[tr709]

OK, I get it on the gears, so who has some for sale

As I Understand it, the 10 bolt and carrier will only accept certain ratios, correct?

Suggestions on converter and mfg ?

Although I'm still thinking a bit like amcmike in that it should still get up and go.

[Ron H]

As Mike suggested. Go through the motions and check everything.

How much tuning have you done?

What is your fuel system?

You never answered if it seems down on power throughout the rpms or just at the hit.

Dougs headers. 2.5" exhaust with good flowing mufflers. 3.42-3.55 gears and a 2500-2800 stall would scream and be great cruising.

[gtome]

Strange.... I had 2:73 gears and a milder set up than yours (although a 455) with a stock converter and mine would FRY the tires at will!!
I would have someone that was good with these have a look at it. I do believe with more gear and better flowing exhaust it would help out, but really headers will gain you maybe 35 hp at best. Somthing else is happening here...
Also I would think twice about changing the gears, I went from the 2:73's to 3:42's and have regreted it ever since. That would be the last thing I would change! that engine should be making AT LEAST 450lb of tq, plenty to handle those tall gears!

[vidguy]

I have 2.73's in my 67 GTO with a mildly modified 25 year old rebuild in it and I can smoke my tires at will and chirp 2nd gear in my TH400.
I think there has to be something wrong with the way the cam was installed or the timing?
Is it worth your time to pull the timing cover off and look at the gears to see how it is installed?

[ta man]

It really sounds like the engine is down on power.A different set of gears will help a little but it is a 428 Butler ported heads and a mild lift roller cam.Even with those 2.93 it should smoke the tires.How many of us run or have ran 3.08's?My car a few years ago with a mild 455 and 3.08's and a stock convertor would fry the tires.Somewhere this engine is being choked off?Exhaust,timing,cam timing,fuel.

[ta man]

[QUOTE=tr709;3801741]exhaust is duals with stock manifolds and flowmaster 40's (was in my combo at first post). Pipes are stock size.

I realize long branch mainifolds would help, but I have to wonder how much given the cost

mainfolds(coated) from RARE approx $600
labor to install $400 (quoted)
new downpipes will be needed cost ???

so I'm looking at at least $1200

based on what I am hearing, maybe start with a higher stall converter? I'm ok with a phased approach, agian looking for bang for the buck.

Thanks!
Just noticed this how big is the exhaust?This may be your best bang for the buck put a good 2 1/2 inch exhaust on it and a good set of headers.If your exhaust is anything around 2 1/4 or smaller your are choking off alot of power.My car years ago picked up three tenths just by getting rid of 2 1/8 tailpipes and crappy mufflers to 2 1/2 tailpipes and walker ultraflos.Just think what a full exhaust would be worth 50 hp?

[67bonnie455]

A few thoughts.

You have all the motor you need, but it not making power. I think something is not right. Does it run smooth? How big it the carb? What is base timing at 600 and mechanical at 3000rpms?

What is your intake vacuum at an idle? This can tell alot about the tune on the motor and if the cam is in correctly.

I just worked on a beast of a 455 today with no power and won't idle. Could not get the carb set. It turned out to be 600 jetted for a 800.

[Cliff R]

Let me know when you are ready for a good converter, and there is no need to change the gearing.

My old 400 at 7.7 to 1 compression ratio, stock converter and 2.73 gears would ROAST the tires at will.

I upgraded the 400 to a 428 at 8.8 to 1 compression and it would annialate the tires all the way thru first gear and part way into 2nd gear, same converter and crappy 2.73 gearing.

I went to 3.73's, 3.23's, then to 3.42's, and tried about half a dozen different converters before I finally extracted the 428 and went to a 455 making 455hp.

The old/tired 428 was a BEAST right to the day I pulled it out, unported 6X heads and all. I used an old HO cam in it, the HC-01A grind.

I feel your pain with less than satisfying power production. The cam is partly at fault. As mentioned earlier, I've tuned, or tried to tune two pretty decent 455's using that very same cam. One of them was a 1971 HO engine with round port heads, and 9.5 to 1 compression. It was a TURD, yes, I'll say it again....TTTUUUURRRDDD! Didn't matter where I set the timing, or how much fuel it gave it or took away, it made no more power than a stock worn out 400 2bbl engine powering a 73 Catalina. Yes, throw rocks at me if you want, the cam was the problem, it was replaced after exhausting all efforts to get the engine to make decent power, and it instantly corrected any and all power production issues with that engine.

That particular cam produced a "crappy" and "jerky" idle in that particular 455, and it pinged like sledgehammers at any attempt at heavy/full throttle. It also pinged at light throttle. When tuned for no audible detonation, NO POWER ANYPLACE.

A classic example of a relatively "small" HR cam on a tight LSA in a relatively large medium compression ratio engine, with an early intake valve closing point, making WAY too much cylinder pressure at low rpm's, and not enough lobes to make a decent top end charge.

I've also had dozens of complaints with owners of 455's that used that same cam, and it's always the same report, seriously lacking in power, with audible detonation in the mid-range.

I can not tell you how it would work in a 428 build, never done it, or know anyone who has. My opinion, WAY better cam choices out there than that particular grind......Cliff

[gtome]

Sounds like he needs a good shop that will go over everything. Anyone know of a place in his neck of the woods?

If it was me, I would start with a compression check...valve lash..vac leak...12v to ignition...plugs and wires...etc

Once all other (free) options are exhausted, then start looking at the cam and converter...etc.

[chiphead]

Yeah, we havent even touched the baseline tune on this engine. A high compression engine on pump gas will be WAY down on power if it's detonating, or if it's had all the timing pulled out to prevent detonation by the mechanic.

Looks to me that the timing curve is coming in too fast. I like to see the curve in by 2800-3000. A quick curve and steep gears is a recipie for detonation.

A set of 1-3/4" headers and 3" exhaust will be good for at least 40-50 HP. Performer RPM will pick up 20+ HP over performer. Lots of potential just in the tuning, ign timing, fuel used, etc.

What is compression ratio? What fuel is used? What is timing curve? What ignition system? What spark plugs? What pistons and rods were used?

Before I change any part on a combination, I check all the tuning and baseline settings. But I do feel confident that the intake and exhaust systems are grossly undersized. That engine would perform better with a wider LSA cam to spread the torque out for the freeway gears. Doesnt have to be a roller, even a good Crower HFT would work wonders.

[screamingchief]

The guys who suggested doing a compression test and a leakdown test get my applause.

Throw in a vacuum gauge reading too,and inspect plugs as was suggested.

Basic diagnostics first when all is not as it should be.

Seeing as it has a HR cam,I would also be really interested to hear if the rocker geometry/pushrod length was properly checked on this?

Too much hydraulic lifter pre-load or valvetrain issues can make even a strong engine run like a pig.

But the first course of action here is to assure the engine is in sound condition.

And those tests are the best way to find that out.

Other items I tend to agree with.
Lose the performer intake.
Degree all cam installs.
More gear.
Better torque converter.
Different HR cam.
Better exhaust.

Also,check to make sure the throttle is giving full WOT when the go pedal is depressed,you'd be surprised how many times I've seen this bite a fella in the a$$.

And last but not least,make sure you have adequate fuel supply,this is a no-brainer.

HTH

Bret P.

[se428bandit]

Like screamingchief said i would check to make sure your getting WOT [wide open throttle].You said the exhaust is stock size,does that mean you have 2 " exhaust.I would at least run 2.5" exhaust.Check the harmonic bal,it could have slipped and be off,sounds like to me the cam is retarded which would kill the power.

[tr709]

Thanks all for your input. Just trying to figure out what to try first. At least I know the carb is ok, cliff did that for me. Looked at the plugs they are fine. I like the idea of a vacuum test idea too.

I have experianced a lot of the detonation issues Cliff mentioned. I have to run 93 octane either mixed with race fuel or a full bottle of Octane supreme (lead substitute) to not get it to ping.

[OINK 1]

Get rid of the CRAPPY EXHAUST MANIFOLDS !!!!

Pontiac Gregg

[ERIC AULL]

Sounds to me like you need a lower 1st gear, or a stiffer rear gear set...my stock 67 GTO can't light em up from a stop either. I have 2.93 rears with a TH400....have you considered a 200r4 or 700r4 swap....the best of both worlds (deeper 1st, and OD)...Eric

[chiphead]

Do you know the chamber volume on those 96 heads? The detonation is a big clue. Was the motor zero-decked? Are you using flattop pistons?

Even with the low-rise intake and stock manifolds, it should be able to spin the tires easily. Can you get it to spin if you power-brake it?

[tr709]

Heads were measured at 93cc. Here's a pic of the pistons when the motor was going together.

Screamingchief - I know the pushrod lengths were checked as different ones had to be ordered. I included a pic showing it as best I could.

Pontiac Greg - I agree with the exhuast manifolds being an issue. I plan to go to long branch manifolds at some point. But Ireally think I have bigger issues here. I kid you not when I say that my bone stock 301 turbo would give this a run for it's money.

[rod cole]

It looks to me like you have 93cc heads and 15cc dished pistons? On a 428 that would be way low comp. All the bad talk about XE cams is fluff I removed a XE284 and put in a large Butler Hyd roller and best to best has been .2 different. Yes one pulls harder above 4500 but dosn't run much different. I think a compression test is in order and then checking the cam degree.

[screamingchief]

Originally Posted by rod cole

It looks to me like you have 93cc heads and 15cc dished pistons? On a 428 that would be way low comp.

Could be the newer KB 428 cid forgings seeing as the RA came from Ace@PPR,those KB forgings are 10cc D shaped dish.

A piston like that would put him right @ 9.0:1 on a .030" over zero decked 93cc combo.

Would be very interesting to see some cranking compression numbers on this engine.

If the cam was'nt actually degreed,there is no telling where it is actually installed,as there is more than one area for "error" to creep into that dynamic,could be the cam was ground off,could be the timing set that is off,could be both are off adding to each others impact,could be the builder goofed and installed the cam wrong,with the multi-keyway timing sets,even the pros can run into trouble,the only way to catch that is in the cam degreeing process.

At that SCR,it really should'nt be having any "ping" related problems,even with that "pressure cooker" XE276HR cam in it.

What specific spark plugs are being used in this?

Because you may be having pre-ignition issues as opposed to detonation issues,the two are not the same,but often they can be mistaken for one-another.

Hard to say where the "smoking gun" will be found,but it's gotta be in there somewhere.



Bret P.

[tom s]

do one thing at a time.IMO,exhaust first,chassis dyno second and gears next.Find the HP first THEN get it to the ground.Tom