I saw this post on an LT1 forum that is looking to replace their LT1 intake systems. Basically they think the HSR might be the best mod for their cars. It kind of goes with Orr's HSR motor. Here is the post. "The main problem with the composite intake we designed is it was a one size fits all. It was good for stock/bolt-on or a mild h/c set up. But if anybody has heads flowing more than 270cfm, this intake would be a restriction. The runners on this composite were not 8 inches like the lsx, they were 6. And because of the way the runners were, you had much less plenum volume. The plenum was like the lt1, a tunnel, not an actual plenum area. The runners on the composite also, we didnt think, would generate the air velocity needed for great low end gains. There were also some other issues. You had to buy after market fuel rails. You had to buy a mono blade throttle body. By the time you add those up, it costs more than a cam swap, with mediocer results. The hp gains would have been 10-20 with little torque gains. Now we could have sold a 'fluff' intake and took advantage of the fact it was plastic. Problem being when you guys would start putting them on your cars and found out the power was so-so, we would have been lumped into the 'nothing but hype' category with some of these other companies, and your out $1500. (manifold, tb, fuel rails) Now, the HSR is a perfect platform for building power over the lt1. First, let me give you some specs on the stock lt1 intake manifold. The runners flow about 225cfm. Thats sufficient for stock heads that flow 200-205cfm. But if you buy after market or get work done by LE or AI, your intake becomes a problem. Now, will you see great gains even with a stock intake? Of course, but your not optimizing the set-ups potential. So you send your intake away to get ported. Good right, it will flow more. LP ported one out for me years ago. Ported the plenum, the works. It flowed 265cfm. Good improvement. But, since it was pratically gutted to get the flow, I lost air velocity and noticed a loss in low-mid range torque. Sure I had better top end power but look what I had to sacrafice. How often am I above 6500rpm? And even with the plenum ported, it was still nothing more than a tunnel with small stubby runners. On to the HSR. It flows, out of the box, 275cfm naturally with no porting. Thats just part of it. The runners are longer, they will give even a stock engine great increases in usable torque. And since it flows the way it does with a shoe box for a plenum, You wont be missing out on power. But the problem with it since its inception is it doesnt fit. People have tried but Holley designed this HSR better then some think. The runners change shape from top to bottom. That increases air velocity which has the potential for tire smoking low and mid range power/torque. What we discovered was if you take even a little of the top of the runners, they start to change shape. That kills the air flow, making each runner a different shape. So there is a fine line to how much you can take off, and I think we have it. Since we had to recess the plenum on the runners slightly, we removed bolt provisions from the inside of the plenum. That increased plenum volume even with the plenum recessed. We also removed all the needless material on the base and between the runners to make it an air gap. We welded the plenum on to the manifold cause of the absence of the provisions along with welding an extra 1/8 thick aluminum plate to the bottom of the manifold to keep the heat from the oil off the runners a little. The engineering is there. Its just a matter of putting it in a usable application. There is no one size fits all. Every HSR will be custom made for every setup. We are pretty confident this intake will greatly increase torque and improve power over the current lt1 intake. Will it raise the power band? no, what it will do is give you more hp/trq through out the rpm band, where it really matters. When we get the prototype build and hand it off, I will be very interested to see 1/4 times and what a sh*t load of more torque can do to lower them. For those with bigger displacement/Forced induction, The HSR can be ported out to more than 300cfm. The runners will still keep their shape and length for great air velocity and torque. We are hoping with the porting process we will use, it will allow for high rpm hp gains as well. I'm sure we wont have a shortage of test subjects for that one. All in all, Im confident this will perform the way we think it will. If it doesnt work the first time, we will keep trying. Like I said, the engineering is there. And if its still not 'fluff' enough, we can always stamp Dolce Gabbana on it and sell it for twice as much." --------------------------------------------------------------------------

interesting. when they say take off alittle from the top they mean shaving the manifold down to lower plenum height to fit under stockhoods correct? when i ported mine i didnt touch the top that much but really opened up the middle and lower as much as i could to match the AFR ports and it came out ok. i hope i didnt hurt anything

this i dont want to buy for a buck. i would expect that to be false since SO many LT1/miniram cars are making big numbers and if 225 cfm was correct it wouldnt be possible

your talking 50whp from ported head swaps on cammed cars..sometimes 60whp. I dont think 225 intake would allow that since stock heads are already at 210-215 cfm in most cases.... good ported heads are 260-270cfm. i would think gaining 10-15 cfm of usuable flow would NOT yeild big gains like that.

this can be debated... i have no idea where this figure has come from other than stealthram.com. i dont think its that high to be honest but i've also never seen another source that has flowed the HSR runners


I will agree with more torque/lowend to midrange power. BUT still will support up to near 6500 rpms even on a 383 inch motor i know this. So the manifold has some flow potential to make numbers, but my motor with a miniram would no doubt make the same power provided the cam was abit more properly matched to the intake. Either way i dont think you can go wrong with either intake

"when they say take off alittle from the top they mean shaving"

The author of the post will be posting pictures so we can get a better idea of what he is talking about. I think they have milled off the top of the runners where they bolt up to the plenum. This will lower the plenum for more clearance.

From what I have gathered it sounds like the runners are tapered from the entry to where they meet the head. This allows the air to speed up as it travels down the runner and has a ramming effect going into the head.

This is what I'm trying to accomplish with the Accel SuperRam setup I'm currently working on. That is why I opened up the entry to 1.80" in order to get a decent taper along the runner. Anyways a few nuggets of information in the post.

yes the runners are definately tapered down but they are not uniform. 4 of the runners are different in shape than the other 4. 4 of them have more of a bend and are alittle smaller at that bend in crossection width than the other 4.

when i ported mine, i opened up those 4 runners and cut down that bend as much as i could. i really opened up that mid-section. But it still tapers alittle so it should still be getting a good velocity ramming effect

Sounds like you did a good job of cleaning them up. Also the results speak for themselves.

the car is doing good i guess. although i must be honest i was hoping for 420-430 whp

Orr, when you ported / opened-up the HSR, did you match it to a 1205 gasket, and, did the manifold runner openings align with the ports in the head? AFR says the 195's (plain ol' Eliminator 195's, not the comps) ports match the FelPro 1205 gasket, except for 3/8" corner radii (on the heads). Just looking for info here as I prepare to finish-up the porting of my HSR. I want to be sure the manifold ports are going to match the head ports, without having the old intake system removed.
Thanx!
Bill

Have you spoken w/Bret since the cam install bro....?

yeah ive been keeping him updated on the progress with the car. 400whp is generally what i wanted to be sure i'd make, but from alot of other builds i've seen 420-430 so i was hoping for more as always

Bret does think the intake restriction could be hurting the car. Told me to check the KPA values at WOT but i have MAF and not MAP so i cant tell whats goin on.


As far as porting, i made a template that matched the AFR ports and put that on my HSR. the 1205 gasket was close but was alittle off the head port.

other than that the ports align very well.

cant really tell but i have some pics of it

Here is a link to the thread I was refering to. It now has pictures. Intersting in how they are selling their modified version to L98 customers. Maybe for Trans Ams?

http://www.ls1tech.com/forums/showthread.php?t=967675

there is a thread on corvette forum about similar intakes, i wonder if its the same ppl. like 799 for intake, and around 1000 with custom rails or something like that

not bad considering its still cheaper than miniram

I asked for flow number verification on the stealth ram. Holley says 275, and those guys modding these intakes for LT1's flow tested two of them