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77Spectra
11-01-2002, 05:02 AM
I need to lower my compression. I have a 460 with c9ve heads and my pistons are flat top not dished. 93 octane just does not cut it. It would be nice if I could use my current rockers but I also have the sled style. What would be the best heads to fix my compression prob?....dc
intimidator
11-01-2002, 05:15 AM
WHY DO YOU WANT TO LOWER COMP? DETONATION OR BLOWER? ETC.
hack job
11-01-2002, 07:22 AM
the best way would be to get lowe compressions heads like a d3ve a2a or some thing new! they are low compresion heads the pistons dotn sound like your problem
my 501 ford puts out about 600hp with d3ve a2a heads with some port work and bigger valves . d3ve heads are cheep cause every one wants the higher compression! good luck! wink
hack job
11-01-2002, 07:23 AM
by the way thats in a 19 ' spectra
wink :D
Blown 472
11-01-2002, 08:52 AM
you should check out reincarnation-automotive.com he sells ported d3ve ported, check out the website.
MikeF
11-01-2002, 09:31 AM
You might even try a new cam w/ alot more duration. That would bleed down the cyl before the actual compression of the gases starts. A boat w/a pump will rev right through the low RPM. Just a thought :) .
Omega21
11-01-2002, 11:08 AM
I don't know how much research you've done already, but I do agree with Mike F's idea as a possible cure if it is compression related.
I believe there's a ton of other things I'd try first to be sure what's going on. Detonation, or things that sound like detonation, aren't always caused by high compression. Have you tried a bottle of 104+ to see if that straightens it out? Have you tried AV gas? Changed the timing any? How old is the gas in the boat? Does it detonate on the water only & not on the trailer? Got a case of reversion goin on?
Todd
77Spectra
11-01-2002, 12:27 PM
I have used the 104 and it's fine with that. Just got a family now and want the thing to start easy when hot and be able to use pump gas. I will keep my current heads for another day. The d3ve sounds like the way to go. Can I use my current rockers? They are chevy with pushrods to match. My jet is also a 19 complete redo, showroom new, a two year bitch.....dc
Keith
11-01-2002, 01:23 PM
Hey 77 Spectra, where is your timing set? I have a bbc with 11:1 compression and can run on 89 octane gas (I add booster if I plan to pull skiers or plan to run hard). My tow vehicle is a 78 ford e250 with a 460 and can pull the boat up any hill in north Texas without pinging with 87 octane gas. My other toy is a 69 cougar (351w) with 58cc heads and flat tops (around 11:1 too) and have the timing set without pinging on 89 octane gas. None of the above have EGR valve. A EGR valve injects exaust gasses into the cyl to cool the charge and stop the detonation. I think if you back the timing on your 460 3 degrees and limit to 30 to 33 degrees at full advance, you could also use lower octane gas. What kind of distubuter do you have? A Mallory should be simple to limit the total advance. This should save you from buying a new cam or replacing the heads. Anyone agree?
Keith
11-01-2002, 01:28 PM
Another thought...a lower initial timing setting should eliminate any hot starting problems. Does anyone want more compression? I gota freind that has a couple of d0ve heads....yea, 70 models
hack job
11-01-2002, 02:04 PM
77Spectra:
I have used the 104 and it's fine with that. Just got a family now and want the thing to start easy when hot and be able to use pump gas. I will keep my current heads for another day. The d3ve sounds like the way to go. Can I use my current rockers? They are chevy with pushrods to match. My jet is also a 19 complete redo, showroom new, a two year bitch.....dcwe need to see some pics of this boat it sounds like a pretty nice boat! email them to me if you dont know how to post them!
77Spectra
11-01-2002, 08:16 PM
Timing is at 8* to who knows. I may just check into the starter for now. As soon as I get a newer carb on it this winter hack, I will post it. There is nothing on this boat that has not been replaced. I spent a year just on the bottom. Interior, gauges, floor, paint, motor, headers, all new. Thats another thing if I get a few more hours on it my problem may go away.
hack job
11-01-2002, 09:25 PM
mines going throught the same yours did ! iam completly , the gell is getting redone with the bottom and all! iam going to redo the interior when it gets back form the gel guy!
you can check out my gel work on
www.havasubarney.com (http://www.havasubarney.com)
i have a new motor already and the pump is most of the way done ! i hope to be back on the water by feb! i cant wait to see those pics! wink :D