How much boost

[SED253]

How much boost can i SAFLEY run..compression is 8.745..iron heads...using 93 octane pump gas(shell)..this is a BBC 496..JE blower pistons...complete roller valvetrain..all forged components.....32* timing.....7-8lbs?????

[ghittner]

5 would be pushing it. @ 8:1 on 93, 8 pds is the limit.

[HEAVYBOAT]

One other variable to consider would be the altitude your running at. If your racing closer to sea level you cant run as much boost as you could at 4000feet.

[78hallett-ss]

One other variable to consider would be the altitude your running at. If your racing closer to sea level you cant run as much boost as you could at 4000feet.
i think you mean overdrive... due to the altitude.. my blown alky motor makes 10-15 lbs more at 200 ft than it does at 4000... i know the gas motors we help with ususally pick up a few pounds at the low alt.

[SED253]

thanks for the replys...i am talking marine application...I ran 7lbs last year on a box stock 454/330hp gen5...always ran 93pump gas...never had an issue...ran all summer...but only turned it 48-4900 revs...yes i changed to full MSD ignition and distributor for this application

[blownzoom440]

i wondered what your cranking compression is?
what stage of supercharger you use[stage 2 BDS?8-71?% overdrive?]
thanks for any info.

[SED253]

i wish i could hide an 8/71 under the hatch but i cant..I have a 250...that i sent to DMPE and they super tuned it....ported the cases...updated double roller bearings...new teflon on the rotors...case is true and perfect with a tight tolerance(.003)..Darren tested it and assured me it will pump 10 pounds...it pumped 7 last summer on my box stock 454/330...and was rich plug checks at different rpms...showed no signs of detenation at all...when i bored and stroked this engine to a 496...i lost 2 1/2 lbs boost and just wanna know if it would be save to change the pulley and get it back up to 7 lbs

[ghittner]

thanks for the replys...i am talking marine application...I ran 7lbs last year on a box stock 454/330hp gen5...always ran 93pump gas...never had an issue...ran all summer...but only turned it 48-4900 revs...yes i changed to full MSD ignition and distributor for this application
That's good luck! I ran 9:1, 30 Deg timing w/ 6 pds boost, blower pistons and dentonated it to hell! 4 Pistons to be exact. I try not to run on the edge any more as I want a tad bit of room for error. Went to 8:1 Aluminum heads, 30 Deg.timing, 10 Pds now and so far all OK after one season...Runnin' on the ragged edge never paid off for me, only for my parts guys!

[SED253]

WOW...thats bad luck...sorry to hear that...what type blower and size...did it dedonate on a long run or what....i never held mine over a couple miles

[Wet Dream]

Mine: 468, AL heads, 8.5:1, 871 spins 6100 making 11-12 lbs with 93. Charts show that I'm borderline on the 93 or race gas threshold. When I run 93, I do not stay in full boost as long as I do with Cam2 or avgas.

[blownzoom440]

i wish i could hide an 8/71 under the hatch but i cant..I have a 250...that i sent to DMPE and they super tuned it....ported the cases...updated double roller bearings...new teflon on the rotors...case is true and perfect with a tight tolerance(.003)..Darren tested it and assured me it will pump 10 pounds...it pumped 7 last summer on my box stock 454/330...and was rich plug checks at different rpms...showed no signs of detenation at all...when i bored and stroked this engine to a 496...i lost 2 1/2 lbs boost and just wanna know if it would be save to change the pulley and get it back up to 7 lbs
i will try to give helpfull info here.my 8-71 has teflon also.it may not be apples to apples but my[intake air] temps were 270*F at 9% OD,idle temps on startup went to 170*F in just a minute or 2.this is relivent to the OD on your combo.do you have any intake air temps?i use a J probe with a volt meter for temps.
the amount of boost may have to do with your iverlap in the cam.i had less boost with a cam with 60* of overlap than i do with a cam with 40*at .050 lift roller/solid but at .646int/.631ex.
on the blower OD again,you may not be able to OD it anymore depending on what OD you are at now.
my dyno run.
http://s27.photobucket.com/albums/c192/blownzoom440/?action=view&current=IMAG0025.flv

[78 propduster]

Here are my dyno #'s on a 467 BBC with a 671 7 to 1 compression at 300' above sea level, 12 lbs boost. motor finished in april and is for sale.

[78 propduster]

Asking $10,000

[ghittner]

WOW...thats bad luck...sorry to hear that...what type blower and size...did it dedonate on a long run or what....i never held mine over a couple miles
At the time, a 489 Hydraulic full roller motor, B&M 420, World steel heads, 625" lift Cam actually 9:1. runnin' 8 Pds boost. Blew up during a hard test run on the lake when we were experimenting with timing. We ran it @ 34 Deg flat out test from start to 5500RPM, heard a funny knock. The boat ran for another year b4 the tick was always audible. Leak down test and pulled the motor. As a result I went 8:1 w/ Aluminum Canfield 350cc Heads and a solid roller 700" lift cam now 498 CI. Pushing over 900 HP but NEVER over 30 Deg Timing and 10 Pds boost!!!!! Not worth the maybe 25 HP I'd gain on the "edge". By the way, I lost 5 pds boost on the new set up and had to re-pulley. I can barely get 10 Pds from it. Hope that helps your choosing.

[MACHINEHEAD]

Customers 35 fountain. Twin 509s/world irons/chillers/8.7:1/6psi/91 octane/32 deg.. Came in with a hurt engine, then found out it was 8.7:1. Went through the totally trashed engine and made it 7.8:1. Dynoed both to match the HP. Needed to put the new engine at 7 psi with 32 deg. to get 805 hp. Had to back off the other from 840hp with a pulley change. This kind of calmed everyone down at the dyno and hopefully would save the older engine. It ate itself alive in 3hours. Ended up doing the other engine and got into the whole pay now pay later thing with the customer. Compression kills. I would much rather have a 7.75:1 engine with 10psi than a 8.75 at 5 psi. Both borderline but I feel better about it. I agree with hitter

[Whipple Charged]

WOW...thats bad luck...sorry to hear that...what type blower and size...did it dedonate on a long run or what....i never held mine over a couple miles
6psi max!! Did you have them install teflon strips on a marine application? Doesn't usually workout so well. Cast iron heads, no intercooler, 32deg timing, if you have it jetted right, then you'll be on the edge at 6psi, especially with a 250 which is a heat pump. Put your hand on it after running for a few minutes.
Dustin

[eemazing]

if interested please call 909-244-6265 must go will give you a great deal

[eemazing]

Did I Mention Its Lime Green With Very Lower Engine Hours