[footjoy]

When people talk about a good tune which my car needs, how much horsepower can be gained by a good tune?

Thanks

[Lee]

Originally Posted by footjoy

When people talk about a good tune which my car needs, how much horsepower can be gained by a good tune?

Thanks

That depends on how far it is off to begin with. By tweaking timing and jetting, I rarely find LESS than 10rwhp on cars I've tuned. 20-30 is pretty common. I've found over 60 a few times.

Mild cam, mild compression, small valves,.... based upon other Pontiacs I've dyno tested, you may have another 15 or so HP. Nearly every stock headed Pontiac I've seen on a chassis dyno has put less than 300hp to the wheels.

What is your torque, though? People focusing on HP with Pontiacs running unported heads, they are studying the wrong end of the dog.

[steve25]

If your air to fuel ratio is good through out the motors rev range which it seems to be from your posting of a average 12.8 ratio then the only thing left in terms of getting your motors needs peaked out is to make some dyno pulls / run's while putting in timing changes and to try out different octane fuels.
One thing to watch out for if you go playing with different octane fuels is that the air to fuel ratio can need to be changed from what it is now .

With your motors current compression ratio I can't see why anything more then 87 octane is needed to keep the motor alive , and don't forget that running a octane level higher then the motor needs only cuts into the power that a motor makes as the RPM goes up!

For a street motor I am not sure if this is a can of worms you want to open because at most your looking at a gain of about 8 hp, and your looking for a missing 30 hp or more, so stick with just trying out some different total timing changes.

[shaker455]

Not a bad number for a conservative build.
I'm sure some in depth tuning will make it pretty snappy.

["QUICK-SILVER"]

Originally Posted by footjoy

217 peak horse power

What RPM did you get the 217? and what did the curve look like coming up to that point?

Originally Posted by footjoy

I didn't think you could build a pontiac with that low of horse power. I was hoping for 300.

Something definitely went wrong.

Greg

May not be anything wrong. Could be closer to 300 raw flywheel horse power than you think. 300 horse 400's had 250 net horse power. That's with all the accessories on the front of the engine. Take away hp required to operate the transmission and rear end....217 wouldn't be off far at all. Transmission by itself could be using 30~40 horse power.

Clay

[footjoy]

Originally Posted by "QUICK-SILVER"

What RPM did you get the 217? and what did the curve look like coming up to that point?



May not be anything wrong. Could be closer to 300 raw flywheel horse power than you think. 300 horse 400's had 250 net horse power. That's with all the accessories on the front of the engine. Take away hp required to operate the transmission and rear end....217 wouldn't be off far at all. Transmission by itself could be using 30~40 horse power.

Clay

It made 217 hp at 4600 rpm and the torque was 276@ 3600rpm

Thanks for the question

Greg

[Lee]

Oh, what do have for exhaust?

If you have decent headers and a good system behind them, then you may see 240's.

But if you have log manifolds still, or a restrictive system, then you are pretty much maxed out.

[GOAT8U2]

Confirm your torque converter slippage, that could be a big culprit here. Autos eat up more HP in general let alone the converter slippage so I thought...

360hp engine then 280whp with everything near ideal. 12.8 AF seems rich but I'm not sure what the whole pull looks like.

A good use of the dyno is to tune on it too, doesn't sound like that happened. Missed your chance to try some fuel, timing and cam tweaks.

[Firebob]

Still sounds a bit weak to me also. I ran my 30 over 400 with badger cast Pistons, 16 heads and a 226/226 110 cam thru a 4sp at 5000ft elevation and it spun up 297hp/360tq some years back on a portable dynojet machine. I had 195-205 compression and eventually wasted the rod bearings and broke ring lands out of two pistons but it ran pretty good till I pulled it down.

[FrankieT/A]

Originally Posted by footjoy

Guess what Horse power this put out?


Build

400 .060
Flat top with one valve relief
Crower 60240 cam
#15 small valve heads 87cc
Performer Intake
HEI 14 initial 35 all in at 3000
Quick fuel 735

AFR 12.8

The answer is right here in the original post...
455 heads on a 400. Low compression no flow...

Try some 12 heads or 48...even 62's would be better.

[68lemans462]

Originally Posted by FrankieT/A

The answer is right here in the original post...
455 heads on a 400. Low compression no flow...

Try some 12 heads or 48...even 62's would be better.

yep!! I'd start over with the motor or lower your expectations.

[HWYSTR455]

Originally Posted by 68lemans462

yep!! I'd start over with the motor or lower your expectations.

Well, I was kind of thinking more along the lines of at least first assessing the currently build before throwing a top end on it in search of more power. If it's a generic rebuild, stock rods, etc, then I personally would either leave it and drive it, build another on the side, or go into and build it in a performance manor.

Clay - Yeah, I've seen the same car dyno on 2 or 3 diff dynos, and the numbers were all over the place. That, and trans/converter also make a diff. You get a sloppy converter that slips 10%, on a 400 flywheel hp build, it makes a fairly large diff. You use a performance built TH400 with high line psi etc on a 350ftlbs engine, you're throwing power away due to parasitic losses.


.

[steve25]

The casting # 15 heads with there stock 1.96" Intake valve peak in Intake flow at 185 cfm, the Exh side even though it only has a 1.66" Exh valve flows 155 to 158 cfm.

The overall flow ratio is in the low 82 to 84 percent range which can mean that even if your pumping out the Exh thru stock log Manifolds you do not need a duel pattern Cam like your running.
At the Intake valve lift of the Crower Cam your getting about 175 cfm, this amount of flow will be enough to make a very optimistic 358 hp at the flywheel.

[footjoy]

Originally Posted by steve25

The casting # 15 heads with there stock 1.96" Intake valve peak in Intake flow at 185 cfm, the Exh side even though it only has a 1.66" Exh valve flows 155 to 158 cfm.

The overall flow ratio is in the low 82 to 84 percent range which can mean that even if your pumping out the Exh thru stock log Manifolds you do not need a duel pattern Cam like your running.
At the Intake valve lift of the Crower Cam your getting about 175 cfm, this amount of flow will be enough to make a very optimistic 358 hp at the flywheel.

What cam do you recomend?

And how do I get anywhere close to that 358 hp?

Thanks

[HWYSTR455]

If it runs good all around, and you want more, just spray it. A 125hp fixed kit is not that expensive, and usually typical ring gaps will tolerate a 125 shot.

Still missing info, like is the intake ported/port matched? Any work on the heads? Converter/trans/rear gear? Type of exhaust? A 72cc head swap would be a good choice, and swap the intake.

735 carb should be fine on that.

If you're considering a cam swap, I don't think you will see any noticeable diff with a 2801, 2802 would be better, but then you're talking about making other changes to take advantage of it.

.

[footjoy]

Originally Posted by HWYSTR455

If it runs good all around, and you want more, just spray it. A 125hp fixed kit is not that expensive, and usually typical ring gaps will tolerate a 125 shot.

Still missing info, like is the intake ported/port matched? Any work on the heads? Converter/trans/rear gear? Type of exhaust? A 72cc head swap would be a good choice, and swap the intake.

735 carb should be fine on that.

If you're considering a cam swap, I don't think you will see any noticeable diff with a 2801, 2802 would be better, but then you're talking about making other changes to take advantage of it.

.

performer intake no porting 2200 converter 3:73 rear stock 15 heads 87cc needs to be streetable

[HWYSTR455]

Spray is streetable, as is the 2802. The 373s, not so much in many's opinion.

72cc heads, Perf RPM (if you can fit it) port matched, and a 2802 would be a considerable bump. Totally streetable. You could even spray that.


.

[1funride]

I have the 72cc heads on my 400 with a cam not much different than the 2802, very streetable, easy cruiser. I made 276 to the wheels with a dyno jet, I had a rusty flowmaster exhaust on it and a flex fan. I changed to a straight through magnaflow and that made a big difference on the mid to top end power. I think with a fan change I could be approaching 300. I would swap out the heads to 72cc and get a little bigger cam, then you will have a snappy engine.

[1funride]

http://forums.maxperformanceinc.com/...d.php?t=822814

["QUICK-SILVER"]

Greg,

Check this thread out. First page has "engine dyno" numbers. And the owner posted professionally tuned "chassis dyno" numbers today. Nearly 150 HP difference.
https://forums.maxperformanceinc.com...=808474&page=5

Your engine could have A LOT more than you think.

Clay