GT40P Valve Size Question

Okay, so I have found a set of GT40P's with the larger GT40 exhaust valve (1.54" vs 1.46") installed but no port or bowl work done. Will I really see a difference in flow without the bowl and port work? Is there any harm in this?

Thanks,
Don

I would say not unless you plan on a huge H.P. engine. The average build see's some increase but. not really. I could be way wrong, but it's my opinion.

Not really looking for huge HP gains, just a nice upgrade to my 5.0 until I finish my 393 and I figure I can sell the 5.0 when I"m done and get my money back on the heads. Plus I think the 5.0 will sell easier with the p heads than teh E7's on it now.

Thanks for the reply!!

Don

Then I would run them as is. Remember, your headers are limited choices.

I plan on running BBK long tubes anyway and they tell me they fit the P heads fine so I'm not too worried about that. Well, I"m gonna make an offer on them and see if they guy bites. I'll post up after.

Thanks agian,
Don

I remember reading (back when the P heads were new) that installing them was bolting on 30 ft-lbs, with no other changes.

Yep, I"ve read 30-40 hp and 30 ft-lbs. I hope to find out soon!

But before I find out I have to complete the rear end install. Now that my son has graduated I'll have some time to myself so I'll get back on it.

D

I've been doing research on ignition timing, and the P heads are supposed to like WAY less total timing advance, due to the central spark plug placement.

I'm hearing 28 to 30º, no more than 32º. and that they will start giving up power way before they start to detonate.

Best of luck.

By the way, I might FINALLY be starting my engine in the new car for the first time soon. I've been messing around with the stupid thing for about 3 years now...so it's due.

Wow, that's something I hadn't considered. Where did you come across info like that? Which leads me to another question...I have one of those GM style distributors that came on the car and I have no idea what it's advance curve is. How do I figure that out?

Don

Actually, a dude from Maximum Motorsports told me on another forum. He seems to know his shit.

As far as finding out what advance curve you have, if your balancer has enough marks, you could unhook the vacuum advance line (plug it, of course), and check the timing with a timing light as you rev the engine to 4 or 5 grand. You should be able to figure out what the total is at that point. I remember back in the day, there were some shops that had "distributor dyno"s. You would send your distributor to these people, and they could adjust and tune it exactly, without it on the car.

Now that I think about it, you might be able to do that sort of thing at home, if you could figure out a way to spin the distributor. At least you'd only need to spin it to 2500-3000 or so, since the distributor spins at half of engine RPM. Then, you'd have to measure how far the base plate moved inside the housing, since that's how the timing is advanced.

Boy, you do like to ask the easy questions, don't you?

HA!! Well, I keep you on your toes don't I?

When I was in high school in auto shop we used to use one of those distributor machines. I recall setting up my shop teacher's dist for his pickup. That was a loooooong time ago it seems (like 30 years) OMG I have become my dad...

Well, when I get my motor back in my car I'll have to research the advance curve.

Now I'll post a cam question in a new thread....c u there!

Don