I've always heard that these are sound mods and really aren't very effective. They show big gains on pushrod stuff so why not a 4 valve? Most of the stuff I've researched goes back a few years so maybe R&D has gotten better? I might be looking at a rebuild soon and pretty much ruled those three mods out due to the cost compared to the gains, probably just raise compression and keep boost the same?
Why do headers, ported heads, and cams show such little gains?
- Thread starter Rambro
- Start date
even in NA cars the 4 valve heads flow very well and the factory exhaust isnt terrible. Cams can show pretty big gains, just depends on how aggressive you go with them but they are a lot of work and expensive (especially if you cant do the install).
Regular positive displacement power adder can mask that stuff until you start pushing North of 800 HP. Turbo can mask it to probably 900-1,000 HP.
Correct, my engine builder told me not to waste the money on porting the heads. The C heads flow very well. The claimed hp gains are NA versions and are minimal on these cars. $3000 for head porting and gain maybe 30 hp..... not worth it.
Stock manifolds flow very well too.
Stock manifolds flow very well too.
Yes very expensive. A good set of headers and cams would tack on at least 3 grand extra to the budget. Would I be ok to run the boost I'm at now with 10.5 to 11:1 compression through the stock logs? 2.70 upper only 2.3 whipple gen 2.
Yeah I know bewst is good but the 3/4 race camz aren't as kind to us cobros. Dat sound though... Makes my pants tight in the crotch.
Like the others mentioned... Its a boost thing.
I spent the money to do heads, cams, and long tubes on my NA 3v... Went from 268 rwhp to 400 rwhp. A buddy of mine that has the same year with a Saleen was making 450 at the wheels. Did all the mods I did, expecting to make 100+ more power, but when everything was done he only made 475.
Lots of money for 25hp.
I spent the money to do heads, cams, and long tubes on my NA 3v... Went from 268 rwhp to 400 rwhp. A buddy of mine that has the same year with a Saleen was making 450 at the wheels. Did all the mods I did, expecting to make 100+ more power, but when everything was done he only made 475.
Lots of money for 25hp.
You are all mostly forgetting that boost is a measure of restriction/pressure to occupy a space.
You may not pick up big power numbers, but you dramatically aid efficiency/longevity. Less stress, less strain.
I made 813whp with 11.75 psi and modular hardware. No coyote parts.
Mill is 9.3/1, this is on 91 octane pump gas too haha. Turbos aren't massive either, 62's on a 5.3, and the intake has 9.5" runners. It's very representative of what boosting an efficient engine does. Same with coyote numbers. It's exactly why a modular mill usually needs lots of boost to make 600-800whp compared to coyote stuff. 300-350whp na mills vs 400-450whp mills.
The heads and cams aren't going to be cheap, and you lose low end power production because you shift the power band and airflow characteristics. Air flow, velocity, and volume all have their scientific role.
My car launches like an na car and hooks damn well. Don't let the skimpy 250-300whp at 2500rpm fool you, it still has plenty of passing power and can leave a light in 2nd or 3rd gear with minimal chatter. This graph is to 7k rpm, I routinely take it to 7500, and it's flat to there/gains slightly. I'd go higher if my transmission could shift up there without feeling like I'm pulling a pole out of concrete.
Heads/cams aren't cheap, but there's no denying the science of airflow.
You could probably make 450whp with a cammed, ported head car running a stock non ported eaton on 8-9psi spinning to 7000rpm. The blower can't match much more rpm, and it'll be the thing holding it back at that point. Look what happens when 01 cobra guys with head/cam work put eatons on their cars. With stock pulley assembly's, they make 400-430whp on 6psi. It is pulled for "8.5psi" but that's because on a stock c head terminator mill, that pulley combo facilitates that resistance to flow. The sc is flowing xyz cfm. The engines ability to use that will dictate psi. This is also why 9psi from a 1.7l is much less useful for hp than 9psi from a 3.0l blower or 50mm turbo vs 76mm turbo.
Superchargers overshadow head flow by forcing it through, but do you really want to have to run 20psi to make 700whp? It's just a time bomb at that point. If you can make the same power with less boost, it's safer.
Anyways, I'm sure people will say I've got it wrong bla bla bla, I took the time to explain it. If it's over anyone's head, read up on if and figure it out with your own interpretation.
You may not pick up big power numbers, but you dramatically aid efficiency/longevity. Less stress, less strain.
I made 813whp with 11.75 psi and modular hardware. No coyote parts.
Mill is 9.3/1, this is on 91 octane pump gas too haha. Turbos aren't massive either, 62's on a 5.3, and the intake has 9.5" runners. It's very representative of what boosting an efficient engine does. Same with coyote numbers. It's exactly why a modular mill usually needs lots of boost to make 600-800whp compared to coyote stuff. 300-350whp na mills vs 400-450whp mills.
The heads and cams aren't going to be cheap, and you lose low end power production because you shift the power band and airflow characteristics. Air flow, velocity, and volume all have their scientific role.
My car launches like an na car and hooks damn well. Don't let the skimpy 250-300whp at 2500rpm fool you, it still has plenty of passing power and can leave a light in 2nd or 3rd gear with minimal chatter. This graph is to 7k rpm, I routinely take it to 7500, and it's flat to there/gains slightly. I'd go higher if my transmission could shift up there without feeling like I'm pulling a pole out of concrete.
Heads/cams aren't cheap, but there's no denying the science of airflow.
You could probably make 450whp with a cammed, ported head car running a stock non ported eaton on 8-9psi spinning to 7000rpm. The blower can't match much more rpm, and it'll be the thing holding it back at that point. Look what happens when 01 cobra guys with head/cam work put eatons on their cars. With stock pulley assembly's, they make 400-430whp on 6psi. It is pulled for "8.5psi" but that's because on a stock c head terminator mill, that pulley combo facilitates that resistance to flow. The sc is flowing xyz cfm. The engines ability to use that will dictate psi. This is also why 9psi from a 1.7l is much less useful for hp than 9psi from a 3.0l blower or 50mm turbo vs 76mm turbo.
Superchargers overshadow head flow by forcing it through, but do you really want to have to run 20psi to make 700whp? It's just a time bomb at that point. If you can make the same power with less boost, it's safer.
Anyways, I'm sure people will say I've got it wrong bla bla bla, I took the time to explain it. If it's over anyone's head, read up on if and figure it out with your own interpretation.
Marcspaz, what was the boost reading you had and your buddy had?
Lots of people do headers and only gain 10-20whp, but drop 2-3psi and make the extra power.
Same thing with heads/cams.
Lots of people do headers and only gain 10-20whp, but drop 2-3psi and make the extra power.
Same thing with heads/cams.
IIRC, he was at 6.5 or 7 psi before and it dropped to under 5... Close to 4.5. Of course, my memory is hit or miss these days... I'll send him a text in the morning and ask if he remebers. Cars been gone for close to 7 years.
That's a healthy drop for sure. If he had sold that sc and got a properly sized sc or turbo for the mill, it'd probably have made 550whp on 5-7psi.
Another thing you run into is having to much engine for the power adder. Same way you get lag when you run a giant turbo or sc on an undersized engine, you get the opposite from running too small a power adder on a given mill
Another thing you run into is having to much engine for the power adder. Same way you get lag when you run a giant turbo or sc on an undersized engine, you get the opposite from running too small a power adder on a given mill
That's the exact issue plaguing compound boost combos that run sc and turbo together. The turbos put way more air in than the sc can have flow through it. They work pretty good on 5-10psi through the turbos, but unless it has a a bypass to flow past the maxed sc, it just creates tons of issues. Those rations aren't clutch type/bypassable, so it's very hard to get great performance from the compound setups. You basically end up setting the eaton up for as low of boost as possible, and still end up holding the turbos back.
Agreed. My son wants to do compound boost on his Challenger. Been trying to explain to him that his money is much more well spent on a proper build, matching the engine and power adder correctly.
If I went 11:1 compression and kept my boost levels the same as now (20-22 psi) would it still be ok with the factory manifolds? I just don't know if I "need" to spend 1500$ on a set of headers unless it's going to really make a big difference as far as efficiency goes.
You can make more power with the CORRECT setup. When you are maxxing out an Eaton or a smaller twin screw, you probably will not see much of a gain. Alot of these guys just throw in "Staged" cams from Comp or Crower which really are not setup well for making power. If you go with a set of custom cams ground to your specific combo, degreed properly and ported heads there will be gains.
For example. A customer of mine ran a very similar combo to mine. Same turbo kit, same tuner, same dyno, same days. Only difference in our combos was he had ported heads and custom ground turbo cams. He would make around 120rwhp MORE then me @ 2#s of boost less.
Moral of the story, if you want to see gains, have a set of custom grinds made taylored to your exact combo and DEGREE them properly and you will see gains. If you buy Comp or Crower stage 3s, bolt them in with no degreeing, you are better off throwing your money in the garbage....
For example. A customer of mine ran a very similar combo to mine. Same turbo kit, same tuner, same dyno, same days. Only difference in our combos was he had ported heads and custom ground turbo cams. He would make around 120rwhp MORE then me @ 2#s of boost less.
Moral of the story, if you want to see gains, have a set of custom grinds made taylored to your exact combo and DEGREE them properly and you will see gains. If you buy Comp or Crower stage 3s, bolt them in with no degreeing, you are better off throwing your money in the garbage....
Yes you can keep the factory manifolds. It's not like they won't work or fail. I ran 27.5 PSI through stock manifolds for years. When I switched to long tubes I changed a lot of other things too so I can't speak specifically as to how much different the long tubes themselves made.
Same with everyone else's car I've ever installed long tubes on, many other changes at the same time. I've never personally had a car to swap on long tubes and nothing else and record the differences.
Not at all. I ran 10.5:1 at 30 PSI with the 2.9 Whipple, new setup is 11.5:1 at 24 PSI with TVS. The 24 PSI on the TVS sounds weak compare to the Whipple but the midrange and torque is much better.
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