Reply With QuoteThose two castings are exactly the same except the combustion chamber was slightly smaller on the 781's. 118cc opposed to 122cc. Both good production heads if there worked over.
I have aquired two sets of heads for BBC one set of 049 and one 781, both are recently rebuilt with low run time, on a mild BBC which set would be best???
Those two castings are exactly the same except the combustion chamber was slightly smaller on the 781's. 118cc opposed to 122cc. Both good production heads if there worked over.
Wow thanks for the rapid reply and the info. Either one will be superior to the ones currently on the motor now.
Just as RCB said, they are essentially the same, but for the small diff in chamber volume, the runners are only a tiny bit different volume as well. They are the favorites of the head shop here in Wichita that ports Duane's stuff, and is going to get mine. They swear there is 75-80 HP just in a stage 1 job, leaving the small stock size valves in place. I have 049's.
Smokinlowriderss you seem to be a well of info, what improvement might I see from the 360 heads on it now to say the 049's according to your desktop dyno?? You said before that my combo spinning the AT AA with inducer was making I think 314hp at 4300rpm.
i prefer the 049 to the 781 only because of the intake runners and what seems to be core shift or ? when i was port matching a set of 781s the intake ports werent even close, and a bit smaller. the smaller chamber my be a benefit on your set up, but id still rather run the 049s and set the motor up for them. a little unshrouding of the intake valves on 781s may help aswell. either set are good heads and ive heard if you cut em for larger valves they really come alive. i have a set at the machine shop getting cut for 2.21/1.88 but it will be a while before i see what they do.
Smokinlowriderss you seem to be a well of info,.
I try my best bh.
what improvement might I see from the 360 heads on it now to say the 049's according to your desktop dyno?? You said before that my combo spinning the AT AA with inducer was making I think 314hp at 4300rpm.
Well, the Dyn-file that I have for ya reads 303HP @4500, has my Isky cam in it, I don't recall (nor have saved) whatever specs we discussed other than "stock 325HP Hardin Marine 454". My "Stock 330HP Indmar Marine 454" had far les cam in it, so please give me an update so I can check my info for certainty.
That said, the 303HP @4500 peak file (404lb torque @ 3500) becomes:
340HP @ 5,000 / 416lb torque @ 3500, no other changes.
Ported to match an airflow file I have becomes:
368HP@ 4500 395HP@5,000, 404HP@ 5500 /Torques of 426@3500, 432@4000, 429@ 4500
That's specd with my Isky 280H cam and Log exhaust. About 40 HP just in the head swap.
Don't know what pump specs we ever discussed, but an AT "AA" to spin 4300 needs 350 HP according to JPCalc.
All I had for data was that the motor would spin that AT AA at what I thought was 3900 rpm but the tach was not correct and has since been replaced and verified to be correct with a max rpm 4300, so it makes more power than I thought it did, cool. It would appear that the original owner may have done some work to the motor and not mentioned it to the second owner who I bought it from who said it had nothing done and was stock. All I have done is add a performer rpm airgap, new 750 holley marine vac secondary and new points set correctly and advance all in by 3200 rpm and a supercoil. This boat is a heavy sucker and gps speed is 57.8 with a full load of fuel, dual batteries, anchor and chain, lawn chairs and umbrellas under the hatch, not too bad I guess and I only pick up 1.5 - 2 mph empty but it gets there way quicker.Sure do suprise a lot of smaller boats that think they are fast!! I hope to be pleasantly suprised with the heads and roller rockers.I will let you know.
Good luck to ya bighead. Yea, apparently the motor has had a bit of work done to it somewhere. If I can be of any help to ya, drop me a line, I'll do what I can.
Thanks SmokinLowriderSS, I am gonna take the pig out tonite and wind it out as usual to de stress a little, life is too good when you live 6 miles from the free boat ramp. I put over a hundred hours so far this season and my season goes year round even between rainstorms when I get jonesin for a ride.More weekdays than not I will go out for an hour or two and sometimes the family goes and we have dinner on board, our favorite is spagetti!!! The kids like how the spagetti spins as it sinks hahaha.. I scored two early untouched except for a couple hundred thousand miles,70's 454 motors, blocks cranks rods and heads so I will parley that pile into a solid motor that I know what is in it with a few more horses and see if I can run mid 60's loaded. Got a bit of work to do over the winter for sure, I will do that E pump shoe loader set-up after new motor and we will see.
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