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Judge not · 04-12-2005, 02:05 PM

Hi all, I just changed cams in my 455. The first one went bad (xe-268). The new cam 230 [email protected], [email protected]. Both cams were not impressive. The car idles with very little lope and I don't have the tire shredding torqe I read so much about. I am starting to wonder if my Th 400 or convertor could contribute to my lack of power. The car is a 1970 GTO, 1973 455 .030 over, Trw forged pistons zero decked. 6x-4 heads home ported to flow approx. 240 cfm. Edel. perf. rpm intake, Edelbrock carb 750 cfm. Hooker comp headers, H pipe, 2 1/2 inch dual exh. 355:1 posi rear end. Could my carb cause sluggish performance? It dosen't hessitate or bog when punched, it just won't shred the tires. Maybe my torqe convertor is locking up to early? Btw Hei dist. 10 deg. int timing 32 deg. in by 2500 rpm. Is my cam too small? I have power brake so I wanted enough vacuum. I want to go sideways

any help in improving performance would be appreciated.

Judge not · 04-12-2005, 02:05 PM

Hi all, I just changed cams in my 455. The first one went bad (xe-268). The new cam 230 [email protected], [email protected]. Both cams were not impressive. The car idles with very little lope and I don't have the tire shredding torqe I read so much about. I am starting to wonder if my Th 400 or convertor could contribute to my lack of power. The car is a 1970 GTO, 1973 455 .030 over, Trw forged pistons zero decked. 6x-4 heads home ported to flow approx. 240 cfm. Edel. perf. rpm intake, Edelbrock carb 750 cfm. Hooker comp headers, H pipe, 2 1/2 inch dual exh. 355:1 posi rear end. Could my carb cause sluggish performance? It dosen't hessitate or bog when punched, it just won't shred the tires. Maybe my torqe convertor is locking up to early? Btw Hei dist. 10 deg. int timing 32 deg. in by 2500 rpm. Is my cam too small? I have power brake so I wanted enough vacuum. I want to go sideways

any help in improving performance would be appreciated.

Lee · 04-12-2005, 02:10 PM

The valvesprings proper seat pressure, and sufficient travel before coil or retainer/guide interference - right?

With a "bad" cam AND poor performance, that is what I suspect.

Judge not · 04-12-2005, 02:32 PM

Heads were set up at JBP. seat pressure is 125 lbs. 300lbs at .500. Coil bind at .900 Installed height 1.70 I believe, I will have to check my receipt.

Junkyard Dog · 04-12-2005, 02:57 PM

Cam isn't too small. I had the 744 in mine (which is smaller), and it would roast those tires . . .

What size chambers are the -4 heads? 91 cc? That is plenty of compression for that cam. Timing should be ok to light the tires up

Hmmm . . . .

tom s · 04-12-2005, 03:08 PM

FYI,with iron heads on pump gas,I have found my motors like more lead,36-38 total with around 12 init.Tom

Judge not · 04-12-2005, 03:08 PM

Yeah JYD I thought it would scream when reassembled I wonder if a Cliff Q-jet would wake her up, or tranny issue?

Judge not · 04-12-2005, 03:16 PM

One other thing, how large of an air filter do you need to feed these engines? I have an open element air cleaner but it is only 1 1/2 inches tall. Tom I tried that much timing but she would ping under heavy load light throttle. My vacuum advance is dialed all the way down but still adding too much.

Half-Inch Stud · 04-12-2005, 03:51 PM

...could be a stripped sprag in the converter. Pull-away torque would be affected.

krisr · 04-12-2005, 03:54 PM

I'd be looking at your converter. Was it matched to the rest of the combo or does it just slip?

My 400 has the same size cam ([email protected]), RPM intake, 750 vac holley, 1 3/4 headers, 2.5" with X all the way to the back, 5 speed toyota gearbox and 3.5:1 rear gear and it absolute obliterates the tires on demand.

Re: the aircleaner, I run a K&N Extreme lid with a 2 3/16" x 11" element.

quick67bird · 04-12-2005, 04:05 PM

My cam is just a little bigger than yours in a 67 firebird and I run 275/60/15s on the street and I can spin the tires till I let off the gas.

70 bird · 04-12-2005, 04:15 PM

How does she pull top end? Could be the carb?I have a 406 with 230 dur cam and a 800 dp it shreads the tires.If your top end isnt good i would look at the carb.I dont know much about eld carbs is that vac secondaries?

74t/a · 04-12-2005, 04:57 PM

Did you degree the cam in????

I could be the cam timing. I have seen this before with other engines that were built similar. I just went in there and degreed the cam, and it was a totally different engine after that.

Also, bump that timing up a bit to about 35-36. 32 seems a bit low.

One way to tell if there is a problem with cam timing is to do a cranking compression test. If you don't have at least 150lbs. then there might be an issue.

Judge not · 04-12-2005, 06:41 PM

I don't believe the torque converter was matched to my combo. The guy that did the rebuild said he put a pick-up truck conv. in it. He said it stalls at 2200. I dont think I trust him. The other day the tranny slipped bad between 1 and 2, ever since rebuild it has had a mushy 1/2 shift. It has a transgo shift kit. The carb is vac sec. It does pull hard to red line. I did not degree the cam. It was a custom grind and did not have intake center line specs, but my last cam I did degree and had the same lackluster performance. That is why I am thinking tranny. How adversely can a torque conv. affect performance?

quick67bird · 04-12-2005, 07:09 PM

I will tell you the timing makes a huge difference. In the 1/4 on my first pass the motor laid down in the top of all gears and would barely pull over 5000 rpm on that pass I I ran a 13.86. Long story short I have a fluidamper that has a chevy marks on them and I had my timeing way off. After fixing my timing and jetting the carb up to steps all the way around it went out and ran a 12.55 at 113 spinning the tires at every shift even into third.

455guy · 04-12-2005, 07:22 PM

If the trans is slipping and not shifting right, you could have a 500 inch stroker in there and it would feel like crap.. A pickup converter? Most trucks are low stall from my experience.. Is this guy trustworthy? He might have stuck you with a junk summit low dollar converter.. My bud bought a 455 olds cutlass with a t400 trans and one of those converters .. It had 300 miles on it and after 1 good burn out, blew the internals to shreds.. Good converters cost money.. Period ...

455guy · 04-12-2005, 07:24 PM

Here's the stupid question of the day.. Have you checked the fluid level on the trans?

quick67bird · 04-12-2005, 07:25 PM

That is true 455 guy and most of the time the cheap converter will take out a good trans. It is better to spend the money on a good converter.

David Jones · 04-12-2005, 07:38 PM

The Performer RPM isn't helping. A regular Performer or 68-70 cast iron would be better suited to bottom end. Have you tried any more initial timing? 12-14 degrees? Get a 3" air filter. That cam in a 455 shouldn't need much stall.

runningbwdog · 04-12-2005, 08:06 PM

Hi,
I have a 462 with cast #15 heads and XE268 cam.
I have a street twin clutch and pressure plate, 4-speed M20 and 3.55 rear gears. 9.35:1 compression. 10* BTDC initial and 34* total adv.
From a rolling start, ie clutch locked up, it will chirp the tires, 215/65R15, and that is about it. I did two chassis dyno runs and have 360 ft/lbs torque and 240 rwhp. I suspect that your cam is mild, just like mine. You should consider an XE274 or maybe even a XE284.
There may be other cams with more LSA than 110 that may perk up your performance.
Just a few data points to consider.
Mike

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