of the more common intakes. An intake that is technically too big for an engine combo will have very little negative impact compared to one that is too small so it's OK to err on the large side in this case. Same applies to throttlebodys and cylinder heads too.
Ok, thanks. It seems like that data may not include the stock 351 truck manifold, and are all the other comparisons in the 302 configuration as well ? Explorer, GT 40, etc ? For instance the Saleen and others - perhaps mustang 302 ? If independent testing happened that might be less biased that asking each aftermarket manufacturer for their testing data ..... If they test using higher rpms for the mustang 302, that data may not be as relevant for a lower spinning truck engine ?
Ok, thanks. It seems like that data may not include the stock 351 truck manifold, and are all the other comparisons in the 302 configuration as well ? Explorer, GT 40, etc ? For instance the Saleen and others - perhaps mustang 302 ? If independent testing happened that might be less biased that asking each aftermarket manufacturer for their testing data ..... If they test using higher rpms for the mustang 302, that data may not be as relevant for a lower spinning truck engine ?
Airflow is important for cylinder filling efficiency which directly relates to torque production so it's not all about high rpms. Other parameters like runner length also aid or restrict intake efficiency with longer runners working better at lower rpms and shorter runners at higher rpms. All of the intakes in that chart can be considered long runner intakes that work best below 5000rpm, the stock truck intakes are in that category too with total runner lengths that are only about an inch longer than the Mustang and Explorer versions. The 5.8 truck intake is closest to the stock 5.0 Mustang intake in terms of flow.. which isn't very good, it becomes restrictive at only 4000rom on this displacement. The 5.0 truck intake is much better, a member over on one of the mustang forums who has done a lot of porting put one on his flowbench and all stock it flowed right up there with the GT40, and with light porting it outflowed it. The Saleen, Cobra, and Explorer are all variants of the GT40 with the primary differences being in the shape of the upper sections to accommodate hood clearance. A couple intakes that are not on that chart are the Trickflow and Edelbrock Victor, both of those outflow the Performer and in the case of the Victor have much shorter runners so it's also targeting higher rpms.
Airflow is important for cylinder filling efficiency which directly relates to torque production so it's not all about high rpms. Other parameters like runner length also aid or restrict intake efficiency with longer runners working better at lower rpms and shorter runners at higher rpms. All of the intakes in that chart can be considered long runner intakes that work best below 5000rpm, the stock truck intakes are in that category too with total runner lengths that are only about an inch longer than the Mustang and Explorer versions. The 5.8 truck intake is closest to the stock 5.0 Mustang intake in terms of flow.. which isn't very good, it becomes restrictive at only 4000rom on this displacement. The 5.0 truck intake is much better, a member over on one of the mustang forums who has done a lot of porting put one on his flowbench and all stock it flowed right up there with the GT40, and with light porting it outflowed it. The Saleen, Cobra, and Explorer are all variants of the GT40 with the primary differences being in the shape of the upper sections to accommodate hood clearance. A couple intakes that are not on that chart are the Trickflow and Edelbrock Victor, both of those outflow the Performer and in the case of the Victor have much shorter runners so it's also targeting higher rpms.
Thanks Paul. So, on the chart above the 5.0 flow is for the mustang 5.0 rather than the truck intake, right ? If that is true using the stock 5.0 truck intake with a spacer to take up the difference between the additional difference between this and the heads might not be a bad option, if that is available ? Then we just have to find the secret on how to do that light porting as described above ?
Thanks Paul. So, on the chart above the 5.0 flow is for the mustang 5.0 rather than the truck intake, right ?
Yes that is right.
Originally Posted by JRS2
If that is true using the stock 5.0 truck intake with a spacer to take up the difference between the additional difference between this and the heads might not be a bad option, if that is available ?
Yes that is an option.. those spacers are expensive though.. like the price of a complete Typhoon 5.8 intake expensive.
Originally Posted by JRS2
Then we just have to find the secret on how to do that light porting as described above ?
No secret, you just have to open up the port exits in the lower where they meet the heads, they narrow down quite a bit as cast.
Yes that is an option.. those spacers are expensive though.. like the price of a complete Typhoon 5.8 intake expensive.
For this one maybe consider my brother a machinist to make them. Would just need to match the current ports, bolt holes, everything. Just as a guess, what might be the thickness, around an inch or so on each side ? I would suspect just an extra lower intake gasket for each side of the spacer and should be in business ? I did a search but did not locate them, what would they be called ?
No secret, you just have to open up the port exits in the lower where they meet the heads, they narrow down quite a bit as cast.
Yep found it last nite, around 300 plus for what I am looking for.
I guess the related question, if I use the 302 truck intake, is it suggested that I go with a different throttle body ? I see some guys go with different sizes from stock to 90 mm, which will not be for me. One in particular went with a 61 mm on an edelbrock setup, seemed to run pretty good ..... I guess all a matter of $$ ....
If I want to go the cheaper route to begin with, stay with stock TB or upgrade suggested ? If I do this build, hope to go with the gt 40 heads, probably your suggested truck cam, hope to do longtubes and probably 2.5 inch exhaust ....
I found this chart some time ago that shows a lot of the more common intakes. An intake that is technically too big for an engine combo will have very little negative impact compared to one that is too small so it's OK to err on the large side in this case. Same applies to throttlebodys and cylinder heads too.
Paul, or ?:
A couple questions, some of the guys on ebay are advertising GT 40 intakes for mustangs and explorers. My question now - is there a difference between a truck GT 40 intake and the mustang GT40 ? Also if a stock explorer manifold or stock ford manifold how do I tell the difference between that and the gt 40, markings on the castings ? I think you mentioned you had an aftermarket one that you are considering selling, if you want to give me a price either PM or here, that is fine.
Sorry, forgot one more question, for the stock truck 5.0 manifolds, is there any difference in flow for instance the 92 to 94 years vs the 96 to 97 years ? Per above discusssions the stock truck 5.8 is not good - I assume for all years ? Still considering making spacers if I find a good 5.0 at the right price ....
I guess the related question, if I use the 302 truck intake, is it suggested that I go with a different throttle body ? I see some guys go with different sizes from stock to 90 mm, which will not be for me. One in particular went with a 61 mm on an edelbrock setup, seemed to run pretty good ..... I guess all a matter of $$ ....
The stock throttlebodys will flow enough air to feed 350hp so they aren't a choke point.
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