TPI VS TBI on a performance intake

[racprops]

The big question of a 1987 Chevy Tuned Port Intake VS an old fashion performer dual plane Intake with a Throttle Body Injection system on it by an adaptor.

The target power and RPM range is 1500 To 4500RPMs, with the main goal is as much torque as possible at 1500RPMs.

This will be on my special 383 engine which is built to have is low torque peek at 1500 to 2000RPMs, and thanks to Rhoads Roller Lifters also switch to the performance profile and have a second torque around 3800/3000RPMs.

So the question is which intake will give the most 1500 RPM Torque?? This range of 1500 to 2000RPMs is the range I am gearing my van to run at 75/85MPH, as in my cruse speed/RPMs.

The specs are:

The cam is #806 cam’s Specs; 207/214 @.050 117 440/454 lift with 1.6 full roller rockers (milder rockers)

I will be running Rhoads V-Max roller lifters, and with Rhoads Lifters running at 10% reduction cam will be at:

180/192 114 .396/408 at low RPMs

These are the cam specs of a low RPM cam, one that had it torque peek at 2000/2200 RPMs not 2800/3000RPMs, it came out of a 90 Cadillac Chevy 350 that was rated at the 2000/2200 Peek, much like the classic Chevy 400 and the Olds 403 did.

Yet at 2500/ 3500 will be running the full power cam.

This will give me a variable cam, mild at low RPMS and HOT at higher RPMs.

The heads are stock swill port 193s, ceramic coated for lean burn running.

The pistons are Keith Black “D” shaped crowns also ceramic coated, and Teflon coated skirts.

The rings are chrome molly with number two as a gapless ring.

The crank is old school 400 turned to fit a 350 Block, with stock 400 Rods.

Compression is calculated at 9.5+

Thanks for your input.

Rich

 

[Schurkey]

The cam is #806 cam’s Specs; 207/214 @.050 117 440/454 lift with 1.6 full roller rockers (milder rockers)...
...it came out of a 90 Cadillac Chevy 350

Sounds like WAY more duration than a typical TBI cam from a Cadillac. I did a search for "GM 806 Cam" and got nothing for useful results.

I've never used Rhodes lifters. Can't help you with that. I'm kinda allergic to having the valves banging into the valve seats as they close. I'm VERY suspicious of using fast-bleed lifters on what is probably a VERY mild cam to begin with.

I don't know what "milder rockers" are. Beware, there's a LOT of crappy, high-failure Communist Chinese "roller rockers" out there.

The heads are stock swill port

Swill port. Wonderful.

The rings are chrome molly

Not likely.

Moly-filled iron top ring I'd believe. Probably with a plain (not chromed) iron second ring.

But if you list a part number we could verify.

Chrome-Moly is a kind of steel. Good for making roll-bar tubing and crankshafts from. Expensive.

with number two as a gapless ring.

That's probably a mistake. For 20+ years, folks have been saying to have MORE gap on the second ring than the top ring, to avoid unseating the top ring.

The crank is old school 400 turned to fit a 350 Block, with stock 400 Rods.

"Stock 400 rods" are not known for their strength. But this is a low-rpm engine, so you're probably good if the rods pass Magnaflux testing and have been checked for big-end roundness.

I guess you're using an older, two-piece rear main seal block. How are you going to hold the lifters in place? Are these "retrofit" link-bar lifters? Or are you using the special adapter to fit a two-piece-seal crank into a one-piece-seal block that's set-up for OEM roller lifters?

You will absolutely want the assembly balanced.

Consider using a thin head gasket so you don't have to shave the block decks as much to get proper quench/squish. The KB pistons fit the bore pretty tight, they won't rock much. Quench distance of .035--.040 should be fine. Tighter might be possible, if you have piston-to-valve clearance--but it may not be all that helpful. BE SURE THE MACHINE SHOP USES A TORQUE PLATE and the same head gasket you've selected DURING HONING. You'll probably have to buy three head gaskets--two to build the engine with, and one for the machine shop to use with their torque plate.

 

[Erik the Awful]

The big question of a 1987 Chevy Tuned Port Intake VS an old fashion performer dual plane Intake with a Throttle Body Injection system on it by an adaptor.

I think the TPI has higher limits, and with a 383 you're going to be maxing the TBI's capabilities unless you either bore the throttle body or manage to find a 454 throttle body. Do you have to tools and experience to tune it yourself? I don't, so I went dual-plane and upgraded to a Sniper. If I ever get froggy about bigger heads and a single-plane, my fuel system is still enough.

 

[arrg]

If you want as much torque as possible from 1500 to 2000 rpm, just use the stock TBI intake. It'll outperform your other choices in this limited use case. TPI and even an Edelbrock performer are tuned for higher rpm ranges than that. Your combination is going to be out of breath before 4000 rpm anyway, so no need to spend a lot of money trying to make it something that it's not.

 

[L31MaxExpress]

LSA is way too wide for low-end torque. TBI on a dual plane will make more torque in the RPM range you are seeking to run. That being said you shouldn't gear it to run that low of a RPM unless you have a big block. My G20 van and Tahoe both cruised at 1,700 rpm @ 70 and downshifted on every hill. I ran an edelbrock performer rpm and it made more torque than the factory TBI manifold everywhere. I had to add fuel everywhere off-idle and some to the AE for the increased plenum volume and better breathing. Combination will likely have good power up to 5,000 or so rpm. TPI works really well if you are geared to run in the 2,500-3,500 rpm range, which happened to be when I was heavy on the throttle in 3rd gear. Down at 1,700 rpm it made less torque but it made up for the low-end torque loss in the midrange. I also made up for the low-end loss using a S10 converter and revised shift points.

 

[L31MaxExpress]

Sounds like WAY more duration than a typical TBI cam from a Cadillac. I did a search for "GM 806 Cam" and got nothing for useful results.

I've never used Rhodes lifters. Can't help you with that. I'm kinda allergic to having the valves banging into the valve seats as they close. I'm VERY suspicious of using fast-bleed lifters on what is probably a VERY mild cam to begin with.

I don't know what "milder rockers" are. Beware, there's a LOT of crappy, high-failure Communist Chinese "roller rockers" out there.


Swill port. Wonderful.


Not likely.

Moly-filled iron top ring I'd believe. Probably with a plain (not chromed) iron second ring.

But if you list a part number we could verify.

Chrome-Moly is a kind of steel. Good for making roll-bar tubing and crankshafts from. Expensive.


That's probably a mistake. For 20+ years, folks have been saying to have MORE gap on the second ring than the top ring, to avoid unseating the top ring.


"Stock 400 rods" are not known for their strength. But this is a low-rpm engine, so you're probably good if the rods pass Magnaflux testing and have been checked for big-end roundness.

I guess you're using an older, two-piece rear main seal block. How are you going to hold the lifters in place? Are these "retrofit" link-bar lifters? Or are you using the special adapter to fit a two-piece-seal crank into a one-piece-seal block that's set-up for OEM roller lifters?

You will absolutely want the assembly balanced.

Consider using a thin head gasket so you don't have to shave the block decks as much to get proper quench/squish. The KB pistons fit the bore pretty tight, they won't rock much. Quench distance of .035--.040 should be fine. Tighter might be possible, if you have piston-to-valve clearance--but it may not be all that helpful. BE SURE THE MACHINE SHOP USES A TORQUE PLATE and the same head gasket you've selected DURING HONING. You'll probably have to buy three head gaskets--two to build the engine with, and one for the machine shop to use with their torque plate.

The rhoads lifters really do not smack the seats atleast not enough to cause problems. Have run them in multiple engines. Have not even experienced any knock sensor issues with them. On the otherhand Comp XFI lobes pound on the valve seats, make a solid lifter cam sound quiet by comparison and drive the knock sensor boonkers.

x2 on the rings. When I used Total Seal rings it was a gapless 1st ring set. My current 383 has the 2nd ring 0.002" wider gapped than the top ring. 0.014 1st and 0.016" 2nd. Leak down is about 4%.

 

[arrg]

LSA is way too wide for low-end torque. TBI on a dual plane will make more torque in the RPM range you are seeking to run. That being said you shouldn't gear it to run that low of a RPM unless you have a big block. My G20 van and Tahoe both cruised at 1,700 rpm @ 70 and downshifted on every hill. I ran an edelbrock performer rpm and it made more torque than the factory TBI manifold everywhere. I had to add fuel everywhere off-idle and some to the AE for the increased plenum volume and better breathing. Combination will likely have good power up to 5,000 or so rpm. TPI works really well if you are geared to run in the 2,500-3,500 rpm range, which happened to be when I was heavy on the throttle in 3rd gear. Down at 1,700 rpm it made less torque but it made up for the low-end torque loss in the midrange. I also made up for the low-end loss using a S10 converter and revised shift points.

You've already been through all this with him last year over on thirdgen.org

 

[racprops]

Sounds like WAY more duration than a typical TBI cam from a Cadillac. I did a search for "GM 806 Cam" and got nothing for useful results.


Sorry, It is not a 806 Cam from GM it is from
Oregon Cam Grinding that is one of their cams. And the spec WAS for 117 but they did a 114 Lobe Separation

I've never used Rhodes lifters. Can't help you with that. I'm kinda allergic to having the valves banging into the valve seats as they close. I'm VERY suspicious of using fast-bleed lifters on what is probably a VERY mild cam to begin with.

I don't know what "milder rockers" are. ( That happen because the original article called for a 1.7 rockers...) Beware, there's a LOT of crappy, high-failure Communist Chinese "roller rockers" out there.

I bought what my machine shop suggested.


Swill port. Wonderful. Darn spell correcter, Swirl port


Not likely.

Moly-filled iron top ring I'd believe. Probably with a plain (not chromed) iron second ring.

But if you list a part number we could verify. Seal Power E-251K 30

Chrome-Moly is a kind of steel. Good for making roll-bar tubing and crankshafts from. Expensive.


That's probably a mistake. For 20+ years, folks have been saying to have MORE gap on the second ring than the top ring, to avoid unseating the top ring.


Total Seal rings they suggested for my engine that convert my second ring to a gapless ring. Second ring gap of the main ring and the second "gapless" was to Keith Black support suggestions.

"Stock 400 rods" are not known for their strength. But this is a low-rpm engine, so you're probably good if the rods pass Magnaflux testing and have been checked for big-end roundness.

They were. And the crank and block as well.

I guess you're using an older, two-piece rear main seal block. How are you going to hold the lifters in place? Are these "retrofit" link-bar lifters? Or are you using the special adapter to fit a two-piece-seal crank into a one-piece-seal block that's set-up for OEM roller lifters?

YES special adapter to fit a two-piece-seal crank into a one-piece-seal block that's set-up for OEM roller lifters? Block was a Roller cam block.

You will absolutely want the assembly balanced.

1000% YES shop said it came out to zero.

Consider using a thin head gasket so you don't have to shave the block decks as much to get proper quench/squish. The KB pistons fit the bore pretty tight, they won't rock much. Quench distance of .035--.040 should be fine. Tighter might be possible, if you have piston-to-valve clearance--but it may not be all that helpful. BE SURE THE MACHINE SHOP USES A TORQUE PLATE and the same head gasket you've selected DURING HONING. You'll probably have to buy three head gaskets--two to build the engine with, and one for the machine shop to use with their torque plate.

The prep on the block, heads bore etc was all done in a great shop in 2005, at that time it was going to be a 350, but I also remember considering going to a 383 which one reason I went with a 400 crank and rods as well as there would be much less machining for counter weight and other problems like clearance for the cam.

It would have meant not having to start over again with a different block and refitting new pistons and all the other work to run a new rotating assembly. Specially with all the complaints about all of them being made in Chins and breaking, I figure I was just as well off with a good GM made 30 year old as a brand new China junk.

Crank and rods were all cleared for block, once balancing was done I degreed the cam and checked it twice along with the lifters setting as per Mr. Rhoads help and advice and checked the rockers for correct action with the valves.

I did not CC the heads and went with factory specs. Pistons Top dead center was checked and deck height tripled checked from all bores, all matched and compression ration check with Keith Black tech support allowing for the Fel-Pro gasket set.

Mains and rods checked by machine shop and the by me using plastic gauge. All came in at suggested clearances. End play also checked.

Pistons were also checked twice. Again with help from the Keith Black sport team.

All torquing was done in three steps to reach full torque spec with cleaned threads and bores and light oil as per suggestions.

Every one I consulted above all agreed that as the engine will spend 70% of its running tine at around 2000RPMs it should be a great one.

As my target was 2000RPM torque peak it should work great, the Rhoads lifters gave me an engine that will not fall on its face at 3000 but have a second power band all the way to 4500/5000.

As reported HERE by other users of Rhoads Lifter that I can expect a nearly flat power band from 1000 to 5000.

And yes I am revisiting the one last major debate of the manifold and injection type as I ran into new data that suggest I might be much happier with a TPI after all.

That the myth of the TPI is tuned for 2800 RPMs was cause by the CAM being tuned for 2800 Torque peak. OR by hot rodders whom want 6000+ RPMs.

And that has been my main problem, to 90% of the auto world Performance means MORE HP and thus MORE RPMs. So nearly every dyno test IS worth a hot cam, heads etc, almost all Dynos START at 2500 and the tests are ran to 6000 plus so I have had a hard time finding any testing done even near what I am trying to.

Writing the last I wonder has anyone stuck a TPI on a stock 400?? That engine was also built with a 2000 Torque peak.

There are two major other items to look into the PCM, and spark systems.

Transmission has been worked out I am staying with the 4L60E transmission and adding a second overdrive via a old Borg Warner devoiced OD unit.

Rich

 

[Schurkey]

.
All torquing was done in three steps to reach full torque spec with cleaned threads and bores and light oil as per suggestions.

You'll need to remove each head bolt, spray the hole with brake or carb cleaner to remove the oil, and then reinstall with thread sealer instead of oil. Maybe oil under the bolt heads, but sealer on the threads

And yes I am revisiting the one last major debate of the manifold and injection type as I ran into new data that suggest I might be much happier with a TPI after all.

That the myth of the TPI is tuned for 2800 RPMs was cause by the CAM being tuned for 2800 Torque peak. OR by hot rodders whom want 6000+ RPMs.

The TPI manifold was designed for 305s. The runner sizes are small on a 350. They're gonna be tiny on a 400. Resonant tuning is determined by length; but cylinder displacement determines runner cross-section.

Transmission has been worked out I am staying with the 4L60E transmission and adding a second overdrive via a old Borg Warner devoiced OD unit.

I simply cannot imagine that working out well. The stress on 4th gear, and the converter clutch will be enormous.

 

[PlayingWithTBI]

You'll need to remove each head bolt, spray the hole with brake or carb cleaner to remove the oil, and then reinstall with thread sealer instead of oil

^^^What he said, almost all of the head bolts go into the water jacket.