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OK, I have been following the 800hp n/a thread and was wondering what I could do to get a few more ponies. I have seen the 502 recipe from cyclone and widowmakers 502 pump gas build. My current engine is a BBC 505 with Merlin oval port heads, comp cams solid roller XR286 (0.653/ 0.660 lift), rpm airgap, holley HP 950. CR is in the mid 9’s. The plan was not to have a full on race high compression motor built that needed to be wrenched on before or after every trip, just a pump gas lake boat that would get going when needed. I just wanted to go a bit faster, but you know how that goes. I am running 81 now in a heavy 19’ Miller 6 seater, through Jacuzzi with the energizer with no real set up other than a custom loader, place’s short droop, and an FTN diverter nozzle. Per Duane’s chart I am at 478.66 hp spinning an AT A to 5100. After seeing these 502 builds at 740 hp, I think I am leaving some power on the table. I know set up is one of my next steps and have been thinking about doing a pump swap to a berk jg I have sitting around. I just think there is a bit more power to be had with my combo.
 

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OK, I have been following the 800hp n/a thread and was wondering what I could do to get a few more ponies. I have seen the 502 recipe from cyclone and widowmakers 502 pump gas build. My current engine is a BBC 505 with Merlin oval port heads, comp cams solid roller XR286 (0.653/ 0.660 lift), rpm airgap, holley HP 950. CR is in the mid 9’s. The plan was not to have a full on race high compression motor built that needed to be wrenched on before or after every trip, just a pump gas lake boat that would get going when needed. I just wanted to go a bit faster, but you know how that goes. I am running 81 now in a heavy 19’ Miller 6 seater, through Jacuzzi with the energizer with no real set up other than a custom loader, place’s short droop, and an FTN diverter nozzle. Per Duane’s chart I am at 478.66 hp spinning an AT A to 5100. After seeing these 502 builds at 740 hp, I think I am leaving some power on the table. I know set up is one of my next steps and have been thinking about doing a pump swap to a berk jg I have sitting around. I just think there is a bit more power to be had with my combo.
Is the 505 a punched 502 or a 4.350 bore with a 4.250" stroke? Have the heads been worked? If not this is where you need to concentrate your efforts. Port work here along with some chamber shaping and larger 2.250 intake valves will gain you the added airflow you need. This along with a single plane intake and a new camshaft will yield you some more power. Alternative choice would be to unbolt the heads and put on some AFR 305's and then a new camshaft.
 

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Man, I thought we were gonna talk about hot rodding our Bridgeports.... damn, I'm disappointed...
 

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Discussion Starter #6
Is the 505 a punched 502 or a 4.350 bore with a 4.250" stroke? Have the heads been worked? If not this is where you need to concentrate your efforts. Port work here along with some chamber shaping and larger 2.250 intake valves will gain you the added airflow you need. This along with a single plane intake and a new camshaft will yield you some more power. Alternative choice would be to unbolt the heads and put on some AFR 305's and then a new camshaft.

Chris,

It's 4.350 bore and 4.250 stroke. The heads have minor work done to them. As far as I was told by the builder and that I can recall, they were pocket ported. They also had larger valve installed. I have been thinking of changing the intake to a single plane, but not sure which one to go with, and some head porting. Then the thoughts of AFR'S along with a rectangle port single plane and a new cam..... decisions, decisions. I guess I need to look at $$$ vs possible gain.
 

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Chris,

It's 4.350 bore and 4.250 stroke. The heads have minor work done to them. As far as I was told by the builder and that I can recall, they were pocket ported. They also had larger valve installed. I have been thinking of changing the intake to a single plane, but not sure which one to go with, and some head porting. Then the thoughts of AFR'S along with a rectangle port single plane and a new cam..... decisions, decisions. I guess I need to look at $$$ vs possible gain.
Budget is key and that will be a big factor in determing what you have to work with to acheive your goal. Here is my advice. The Merlins are a good head and respond well to port work but grinding cast iron is no fund and you could sink another $1000 in these heads before your able to gain a decent increase. Also consider if this 505 is it for you on engine builds then spending some money on what you have is more budget friendly. This route with a single plane intake and a matched cam to the induction system should yield a nice gain.

Now if your out for every bit of power and have future plans to go bigger the purchase of a set of AFR's makes sense. Sell the merlins and recoupe some money to put on the AFRs. These heads out of box have good clean air numbers and make good power. They will also give you some room to grow if that is in the future. A set of AFR 305 with a Dart intake and a matched camshaft will make extremely good power.
 

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was wondering what I could do to get a few more ponies. around. I just think there is a bit more power to be had with my combo.......
Per Duane’s chart I am at 478.66 hp spinning an AT A to 5100.
Your not spinning your impellar to your cam's peak power range. Or, you cammed outside of your impellar's power range. Either way you want to look at it, your not using the boat in the engine builds proper range.

Your XR286 SR has following specs:
.015" 286°, 292°
.050" 248°, 254°
.653" , .660" lift
ICL 106°, LSA 110°

Anyway, yes, you can change engine parts to gain more power. That's easy. However, is your boat set up to use the power you are making currently ?
Do you throw hp at the boat or do you throw the boat at the hp ?
 

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cfm i'm not sure what your saying ? i have always looked at jets as not knowing that there in a boat , just a torque brake , then after getting the engine tuned and matched to a impeller set the boat up to make the best use of the available thrust . with the parts in this engine i would think it should spin his A impeller another 500 rpm . bulldawg i would try retarding the camshaft 4* to a 110*icl. to try and flaten the torque curve past it's peak . a single plane like a victor jr. should help in carrying more torque past peak as well , although a lot of guys are saying the rpm airgap is just as good up to around 5500 . i don't have the dyno or the charts to prove or disprove that but with a 505" stroker in a boat like yours i wouldn't start shaving a A impeller till i tried a little more engine tuning with what you got i think your not to far off :)grn
 

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Discussion Starter #12
Thanks Guy's.

Cstraub,

I am considering the heads/cam swap. I am also going to poke around in my area for a head porter to see what it would run. I do like the idea of having room for growth going with the AFR's.

cfm,

This winter I was hoping to throw more hp at the boat as well as throwing some boat at the hp. I think I am going to go ahead and swap out the jacuzzi/ energizer for a berk and get my hardware act together. I am running near sea level at about 750' above.

canuc,

The motor use to spin 5500-5600 with the jacuzzi before the addition of the energizer kit. I knew the rpms would come down a bit. Didn't expect so much....

I just figured I would work on both setup and squeezing a bit more power of of the motor this winter.
 

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Thanks Guy's.

Cstraub,

I am considering the heads/cam swap. I am also going to poke around in my area for a head porter to see what it would run. I do like the idea of having room for growth going with the AFR's.

cfm,

This winter I was hoping to throw more hp at the boat as well as throwing some boat at the hp. I think I am going to go ahead and swap out the jacuzzi/ energizer for a berk and get my hardware act together. I am running near sea level at about 750' above.

canuc,

The motor use to spin 5500-5600 with the jacuzzi before the addition of the energizer kit. I knew the rpms would come down a bit. Didn't expect so much....

I just figured I would work on both setup and squeezing a bit more power of of the motor this winter.
Let me know if I can be of help and feel free to call if you have any questions.
 
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