Final configuration of rebuilding my 502
03-23-2018, 07:23 AM
#32
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Trim your Intake gasket at the head , looks like your interfering in the corners. I wouldnt worry about the mismatch of a smaller manifold. It kind of creates a small anti reversion step back to the plenum.
You can get up to a .060 MLS head Gasket from Cometic or Fel Pro . I would have a head porter soften those chambers alittle . The Edl head was designed for drag racing to get up the compression . Probably not the most
optimum set up for a marine .
You can get up to a .060 MLS head Gasket from Cometic or Fel Pro . I would have a head porter soften those chambers alittle . The Edl head was designed for drag racing to get up the compression . Probably not the most
optimum set up for a marine .
03-23-2018, 10:40 AM
#33
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I would measure the height and width of the intake runner on the head and get a gasket that fits it correctly. Felpro has the sizes listed in their catalog. Don't worry about the intake being a little smaller, most are. Optimal, no, but it will work fine
03-23-2018, 11:22 AM
#34
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I see what snap is saying however I'd be getting after that intake big time. You can actually loose some velocity. Look at it like a funnel effect. It will be fine as is just power to be made. Been down that road. Many intakes are manufactured to be ported to match up to heads rather the other way around. I use to play around with a lot of that stuff and even ran an rec port intake up against raised dart floors. That's a whole other story but anyway will gain power opening up the intake ports. That can actually be an easy 35-50 hp gain depending on build. I wouldn't say it i didn't see it on the dyno. Just an FYI.
03-23-2018, 02:35 PM
#35
I’ll grind out the intake to better match as well. In particular on the end runners it looks like the mounting bolts get in the way quite a bit but there’s a ton of casting flash everywhere that needs to be cleaned up.
These guys did a fun little experiment of some at home head porting and got nearly 100hp with no other changes.
These guys did a fun little experiment of some at home head porting and got nearly 100hp with no other changes.
03-23-2018, 05:10 PM
#36
Platinum Member
Platinum Member
Port matching is NOT always better..
Plenty of BBC intakes run great with smaller port opening than the heads, and artificially "opening them up to match" doesn't always result in gains.
The ONLY way to know is if you have a flow bench in your garage.
The next best is to find a dyno comparison on the web where your heads and intake were compared to others. Some intake shootouts are very detailed and actually mention whether they played with port matching or not.
When I was a teenager, I port matched EVERYTHING, I ported bowls, unshrouded valves, notched bores, airfoiled and trimmed valve guides, ruined the short-side radius of many intake ports, lapped too-wide valve seats, used bad valvetrain geometry theory, etc.
As with all things in life, you eventually learn that "speed tricks" sometimes work against you.
MC
Plenty of BBC intakes run great with smaller port opening than the heads, and artificially "opening them up to match" doesn't always result in gains.
The ONLY way to know is if you have a flow bench in your garage.
The next best is to find a dyno comparison on the web where your heads and intake were compared to others. Some intake shootouts are very detailed and actually mention whether they played with port matching or not.
When I was a teenager, I port matched EVERYTHING, I ported bowls, unshrouded valves, notched bores, airfoiled and trimmed valve guides, ruined the short-side radius of many intake ports, lapped too-wide valve seats, used bad valvetrain geometry theory, etc.
As with all things in life, you eventually learn that "speed tricks" sometimes work against you.
MC
03-23-2018, 09:31 PM
#37
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iTrader: (7)
Not always. Depends on build. I've seen it on the flow bench and dyno both. Along with actual boat speed and rpm. Good example and test was 5/16" raised floor dart rec port heads done by Valako in 89 as well as intake. Intake manifold floors raised to to match. Engine made great power. Removed the expoxy from intake as I was having another one done by Jim and prior to being complete I put the other on with NO raised floors to get by for a weekend and made ZERO difference in boat speed and rpm. We called it the tumble effect. Air tumbling into intake port perhaps even helping fuel atomization.
Who knows but it's been done as well by others with using a rec port intake manifold bolted up to oval port heads.
never tried an oval port intake with rec port heads. Although i have witnessed 502/540 builds ported by Jim and dynoed with stock dart intake and were no happy with the dyno results as customer didn't want to spend the extra money on intake work. To make a long story short after getting port matching along with other manifold work there was a 55-57 hp gain. True story.
Its amazing how far off out of the box dart heads can be off with out of the box dart intake. I've seen a port here or there with one side or the other being off up .060.
So not always is very true statement.
Who knows but it's been done as well by others with using a rec port intake manifold bolted up to oval port heads.
never tried an oval port intake with rec port heads. Although i have witnessed 502/540 builds ported by Jim and dynoed with stock dart intake and were no happy with the dyno results as customer didn't want to spend the extra money on intake work. To make a long story short after getting port matching along with other manifold work there was a 55-57 hp gain. True story.
Its amazing how far off out of the box dart heads can be off with out of the box dart intake. I've seen a port here or there with one side or the other being off up .060.
So not always is very true statement.
Last edited by getrdunn; 03-23-2018 at 09:34 PM.
03-25-2018, 12:48 PM
#40
The holes machined for the rocker bosses. Any reason not to epoxy those those up and smooth them out? I figure pull the guide plates off, grease the bottom of the rocker stud so the epoxy doesn’t glue to them, and fill it up with epoxy. I’ll leave the boss material there but that sure looks like an ugly snag.
