GT40P Heads - How Much Performance Improvement?
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=41186
Printed Date: October-07-2024 at 12:22am
Topic: GT40P Heads - How Much Performance Improvement?
Posted By: Jonny Quest
Subject: GT40P Heads - How Much Performance Improvement?
Date Posted: June-04-2017 at 8:56pm
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Gents: I have a 1994 PCM High Output "Pro Boss" 5.8 engine. 700 hours on the clock. I keep reading about people upgrading to the GT40P heads. What improvement could I look forward to if I were to add the "P" heads to the current configuration over the standard GT40 heads that I currently have? JQ ------------- Current 2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum |
Replies:
Posted By: velde99
Date Posted: June-04-2017 at 9:22pm
| Think you already have the GT-40 heads on that motor. I'm sure others will chime in- but the HO has Gt-40 heads. Look on your motor. That year would have three lines on the end of the head. |
Posted By: velde99
Date Posted: June-04-2017 at 9:23pm
| To answer your question. PCM told me 50 HP. |
Posted By: KENO
Date Posted: June-04-2017 at 10:05pm
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Going from GT-40 to GT-40P heads with all else being equal will lighten your wallet and provide negligible gains. With only 700 hrs your heads should be in good shape and doing the swap, I'd say you wouldn't see any difference at all in performance. It would be easier to change spark plugs though  Going from the earlier 240 HP heads to the 40's or 40P's is where people see some impressive gains especially with cam and intake changes |
Posted By: Gary S
Date Posted: June-04-2017 at 10:15pm
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But if your GT40's are cracked which many have done, the P's will will leave your wallet heaver than getting another set of plain 40's . Not many Fords came with 40's but every late model V8 Explorer and Mountaineers had the P's so they are easier to find. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: Gary S
Date Posted: June-04-2017 at 10:24pm
Here is a flow chart from a Mustang site ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: gun-driver
Date Posted: June-05-2017 at 12:48pm
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I put P's on my '95 GT-40 motor because I had a crack in the original head, mostly because of cost and availability. Can't really say if I got any more performance because I also changed the cam at the same time. I can say that the combo netted me some nice performance gains, mostly hole shot and mid range performance. Can't seem to get it over the 50mph mark. All that being said I wouldn't change heads unless you needed to, if your going to upgrade other parts for more HP there's much better power to be made from other heads for a few dollars more. JMO |
Posted By: MrMcD
Date Posted: June-07-2017 at 5:06pm
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Remember performance is limited by the exhaust. The Marine exhaust may be the limiting factor for higher RPM. I think there are notes on this in this forum to look up. ------------- |
Posted By: TRBenj
Date Posted: June-07-2017 at 6:56pm
| I'm not sure how much merit that argument has, the PCM pyramids look a lot like shorty headers internally (there are cross section pics from Alan if you do a search). Only a few folks have built engines that want to spin more than 5200 or so for peak power, but that doesn't mean it couldn't be done. Even with stock exhaust. |
Posted By: fgroce
Date Posted: June-07-2017 at 9:59pm
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If you are going to turn up over 5000 I would highly recommend ARP rod bolts, The stock ones are okay but most Mustang sites recommend not going over 4800 rpms. ARP makes some awesome bolts that can take a beating and stay together. But they are not cheap. You can look at there web site for all the technical details., ------------- FGroce 88 Ski Nautique For 28 years Now 2002 Ski Nautique |