My 455 is still overheating! Heads up...long post ahead. Bought a '70 Skylark 455 knowing it had oil pressure issues and was overheating on the way home, vacuum advance was disconnected at that point and heater core was not in use. Pulled motor, bored 40 overdue to some rust in the cylinders before realizing I should have went 38 over for a 470 build. Changed directions, built a quickie/cheap 60 over using a spare block and pistons/rods along with the crank, assembled heads, cam (unknown Lunati...pic atttached) with lifters back in their original spots, Performer Qjet, B4B, distributor converted with Mallory electronics, 3 core stock radiator, 7 blade 18" fan, 70 shroud from the car. Block was cut for pi stons -5 in the hole...cc'ed heads and should be near 10:1...intake cut to accommodate. Cam reinstalled straight up like it came out...without degreeing it. All this was done to buy time to build a better 470. After motor was back in, vacuum advance and heater core were both put back in use. Timing set for 12 advanced. Motor starts up and temp gauge starts climbing slowly very soon (which is different from my last 455 that took much longer to heat up and gauge jumped to 160 once the thermostat opened...and didn't overheat.) Temp at idle 180-190, driving around slowly goes up to 220+, much quicker if I get on it. Temp drops 10 degrees when stopped at 2000 rpm but rev'ing any higher while stopped causes temp to go back up. Fan seemed to be moving a lot of hot air as was the heater. Vacuum 10" at idle which seems low for the cam. Checked fairly well for external vacuum leaks but found none. Got to reading up and looking around more, ordered a TA HP short water pump but then realized there was a long pump set-up on the car and the fan was buried into the 455 shroud about 1/4". Looked around for early brackets and pulleys but couldn't find them quickly/reasonably so went with TA long HP pump, shorter fan clutch (thanks to BPG site for the info!)...fan now out of shroud about 1/4", put a spring in lower radiator hose, did best to get air out. Bought an aluminum 2 core radiator but have not installed it yet. Fan is off-center in shroud 1/2" high/low and also 1/2" side/side but haven't realigned the front end yet. Started motor expecting cool cruising but still overheating! Since then I've checked TDC to make sure the balancer outer ring hasn't spun and it looks good. Plugs looked decent (pics attached), nothing that stuck out to me. Lots of coolant flow with the new TA pump. I don't think the new uninstalled radiator is the answer so looking for help with ideas/next steps. Potential issues? Stock radiator issue Still not enough timing Internal intake vacuum leak Head gasket leak (don't think I have the symptoms of that though) Fan still too far into shroud and also not centered Cam cut retarded and needs to be advanced Thanks in advance for any ideas.
What kind of radiator is in it now? How old is it. Initial timing can’t tell me much, I need to know what the timing is going down the road. Vacuum advance might be connected but is it working?
Not sure if you are having the same issue I was having but bear with me. How many miles on it since break in? Mine ran much hotter (200-210↑) than I liked with a 180° thermostat for about 200 miles before it all of a sudden dropped to running at thermostat temps. I changed fan clutches, fans, radiators and tried pure water with wetter and nothing helped until it hit around 200 miles and it was like a light switch was thrown.
Are you sure the temp gauge is accurate? What is the cranking compression? Does it seem reasonable based on estimated compression ratio and camshaft guesstimation? Isn't there a problem with some timing sets being mis-marked? I will never install a camshaft without spending fifteen minutes with a degree wheel and dial indicator. As usual, WHAT IS THE ACTUAL IGNITION TIMING figures--including vacuum advance. Getting the fan pulled far enough out of the shroud should help. Was that radiator ever used in a cold climate--salt/brine used to melt icy roads? Road splash can corrode the air fins where they attach to the coolant tubes. The radiator flows just fine, but won't transfer heat.
Looks to be a stock 3 core radiator, not sure how old but guessing original. Checked again for vacuum leaks and found the intake was leaking at both back ports, retorqued to 45 and was leaking less then 50 and so far looks like it's holding. Taped and marked balancer for 1.76"/30 degrees. Pulled and plugged vacuum advance. Adjusted idle mixture screws and ended a little over 2 turns out. Checked vac advance with a vac pump and it works. Idle: 800 RPM, 14 degrees advance, 10" Mechanical all in at 1400 RPM, ~28 degrees ...seems to be too little too early
That radiator is almost guaranteed to be at least partially clogged. They were barely adequate when new. If you bought a decent aluminum 2 core with at least 1" tubes, it should be much better. Add some vacuum advance to get the timing up around 40-44* at light load cruising RPM. Should run very close to the stat rating.
Greg, you may be on to something. Only about 50 miles since rebuild. Not sure how to explain what you experienced though... Schurkey, yes, now kicking myself for not buying/borrowing a degreeing kit as I've done in the past. Have not checked compression but will put that on the list. The car was from central Jersey near the shore (that's the beach for non-Jersey people out there) and may have been involved in Hurricane Sandy so radiator corrosion is possible. It and the fan do kick out a ton of heat at idle though.
My car 1970 GSX455 Stage 1 was bored 40 over and my temp. was well over 200-210...Larry the Wizard suggested an aluminum radiator and that did it and now she stays put at 175 to 180 unless its 95+ outside then she only goes up to maybe 190. Runs like a top now for 10 years. Get your distributor set up properly too and I would think you're good to go.
US radiator (via OPG) with 1" tubes waiting in the wings. Was hoping the other improvements would help. Between the radiator kicking out a ton of heat at idle and the heater also kicking out heat I'm not so sure the radiator is it though. Will check timing at cruising speed with vac advance tomorrow.
Do you still have the TA HP short water pump and is it for sale or did you exchange it for the long pump?
A LITTLE too early? Holy crap, I'd want it "all in" around 2800--3200 rpm, and you've got it at half that much. I'd also want a little more advance--perhaps 32--35 degrees at that 3K instead of 28. HOW MUCH vacuum advance, and at what vacuum level? 10--15 degrees is fairly typical, OEM may be 25 or even more.
Yes, the mechanical advance is wack. I had a new spring and weight kit sitting around for the last 20 years but now that I need it I can't find it. Will shoot for more centrifugal advance and have it come in a little later. Will also put the new radiator in and get more details on the vacuum advance this weekend.
Aluminum radiator is in and so far looking good. 88 degrees today, left the driveway at 170, hung mostly at 182, up to 190 when getting on it then in stop and go traffic, back to 180 when cruising. This was all in about a 5 mile trip. Seems a little high compared to the 160 stat but an easy 20 degrees better than before. So far so good and will push it farther next trip. Found my 20 year old advance and weight kit. Going to work on the timing situation next.
Another test run and still good on temperature. Took it for a ride in 90+ weather down the expressway and back through stop and go traffic. <190 max and back down to 180 while moving. Thanks to Larry and all for recommending getting rid of the old radiator which seems to have been the main issue. Also thanks to Larry's posts elsewhere I've found out the car has a 1112109 converted 350 distributor with 12-16 mechanical advance. It also has a Mallory points conversion kit installed with what looks like an advance limiting bushing so that explains the too little advance. May try pulling the bushing out to see what advance that gives. If that doesn't work I'll be looking for a proper 455 distributor.
Barry, is there a certain number on the distributor you're after? I have one that needs a rebuild from my 70 block I bought I won't be using it.
Hey Bob! That is an interesting offer but it looks like a 69 400/430 distributor with 30-34 mechanical advance. That would be going from one extreme to the other. Not sure if 0 initial advance would work with my motor.
No prob, if you want it just let me know. It came on my 70 455 block engine that also had 68 430 heads and intake on it. It could have been recalibrated to work on that engine I'm not sure I don't really know the history of it.
Don't toss the original radiator, the tanks are valuable. You can have it re-cored with a high efficiency or extra high efficiency core that will work as good or better than most aluminum radiators. At the very least, cut the core out and keep the tanks rather than throwing the whole thing away.
