View Full Version : Need help with carb'ed roller 302
clueless_racing
04-03-2009, 11:43 PM
Me and my buddy just got back one of our old cars and it runs ok driving around normal,but when you get onto it,it doesnt seem to have any power.The set-up is as follows
86 roller motor.stock bottom end
ported e7s with new valve springs
lunati .521 lift .292 duration cam
edelbrock performer 289 intake
brand new demon 625cfm.vac sec
mid-length headers.
The car runs at about 190 degrees and stays there.oil pressure is normal for a untouched roller short block.The timing was retarded so much the car didnt even sound like it has a cam in it.Put some timing in it and adjusted the air/fuel mixture and idle on the carb.IT sounds alot better but not like it should.almost sounds like its on 7 cylinders.If anyone has any ideas where to start id really appreciate it.Thanks everyone
85_SS_302_Coupe
04-04-2009, 06:18 AM
Well i'd say there's a decent chance you may have bent valves since the '86 pistons have no valve reliefs cut into them and you have a pretty healthy cam in it. Time for a cylinder compression test.
With that intake, you would be better off with a stock H.O. cam and some 1.7 rockers.
I agree with David, check compression and go from there.
clueless_racing
04-04-2009, 08:38 PM
wel whats funny is the motor had the stock cam and 1.7 rr on it until the guy we got it from changed the cam and put stock rocker arms back on it.Thanks for the advice on checking compression.Thats where i will start at.What should compression be around for each cylinder?
85_SS_302_Coupe
04-05-2009, 07:36 AM
I can't say on the numbers as i've actually never done one...but if you have bent valves that should let you know because whatever cylinder has the bent valve won't seal and the compression will be super low.
clueless_racing
04-05-2009, 09:22 PM
yeah i got you on that.i plan on getting busy with it towards next weekend.Im going to do the compression test and if its bad then im tearing the top end off and starting over with it.
cmetalbend
04-06-2009, 12:32 PM
Sounds like a serious vacume leak. I wouldn't get so jumpy to tear it apart, it doesn't sound like a comp problem yet. "Bent valve" I highly doubt. It would run like total dog shit all the time. Based on the state of tune when you got it back it could be a number of things, like vacume , valve adjustments, blown power valve, and so on. good luck
IEATLT1
04-06-2009, 12:55 PM
I would also go with carb gasket vac leak, blown power valve, or valve adjustment.
85_SS_302_Coupe
04-06-2009, 01:17 PM
The only reason i suspect a bent valve is because of it being an '86 block with no valve reliefs. I'm sure that's a worst case scenario but with that much cam and no valve reliefs at all...it wouldn't surprise me in the least.
IEATLT1
04-06-2009, 02:04 PM
I do not at all disagree with you.
I believe .460 or .468 is all they said you could run with a 86 motor. so it's very possible that he did
cmetalbend
04-06-2009, 02:56 PM
The only reason i suspect a bent valve is because of it being an '86 block with no valve reliefs. I'm sure that's a worst case scenario but with that much cam and no valve reliefs at all...it wouldn't surprise me in the least.
I'm not sayin it's not poss, just not by the sounds of the description.
85_SS_302_Coupe
04-06-2009, 03:03 PM
I've heard that with the E6 heads you can run a very mild cam because the chambers were huge in those heads which puts the valves further away from the pistons...but still.
Stangman
04-06-2009, 03:26 PM
Running an automatic or manual?
If it's a stick, I'd chuck that vacuum secondary carb and get a mechanical, and vise versa...
cmetalbend
04-07-2009, 02:37 PM
Well i'd say there's a decent chance you may have bent valves since the '86 pistons have no valve reliefs cut into them and you have a pretty healthy cam in it. Time for a cylinder compression test.
To do this test, What your looking for is consistancy in all cylinders more over than anything. Now, if they are coming in below 120 psi you got problems.
NUTTSGT
04-11-2009, 06:50 PM
Actually, I'd pull the valve covers and check for bent pushrods. Been there and done that with a '86 short block and '87 heads.
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