TPI Torque Monster

[SRD art]

Just thought I'd throw this out there for opinions...

Trying to get max torque from a budget TPI SBC build. I have a 406 (.030 400) with 5.7 rods and eutectic flat tops. Factory 400 heads (9.3:1 compression) with the bowl area nicely blended and gasket port matched on both sides, exhaust ports cleaned up a little too. Just 1.94 and 1.50 valves tho'. 1.5 roller rockers. Basically stock 91 'Vette TPI system. Long tube headers and large single exhaust through a Flowmaster 40. Will have a ram air intake system hooked up too. I have an 1800 stall converter but was considering getting a 2200.

Any thoughts about cam selection? Probably will stay with a traditional flat tappet hydraulic to keep costs low. Would love to see 300+ hp and 450+ ft lbs at the flywheel. This is my first efi/ tpi motor so I don't know how they respond to cam specs compared to typical carbed motors.

Car will be used as a driver and flogged on the autocross. RPM range is somewhere like 1800-4500.

Thanks for any thoughts!

[Johnny Blaze]

Interesting.

[ajg87]

A good source for TPI cam selection would be thirdgen.org!

[Johnny Blaze]

For cam, wide lobe seperation, 114 or more, keep duration reasonable. A lot of guys were using HOT cams a few years back.

You know, I am planning a 408 sbc, you may have seen my other thread. I plugged in the number in the sim, and switched intake to a tpi, and it made like 600ft lbs at 2000 rpms! It was done by like 4000 grand, but the touqe was unbeleavable! Not sure how accurate it could be.

[70camaro406]

I wanted to do this a while back and put it in my old '89 3/4 ton Suburban. I was going to use Vortec heads on a 406 with dished pistons (9.5ish:1), using the Eddy Vortec TPI base too. I'd go with this cam from Lunati:

EFI Cam - Chevrolet Small Block 265/275
Product Description

Hydraulic, good idle. Good low and mid-range torque and horsepower. For street performance vehicles.

Advertised Duration (Int/Exh): 265/275
Duration @ .050 (Int/Exh): 215/225
Gross Valve Lift (Int/Exh): .453/.477
LSA/ICL: 112/108
Valve Lash (Int/Exh): Hyd/Hyd
RPM Range: 1600-5400
Includes: Cam Only
Part Number: 30138
Jobber Price: $187.06

That should be a stump puller, and the RPM range will be lower on the 406.

[Johnny Blaze]

Bringing this back.

As things change so much, I am once again looking at what to do with my IROC. I still have TPI stuff and I still have a 409 SBC shortblock. Makes sense to put them together! The TPI was one of the reasons I wanted a 3rd gen in the first place.

Looking over at Thirdgen.org I see a lot of bad info like,

"a TPI and a 400 SBC are mismatches, the tpi is made for low end torque and the 400 sbc is made to make lots of power at high RPM's"

Now, I know the TPI is done by 5000 rpms. But the 400's being high RPM motors? Maybe a fully modded one.

All the responses regarding this combo on there say its all bad because you are going to be done making power by 5000rpms. Whats wrong with that? If we are building a street car (why el;se would you wnat tpi) the 5000RPM seems like a good limit.


So, I would like to see what others think here, where the real experts are!

For a street car, how does a 10:1 400 sbc with good heads around 180cc and a tpi set up sound? Perhapes with a ported base? And, maybe some after market runners?

[Randy67]

400 SBCs aren't known as high rpm motors stock, I think it would work with the TPI. The 10:1 compression may be a bit high, requiring high octane gas higher than 93. My stock 86 305 TPI IROC would stop pulling by 4500 rpms, 400 would run out of air a bit sooner. A better aftermarket base manifold and runners could help with that. Maybe Vortec heads with the Vortec base manifold would be a good choice.

[Johnny Blaze]

TPI Specialties response to my question,
"A TPI would work just fine on your 400 shortblock, however a stock one will not! You need to upgrade to a high flow base, large tube runners and a port matched plenum with a 58 mm throttle body. Keep the compression 10.5 or lower. This engine will make a ton of torque(around 500ftlbs) but they don't make a lot of hp, just keep that in mind, you don't want to run 4.11 gears! The usable rpm range is 1500-5000. We can get you the parts you need, just give us a call. Also I would run a speed density system, it works better and saves buying an expensive mass air sensor."


Also came across this article, very interesting

http://xtremecarzone.com.au/index.php?showtopic=386

[jlcustomz]

I was going to reccomend checking with tpis on this subject.Still have one of their older printed catalogs .I ran a tpi motor years ago & researched all this stuff back then.
For a budget, I d port the stock base& plenum, I did on mine. Made my own air foil from aluminum mesh & jb weld. You could polish the inside of the stock tubes for now to stay in budget.I,d save $ on these parts for now & spend more on a solid engine setup.The roller cams can definitely make more power.
tpis had some optimized versions. Better heads will definitely build power, even with the restrictive upper rpm range on the intake, yours may do fairly well.
I think the 91' system was speed density & had the cold start injector of the older units like mine eliminated. Computer tuning will be very important, there are several mail order places that are more reasonable than tpis.
Doesn't 500 ft lbs sound cool?
If you're capable of porting your own parts, it'll definitely give you more power for your money than forking out well over 1,ooo for basically the entire intake unit & throttle body. My thoughts.