Inliners International Forums General Discussion Blown and Injected head work importance

Hello all!

I am sure this has been done to death, but, I am going to ask anyway... I never have too much luck with the search engines when I am looking for specific answers!

How important is head work when it comes to forced inductiion engines? By that I mean, is it THAT important to do lump ports, bowl blends, bigger valves, port & polish, etc? I know very well that it will all help, BUT, how much help is that going to be?

I ask because I am building a 250 with an eaton M90 and I would like to know if it is better to spend my very tight budget on head work, or on the rest of the engine... machine shop labor is not cheap!

Please do give me a hard time about this post... I'm tired of people doing that (not necessarily on this forum but in general)!

Thanks for your time!

Well, many engines have been built that did not include much, if any headwork ie, porting, large valves, bowl work, etc... Its just that the benefits you gain from doing those mods further enhance your engines output, and is sorta' like an extra bonus that you wouldn't have gained without doing them in the first place. It is likely more a "what are your expectations" of this build, rather than doing these mods because it is just done out of tradition with no real goal as a target. I think everyone understands budgets, and only having a certain amount to spend. Just make the most out of what you can spend, it wont be a tragedy if you can't work it into your build at this point. You can always do it later if you have more cash to put in it down the road.

I don't have high expectations... well, sky-high anyway! I woul LOVE to see 375-400hp out of this engine with around 10psi boost.
After talking with a fellow from Eaton, I am not out of line with that number.

Would you be able to tell me... I have heard that the blue block 250's have a forged crank and rods. This doesn't sit well with me, but I really don't have a clue.

Anyway, that is the engine that I am building. It will be forged pistons, stock rods and crank, I am hoping for a roller cam/lifters/rockers, clifford 4 barrel intake, Holley 500cfm 2 barrel carb (only because I have one brand new in the box), maybe split exhaust manifold.

The head work WILL follow... when the money allows. I just can't afford to do it all right now.

The rods will be forged but not the crankshaft. The Canadian blocks were a little thicker in the cylinder walls than the US blocks, so that could be plus.

When you are going with forced induction, a great flowing head is not as important as a naturally aspirated engine is.

Having a bad flowing cyl head on a naturally aspirated engine has a big impact on how the engine is going to make power.(it will make bad/low power because the the bad flowing cyl head.

On a N/A engine it is hugely dependant upon a great flowing/high port velosity cylinder head to get some good/great HP & torque numbers.

When naturally aspirated,,, If you open up the port windows too big on our siamesed cyl heads, the port velosity will drop too much & in return, you will have a doggy, no low end low torque engine.

Being said that, when you are forcing air/fuel into your engine, you need to see where the ports narrow down the most & you would benefit by making these areas wider/taller up to a point, (don't go overboard with the porting)

Also, if your valves are only so big/small, they can only allow a certain amount of air/fuel through the valve throat areas (another bottle neck)

So the minimun head work I would do is go w/oversized valves intake & exhaust.
Open up the bottle neck areas/port windows, basically anywhere the intake port gets smaller, open those areas up.

Profile the intake boss on the cyl head into a wing shape profile, but not so far where you are going to get into the head bolt hole.

Machine & install screw in studs, because you are going with a roller camshaft, or bare minimun pin the studs.Doing this type of basic work on your cyl head will pay off & will not cost an arm & a leg, or so to speak.

If you do not do @ least these type of basic mods, it will be harder to make 400 HP.

My 262 V-6 only made 386 HP & was pushing 21 psi though it.
560 ft lbs though.
Rating is from R.W.H.P.
I would be more concerned with the torque output & not focus too much on the HP.

With having a siamesed cast iron cyl head, they are not going to make a lot of HP as compared to torque.

Just saying, it is not going to produce a lot of HP like a 4200 engine does, & the main reason is because the 4200 engines cyl head, it flows great & is a much better design.

Hope this helps.

MBHD

MBHD~ That does help me. Cheers!

I had planned on going with a 7/16 screw in rocker studs and use BBC roller rockers. I know they have a lower ratio (1.70 vs 1.75) but how much is that .05 really going to make a difference?!?!

I think that I will use a stock head while I am saving money/ working on the new head. That said... Do you think that I should do the lump ports? In reading the inline power manual a stock head would suffice for street use.

I understand the torque vs HP of these engines, too. I am only interested in turning 4,800-5,000rpm. Torque is what gets you moving and HP is what keeps you moving!

dodgycanuck,

not a problem. I am glad I made some sense.

You can run 1.8 BBC rocker arms if you choose, don't need to stick w/standard BBC ratios. Might require opening up the pushrod guide holes & run pushrod guide plates?

I personally have not tested nor have heard/read any testing of a blown/turbocharged 250 engine running lumps & testing w/out lumps on a dyno or testing track testing.

But, IMO, I do not think there will be a day & night difference between the two scenarios, a boosted engine w/& w/out lumps.

If you want to get every bit of HP & torque out of your 250 engine, I think there will be a slight advantage of using the lumps on a blown/turboed engine, they improve port velosity & improve the short turn radius.

Where it (the 250 engine) will see more of a benefit I.M.O., is from increasing the port velosity ,(decreasing intake port volume) as compared to the better short turn radius, not as important when forced induction comes into play.

A stock head will do, but if you want every bit of power out of your engine, just remember this ,,,, most all of the power comes from a decent flowing cylinder head.

If you use stock size valves, that will be a hindrance.
If you do not cut down/profile the intake boss that will be a hindrance, if you use a muffler w/chambers that = hindrance, If your exhaust system uses 2" pipe that = hindrance. Get the point?

If you can improve any or all of these things I mentioned, it will all add up to a more powerful engine.

It just boils down to how much effort you want to put into your engine/exhaust system combo.

When you get a camshaft for your blown 250, get a custom grind camshaft from CompCams & go with what they recommend.

I would recommend a camshaft w/a lobe center of 115 or wider.

MBHD

If your not planning to put larger valves and do any mods to the stock head at this time, putting 7/16" studs in it will be of no use for you at this time, especially if your going to do another head. Also, there are 1.75 roller rockers available specific for these engines, so there isn't really any need to use the 1.7 BBC rockers. Also, using the BBC 1.8 ratio on a stock, unported head will also be of no benefit for you either.
Like Hank said earlier, its going to be harder to reach the HP level you are seeking without doing some major head work and modifications to remove the restrictions that will limit you.
The 250 engine dyno tests done a few years back reached 350 HP with only 5 psi of boost, but with a big valve, lump ported head. The difference between the small valve, non-lump ported head vs. the big valve, lump ported head on the N/A combos was around 50 HP. The stock head is likely going to be more of a restriction when using forced induction than when N/A, so the power difference between the 2 heads will possibly be even greater with the ported head, and farther away from your goal than you think it might be with the stock head.

I know that an engine is is an airpump and the better the air flow, the higher the volumetric effiency will be! On a N/A engine, I wouldn't even consider building without doing major head work! But since I am new to the forced induction game, I would like as much info as I can get!

Thank you for all of your input! BOTH OF YOU!

I hope you won't mind if I continue to pick your brains on this build!

So, what I am getting out of this is that I should really build the head in order to get where I want! That is fine!

I will probably bolt the supercharger to my stockish 250 and run the factory 4.5psi while I build the other engine. If the current one grenades... so be it! My big problem is that I drive this car daily and cannot afford to have it down long term while I have the engine out being built. So, the current 250 has a 194 head and a severely ported factory intake. Plus a petronix ignition. The car really pulls like a school boy with the TH200R4 in it! BUT, after driving a 635HP Camaro a few weeks ago... peppy just isn't going to cut it! I am looking for some serious fun and I DO NOT want to go the SBC route! BORING!

Anyways, Thanks again!!!!

As a rule, superchargers and turbos are a great equalizer. And yes, with a stock head they can achieve some pretty amazing things, but you can only blow so much air thru a straw as well, either with your mouth or an air hose. The first few psi of boost with really seem impressive, so will the next 1 or 2, but soon you will hit a wall where the more boost you throw at it, it really doesn't seem to make more power or gain. The stock head will help you while you transition to the better cylinder head, but it will have limitations as well, unfortunately, it will likely be much lower than what your expectations are wanting them to be. I would at least put larger valves in the stock head, and remove the bolt bosses, even if you don't install lumps at this point, that should be easy and cheap enough to do right now.

Here is where I went when I was looking for my cam. Recommended.

LUNATI CAM TECH HELP: steve - turbo cam w/ emphasis on torque and efficiency - reverse design
212/202, 270/262 adv. dur , 114 LSA, .465/ .458 lift - hydraulic flat
$187 plus shipping -- $66 hydraulic lifters

That cam is OK, but I do not like the shorter duration on the exhaust.

It will make the engine get into boost faster & be as they described, "emphasis on torque and efficiency " but it will not make much top end power. It will hamper high HP numbers when you go w/a cam as such.

It depends on your goals.
The Lunati cam will work great for a daily driver.

MBHD

all the horsepower is in the head , the rest of the motor is just structure to hold it together. The blocks are quite bullet proof with SBC bearing sizes and two more to boot. And with the turbo you dont have to buzz it so tight, but do use forged pistons. There are folks on this site that have torque numbers that make a lot of diesels blush.

I have had no luck finding forged 307 pistons, or even old stock inline ones. I dont want to have them made because it is costly! That is the priority though!

Modesty here... what kind of numbers would I be looking at with the head work done and an intercooled T4 at around 10psi? Torque monster or fun on the street?

Ok... so after searching for a bit I found flatlander racing... forged pistons are $53 each (sold in sets only).

I recall seeing their site before, but it slipped my mind!

Does anybody know of these pistons/ company?

I would verify with them that they are forged and not hypereutectic. Which brand of pistons are they. The ones that Tlowe sells and used in the dyno testing were Ross and made specifically for turbo useage, so an off the shelf non-forced induction specific piston might not be a good choice(even if it is forged) since your going to be considering 10 psi of boost. There are certain elements in a stock replacement forged piston that will not work or be desireable for use in a piston to be used for your application. Chances are you still will need to contact a piston company about a custom piston for your needs.

The pistons are TRW and are listed as forged. Like you say... Check with the manufacturer for specific application!!!!
I was in on Tlowe's dyno testing of the 250... I didn't realize he was selling Ross pistons! Perhaps I should talk with him again!

Side note: For an engine running 10psi or slightly higher, what would be an ideal compression ratio? Around 8.5:1? I know there are 100 factors that determine all of this, but I like to ask questions! Assume it will be intercooled with some form of alcohol/methanol injection, so the heat will not be crazy!

TRWs used to be (circa 1970)of such high quality that machinists would go ahead and bore the blocks without the pistons in hand, knowing there would not be a thousandth diff in a set. Traco eng. used to use TRWs in all the Penske TransAm cars, and anyone with a big name would use Traco (Travers-Coon) emgines (emgine- same as engine, only meaner).

Who had the TRWs for 53 bucks ea? Oops-Flatlander, like you said.

I would run 9.0:1

If you are only going to run 10 psi, intercooled, meth injection,
you could run cast pistons, that will save some $$$$

Just do not let the engine detonate.

My Syclone has Hyperutechnic pistons stock, they are brittle, but I run as high as 25 psi of boost pressure w/those weak pistons,,, but the engine has a knock sensor & I use a J&S safegaurd system on it. http://www.jandssafeguard.com/ My friend is good friends w/the owner & is a distributer for J&S..
I would highly recommend a J&S, they are pricey, but it can save your engine. Also some F.Y.I., you cannot always hear detonation , but w/having a knock sensor installed, it can hear the knocking when you cannot.

Here is a set & you will have 2 extra. http://www.ebay.com/itm/380443032714?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Untimately, forged pistons are the way to go. But,,, it is not manditory.

It just depends on how much you are willing to spend on a good bottom end.

Buick GNs/Regals used cast pistons stock, ran 14 psi.

Syclones & Typhoons used cast pstons & ran 14.7 psi boost pressure stock.

Both examples have factory knock sensors installed.

MBHD

My 7 cents: Spend the money on the bottom end. Spec the cam for the head you are eventually going to run. Do a minimal refurb on the stock head. Buy the good-flowing head later when budget allows. A big power head on a sketchy bottom end is no good when a connecting rod is stuck through it. A rock solid 250 short block built right will last forever.

Here you go!
Here!

I just did a quick google search to look for heads that already have the work done... came up with nothing!

I looked at the TR6 site and didn't see them, either.

Maybe I'm blind!

Anyway, who/where would I contact to do such work or to buy a pre-built head?

I don't know of any shops in my area that meet the requirements!

Tom has them, you'll just need to contact him directly by email or phone. He at the Inliners Convention now, so you'll need to wait till he gets back to get anything shipped to you.

Ok, so. Riddle me this!

Would it do to make a twin turbo setup using the split manifolds and two smaller turbos? Again, for my 250.

This setup would NOT be intercooled, though a quality alky injection would be used.

Am I a doofus for thinking about this, or is it really not much more complicated?

just wanted this to come back up to see if I get a response to the twin turbo idea.

Well it would add to the complexity and require more engine compartment space. Can your vehicle accomodate 2 turbos under the hood.

I have a 66 nova... which will have a mustang II front suspension. There will be ample engine bay room.

Before you think more into installing a twin turbo set-up, how much power do you want to make, street car, race car?
How fast do you want to go in the 1/4 mile? 1/8 mile?

Are you set on a twin turbo set-up or is there a reason you want twin turbos over a single?


MBHD

I was just curious more than anything. I have never seen one done that way.

I am looking for 350-400Hp-ish and as much torque as I will get!

This is a pure street car! I would consider hobby auto-cross... but only for fun.

My main purpose with it is to have as much grunt as a SBC without using the SBC! I had a 400HP SBC in my last Nova and as fun as it was, it was boring! Same old! I like the inline and am hoping for some fun!

No need for twin turbos to attain that power level.

You can run a single turbo to suite your goal.

Easier to install, less cost etc.


MBHD