[Judge not]

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.

[Half-Inch Stud]

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

[Judge not]

Thanks guys. The mechanical advance is all in by 2500 rpm, I lined up the dots on the cam, cam at 6' and crank at 12'. I just don't get this, I am very disappointed

[mikeb]

Sounds kind of like a comp cams magnum 280 cam. I went in the 11's with that cam in a 3600lb bird with a 455.

Your combo doesn't sound that bad at all. It sounds like maybe your mechanical advance isn't working at all, or the cam was installed one tooth off. Something is way wrong.

[grandville455]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by quick67bird:
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. </div></BLOCKQUOTE>
Wow .dont mean to hijack...But what was the timing before and after?

[Goin' Topless]

Vacuum advance not working? Centrifigal springs too stiff?

Lack of advance early on can make it feel like a dog.

[Junkyard Dog]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by 69FBConv:
Since timing doesn't seem to be helping much - </div></BLOCKQUOTE>
He only moved it 2 degrees!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">You said it's a vacuum secondary??? If it's a Performer 1407/ 1411 it's mechanical. The secondaries usually come in too quick . . . </div></BLOCKQUOTE>
If they were coming in too quickly, wouldn't the engine bog?

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Are you running full manifold vac adv or ported? </div></BLOCKQUOTE>
Hopefully, he wasn't running either for testing purposes.

[Judge not]

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

[Junkyard Dog]

Try simple stuff first. Advance the total timing 2 degrees at a time and run it full throttle to see if there is any improvement. If your timing marks are off, it won;t matter because you will be setting total timing for maximum performance, not according to some number. If you can time your acceleration run, all the better, but this will at least confirm whether the spark timing is the issue. Make sure to disconnect your vacuum advance during this.

Something is definitely wrong, but try the simple things before tearing the engine apart to check on the cam.

[krisr]

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.

[David Jones]

What kind of timing chain is it?

[nightwrencher]

have a 400 with 11 heads and 230/240-112 lca (ported/polished heads) and I've spent a heck of a lot of time towards trying to get better traction. will go sideways through third. haven't raced it yet but my 400 has similar setup and even before the 4.56's. ripped it up with the 2.56 or whatever it had. I disconnected the vaccum advance, ran 16* initial with total 34* (I use 50/50 w/race fuel)
ran aggresive with a th350 with cheapo jegs 22-2400 converter and with 200r4 w/ 2600 stall.

the cam being a tooth off sounds worth checking, but how good did you break in the cam? Is it possible you could have worn the lobes of the cam on break in? I usually do around 25 minutes around 2500 rpm. (to try to prevent overheating, I use clean water and keep the cap off with a running hose)

just my two cents

[70 bird]

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?

[Judge not]

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?

[Junkyard Dog]

Hey, now, wait a second, you said the timing was 32, all in by 2,500 rpm, way back in your first post!

Try 34 and then 36 and even 38 if the situation keeps improving. Maybe even 40. Just keep going until it doesn't improve and then back off a little. Who knows if your timing marks are correct?

14 initial won't hurt anything. The only thing that matters is if you have problems kicking back against the starter when starting. If so, then change your curve (i.e., more difference between initial and mechanical advance, like 20 or 22 rather than your current 18). If you aren't encountering problems on starting, then it is not too much advance.

Since moving your timing (even though you said 32 in both posts) improved the situation, keep it up until you get it to the best setting.

[Junkyard Dog]

Ok, so it did or did not improve some (a little more screaming tires, I guess, being the definition)? If it did, then I say advance it another two degrees and see if that helps. I reiterate that you don't know right now if your timing marks are off.

Starting problems don't matter while its running. You can correct the initial timing and starting issues by broadening the amount of advance later, if you find that more timing is what you need to turn those tires over!

[tom s]

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]

Yeah, he is a skeezer

[runningbwdog]

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

[Judge not]

David it is a new double roller I bought from Summit, forget the brand.