daredevil95

Hi, I have a 90 LX 5.0 with a fresh rebuild, GT40 heads, E303 and a old/rebuilt SN89 Paxton-6lbs boost, the car has about 500+ miles on it at this point and all has been well with no issues until yesterday. I got home and parked the car and I lost about a gallon of antifreeze from the overflow bottle with NO over haeating issues and like I said I had no problems up until this, the car has a new thermostat, new WP, new large aluminum radiator and a new 16lb radiator cap and hoses. I'm not seeing any signs of head gasket problems...water/oil mixed, no engine anti freeze leaks or mist coming out of the exhausts. So, 500 miles with no issues until this, could I have the wrong size 16lb radiator cap? or what else could cause excessive pressure in the cooling system? or are there any other ideas I'm not thinking of? I was thinking of getting a cheap hydrocarbon tester to check the anti-freeze and this would be my next step unless someone has a suggestion/advice?

Steve@Tasca

I think you're on the right track with the hydrocarbon test.

daredevil95

yea, I'm gonna stop at the parts store tonight and see if they have hydrocarbon test kit. Another question, could timing cause an issue with pressure in the coolant system, I have the timing up there at around 16, I never really sorted out the engine timing, it was more or less of a drive it with a loose distributor/adjust and romp/ adjust / romp on it until I liked the results then check the timing with a timing gun and then that's the number?! The car runs good and very cool...but, I could tinker with the timing later.

mjr46

has this car been tuned?? or are you relying on the ecm for total timing advance?? if so with the boost even though at 6lbs, could of popped a head gasket/started to burn through a firing ring......oops, I just saw you have base at 16?? correct?? if so that'd put total well past 40 on the ecm side.....if you've ever seenthe GFUB document and the schalar tables for total timing advance on the eec iv, 16 base + what the ecm adds in + boost + you romping on it/tuning by feel may have you pulling the heads to do gaskets now. I run 12 lbs and with meth total timing is at 21 iirc on mine make 556+ rwhp. but mine is tuned. timing is not something you tinker with later on a boosted engine, I ran a boost retard on mine until the motor was broke in and had it set very conservative, so mush so, that after 4500 car fell flat, once it was broke in I took it to the tuner and let him work his magic, needless to say when I got the car back it was a whole new animal.

daredevil95

The car was tuned by a buddy who came over with another ECM and laptop to get the car drivable and break in the motor, went to the dyno tune and started the set up and the dynometer broke, at that point the car was making 6.1lbs of boost at 4900 with an AF ratio 11.7 with 8 degrees base timing (24 degrees total on ECM as is) the car made 298hp and 334 TQ at this point, will be going to tuner asap but, i was playing around with the timing for a few romps...hope it's ok....seems to be? The car has cometic HG and studded block, nothing bad at this point but, concerning! The coolant over flow only happened that one time and seems to be ok.