Opinions on running this truck lower...

CarCrazyRDM

Member
May 19, 2010
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Let me start by saying the car came with all of these components on it which is why I am kind of lost as to what all has been done, why, etc. But I popped a head gasket last weekend. So I've pulled the heads (ported/polished GT40X) off and I am weighing my options as whether or not to replace them with a set of used AFR 185's. The upper intake is a Holley Systemax II (I believe) and the lower is apparently a truck lower that has also been ported/polished (pics of all below).

Now I am wondering if I replace the heads is this lower going to be a restriction? I don't know how it compares to the standard Holley lower that is suppose to go along with this upper. It looks like it has been ported nicely but again I have no reference as to whether the runners are any bigger/smaller or more direct on the Holley lower vs this one.

The goal here is not to spend but a few hundred dollars and upgrade heads but if I'm only going to see a potential increase of 10-15 rwhp then I'll just keep what I have. I think the AFR's will give me 40+ rwhp up top over what I have but not if there is a huge bottle neck in between. The car has currently put down 510/490 with ~12 psi but power starts falling off after ~5300 rpm (we believe this is b/c of the heads).

Any thoughts/opinions would be greatly appreciated. Thanks, Ryan

FYI - Motor is a 331 built on a Sportsman B50 block with a girdle.

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I use AFR 185's/58cc with the systemax II lower + upper and from your pic, that lower looks very similar to mine. I don't think it would hold you back that much, id still run with it. If you happen to see a systemax II lower for sale one day, just grab it, only a gasket swap and a few hours to switch it out.
 
The Holley Systemax 2 lower is a identical to the truck lower. They actually just used the Ford design for it. It's great, because you just have to buy Ford truck gaskets for the plenum, unlike most intakes where you have to wait for the gaskets to ship from Summit or Jegs. There will be no flow difference between reusing that lower, and buying a new Systemax one. I run a Systemax intake on my setup, and my heads are bigger than an AFR 185. They flow a little less than an AFR 205. You definately won't have a problem with that intake on AFR 185s. There are plenty of guys getting 600 hp n/a engines with an untouched Systemax 2 intake.

I'm not sure a set of AFR 185s are a good investment. They are an excellent head, and definately better than the GT40x heads, but I'm not sure you will see enough of a power gain to justify the cost. You might be better putting that money towards another engine mod. If you intend to do some sort of forced induction in the future, then it is definately not worth the money.

Kurt
 
The Holley Systemax 2 lower is a identical to the truck lower. They actually just used the Ford design for it. It's great, because you just have to buy Ford truck gaskets for the plenum, unlike most intakes where you have to wait for the gaskets to ship from Summit or Jegs. There will be no flow difference between reusing that lower, and buying a new Systemax one. I run a Systemax intake on my setup, and my heads are bigger than an AFR 185. They flow a little less than an AFR 205. You definately won't have a problem with that intake on AFR 185s. There are plenty of guys getting 600 hp n/a engines with an untouched Systemax 2 intake.

I'm not sure a set of AFR 185s are a good investment. They are an excellent head, and definately better than the GT40x heads, but I'm not sure you will see enough of a power gain to justify the cost. You might be better putting that money towards another engine mod. If you intend to do some sort of forced induction in the future, then it is definately not worth the money.

Kurt

Kurt,

Thanks for the input. One note though, I'm already running forced induction (Si-trim Vortech) with approximately 12 psi of boost. My hope would be if getting AFR heads to increase power to at least 550 rwhp at the same boost level or possibly go up in power (whatever amount) and have boost drop just a touch due to less restriction.
 
It's a sportsman B50 with a girdle. Suppose to be good to 550-600 rwhp but as is usually the case that depends on how well everything is balanced, put together and tuned. I'm comfortable pushing it to 550. It is 90% street car and may see the drag strip twice a year and possible an HPDE event once to twice a year.
 
Yeah, then maybe the AFRs would get the extra edge to get the power up. Usually I would say more boost to it, but it's probably best not to push any more boost out of an Si.

Kurt
 
Who ported the heads? The "D" shape on the exhaust side port is upside down? The exhaust flows the most air on the long end (top side) of the runner, not the bottom? There is very little flow gained from opening it up on the short side and more chance of slowing the velocity by making the port "lazy".
 
I don't know who did the port work. The guy I bought the car from I think had them done some where out in CA. They seem to make decent power but I believe they're a bottle neck up top in my combo.
 
What's wrong with the lower you have?

Kurt

Well that is kind of why I started this post... I'm not sure anything. But I wasn't sure if this ported truck lower differed much from the Systemax lower. If it has significantly smaller runners or they aren't as straight etc I didn't want to spend the money on nicer heads just to have the lower intake be a bottleneck. But from what most are saying it does not sound like this lower differs much, if any, from the Systemax lower so I will probably continue to use it.

The bottom line is if I can spend a total difference of maybe $300-$500 to upgrade heads then I will. But if I am going to have to buy additional parts (outside of gaskets which I am going to have to buy anyway) then I'll just stick with what I have. Or if I am going to go to the trouble of selling my heads, buying new ones and spending additional money only to gain 10-15 rwhp then I'll also just keep what I've got.
 
I'm sorry, I read someone else's post and thought it was yours. My bad. $300-$500 for upgraded heads is a low estimate I think. Those AFR 185s are pretty pricey. it's also become harder to sell used parts. GT40x heads have become a budget head, and therefore command budget prices. It's kind of like the GT40p heads where people buy them simply because they are cheap, and better than what they have.

Kurt
 
Anyone got a part number for the gasket on that truck intake? I'd rather be ordering those than the holley ones. Thanks

If you want to order it to save money, then you are probably better off buying the Holley one. Undoubtedly if you get the Ford original part number and try and order it, it's going to end up costing twice or better than what Holley wants for it. I seriously doubt there are any aftermarket suppliers for it. If you can find one in U pull it, then it's worth it. It shouldn't be too hard to find, because it's standard equipment on a bunch of trucks. I know that all the 95' 302 trucks have that intake, but I'm not sure how many years either side of that they were standard equipment.

Kurt