cam talk (spec's)
09-18-2002, 11:15 PM
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cam talk (spec's)
With all this talk of cams dose any one know the specs on the stock 7.4 bravo cam and the Mag cam in the carberated motors? wondering how bad it could be sence it has been the hot topic lattly for replacement. Charlie
09-18-2002, 11:32 PM
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According to the Merc service manual, the 7.4L with flat tappets is: I238 .282"(lobe lift? not sure how this translates to actual lift) E234 LL .271" @.050, rollers I209 LL.282" E209 LL .284" @.050.
454 Magnum: flat I224 .510" E224 .510" @.050, rollers I211 LL .342" E227 LL .342" @.050
Hope this helps.
Warren
454 Magnum: flat I224 .510" E224 .510" @.050, rollers I211 LL .342" E227 LL .342" @.050
Hope this helps.
Warren
Last edited by wwbobb; 09-19-2002 at 12:06 AM.
09-19-2002, 12:08 AM
#3
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Merc service manual
The factory GM specs are;
The flat lifter 7.4/330 horsepower camshaft is an old design camshaft from the 60's with 213/217 duration .460/.480 lift 114 LSA.
The 454/502 Magnum flat lifter camshaft has 224/224 duration .510/.510 lift 115.5 LSA.
The roller lifter 7.4/Gen VI/Vortech L29 camshaft has 206/211 duration .480/.483 lift 115.5 LSA.
The roller lifter 454/502 Magnum camshaft has 224/224 duration .483/.483 lift 115.5 LSA
These camshafts were removed from marine engines by me and measured by Comp Cams for my book BIG BLOCK CHEVY MARINE PERFORMANCE. They each came back from Comp Cams with specs that showed one degree more duration on each lobe than the factory GM specs (above).
Although these camshafts may seem to have a large amount of duration at .050 check they are very mild because they have slow opening and closing flanks for durability reasons. The flat lifter 7.4 camshaft is extremly mild compared to a new aftermarket camshaft.
Using an aftermarket camshaft with the same specs except for faster opening and closing flanks would result in a good horsepower increase.
Hope this helps someone!
Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE
The flat lifter 7.4/330 horsepower camshaft is an old design camshaft from the 60's with 213/217 duration .460/.480 lift 114 LSA.
The 454/502 Magnum flat lifter camshaft has 224/224 duration .510/.510 lift 115.5 LSA.
The roller lifter 7.4/Gen VI/Vortech L29 camshaft has 206/211 duration .480/.483 lift 115.5 LSA.
The roller lifter 454/502 Magnum camshaft has 224/224 duration .483/.483 lift 115.5 LSA
These camshafts were removed from marine engines by me and measured by Comp Cams for my book BIG BLOCK CHEVY MARINE PERFORMANCE. They each came back from Comp Cams with specs that showed one degree more duration on each lobe than the factory GM specs (above).
Although these camshafts may seem to have a large amount of duration at .050 check they are very mild because they have slow opening and closing flanks for durability reasons. The flat lifter 7.4 camshaft is extremly mild compared to a new aftermarket camshaft.
Using an aftermarket camshaft with the same specs except for faster opening and closing flanks would result in a good horsepower increase.
Hope this helps someone!
Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE
09-19-2002, 08:44 PM
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asking the wrong guy
I think that the only place you will get a good answer on that question is from Arizona Speed and Marine.
Did you know that they are the original designers of the 500 HP EFI intake manifold? They sell them to Mercruiser.
If you follow their cam suggestions then they will be able to program the engines ECM without guessing.
Like I have said before, they aren't God but you should listen to them carefully, also remember (like all good businesses) they are there to make a buck off of you!
Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE
Did you know that they are the original designers of the 500 HP EFI intake manifold? They sell them to Mercruiser.
If you follow their cam suggestions then they will be able to program the engines ECM without guessing.
Like I have said before, they aren't God but you should listen to them carefully, also remember (like all good businesses) they are there to make a buck off of you!
Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE
