351W different varient specs?
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=28561
Printed Date: November-21-2024 at 6:46am
Topic: 351W different varient specs?
Posted By: E4ODnut
Subject: 351W different varient specs?
Date Posted: December-18-2012 at 2:16am
|
Here's another question somewhat related to my earlier post about cam specs. As I understand things, the 351W marine was offered in 3 flavors, possibly more. The first being the base model. The Ford spec I have on this was rated at 236 HP @ 4200 RPM. 8.3:1 compression ratio, 4 bbl Holley. I suspect that it is the same as the PCM version @ 240 HP @ 4400 RPM. Then there is the "HO" version which I think was rated at 285 HP @ 4400 RPM. Then we have the GT40 fuel injected version which I have no information on. First of all, does anyone know what the differences are between the standard and HO version? Next, Does anyone have the specs for the GT40? For the mechanically obsessed, I have an old faxed copy of the Ford publication WG-858-M which is a brief description with HP and torque curves for the standard version engine. I also have a copy of the Ford publication WG-858 which is the industrial version of the engine and includes gross HP and torque curves, continuous HP and torque curves and the BSFC curve. I addition, with the manual that came with my motorhome I have the HP and torque curves for the 1992 model year EFI truck 460 and 351W engines. If there is any interest, I can scan them and e mail for the reference files or whatever. ------------- Robert 1993 Bayliner 3288 "Hocus Pocus" 351 Fords, converted to tuned port programmable EFI |
Replies:
Posted By: kapla
Date Posted: December-18-2012 at 2:30pm
|
as far as I know almost same engine, difference is ho was carbed (or also protec FI) and the gt40 has the multiport fuel injection ------------- <a href="">1992 ski nautique |
Posted By: TRBenj
Date Posted: December-18-2012 at 2:44pm
|
Kap is close. I dont believe there are any differences between the long blocks on any of the HO versions- be it carb, TBI or multiport (GT40). All horsepower differences (285-310hp) were due to induction and ignition systems... along with some marketing, perhaps. The main difference between the HO and non-HO motors were the heads (GT40 vs. E7). The cam was slightly different, and Ive heard that they changed the ignition (Protec- so presumably timing curve?). Pistons were also a little different, but the compression ratio did not change much (low-mid 8's) between the 2. You could get 95% of the performance out of a standard motor (as compared to the HO) by adding the better heads. ------------- |
Posted By: JoeinNY
Date Posted: December-18-2012 at 6:52pm
|
Basically and someone will come along to correct me if I am wrong PCM engines were available in stock carb (approx. 240 hp) versions in both righthand and left hand rotation with relatively mild cams.. By 1989 the vast majority were standard rotation and hooked up to a gear reduction transmission to turn the RH prop that has been a Correctcraft mainstay for many decades. In 1991 they released an optional ProTec engine management system.. Which was electronic ignition with nanny functions. In 1992 there came an optional 285 hp “Pro Boss” option. The primary difference is the GT-40 heads and a slightly hotter cam. In 1992 this was still a carb engine, also in 1992 on both standard and pro-boss engines the “Pro Tec” engine management system became standard equipment. Around 94 through early 95 there was a ProTec TBI Pro Boss that utilized a Holley copy of the GM 4V throttle body. It also used GT40 heads and likely the same cam as the proboss. When this system fails (coil packs are a typical first failure) unlike the earlier pro tec ignition system boats you cannot simply convert to a regular distributor because the fuel and ignition are both handled by the same computer. In 95 they started the EEC-IV based tuned port “GT40” engine. It also utilizes the same heads and cams as the earlier pro boss engines. As you noted it has a difficult to find upper and lower intake manifold – very early ones utilized a more rare tubular upper intake manifold, later ones a cast version. There is a pcm version of a marinized TFI distributor (still available) and the whole thing runs open loop but is otherwise basically automotive/truck components. In the reference section there is a detailed manual covering theory of operation. It does utilize a knock sensor (listed as optional in the manual). It really is a pretty cool system, compact and efficient. Just very expensive to put together from scratch. The tuning is PCM proprietary and locked.. unless you know a guy who can do a thing… which would be useful if you wanted to heavily modify your engine, apparently switching from a GT40 head to a GT40P head doesn’t cause any noticeable difference. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
Posted By: TRBenj
Date Posted: December-18-2012 at 7:02pm
Nice summary, Joe... just 2 corrections/clarifications!
I cannot say that Ive ever seen a 1991-1992 Correct Craft without the Protec system... so it may have been standard equipment. I believe thats CC-specific though, as Im pretty sure PCM still offered non-protec engines during that time period. CC offered non-protec equipped boats in 1993-1994 in their "Standard" model, so it would have technically been an option during those years.
This is true... but dont forget that a non-HO "Pro Ski" version of the TBI was offered as well (rated at 260hp, IIRC) and utilized much of (if not the exact same) ignition and fuel set up as the ProBoss TBI version. Tidbit: Pro Boss is PCM speak for HO 351w... they put that label on the carb, TBI and multiport flavors. ------------- |
JoeinNY wrote:Posted By: E4ODnut
Date Posted: December-19-2012 at 10:32pm
|
So, if I understand things right, the 285 "HO" is a 240 with better flowing heads and a cam to shift the torque curve up a bit in the RPM Range. The GT40 is a 285 with port EFI. Was it rated at 310 and at what RPM? ------------- Robert 1993 Bayliner 3288 "Hocus Pocus" 351 Fords, converted to tuned port programmable EFI |
Posted By: TRBenj
Date Posted: December-20-2012 at 11:36am
Sort of. There are other differences between the HO and non-HO besides the heads, but theyre not huge differences. The cam is different, but not by much. I havent seen the torque curves compared between the 2, but I would wager that the HO isnt shifted to the right- rather, it just extends further to the right. It doesnt give up any low or midrange power to the standard engine. All of the HO's tend to run best when propped to turn 4800-5000rpm, and this is how CC propped them from the factory, for the most part. 4800 is the number commonly reported being the hp peak for those motors. Ive seen 4400 mentioned for the HO motors in a manual or 2, but it makes little sense to me. ------------- |
Posted By: E4ODnut
Date Posted: December-20-2012 at 12:46pm
|
If the HO doesn't give up any low end, then I suspect most of the top end gain is due to the different head design allowing the engine to breath better and spin up higher. I'm with you on the rev thing. If the HO makes more power than the Standard at the same RPM then it has to be developing more torque at this RPM. If it makes more power at a higher RPM then the torque doesn't have to increase, only the revs, thanks to better breathing. This has probably been covered in other threads, but to save me some searching time, do these HO heads have an automotive equivalent? ------------- Robert 1993 Bayliner 3288 "Hocus Pocus" 351 Fords, converted to tuned port programmable EFI |
Posted By: TRBenj
Date Posted: December-20-2012 at 12:59pm
|
The HO heads are factory Ford cast iron GT40 heads, which came on a few vehicles like the '93 Mustang Cobra and '93-95 Lightning. The common upgrade to standard (non-HO) heads now on our boats are the GT40p heads, which came on '97-01 5.0L Explorers and Mountaineers. Theyre cheaper to buy, more readily available, outflow the GT40's under .500 of lift, and have smaller combustion chambers (which raise compression by about a point). ------------- |