351w is slow and weak...please help

ka_dawg98 · 10-05-2003, 03:09 PM

i built a 1978 351w engine from a van 5 years ago just before i went to college.(my first engine build)... and it gets beat by everybody i race and i NEED help. it was fuel injected and i thought that was the problem, so i carburated it 3 months ago. 5 years ago i put a stock replacement full rebuild kit in the lower end with hyper pistons. a stock timing chain and gear. a crane cam that is 494/512 and 218/224(numbers might be off a coupld digits but those are real close). i didn't degree the cam in, i just put it in where the wholes lined up at top dead center and bolted it down.(serious mistake?i don't know) the heads were the original van heads that i ported and polished myself(first time i ever did this too). my machine shop put 194/160 valves in them but the valves are of different lengths with my pedistal mount rockers. didn't have the money to put stud mounted/adjustable rockers in it, so i put different size rods to take up the slack

i now put a air gap intake on it, 750cfm carb(down jetted), billet distrubutor, 6a box, blaster coil. the engine sounds mean as hell now. revs up great, but is slow as all hell. can't even bearly break the tires loose unless i slip the clutch. what the hell is wrong. even if i put a stock 351w engine from a van in a little light mustang i think it should still kill the tires, but my buddy's mustang (306 w ported e7s, bigger valves, 303 cam, and stock everything else including rear gears) kills me... it just walks away from me bad. how bad did i mess things up on my engine... did i need to degree the cam... can i loose that much power from my mistakes, or is it just a simple timing problem... i 'm afraid to sink more money into it untill i can figure out why the dam car is so slow....
thanks.

BilLster · 10-05-2003, 04:22 PM

it could be the heads and timing but how bad is it ?

have you run it at the track.any numbers.

sounds stupid but hopefully its something simple like your throttle linkage isnt opening the carb all the way. what type of fuel pump are you running ? mechanical right. the stock electric pumps to much fuel and can damage a carb.

timing set at ?

compression in all 8 cyl ?

so check compression then timing then throttle linkage then check exhaust for obstructions then all 3 basics fuel , air , ignition.

if you have those three you should have hp.

good luck.

ka_dawg98 · 10-05-2003, 04:47 PM

no i haven't run it at the track, but my brothers have build camaros and it really isn't even close.. its just slow... like i said about my buddy's car. we'll be in second gear and stomp on it, and he immediatly starts pulling and before im half way into 3rd, his door is at my fender and keeps pulling.

i checked trottle cable and that is working correct.

base timing is set at 12. with advance coming in at 750 rpm with idle at 700 rmp and max advance is 34 degrees at 2500 rpms.

mechanical edelbrock fuel pump

haven't checked compression in all cylinders.. HOW DO I DO THAT?

if any of these are messed up, how much power can i actually be loosing with these malfunctions...? can it be that drastic?

BilLster · 10-05-2003, 06:16 PM

with timming or a compression problem ie valves to tight you can lose all hp.

to test compression you need a compression tester that screw's in where the spark plug goes (remove all spark plugs)follow the instructions for your tester (remove the coil wire ect) do both dry and oiled checks a leakdown tester can tell more of what the problem is but is a little more complicated.

sometimes its obvious like 4 cyl on one side are losing compression or one cyl is dead or all 8 are down so try running a compression test or leak down if you can and post the #'s

check plugs and see hoe they are white black ect.

b055 · 10-05-2003, 08:13 PM

the compression might be lower than a stock 5.0 ho.. like 8.5 or something.. not that it would make a HUGE difference or anything..

i would do a compression check, leakdown and go from there. if thats ok then i would put it on the dyno and see the a/f ratio and curve.. that should get u going in the right direction.

HotRoddin · 10-06-2003, 06:08 PM

My guess is the problem has something to do with this
---------> 750cfm carb(down jetted),

>>i checked trottle cable and that is working correct.<<
Did you physically push the throttle to the floor and look down the carb ??? I went to work for a company that had a crane truck with a 454 chevy in it ... everybody pissed and moaned that for the last year it was so down on HP that every little hill they came to you would be down into 2nd gear to get over it ... I got out, told the guy to push the throttle to the floor looked down the carb and the butterflies were open about 1/4 of the way ... i adjusted the linkage ... the truck destroyed hills from then on ... sometimes its that simple. Is it vacuum secondaries ? are you sure they're opening ?
Does it start to pull better once the RPM's get up or does it get worse ?
I'd check the simple things first because it doesn't sound like you're down 4 or 5 HP .. it sounds like you're wayyyy down.

rwhite65 · 10-06-2003, 08:30 PM

you said it sounds good when idleing? Right? Has anyone messed up and not put the firing order as the 351w -302 HO? Would it still run at all, most likely rough as #$#@ I suppose....could not hurt to check it.

I think the secondaries need to be looked at...but you really need to do the tests these guys described.....the heads on that make me wonder.

A 351w with a clutch should be able turn the tires pretty good.
Ryan

Rev · 10-06-2003, 11:48 PM

Could be that the cylinder head porting is not so great? Just a thought.

Rev

silver_pilate · 10-07-2003, 10:50 AM

Quote:

Could be that the cylinder head porting is not so great? Just a thought

My thoughts as well....if it's not the carb.

--nathan

10-05-2003, 03:09 PM	#1
ka_dawg98 Registered Member Join Date: Oct 2003 Location: merritt island, florida Posts: 3	351w is slow and weak...please help i built a 1978 351w engine from a van 5 years ago just before i went to college.(my first engine build)... and it gets beat by everybody i race and i NEED help. it was fuel injected and i thought that was the problem, so i carburated it 3 months ago. 5 years ago i put a stock replacement full rebuild kit in the lower end with hyper pistons. a stock timing chain and gear. a crane cam that is 494/512 and 218/224(numbers might be off a coupld digits but those are real close). i didn't degree the cam in, i just put it in where the wholes lined up at top dead center and bolted it down.(serious mistake?i don't know) the heads were the original van heads that i ported and polished myself(first time i ever did this too). my machine shop put 194/160 valves in them but the valves are of different lengths with my pedistal mount rockers. didn't have the money to put stud mounted/adjustable rockers in it, so i put different size rods to take up the slack i now put a air gap intake on it, 750cfm carb(down jetted), billet distrubutor, 6a box, blaster coil. the engine sounds mean as hell now. revs up great, but is slow as all hell. can't even bearly break the tires loose unless i slip the clutch. what the hell is wrong. even if i put a stock 351w engine from a van in a little light mustang i think it should still kill the tires, but my buddy's mustang (306 w ported e7s, bigger valves, 303 cam, and stock everything else including rear gears) kills me... it just walks away from me bad. how bad did i mess things up on my engine... did i need to degree the cam... can i loose that much power from my mistakes, or is it just a simple timing problem... i 'm afraid to sink more money into it untill i can figure out why the dam car is so slow.... thanks. __________________ 1978 351w block, stock heads(self ported and polished), 494/512 218/224 cam, stock timing gears and chain, edelbrock performer air gap intake, edelbrock 750 carb, msd distributor/6a box/blaster 2 coil, 1"5/8 shorty unequal headers, h-pipe, 327 gear, 16"rims.

10-05-2003, 04:22 PM	#2
BilLster Registered Member Join Date: Oct 2000 Location: Ontario canada Posts: 446	it could be the heads and timing but how bad is it ? have you run it at the track.any numbers. sounds stupid but hopefully its something simple like your throttle linkage isnt opening the carb all the way. what type of fuel pump are you running ? mechanical right. the stock electric pumps to much fuel and can damage a carb. timing set at ? compression in all 8 cyl ? so check compression then timing then throttle linkage then check exhaust for obstructions then all 3 basics fuel , air , ignition. if you have those three you should have hp. good luck. __________________ 89 with 331 t3'/t4 hybrids. upr Suspention worked out finnaly . 9.89 144 mph .

10-05-2003, 04:47 PM	#3
ka_dawg98 Registered Member Join Date: Oct 2003 Location: merritt island, florida Posts: 3	no i haven't run it at the track, but my brothers have build camaros and it really isn't even close.. its just slow... like i said about my buddy's car. we'll be in second gear and stomp on it, and he immediatly starts pulling and before im half way into 3rd, his door is at my fender and keeps pulling. i checked trottle cable and that is working correct. base timing is set at 12. with advance coming in at 750 rpm with idle at 700 rmp and max advance is 34 degrees at 2500 rpms. mechanical edelbrock fuel pump haven't checked compression in all cylinders.. HOW DO I DO THAT? if any of these are messed up, how much power can i actually be loosing with these malfunctions...? can it be that drastic? __________________ 1978 351w block, stock heads(self ported and polished), 494/512 218/224 cam, stock timing gears and chain, edelbrock performer air gap intake, edelbrock 750 carb, msd distributor/6a box/blaster 2 coil, 1"5/8 shorty unequal headers, h-pipe, 327 gear, 16"rims.

10-05-2003, 06:16 PM	#4
BilLster Registered Member Join Date: Oct 2000 Location: Ontario canada Posts: 446	with timming or a compression problem ie valves to tight you can lose all hp. to test compression you need a compression tester that screw's in where the spark plug goes (remove all spark plugs)follow the instructions for your tester (remove the coil wire ect) do both dry and oiled checks a leakdown tester can tell more of what the problem is but is a little more complicated. sometimes its obvious like 4 cyl on one side are losing compression or one cyl is dead or all 8 are down so try running a compression test or leak down if you can and post the #'s check plugs and see hoe they are white black ect. __________________ 89 with 331 t3'/t4 hybrids. upr Suspention worked out finnaly . 9.89 144 mph .

10-05-2003, 08:13 PM	#5
b055 Registered Member Join Date: Mar 2003 Location: philadelphia ms Posts: 180	the compression might be lower than a stock 5.0 ho.. like 8.5 or something.. not that it would make a HUGE difference or anything.. i would do a compression check, leakdown and go from there. if thats ok then i would put it on the dyno and see the a/f ratio and curve.. that should get u going in the right direction. __________________ i got mustangs. do u?

10-06-2003, 06:08 PM	#6
HotRoddin cranky old man Join Date: Sep 2001 Location: Longview Texas Posts: 683	My guess is the problem has something to do with this ---------> 750cfm carb(down jetted), >>i checked trottle cable and that is working correct.<< Did you physically push the throttle to the floor and look down the carb ??? I went to work for a company that had a crane truck with a 454 chevy in it ... everybody pissed and moaned that for the last year it was so down on HP that every little hill they came to you would be down into 2nd gear to get over it ... I got out, told the guy to push the throttle to the floor looked down the carb and the butterflies were open about 1/4 of the way ... i adjusted the linkage ... the truck destroyed hills from then on ... sometimes its that simple. Is it vacuum secondaries ? are you sure they're opening ? Does it start to pull better once the RPM's get up or does it get worse ? I'd check the simple things first because it doesn't sound like you're down 4 or 5 HP .. it sounds like you're wayyyy down. __________________ Under Construction: 64 Falcon 372 cu in. stroker 1:72 rod ratio 6.250" rods (long rod), Comp Cams XE274 230/236 520/526 @ .050, Scorpion Rollers, Roush 200 irons, 10:1 Keith Blacks, Hedman long tubes, 750 Holley DP, Edelbrock Victor Jr., C4 3500 stall, gears and tires to be anounced.

10-06-2003, 08:30 PM	#7
rwhite65 Ride Hard Join Date: Oct 2000 Location: Wyoming IL Posts: 1,094	you said it sounds good when idleing? Right? Has anyone messed up and not put the firing order as the 351w -302 HO? Would it still run at all, most likely rough as #$#@ I suppose....could not hurt to check it. I think the secondaries need to be looked at...but you really need to do the tests these guys described.....the heads on that make me wonder. A 351w with a clutch should be able turn the tires pretty good. Ryan __________________ 65 Fastback 91 roller 306, H/C/I AOD-Bauman, PI Stallion, 4.10's and traction loc 04 Grand Cherokee Freedom Edition 79 Ford F-250 4x4 - Restored

10-06-2003, 11:48 PM	#8
Rev Registered Member Join Date: Nov 1998 Location: Houston, Tx. Posts: 3,887	Cyl head porting? Could be that the cylinder head porting is not so great? Just a thought. Rev __________________ '66 Coupe, 306, 350-375 HP, C-4, 13.07 e.t., 104.8 mph, 1/4 mi. O.B.C. #2 '66 coupe