Posted By: 64legacy
Need help on detination........ - 07/07/11 01:26 PM
Been awhile since posting and I have read as much as I can find to help me in my quest to stop my problem. I have a D-440 engine which I presume to be a 68 model engine. This was rebuilt in 1991 basicly to stock specs.Camshaft is from dealer, #P4286631 with matching valve springs. Heads are the 67 closed chamber ones.Pistons are part number 2292P-030.Intake RPM Performer,Holly 750 and headers. Is this setup too high on CR to run on pump gas? I've tried all grades from 87 to 94. I've managed through adjusting timing to get to only about half throttle now before the rattling starts.
Oh..distributor is a Mallory Unilite...no vac advance. I have read that I might need to get a proper quench on this engine, but right now thats not an option to do any machine work.Timing right now is 8 degrees intial, with 24to 25 mechanical all in by 2000rpm. Any advice would be helpfull.
Posted By: RapidRobert
Re: Need help on detination........ - 07/07/11 01:39 PM
Need a baseline on what you have: get a cranking compression #. W vac adv plugged, set initial w vac gauge method then shorten slots to get 36 total then heavier spring(s) staying just under the pinging point at WOT up thru the gears on your hottest/driest day then hookup vac adv & want the fastest tip in it'll take at steady PART throttle (high vacuum) at a RPM at or above the RPM where your mech curve (slots) are maxed out. If your cranking # is too high you may need to proportion in a % of race or av gas as slowing timing from ideal severly hurts performance & in this case might not even touch the prob so feed it what it needs to b happy. In a nutshell your curve is too fast (& DCR may be too high for 94/proper curce)
Posted By: Mr.Yuck
Re: Need help on detination........ - 07/07/11 01:56 PM
A stock 68 rebild even with 915/516 heads and steel shims should be maybe 10:1. I can't think of a reason that wouldn't work on pump gas. That is a small 430/455 cam. Are those domed pistons? Are you sure your carb is set up right? Is your timing advancing? You need a good timing light w/ an advance on it. If that were my engine I'd have it set at 16-18* initial and 36-38* total in full at 2200. I'd start with your carb. 1st if you don't have a carb spacer or thick insolated gasket do it, 2nd make sure your getting full open throttle. What 750 is it? What jets? what squirtters? what PV? I'd probably start w/ 74/82's 31 squirters and a 6.5PV.
Posted By: Mr.Yuck
Re: Need help on detination........ - 07/07/11 03:18 PM
whoops sorry yeas that the 474 cam. 135 is not a ton of compression. So your problem is somewhere else. You have a good carb, I'd step up on the jetting and see how that works. 70 jets are pretty small if it has 70's in the front it probably has 74-76's rear and that's not enough. The squirters should be 31's if they are smaller you might need more. Also what thermostat are you running? How hot is your engine getting? Gas shouldn't be boiling with that tall intake, unless you didn't block off your crossovers. Bump up the jetting and see what happends.
Posted By: 1972challenger
Re: Need help on detination........ - 07/07/11 03:54 PM
I've had to enrich every car that comes into the shop. Go up 2 to 4 jet sizes reset your idle mixtures and it should do the trick. Also you may want to de-carbonize the combustion chambers too.
Posted By: Mr.Yuck
Re: Need help on detination........ - 07/07/11 05:13 PM
wonder if you PV is blown???
Posted By: Dodgem
Re: Need help on detination........ - 07/07/11 06:02 PM
I would put RJ12YC in and 74 jets in the front! check your in gear idle vacuum and get a power valve that is 1.5 to 2.5 below that. If idling in gear is 9 get a 7.5 if its 10.5 get an 8.5 and so on!
You sure your timing mark/ outer ring on the balancer is correct and has not moved?
Posted By: Dodgem
Re: Need help on detination........ - 07/07/11 08:29 PM
They use the same balancer might need to make a piston stop to get a true line on your TDC/0 mark.