does head design/ flow numbers really matter?
does head design/ flow numbers really matter? i did a little looking around and i was considering using a few different types of heads based on flow numbers, chamber size, port shape ect. but when running FI does it really make that huge of a difference? I mean bc we're forcing the air in anyway wouldnt just turning the boost up be all you need to make more power. i know theres a limit to how high it can go before something breaks or the turbo is maxed out but should i bother porting my 317s, or buy aftermarket heads. or switch to LS3s? i would think the exhaust flow would be important considering a turbo runs off the exhaust but ive seen turbo cars make over 1000hp on stock ls1 heads. Id love you use the money elsewhere if the heads arent going to have huge differences stock vs. ported/aftermarket.
its a 6.0L build, PT88, shooting for 650hp street. 850+ for showing off so to speak. any advice? thanks
its a 6.0L build, PT88, shooting for 650hp street. 850+ for showing off so to speak. any advice? thanks
thats while im still sitting on a stock 10bolt and suspension. once that is upgraded skys pretty much the limit really. 850+ should be the real number we're looking at here
I would spend the money on free flowing exhaust and good quaility intercooler so your not loosing much boost through the cold side. Im on stock 241s, a crappy ebay IC and made 900whp with an auto with comp turbo using pt88 specs.
317s are probably the best flowing for fi applications from what ive gathered. But really when people are choosing their head theyre looking more towards keeping their CR in check
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Launching!
Joined: Jan 2008
Posts: 225
Likes: 1
From: Fargo, ND
BOOST PRESSURE= restriction of flow.
Would you rather run 10psi and make 600hp or run 7psi with ported heads and make 600hp with a better curve?
Lots of people dont understand the concept. Id much rather run a lower boost pressure than a higher one to make power.
Would you rather run 10psi and make 600hp or run 7psi with ported heads and make 600hp with a better curve?
Lots of people dont understand the concept. Id much rather run a lower boost pressure than a higher one to make power.
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Intake shape and flow characteristics aren't as important in a boosted application. The air is being forced in so runner volume, and port velocity don't make as much difference like they would on a n/a or nitrous motor. Exhaust is where you really pick up gains with boosted engines. Most people in the know on camshaft design will widen the split on a boosted application, and use much more exhaust duration to try and even the amount of air getting out to the amount getting in. That said porting will benefit any engine, but the boost pressure may go down as the port efficiency rises. In laymans terms you will make the same power on say 20 psi of manifold pressure if your using stock ports, where with no other changes except porting that might drop to 15 psi but would make a little more power at that boost level.
Not sure if it's apple to apples, but on my old Cummins I made 1200hp at 72psi of boost while most were going over 100 psi to break the 1k barrier. It was alot easier holding 70 psi than 100.
well i have a little bit of mixed reviews but it seems i should be ok either way. ill do a light port job myself and get a valve job. that should help enough to reduce to PSI needed to make certain power goals. and as far as the exhaust goes its going to a be a 4" out the fender, F*ck it right? haha
Boost is a measure of resistance. Making HP is about flow. The more flow that all of your components allow, the more power you will make at any boost level. Just turning up the boost is not necessarily the answer because it will heat up the air charge more, which leads to other problems.
The goal of any forced induction build should be to maximize flow and achieve your power goals with the least about of resistance (read boost) possible.
Andrew
The goal of any forced induction build should be to maximize flow and achieve your power goals with the least about of resistance (read boost) possible.
Andrew
Speak to a good speed shop who dyno's a lot of different parts. When I asked about changing out my stock intake for a high end piece they showed me proof that while it will increase HP given the same boost pressure it didn't make sense to spend the money on it since it only added 8-9HP.
Then again mine was more of a budget build. CNC'd heads with no hand porting. Stock exhaust truck manifolds with no porting. Stock throttle body.
Springs were updated and a good set of studs into a solidly built motor with forged parts for strength.
Could I get more out of it? For sure but you have to think about bang for the buck when you're on a budget. Hell I choked when I bought the big injectors and had to spend a load of time with the tuner on the dyno to redo all the fuel maps versus boost.
Then again mine was more of a budget build. CNC'd heads with no hand porting. Stock exhaust truck manifolds with no porting. Stock throttle body.
Springs were updated and a good set of studs into a solidly built motor with forged parts for strength.
Could I get more out of it? For sure but you have to think about bang for the buck when you're on a budget. Hell I choked when I bought the big injectors and had to spend a load of time with the tuner on the dyno to redo all the fuel maps versus boost.
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Joined: Oct 2012
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Get a head with good exhaust numbers. U can throw in more air to compensate for the intake. I would rather make the same hp with less boost. Get a 317 with good exhaust number and u can make ur goal on 4lbs. The cou I hade made more to the rear wheels than u want on 4lbs and 93
If the goal is 650-850hp... The $ invested VS HP received isn't there in fancy port work or aftermarket heads. Improving NA power is by no means the cheapest route.
IMO the goal of any build would be to reach your power goal with as little time/investment as possible...
In the OP's case I would slap an untouched 317 head on and let it eat. Many times the DIY port jobs do more harm than good. An untouched 317 head is more than capable of meeting your goals with your combo.
i think ill be safe there. i think id get in to trouble if i tried to dig out that rocker arm stud or mess with the swirl ramp, probably couldnt make them even across the board so ill just leave them.
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Joined: Mar 2014
Posts: 7,192
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From: Ohio
Why? when building a turbo engine, I prefer to let the turbo do the work.
If the goal is 650-850hp... The $ invested VS HP received isn't there in fancy port work or aftermarket heads. Improving NA power is by no means the cheapest route.
IMO the goal of any build would be to reach your power goal with as little time/investment as possible...
In the OP's case I would slap an untouched 317 head on and let it eat. Many times the DIY port jobs do more harm than good. An untouched 317 head is more than capable of meeting your goals with your combo.
If the goal is 650-850hp... The $ invested VS HP received isn't there in fancy port work or aftermarket heads. Improving NA power is by no means the cheapest route.
IMO the goal of any build would be to reach your power goal with as little time/investment as possible...
In the OP's case I would slap an untouched 317 head on and let it eat. Many times the DIY port jobs do more harm than good. An untouched 317 head is more than capable of meeting your goals with your combo.
If you have a 100% stock motor and your turbo seems to be maxing out at 600 HP.. you can either spend $2200 on heads and $1100 on an intake and throttle body, or spend $800 on a bigger turbo from BW and hit your goals.
Spending money on ported heads and intakes isn't really justified cost wise unless you're restricted to a certain turbo size or only have something ridiculous like 87 octane available in your area.
Reducing restriction to reduce boost is also a diminishing return. If your heads aren't much of a restriction to begin with (like on a 4.8 or 5.3), then buying heads that flow 320 CFM isn't going to help you reduce your boost pressure. There are also easy/cheaper ways to increase head and manifold flow, like lowering IATs through 100% methanol injection and a high efficiency intercooler.
Getting heads with large exhaust ports doesn't always help either. Backpressure will determine how much CFM you can run on the exhaust port in the same way it dictates camshaft specs. You can get huge nitrous ports on the exhaust side if you want, but if your hotside piping doesn't require increased flow or your turbine can't do anything with it either, you aren't reducing any restrictions.
Your head flow should be dictated by the power needs of your engine while N/A, not its power needs while under boost. There are other factors, yes, but this should always be the base-line. Larger motors need larger port heads so they aren't a restriction. A 4.8 could make 1500+ HP on a stock casting head with mild clean-up and a low IAT.
There are some small things you can do to the 317 heads for a small improvement. I just did a set.
And since it doesn't matter anyway according to some, and you like grinding, go for it.
The only way to really tell if it helps or not would be to do a before and after. And who is going to bother with that?
You will likely notice pits in the exh valves and seats. They will lap out. Or clean up nice with a valve job.
You can't port the exh manifold. It's ports dwarf the head ports.
You can do a nice clean up of the welded area if you use V bands.
Have fun with it!
And since it doesn't matter anyway according to some, and you like grinding, go for it.
The only way to really tell if it helps or not would be to do a before and after. And who is going to bother with that?
You will likely notice pits in the exh valves and seats. They will lap out. Or clean up nice with a valve job.
You can't port the exh manifold. It's ports dwarf the head ports.
You can do a nice clean up of the welded area if you use V bands.
Have fun with it!
well the motor i just bought from Thompson Motorsports is made with some pretty sweet parts so turning the boost up shouldn't be a problem. ill just go with my head clean up and valve job and call it a day. thanks for all the info fellas.