I was inspired by a couple threads on here over the last year or so about trying to get nutty with the first injections intake. I needed an engine to put it on, and wanted something out of the ordinary.

So I decided to stretch it a bit and build a 427ci tuned port. This has been in the works for awhile, and I finally got the bugs worked out of it. Now I just need to get started putting together...after my time in Iraq is up

I wanted something to look stock and sound close to stock, but I wanted it to run like a bat of hell. So I decided on a first injections base and runners, and a modified stock plenum reworked to accept the first injections runners, sandblasted and powdercoated to look as 'stock' as possible. Stock valve covers, AFR eliminator heads, and a late model bowtie roller block with an internally modified oilpan (scraper, baffles, etc) to go with the stock theme.

I'm thinking the injections base and runners dont need to be ported to work with those heads as much as it flows, but I am going to clean them up a little bit. I figured maybe a 454ci engine would need the intake ported and bigger heads, but right now I'm thinking velocity.

I want to do an OBDII engine, meaning I will be using certain vortec components in the build. I dont think a stock ECM would like this engine very much, but the OBDII PCM should be able to handle it without a problem.

I'm also going to be using crossover longtube headers, which is something stupid I came up with. The driver's collector crosses under the oil pan (with lots of work, mind you) and turns to run parallel alongside the other longtube to make running duals easier. Those are a pain in the *** to make, but I have a prototype set made up for the 382ci tuned port LT1 in my '86.

What do you guys think? I'm hoping to have this running on a breakin stand early next year...

 

hi my name is michael krusmark, i am from southeastern minnesota and when i found out you are going to build a 427 TPI. i just wanted to let you know that at this time i run a 440 all aluminum smallblock with a fully ported edelbrock TPI manifold and runners. i have it in a 87 iroc, with a full corvette rear end. and i use it as my daily driver. so if you need and help with the build i am more than welcome to give you the information that i have gathered to aid you in your project.

 

wow, id really like to see that.
and a 427 with tpi = torque munster!!!!

 

plus a c5 IRS, definately need to post pics of that, I would road race the **** out of that car

 

yeah, thats what i wanna see, the irs in a thirdgen.

 

I think that your project needs alot more planning. What do you mean by OBD II,,, what year is the PCM and where are you going to get it?

I think that you are talking about an LSx engine, being all aluminum. You mentioned AFR Elimenator heads. The Gen I and Gen II SBC heads will not work on the LSx blocks.

Some suggestions: get a PCM for 1999 or newer F-bodies. The '98s were not as good. Purchase or build yourself an L92 short block that specs out to be your 427. Top it off with L92 ported heads and an L76 intake. The TPI will choke any 427.

 

Sounds like a fun setup , what ECM are you running? And any HP/tq or track numbers?

 

I dont need any more planning. I have a built 427 for my Corvette, and I've built plenty of small blocks, so I know the difference. I've planned to do this motor for the better part of 2 years. This build is a gen 1 small block, based on a bowtie large bore late model 1pc RMS case. I plan on using the '99+ PCM, my '98 Vette is getting one as well because of the differences in them. As far as the tuned port goes, a stocker will choke damn near any engine you use it on...aftermarket will choke healthy 350's and 383's...and I'm expecting the first injections intake the choke the 427 somewhat. Why build it? Easy.

Tuned ports rely on flow 'pulses' to gain speed in the intake manifold over it's runner length, and enter the combustion chamber at the right time (using the right cam). It's a no-brainer that a large x huge flowing port will not have as high of velocity, even though it can flow the numbers. With larger ports, you have to either have a larger engine (pulls more air at the same engine RPM ie adds velocity in the intake), raise the target RPM (not an option with a TPI) or go with smaller ports to keep from loosing torque. But simply put, because a tuned port relies on flow velocity at a certain RPM, paired with a matching cam (TUNED port injection), there will be a certain level of flow loss in the name of velocity. Everyone likes to bitch about how TPI motors choke engines, which is true, but thats how the TPI makes its torque. If it did not choke the engine it was mounted on to a certain extent, it would be a worthless pile of metal as an intake manifold. By trying to add too much flow, you will most likely kill off your torque, which makes no sense. A better approach would be to improve flow by not making the passages larger, until AFTER you maximize velocity through the port by removing all the restrictions and turbulent problem areas first, (like port matching/port cleanup and the stock tuned port entry angle into the head) then deciding if there is a need to do so.

If you want an engine with a manifold that doesnt choke the engine, choose an intake that flows the same as o slightly less than the heads. Like a single plane on a stock tuned port. Problem there is if at a certain point, the intake outflows the heads, it will tend to make the intake pulse stall out for a second, and the port goes stagnant. Then the pulse has to reaccelerate all over again, and there you go, instant torque loss, because you are loosing what time you have for cylinder filling. That sucks. If you want decent HP and torque without leaving much on the table, get a dual plane or a stealthram or equivalent. I want tons of torque, so I am going tuned port on the 427. I will probably loose HP wise to a dual plane, but this is supposed to be a fun, torquey street engine that looks stock anyway.

The engine will be run with AFR Eliminator 195 sbc heads. The intake runners flow the numbers to make power, but are only slightly larger than stockers (170 I believe) and if this was just dimensionally larger, I would most likely go to the 210cc head. BUT, basic rule of thumb is in the name of torque, to go with the smaller head that meets your head flow requirement. So, I am not going with a larger head, but the 195. This will give me a higher speed in the head prior to discharge into the chamber (more torque).

The intake flows right at 300 cfm through the base. I will loose a little through the runners, however, I will be port matching the intake and having it honed throughout to gain back the flow. This will put intake flow right under that of the heads, while outflowing the stock tuned port by almost 50%. But the engine is only 22 percent bigger. Even the relationship between bore size and stroke is somewhat similar (though rod length to stroke ratio isnt as nice as I'd like, but there is only so much you can do with a 9.025" block)

And the worst case scenario? I have a nifty engine to put into my '37 Chevy coupe, and yes, it has a complete C4 suspension under it, so there is IRS that WILL break but I have a L92 headed LS2 for that, I was kind of thinking of putting this into a black GTA and yeah, throwing IRS under it with the crossover longtubes. That still needs a few tweaks. I've also considered using a C4 though, since the engine is supposed to be stock looking.

Long story short, there will be some chokage going on in the 427, even with the monster base and runners. But what people dont understand is that is the reason the tuned port is such a great torque engine. The choking is what causes acceleration of the remaining air through the intake, making that torque that people love. Kind of odd, huh? The key to a good tuned port intake is getting good flow by eliminating turbulent air and frictional flow loss without a larger port, and choosing a cam to work right in the sweet spot of the intake manifold.

Just need the right roller cam. I also wish I could have used a 6.125" or 6.2" or longer rod to get more piston dwell time @ TDC, but because I wanted to look stock, intake spacer gaskets and a raised deck block were out of the question. Tuned ports love long rods.

 

Nice write up.

Here is part of a write up from Tom Moss Porting.

240 ft/sec - intake - ram effect faint
- exhaust- scavenge faint

260 ft/sec - intake - ram effect moderate
- exhaust- scavenge weak to moderate

280 ft/sec - intake - substantial ram
- exhaust - scavenge moderate

300 ft/sec - intake - * ideal ram
- exhaust - substantial scavenge

320 ft/sec - intake - possible loss
- exhaust - * ideal scavenge

340 ft/sec - intake - likely loss
- exhaust - possible loss

What range were you looking at on your intake?

When I spec'd out my 383, I wanted to stay close to the 1000 - 5000 rpm range. Because this is where everything on the car is Factory tuned for. The engine and also the car, so I wanted to be a little better then stock, without doing major changes to everything about the car.

Like you said this is a fun daily driver car to drive. For more go I run my HD which is a lot more radical.

 

And this is the reason small diameter / small cross-sectional area TPI intakes and runners "choke" the larger engines. It has more to do with intake port velocity than the runner length. The length helps dictate the peak RPM,,,, the cross-sectional area determines the average port velocity (for a given flow) and the port velocity determine how much power you can make under the curve or up until the peak RPM limitation of the runner length.

Small cross-sectional area intakes and small diameter runners means you're going to hit 300ft/sec very early in the RPM band with high flowing heads capable of moving a lot of air,,, especially with larger cubed engines. You want to pick out a combination (heads, cam, exhaust) and match that with a cross-sectional area large enough to make 300ft/sec closer to the rpm limited by the runner length (well,,, for a long runner intake anyway).

It is a science to it for sure,,, going too large does give up lower RPM power (decreased the port velocity), but going to small chokes it up top (hits "terminal" velocity too soon). Same can be said for length,, too long and you cap the top end too soon,,, too short and there goes the midrange rush. Single fixed runners are definitely a compromise,, you just have to figure out what you want then determine the combination that will get you the closest to it.

 

The true terminal velocity is the speed of sound at 1200 ft/sec.

Quote David Vizard's book "The engine will become port limited at a velocity of around 690 ft/sec"

That is a bit higher then 300 ft/sec.

Davids math numbers come out for the "stock" tpi, a 383 at 5100 rpm, for peak power. And 5450 rpm for port limiting.

Everything has to size match - the heads, cam, intake, runners, and plenum.

 

I'm not questioning Vizard or his formula using a limiting port velocity of 690 ft/sec. Used the math and it served me well over the years before the price of a good engine dyno simulation came down low enough for me to afford it.

Yeah,, bad choice of wording using "terminal", which could be consider and is used for the theoretical maximum port velocity,,, or speed of sound. I should have said something along the line of peak power velocity.

Sorry, I didn't know that Tom Moss's write up didn't explain how he arrived at the verbiage used with the AVERAGE port velocity numbers you posted and just said "In practice rules of thumb have developed saying that at peak power, the ft/sec figure should be somewhere within 280-380 exh and 240-355 intake." The numbers and verbiage look about right to me from crunching numbers from real pulls and from what the simulations are showing - regarding the correlation to peak power and average intake velocity,,, which he did explain how to calculate.

 

The challenge with any engine is the air flow is not linear, it is pulses. The speed of sound is a true limit, but the air flow only approaches that amount at the narrowest point, with the most curve (change in direction). That is why they use an average number and say, only to the .55 Mach number. This keeps the peak pulse air flow below the 1 Mach number. Also remember that vacuum, pressure, air temp, port shape, texture, and gas mixture amount will all "play with" the final air speed limit.

The fastest point of air flow will be affected first, developing a small shock wave. This shock wave will then upset the rest of the air flow stream.

Peak air flow is not necessarily the same as the peak power air flow.

The limit is not really a terminal wall, but a point were more is less.

A flow bench number will look better, then the actual, as running, engine air flow number.

The path of air from the front of the car, through the engine, and out the tail pipe is affected by everything along the way.

 

Lots of good points here. I'm going for the maximum ram effect on the intake, and I'm going for maximum scavenging on the exhaust in an effort to 'pull' the air and exhaust through the engine for better torque.

I also agree that it's a tradeoff...it's several factors coming into play that all effect another. For example, longer runners increase torque, but add more surface area for flow restrictions that lessen flow (HP potential). Shorter runners generally add HP, but sacrifice the tuned effect of the manifold. Small runners increase velocity, too large hurts velocity down low but aids flow up top, and too small makes for great bottom end torque but hurts flow higher up.

To be completely honest, I was actually going to do this kind of the old school way. Trial and error. It should give me some good data which is part of the reason for doing it that way. First, I was going to complete the manifold and after it was all done, get flow numbers through the runners and base, making sure to limit the flow to a little under the flow of the heads, taking .400" + into consideration. Then I'm going to order a camshaft for it, taking the flow and intake characteristics also into consideration, probably something in the ballpark of a 222/232/114 or even a cc305 with 1.6 rockers for an engine of that size. That should give stock like running characteristics. Then I will take it from there and see how she goes. Kind of like educated parts selection using off the shelf parts...

This is the first engine I know of that runs at this size with TPI with an intake like that, so right now, I can run tons of equations, but it's still going to be just an educated guess, because there is no hard data to go off of. I'm going to just use my experience mostly on building this thing, and test and tweak it from there. Check computer data and dyno graphs...idle vacuum...throttle response...and see what it likes in the real world.

Cam might be a tad small or large, but it should be in the ballpark... it might want a little less compression (not likely, but possible) since it is rather high compared to a stock tuned port...exhaust should be fine (I figured dual 2.5" was a little too small, and they dont sell much in the 2.75" size) at a full length 3". I'm hoping that the cubes tame some of that, and it's also an OD size...meaning the inside of the pipe is actually slightly smaller than 3". I'm building a larger variant of the crossover longtubes I have for my '86 LT1 Z. Those are 1 5/8-1 3/4, these newer ones will be 1 3/4 to 1 7/8.

Should be fun!

 

The engine you have proposed will have a lower peak HP number but a higher avg HP number. Maybe not the perfect "wot only drag race" engine but a very potent street one.

 

Yeah, thats what I am going after. something stock looking, stockish sounding, and something that makes more torque in the range as a stock tuned port in spades. Something that can still pull off decent mileage with a good tune, that I can drive guilt free. Who knows? Might be able to do it cheaper than some of the 383 tuned ports I've seen. It'll take a creative hand in doing the intake, though. I'm stoked and I cant wait to get it done...just wish I had deeper pockets...

Did I mention the muffler is going where the stock cat was? I'm going to give one of those tru-X magnaflow mufflers a shot...and yes, it will be catted

Not looking for peak HP numbers, just potent torque numbers. I have other toys if I need a HP fix.

 

dam i want the exact same setup..... stock looking tpi stock sounding..... but heads cam ls1 killer......