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Old 05-21-2007, 04:57 PM
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blaaa

hi everyone just wanted to pick everyones brain that is willing to have ut picked. i just finished restoring a 1967 impala for my daughter. i installed a 60 over 350 with 305 heads. the valves are not the 195 but around the 175 range.i did run a diegrinder and smooth out the ports both intake and exaust. also took the sharp edges of the casting around the chamber i put a performer rpm intake and cam shaft in the motor with a 600 edlebrock carb. i am not sure what the compression ratio of the engine is or the fresh reman botom end was that o bought. the problem i am having it is just dead. it sounds great at an idle i have played with timing but it pings as soon as you get into it at any rpm. it stops pinging with a base of 0 and a total of 30 but with the setting there it is a total dog i bumped octain thinking it would help. it did a little but still dead and pinging. it is infront of the original 2 speed glide.i have never had a glide before and my last build was a 13 second 454 in a 1980 truck. it worked well. i think honestly the way it pulls now id been better off with a stock 4 cyl..... any sugestions? also the cam is degreed at zero. i dont want or expect it to run 10s but something would be nice. it has a hei replacment msd billet dist.. thanks and hope you can help..

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Old 05-21-2007, 06:03 PM
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Quote:
Originally Posted by billlt583
hi everyone just wanted to pick everyones brain that is willing to have ut picked. i just finished restoring a 1967 impala for my daughter. i installed a 60 over 350 with 305 heads. the valves are not the 195 but around the 175 range.i did run a diegrinder and smooth out the ports both intake and exaust. also took the sharp edges of the casting around the chamber i put a performer rpm intake and cam shaft in the motor with a 600 edlebrock carb. i am not sure what the compression ratio of the engine is or the fresh reman botom end was that o bought. the problem i am having it is just dead. it sounds great at an idle i have played with timing but it pings as soon as you get into it at any rpm. it stops pinging with a base of 0 and a total of 30 but with the setting there it is a total dog i bumped octain thinking it would help. it did a little but still dead and pinging. it is infront of the original 2 speed glide.i have never had a glide before and my last build was a 13 second 454 in a 1980 truck. it worked well. i think honestly the way it pulls now id been better off with a stock 4 cyl..... any sugestions? also the cam is degreed at zero. i dont want or expect it to run 10s but something would be nice. it has a hei replacment msd billet dist.. thanks and hope you can help..
Yeah dyno-mite, 305 heads on a 350 have shot the compression to the stars. Now that's not to say there aren't other issues, but you can count on this one.

You need to go back and look at the static compression ratio which means you need to know the thickness of the head gasket so you can compute it's volume this also applies to the clearance, if any, between the piston crown and the block's head deck. Chamber size of the heads, 305s run around 53 to 58 cc, and the volume of the piston's dish if it has one. The static compression is the sum of these divided into the sum of these plus cylinder displacement. If you're getting up over 9 to one, you've got trouble.

Your choices range from replacing the heads with something with bigger chambers to playing with head gasket thicknesses. GM gaskets can be had from steel shims at.020 or so to composition at .058 inch. With a cast iron block and head, gaskets can be stacked and composition can be mixed with steel shim to dial the thickness in. This isn't the best solution technically but it's the cheapest. The best solution would be "D" dish pistons with the dish selected for the head volume to get around 9 to one on a shim gasket.

Bogie
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Old 05-21-2007, 06:23 PM
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Yep, those small chamber small valve 305 heads are really a killer on a 350. Like was stated, the compression is now most likely way too high for pump gas. Zero timing will kill off any performance too. Any stock/modest 350 can use 10-15 initial and up to 36-40 total, not counting the vac advance.

Do you know what piston went into the build? Dish, 2 valve flat top, 4 valve flat top? Was the block decked or still at stock height? This info will help us figure where the compression ended up.

Mark
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Old 05-21-2007, 06:45 PM
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I agree that the biggest, but not only, problem is the heads. The LT1 in my 95 Z28 is rated at 10.5-1 with the stock 58cc chamber. So you can see there is a compression issue to deal with. There are special pistons made for a 350 to use 305 heads.
Another item you need to look at is the cam. If I read your post correctly, you are using the Performer RPM intake and cam. That is a lot of cam and intake for a heavy car with a Powerglide. You didn't mention stall speed on the converter or rear gears.
I used to have a 67 Impala conv. that had a 327. I rebuilt the engine stock with the exception of the camshaft and intake. I used a short duration, high lift cam with 108 of lobe separation and a Performer intake. The carb was the stock Q-jet. The trans was a T-350 with a 11" converter. The rear gear was a 3.08.
The engine had a nice lopey idle and would light the rear tires for quite a distance from a dead stop. Mileage was good at around 16 around town and about 19 on the highway if memory serves me correctly.
It appears to be an issue of some mis-matched components. The worst of which is the heads. Invest in some Vortec heads, a smaller cam and a stall converter. You won't believe the difference.

Barry
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Old 05-28-2007, 10:37 PM
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wich head??

hey gang..they are flat top pistons. these are the cam specs..part num#12-246-3 int..first exaust second..adv dur:274 int 286 exh dur@ .50...230 intake 236 exaust lobe seperation 110.0 valve lift .49 .49 i am getting the idea i had a bad choice in cylinder heads. that is ok.. what i am looking for is drivability i am putting lots of miles on the car.. and long trips.. we all know what fuel costs and its more in canada at least hear. any recomendations on heads. i dont want a race car but i also cant have my chrysler parteners cuda beeting on me either... any ideas.. please help chevy guys? edelbrock? valve size? cc? any input would be greatly appriciated.. i know rite now he would crush me and he uses his for the same purpose..thanks also of course cheeper is better and i am not aposed to cast iron..

Last edited by billlt583; 05-28-2007 at 10:44 PM.
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Old 05-29-2007, 05:58 AM
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Do a compression test and let us know what kind of psi she is pumping, I really think you can make this combo work as is but we need to find out what the problem is. What spark plugs are in it now? Try some R42T AC plugs and run premium and also recurve that timing if need be. It should want about 15 degrees initial with a total of 38ish. Disconnect the vacume advance for now untill the ping is gone then add it a little at a time on a ported source-the MSD distributor should have an adjustable vacume diaphram I think.
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Old 05-29-2007, 02:34 PM
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Quote:
Originally Posted by F-BIRD'88
Your combinstaio is severly mismatched. It will neither get good fuel mileage or beat anything in a race.
Your cr could be as high as 11.25:1 (53cc head) It will always ping unless you severly retard the timing or run high octane racing fuel. If the heads have the small 1.72" valves you're never going to make any power.

Changing to a high flow 64cc head will get you the power and tame the cr.
Vortec heads are the cheap way to go fast.

A powerglide trans just does not have enough low gear ratio to make a heavy Impala move off the start. When combined with a stock rear gear ratio and stock stall converter off the line acceleration is pretty soft. using a large cam like the XE274 just makes it worse. The XE274 startes to get busy around 2800rpm. use a 2800stall (11" converer) and 4.10's.
Unless you are willing to change the rear gear ratio and converter stall, change the camshaft.
Comp #12-234-2 XE256-10 is a good match for a stock stall PG and stock gearing (likely 2.73 or 3.08's).
Good advice....well said
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Old 05-30-2007, 02:03 AM
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hey gang. first off thanks for all the help. i bought a set of 400 heads from a local racer. they have 195 and 150 valves with extencive porting. they looked great. he said try them. well i bolted them on here tonight. they have a 72 cc chamber. i got to say in the shop the throttle responce is better and the power has increased but the builder said they could handle the lift. but after 3 trys and trying to get the rocker noise out i am guessing they are stacking the springs. i want to rip my hair out. i have a line on a set of ported and polished edelbrock rpm 202 150 heads. with 64cc chambers. good idea? bad idea? also a 2500 stall converter is on order. the gears are 336 weard i know but after the division thats the figure. i expect the low end lag and expected it. do you think the rpm heads are what i need? or should i just change the springs and run these ones i have?
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Old 05-31-2007, 10:52 AM
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cant win!!

hey gang back again. the top end noise that i stated is only there when the engine is up to operating temp.. i have tried several adjustments. but still there.. any ideas?
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