Well, here we go. Starting my build thread of my Siamsed TPI project taking place this winter. 1989 Pontiac Firebird Formula. Originally a near mint, 94k mile 305 TPI/700R4 combination, with 2.73 posi in the rear. I bought the car for $3500 in April 2012, and of course, immediately started racing it at Summit Motorsports Park, in Norwalk, Ohio. It managed about 15.6x @88 or so MPH while stock. Added headers, started tuning, and managed a 14.78 @91 MPH. One week later, I ran 9.30 on 1/8th mile, which converts to roughly 14.5x 1/4. Of course, that's not fast enough for me. Video of a pass:
I suppose I'll get right to the point!

The Goal: 11s in the 1/4 mile, slowed down to 12.0x for the bracket class I'm in. Pull the tires up a bit

The Gear: My budget list turned not so budget

• 385 CID Flat-Tappet 2 bolt main 010 block
• Tuned Port Injection, siamesed SLP runners, siamesed Edelbrock base
• Dart Iron Eagle Platinum 200cc heads
• Comp Cams XE268 grind, 224/231 @.050", x2 .480 duration @1.5 ratio, 110 LSA
• Built TH350 full manual valve body, by Mark Frazier
• 3000 TCI Streetfighter torque converter
• Moser 9" rear end, 3.70 Detroit Truetrac, LS1 disc brakes
• MAF on 165 ecm, tuned by yours truly with Moate's chip burning equipment

And of course, a few pics. This is the siamesed TPI of which I'm referring to. I purchased the set from a board member, with the understanding of the parts being ported. Not what I expected, but I feel there's still some potential in the parts, and we're going to find out for sure next racing season!


Aftermarket TPI parts nice and shiny after bead blasting them at the shop


Lots of goodies from Summit


Siamesed intake base


Siamesed runners

I'm honestly not quite sure what to expect from the siamesed base. Research shows people have reported gains from the modification, including top end power (which is a good thing for me, considering the cam's range and the stall I've picked out). However, this cripples the wave tuning of the Long Tube Runner system, as explained to me by Allen (1989GTATransAm). Essentially, the siamesed section of the base and the runners, roughly 5-6" of runner without a divider, will act as a secondary plenum as opposed to a large runner. Basically, the air travels through the throttle body, into the plenum. Then it flows through the short length of runner left in the SLP runners, into the open area of the base, which now acts as a second plenum. The air is then pulled into the head from this plenum, so it's basically the length of the runner in the head and what's left of the runner in the base, I'm guessing 8" total. Compare this to LTR systems which are around 20" from plenum to valve. If anyone has any further information on the physics behind a siamesed base, I would absolutely love to read up on it.

As of now, the car is sitting right outside the door of the new garage. It WILL be inside before the snow starts accumulating. Unfortunately, wiring and insulation must be done ASAP. Should be starting on the teardown within a week. Can't wait, updates to come!

Subscribed

Signing on to follow the project.

double that..

I've got the same intake set up on my car. I'm running a stock heads and cam L98 with 1 5/8 inch primary tube hooker headers & matching 3 inch y-pipe to a single 3 inch cat and flowmaster cat back exhaust.

On the intake side I've got Hawks thirdgen ram air boxes, K&N air filters, BBK 52 mm throttle body, and gutted factory air box.

I'm also running a Bowtie Overdrives Level 3 700r4 with a 2,400rpm stall converter. I'm also still running 2.77 gears in the 9bolt rear but, I'm going to change those to 3.27's.

I bought an Edlebrock TPI base, SLP intake runners, and port matched all those components to the factory plenum.

The porting work helps out all around. The engine is much smoother in the lower part of the power band say from idle-3,500rpm. There is more torque down low aswell. Also where the stock TPI set up signs off at 4,500rpm there is a big power gain in the 4,500rpm - 5,500rpm part of the rev range.

Thanks everyone!

Already have more progress, check out this beauty




And the official cam card.

Id rather see someone seriously port the passages rather than leaving them stock and siamesing. All you can do is put it on and see how it feels.

I agree, I'd rather have individual runners. It was just a mistake of jumping on a deal in the classifieds too fast lol. $400 for the runners, base, and plenum. I intend on opening them up more, as the runners weren't ported at all, just the middle divider cut out. They measure 1.61" diameter, the same as out of the box SLPs. The base appears to have been opened up a little bit though, it measures 1.73" if I remember correctly. I'll work with it though. The biggest downfall anyway will be the 083 heads. Aftermarket heads are just not feasible at the moment. I figure I'll just match the heads as best I can to the intake, and run it for the season. Aftermarket heads may be in the cards by next winter.

Also with the 305 the gains won't be as substancial as with a 350 motor. TPI was originally designed for the 305 so the system is not as restrictive on the 305 compared to the 350. You will still get good gains over stock though.

+1 for the 89 Formula choice, subscribed.

Im watching also.

I'm very glad to see that there are still folks out there like me that are still working with the Gen 1 small block and the TPI system! I like the LS-style motors as well but I still really like the Gen 1 small block!

Is that a roller or flat tappet cam?? Edit, never mind I see you have a non roller block.
I'd try to find a roller motor if I were you..

That would be optimal, but the current block is a free low mile block. Can't beat free lol.

Thats not a huge cam but its way too big for any stockish TPI setup. If you didnt siamese the runners and intake ports that far you'd leave a bunch of power on the table. The tuned long runner was an artifact of the 80s when they knew they couldnt make the power yet, and they were constantly needing to drop displacements down. They wanted it to feel like a 350. It worked, but you're ALWAYS going to be horsepower crippled by a stock TPI setup regardless of how well it flows.

Torque x RPMs x conversion factor = horsepower

Torque is limited mostly by displacement and airflow of the hard parts. Hard to improve that without serious, serious work. Where in the RPM range that torque is made determines horsepower. If you want the torque curve of a diesel truck engine, keep the TPI. If you want the torque curve to hit serious power numbers, you've got to let that go. Especially on a 305. The only way to amke power on a 305 with stock heads is just to spin it faster. The faster you turn your torque, the more power you make.

With that cam I dont think you made a mistake at all. It would have been a mistake to try to make a stock TPI setup work. You would have had, at most, a 2000-4500 RPM range, and that cam iwll take a 305 probably to 6000. Thats a lot of horsepower you're leaving on the table.

LSA is pretty tight on that cam. Curious to how it will work with the EFI setup.

I have the exact same cam but with a 114 LSA. easier to tune with EFI.

I suspect with the base ported in the manner that it is the intake system will act something like a Mini-Ram. I would say low end torque has been traded for some upper end horsepower. We will find out with a chasis dyno run.

I'm not sure this can be considered traditional stock TPI anymore, really. With the total runner length down to a whopping 8", it's not really a long tube runner setup anymore. I'm referring to what I wrote at the bottom of the first post. Also, remember this is going on a 350, not a 305.

In regards to stockish style TPI, I don't feel it's not capable of high rpms, with work of course. Allen's LTR project thread shows that, and that's the base of the motivation for this build. Mine won't be the same, but the concept of reworking the base, runners, and plenum is still there. With any luck, this intake system will allow me to make power up to 6k. I plan on shifting anywhere from 5500-6000. That's what the cam, stall, and rear gear are set up for. Most all research shows that the siamesed base moves the powerband up, the more divider removed, the higher the powerband is shifted. It will be interesting to see, as this isn't a very common modification. You all have to wait until April or so to see some track times though

As for the tight LSA, I was actually going to go with 109 originally, until Comp claimed that would add $80 to the bill. For one degree, no thanks. When I get off work I'll post a vid of the cam that sparked my interest, I believe paired with a miniram. I'll be tuning this myself, so it'll be a learning experience if nothing else.

Youll be fine. The best way to learn is like this.


SO have you decided on how your going to run the tune yet?? Mask? $59, $8D, and so on??? Dont forget I have that 1 bar map sensor for ya.

For now I'm going to stick with MAF on the 165, mainly because of my experience with it. However, that could change VERY quickly if the tight LSA of the cam is too much for the MAF. I'm not worried about adjusting the tune for the cam, but rather I've been reading around, and some people have mentioned that too much overlap throws off the MAF readings. Can anyone give any input on this?

If it does turn out to be a problem, I have a 730 ecm ready to swap in, and thanks to you Mark, a MAP sensor as well as your SD tuning knowledge Thanks!

Here's the vid of the cam that I based my grind off of. He is also a member on TGO, Justin89Formy I believe. And as I thought, it is paired with a Miniram.

Justin's car makes good power, I watched it get tuned and dyno'd in person. But there is a huge difference in a miniram and any style LTR setup. All I can say is give it a try and see how it works out. I also agree the 110 lsa is going to make it harder to tune for cruising around.

I was responding to your concerns about the siamesed setup "crippling the wave tuning" of the TPI system. You WANT to cripple the wave tuning, it is great for getting good fuel mileage and making a 305 feel like a 350. But its not good for horsepower, because horsepower requires RPMs.

its not the lsa so much as the overall overlap that can make it harder to tune although to an extent lsa can be an indicator of more or less of it sometimes.

I love Justin's car, it's a beauty. I only mentioned the Miniram because that's what Allen referred to when describing the characteristics of the base.

Ah, I see where you are referring to. I just wasn't sure how the 305 got brought in lol. But keep in mind, with those modifications to the intake, it is meant to rev higher. That's the part of the first post I meant to refer you to. Where the amount of divider wall removed from the base is a factor in moving the powerband up. Also, fuel mileage is out the window lol. I don't think a 1:1 final drive with a 3.73 gear is going to help much with fuel mileage. I'll be driving to the track around 3000 or so

Correct, that's what I'm referring to. I wish I could find the page I read about it. It mentioned something about the overlap can cause the MAF to give false readings.

Well, much progress made in the last 3 days or so. Thursday night I got the go-ahead from my dad to start tearing down his old motor. Although the motor is in great shape, it's been sitting for a few years, and some sawdust and sand have probably found their way in. In about half an hour, I had the motor and tranny seperated, converter and flexplate off, intake and heads off. The discovery was very positive. My wish for flat top pistons came true, giving me a compression ratio right in the ballpark I was aiming for. Flat tops with four valve reliefs to be exact. Better yet, the cylinder walls still have very distinct cross hatching. Didn't get much accomplished Friday night, Christmas party for Summit Motorsports Park .

Made a bit more progress today though. Freeze plugs removed, balancer pulled, timing cover pulled, old cam and lifters yanked. Re-assembling our engine hoist right now, getting ready to pull crank and pistons, all that's left of the motor. Cursing like a sailor moving this heavy SOB hoist from the basement to the garage...I can say with confidence that this base piece alone weighs more than I do .

Probably won't finish tearing down the block until tomorrow, at which point it'll undergo a bath, new freeze plugs, and possibly some paint. Red or black? I'm leaning towards black...Anyway, here's some eye candy .


#5 cylinder wall.


Progress on the new shop/garage.


Current garage inhabitants. My grandfather's 40 Ford Coupe, and Dad's 77 Vega.

Nice show man. When you get that bad boy insulated, and a lift, it will be a nice shop forsure.

Is that block bored out at all?

When you start takeing out the main caps and the crank make sure you use a metal stamp on all the caps so that they go back on the original rods...exc

Yeah, the shop is coming together nicely. Just have to finish framing the inside walls until my car is moved in. There is currently a stack of lumber where my car will be lol.
But nope, that block has never been bored. Fresh low mile block that's been sitting a couple years.

That cam is too big for the stock L98 heads no matter how much porting you do. Also the cam should be on an 112-114lsa. Easier tuning and it works better with the TPI.

I do think the tuning will be hard with MAF and that LSA.

Andrew personally if your thinking of going with the speed density set up you might as well do it now over the winter. Reduing the pin outs will take some time and just making sure it all hooked up right. Rather start tuning with something you know will be easier. And IMO speed density is much easier.

After a lot of thinking, I'm starting to lean towards a set of bare aftermarket heads...Dad brought up the point of it not limiting the lift of the cam anymore, so I may be returning the cam in favor of one with higher lift, if I do go aftermarket heads. Then I wouldn't necessarily have to spend time porting the new heads (I'd go with ~195s, to leave room for improvement), and that opens the door to low 12s/high 11s or further, depending on the rest of the setup. So let's here it guys, favorite aftermarket heads? I like the sound of AFRs, everything I've read points to their numbers being untouchable.

In other news, the block is bare! Getting it washed up tonight at some point. Bearings are in great shape, as is the crank. Looks like it's only getting new freeze plugs, paint, and gaskets. Should have the bottom end back together this week some time. That's all for now folks!

if you decide to return the cam, what ever cam you go with next i highly sugguest spending the funds and go roller.

"like the sound of AFRs, everything I've read points to their numbers being untouchable."

I think the AFR 195's will be the best bang for your buck. We had a guy yesterday at our dyno session make 431rwhp with a set and with 355ci. Also seriously check out a roller cam as suggested above.

I wish I could help on the heads selection but my knowledge is limited on V8's. But I think youll be happy down the road when you have those better heads forsure. Should make hitting those 12's or even hitting the 11's much easier then with the iron headed ones.

You marked all the caps and rods correct?? Make sure you use tons of assembly lube and make sure everything is back in the exact same place you took it out of.

Get an aftermarket hydraulic roller cam, retrofit hydraulic roller lifters for that block you're using. Don't settle for less..

The problem is, I'm not looking for an all out race car. Not to mention, the cost of the build will increase at least double. $1500 for new assembled AFRs. $474 for a set of Comp retrofit rollers, compared to what, $85? Cam price jumps from $121 to $400+. Not to mention, the stock rear won't hold up. At least $1200 for a 9"/12 bolt. Then I'm running too fast, need a cage. That's what is stopping me from pulling the trigger on a nice set of AFR 195s. One thing leads to another, and this doesn't become a mild street build anymore. Racing season starts in April, and I'm back to the planning stages? I'll never have it done by season opener. And although it's the least of my concerns, it may be TOO fast. I'm running a points class that's 12.00 or slower.

You all have to realize that 1. It's not a full drag car build. This car never will be. The only way it'll ever see a trailer is if I go to Indy for the division SMP is in. 2. There is a budget involved, and I'm not where I want to be in my life. College is a priority that's stopping me from blowing every last dime on my car. I know plenty of people can relate.

I appreciate the constructive criticism, I genuinely do. Don't mistake parts of the build for ignorance of the better alternative out there. I've thought about these things countless times thus far. Hell, I've had dreams about searching a junkyard for a roller motor lol. I may stick with the 083 heads just to keep from falling into that "needs something more" cycle. I probably will stick with the flat tappet block because it was free, and for the $206 I have in the cam and lifters, it's ready to go. I'm going to focus all my efforts on making the intake system as good as I can, and let's hope for the best.

Side note, still keeping an eye out for used heads

If you do any upgrade at least do the heads...HR cam if you can it really helps.
Money WELL spent!
Do not take a grinder to them in hopes youll pick them up trust me on this.

Do the rearend later IF it needs it just get the motor done work the bugs out/drive it etc.

If the build takes longer to be right then so be it.

"The problem is, I'm not looking for an all out race car. Not to mention, the cost of the build will increase at least double."

What we are talking about is not for an all out race car. We are talking high performance street cars that can be grocery getters and tame enough to pass the strict California smog laws. I understand your budget concerns. Some of these parts can be had for a lot less than the retail price you mentioned. You can buy used if you keep your eye out for deals.

On that note, I'm looking into a set of Dart Iron Eagle Platinum 200s. Anyone have experience with these?

I have experience with the World Sportsman II's. Back in the late 80's early 90's world and Dart were operating as the same company and then later split. Both heads from my knowledge are very similar in design. I do know that a 200cc intake runner on a 350 will need a lot of airflow and rpm's to make use of its designed powerband. Your cam is a bit bigger than what most TPI guys like to run which is good but I am not sure if the actual long tube runners themselves will be a good match. I would think you would want to shift a bit higher than 6000 with those heads. Dart offers a 180cc head that you might consider as well. http://www.summitracing.com/parts/dr...make/chevrolet

"but I am not sure if the actual long tube runners themselves will be a good match"

Everyone has to remember that with the base being "siamesed" the way it is, it effectively is no longer a long tube runner design. Each cylinder will draw air through a pair of runners. His effective runner length in the base may only be 3 inches long.

So what would be your suggestion on the 200cc heads as opposed to the 180's with his proposed setup? Will the porting work support enough airflow to maximize on this selection?

I do understand when shopping for second hands parts one must be willing to compromise a little based on what is available. Would you say this is a good buy? https://www.thirdgen.org/forums/clas...good-true.html

In a 350 I would to with the 200cc heads. I bet if the intake runners were poured they would be closer to 195cc. If he opens up what is left of the real runners in the base to match the head or maybe .030" or so smaller his intake should have no problem feeding those heads. As to whether or not that is a good buy on the heads I would say that "appears" to be a decent price. Seeing as they are iron heads he needs to keep a sharp eye on his compression ratio.

334 ci Id err towards the smaller head

Well I suppose this is a big update: Went ahead and pulled the trigger on the deal for the Dart Iron Eagles. I'm paying $500 for them pretty much bare. I have a set of springs from Comp, now I'm just getting some Manley valves. So here's question #1. 2.08 or 2.055 intake valves? Question #2. FelPro 1205 or 1206 intake gaskets? I probably won't do any work to the intake ports of these heads, yet anyway. Need to get a gasket set for the bottom end ASAP, and I may aswell get a full gasket set.

Simple question really. Are the valve reliefs on these flat-top pistons a variable in calculating compression ratio? I would imagine yes, but it doesn't hurt to check. I'll be running the typical 4.00 x 3.48 bore x stroke, with 64 cc head chambers. What do you guys think I should go with for a head gasket thickness? I'll be running 93 octane only, so I'd like to be higher CR, yet on a safe level of course.

With any luck, the motor will be done by New Year's, except the intake. Air compressor is broken so looks like I'm not finishing up cleaning the block for a few days

Yeah depending on the piston, the valve reliefs are anywhere between 3-8cc's of extra volume. You can cc them to check probably if you cant search the part number.

Head gasket thickness should be as close as possible to what it will take to get the top of the piston .040-.044 inches from the quench pad on the cylinder head. If the pistons are .025 in the hole (this is what they would be factory if the machinework and tolerances on every single relevant part were perfect) you would want a .015" thick head gasket. Thats not really super practical... not many options there, but just measure and try and see what you're working with. A quench in that range will improve power, fuel efficiency, and even though it may raise compression it will make detonation less likely. Make sure you check piston-valve clearance, though.

http://forum.grumpysperformance.com/...3&t=726&p=9291

I hope that helps, its one of those things I raelly wish I had paid more attention to when I was putting mine together.

We use the best head gaskets from GM. They are for the hi performance Corvette from 87-91. They are .028 thick. You can also get them from TPIS. They boost the comrepssion by half a point. With your combo you will not exceed 11.0 to 1. With a 2 valve relief piston. It will be somewhere from 10-10.8 to 1. This is an old school trick.

These are 4 valve reliefs, and it appears they are 2 CC each, so 8 CC per cylinder. I won't know the deck clearance until the bottom end is back together, so I guess I'm waiting on head gaskets. But here's the money question. What should be the highest compression I can run with 93? I know it's dependant on dynamic compression, but static is at least a ballpark figure. Keep in mind these are iron heads, not aluminum. Naturally I'd like to run max compression with full timing without detonation. If the thinner head gasket puts me at a decent quench, what if it's too much compression for 93? Hopefully heads are here next weekend, so at least that gives me a bit more than a week to figure it out.