Building engine tips.
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Freshman User
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Building engine tips.
Okay, so I did a compression test on my 351w and here's what I got.
1-130
2-129
3-128
4-118
5-117
6-129
7-125
8-130
I'm not sure if this is good or bad..but I'd like to rebuild it either way, I'd just like to know if these are indication of needing bored or not, the engine is completely stock, and I want to keep the intake and heads stock, just make them flow better and perform better, any tips or info on what I should do/ can do to get more out of it?
1-130
2-129
3-128
4-118
5-117
6-129
7-125
8-130
I'm not sure if this is good or bad..but I'd like to rebuild it either way, I'd just like to know if these are indication of needing bored or not, the engine is completely stock, and I want to keep the intake and heads stock, just make them flow better and perform better, any tips or info on what I should do/ can do to get more out of it?
Lead Driver
Joined: Apr 2011
Posts: 6,399
Likes: 40
From: El Dorado, Arkansas
Okay, so I did a compression test on my 351w and here's what I got.
1-130
2-129
3-128
4-118
5-117
6-129
7-125
8-130
I'm not sure if this is good or bad..but I'd like to rebuild it either way, I'd just like to know if these are indication of needing bored or not, the engine is completely stock, and I want to keep the intake and heads stock, just make them flow better and perform better, any tips or info on what I should do/ can do to get more out of it?
1-130
2-129
3-128
4-118
5-117
6-129
7-125
8-130
I'm not sure if this is good or bad..but I'd like to rebuild it either way, I'd just like to know if these are indication of needing bored or not, the engine is completely stock, and I want to keep the intake and heads stock, just make them flow better and perform better, any tips or info on what I should do/ can do to get more out of it?
The stock 351W heads can be port matched for better flow but, they still aren't going to flow that great.
As far as factory iron heads go, the best factory iron heads to have would be from the 5.0L Explorers. Prior to 1997.5, the 5.0L Explorers had the 3-bar GT40 heads (basically the same as the '93 Cobra Mustang heads).
From '97.5-2001, the Explorer 5.0L heads used were the slightly improved GT40P 4-bar heads. Either one of these iron heads are vastly superior to any other Ford small-block iron heads --including the old 289 Hi-Po heads.
This is a set of Explorer 5.0L GT40P 4-bar heads I have --$50.00 bucks for the pair from the wrecking yard. Notice the 4 "bars" cast into the ends.
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Freshman User
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What year model 351W? Is the intake 2-bbl or 4-bbl?
The stock 351W heads can be port matched for better flow but, they still aren't going to flow that great.
As far as factory iron heads go, the best factory iron heads to have would be from the 5.0L Explorers. Prior to 1997.5, the 5.0L Explorers had the 3-bar GT40 heads (basically the same as the '93 Cobra Mustang heads).
From '97.5-2001, the Explorer 5.0L heads used were the slightly improved GT40P 4-bar heads. Either one of these iron heads are vastly superior to any other Ford small-block iron heads --including the old 289 Hi-Po heads.
This is a set of Explorer 5.0L GT40P 4-bar heads I have --$50.00 bucks for the pair from the wrecking yard. Notice the 4 "bars" cast into the ends.
The stock 351W heads can be port matched for better flow but, they still aren't going to flow that great.
As far as factory iron heads go, the best factory iron heads to have would be from the 5.0L Explorers. Prior to 1997.5, the 5.0L Explorers had the 3-bar GT40 heads (basically the same as the '93 Cobra Mustang heads).
From '97.5-2001, the Explorer 5.0L heads used were the slightly improved GT40P 4-bar heads. Either one of these iron heads are vastly superior to any other Ford small-block iron heads --including the old 289 Hi-Po heads.
This is a set of Explorer 5.0L GT40P 4-bar heads I have --$50.00 bucks for the pair from the wrecking yard. Notice the 4 "bars" cast into the ends.
Lead Driver
Joined: Apr 2011
Posts: 6,399
Likes: 40
From: El Dorado, Arkansas
A '73 351W will have (16) intake bolts vs. (12) for '77-up 351Ws. Pre '77 351Ws will have L-shaped water passages in the ends of the heads and will have 13/16" (18 mm) spark plugs. '77-up 351W heads will have rectangular water passages and 5/8" (14 mm) spark plugs.
If you're looking to improve engine performance, a 2-bbl stock intake and carburetor isn't a good way to get there. A decent dual-plane 4-bbl intake and a 4-bbl carburetor ~600 CFM will be a greater improvement, along with good flowing exhaust, mild cam and a rear end ratio in the 3.50:1 range.
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Freshman User
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Dimensionally, the GT40/GT40P heads are the same length/width/spacing as the 351W heads. They will bolt in place of the stock 351W heads, without changing the width between the heads where the intake will be.
A '73 351W will have (16) intake bolts vs. (12) for '77-up 351Ws. Pre '77 351Ws will have L-shaped water passages in the ends of the heads and will have 13/16" (18 mm) spark plugs. '77-up 351W heads will have reqtangular water passages and 5/8" (14 mm) spark plugs.
If you're looking to improve engine performance, a 2-bbl stock intake and carburetor isn't a good way to get there. A decent dual-plane 4-bbl intake and a 4-bbl carburetor ~600 CFM will be a greater improvement, along with good flowing exhaust, mild cam and a rear end ratio in the 3.50:1 range.
A '73 351W will have (16) intake bolts vs. (12) for '77-up 351Ws. Pre '77 351Ws will have L-shaped water passages in the ends of the heads and will have 13/16" (18 mm) spark plugs. '77-up 351W heads will have reqtangular water passages and 5/8" (14 mm) spark plugs.
If you're looking to improve engine performance, a 2-bbl stock intake and carburetor isn't a good way to get there. A decent dual-plane 4-bbl intake and a 4-bbl carburetor ~600 CFM will be a greater improvement, along with good flowing exhaust, mild cam and a rear end ratio in the 3.50:1 range.
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Freshman User
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Good to hear!! For this to be a 42 year old motor and I have those numbers, does this mean that those weren't hard miles? Rebuilt/re ringed, or does it mean absolutely nothing? Just good compression?
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Fleet Owner
Joined: Dec 2009
Posts: 20,678
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From: NorCal
I wouldn't rebuild it unless it is burning oil or leaking from every mating surface.
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Thread Starter
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Freshman User
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Engines can be worked hard and still have good numbers. It's all about maintenance like oil and oil filter changes, air filter replacements, carb tuning, and long periods of operation instead of short periods where contaminants aren't allowed to cook off.
I wouldn't rebuild it unless it is burning oil or leaking from every mating surface.
I wouldn't rebuild it unless it is burning oil or leaking from every mating surface.
Fleet Owner
Joined: Dec 2009
Posts: 20,678
Likes: 82
From: NorCal
2x with ultraranger's recipe for improving HP and TQ.
Be advised that GT-40P heads use P-specific headers that are slightly different than typical Windsor headers.. I understand non-GT headers will result in spark plug/boot clearance issues or something like that.
Lead Driver
Joined: Apr 2011
Posts: 6,399
Likes: 40
From: El Dorado, Arkansas
I recall in 73 the figure is net HP.. with all driven accessories installed.
2x with ultraranger's recipe for improving HP and TQ.
Be advised that GT-40P heads use P-specific headers that are slightly different than typical Windsor headers.. I understand non-GT headers will result in spark plug/boot clearance issues or something like that.
2x with ultraranger's recipe for improving HP and TQ.
Be advised that GT-40P heads use P-specific headers that are slightly different than typical Windsor headers.. I understand non-GT headers will result in spark plug/boot clearance issues or something like that.
There are headers designed specifically for GT40P heads, because of their plug angle (or lack of as much angle). However, many (but not all) regular 302/5.0L headers will fit the GT40P heads IF 90° angled plug boots are used.
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Unlike previous Ford small-block heads, the revised plug angle on the GT40Ps only have a slight angle to them, compared to the very noticeable plug angle on other Small-block Fords.
There are headers designed specifically for GT40P heads, because of their plug angle (or lack of as much angle). However, many (but not all) regular 302/5.0L headers will fit the GT40P heads IF 90° angled plug boots are used.
There are headers designed specifically for GT40P heads, because of their plug angle (or lack of as much angle). However, many (but not all) regular 302/5.0L headers will fit the GT40P heads IF 90° angled plug boots are used.
Hotshot
Joined: Mar 2013
Posts: 14,255
Likes: 199
From: Phoenix, Az.
The heads do not change the "deck height". The deck height is the block. The GT40(P) heads will fit on a 73 351W. You will need the newer model and/or aftermarket intake manifold Ultra mentioned above though. And not 1973 intake gaskets.
Lead Driver
Joined: Jul 2011
Posts: 8,679
Likes: 191
From: On the Edge of the Desert
Any "RV" cam will be a big improvement. Or go bigger.
What kinda driving are you doing? Summits line of cams are affordable and have grinds for most purposes. I'm running one in my Cleveland. It was almost identical to the edelbrock performer cam. Makes my truck run good with the matches carb/intake and cam.
What kinda driving are you doing? Summits line of cams are affordable and have grinds for most purposes. I'm running one in my Cleveland. It was almost identical to the edelbrock performer cam. Makes my truck run good with the matches carb/intake and cam.
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