big block owners WTF?

[SOON2BLAZE]

Took the blazer out today for a cruz in 100 + temp and found out I have a vapor lock issue. Plan on putting a carb heat shild and a phenolic spacer between the 454 and the quadrajet. Then I'll wrap the fuel line from the pump to the carb with some be cool wrap sumit racing has. Any other suggestions??? Even After sitting in my garage for 2 hours, the alternator is hot to the touch. Would a oil cooler help any? The twin puller fans I'm running work good as far as keeping the temp gauge where it should be. This is my first BBC, I had no idea they put off so much heat.

[1956cameo]

I'm not exactly sure why you are having so much trouble but here are a few things I can think of. I drove a big block 70 for years in the Texas heat and rarely got over 200, and usually ran around 185 in the summer. Do you have a big block radiator, or radiator built for small block? Also is the radiator new or is it old and possibly got blockage? Also I always run my trucks with the manual fan off the water pump. Do you just have the electric fans? My trucks always seem to run warmer if they just have electric fans. The only other things I can think of is that possibly your water pump is worn, or you could try and put a cooler thermostat in. I usually put 160 degree thermostats in my trucks. I am sure someone else can help you further but those are the only things that come to my mind. I put big blocks in all of my stuff and they usually run cooler for me than small blocks.

[silverstreak]

If the things you mentioned don't work, (spacer and insulating the fuel lines) an electric pump may help out. You could also try running a regulator with a return line to keep a constant supply of cool fuel. I'd try the simpler, cheaper things first. I put a plastic spacer under my carb, which helped out a lot.

[72Levi]

Are you running an Edelbrock carb? I bet you are, if so, change it to Holley.

[gssmith89]

Not too sure if this would help your situation but I installed some fiberglass header wrap on my headers and it significantly lowered the under hood temp with my 454.

[dwcsr]

Originally Posted by 72Levi

Are you running an Edelbrock carb? I bet you are, if so, change it to Holley.

he said qjet

[Zoomin]

Originally Posted by 72Levi

Are you running an Edelbrock carb? I bet you are, if so, change it to Holley.

I'll bite - why would that make a difference? Too lean?

[prostreetC-10]

Originally Posted by Zoomin

I'll bite - why would that make a difference? Too lean?

No.....because Holley's rule!

Weird! I have two BBC's that run cool as a cucumber. Never over 190*. I'm sure you have checked this but are you sure your fans are wired to spin the right direction for the way they are mounted (push vs pull)???

[raisinracer]

Check your timing, and dist. for advance. Too far retarded will heat way up.

[Shyguy]

I have a big block in my '92 GMC and thought it would be neat to install a dual fan set-up so I bought one from Summit. This was quite a few years ago now.

I installed the set-up and it did not keep the engine as cool as the stock set-up with the clutch operated fan.

That expensive dual fan setup is now on a shelf waiting for me to try it again in one of these old trucks. It may never happen, but I got it if I need it,lol.

The 454 in my '71 runs real cool with a stock clutch fan setup and 3 core radiator.

[My72BB]

Couple of ideas for you...Went thru this many years ago when we swapped a 350 out and put a 454 in a 1973 3/4 ton 4 X 4. It would not go more than 20 miles in the AZ heat before it vapor locked...Did everything under the sun...The final thing we did was install a stock fuel pump with a return fitting and a return line back to fuel tank. Problem solved...!

I am not sure what year you are working on but by your avatar it looks like a 69-72 blazer?

If you are using the stock setup then you only have a feed line. Install a new manual fuel pump for a truck w/Big Block and it will have return line.Then run back to tank. You will need to install a fitting somewhere on tank for return.

This will keep the fuel moving and I will pretty much guarantee that your problems will go away.

In my opinion forget about rerouting fuel lines/ice cans/heat shields etc...Been there...done that. Jus a waste of time.

[kwmech]

Originally Posted by Shyguy

I have a big block in my '92 GMC and thought it would be neat to install a dual fan set-up so I bought one from Summit. This was quite a few years ago now.

I installed the set-up and it did not keep the engine as cool as the stock set-up with the clutch operated fan.

That expensive dual fan setup is now on a shelf waiting for me to try it again in one of these old trucks. It may never happen, but I got it if I need it,lol.

The 454 in my '71 runs real cool with a stock clutch fan setup and 3 core radiator.

I had the same problem in both my tow truck and my pickup. I never had any luck with the electric fan set-ups. Went back to the correct shroud and a fan clutch. Never had an overheating problem since

[SOON2BLAZE]

Thanks for all the replies. More info on what I'm running: 185 thermostat, stock fuel pump with a return, Stock exhaust manifolds, and a 4 core radiator with an overflow tank. The issue it self is not over heating, but the amount of heat coming off the engine. At this point I think that whats causing the vapor lock. Checking the timing sounds like a good place to start aside from the carb spacer and wrapping the pump to carb line. When I assembled the cooling system I used some water wetter and a 50 / 50 mix. The temp needle sits just a hair past the line on the gauge when warmed up, so I'm good there. Sits at a nice 800 rpm at idle and doesn't smell rich, but we'll see what the timing light says about the advance.

[1971 GMC SHORTY]

I Took The Stock Fan Clutch Out And Installed A Black Magic Elec Fan Set Up My 502 Hated Them, Put a brand New AC Delco Fan Clutch It Runs A Lot Cooler, It Just Hates To sit and Idle With A/C On For A Long Time.

[SOON2BLAZE]

Found this over on the HAMB :http://www.thecarburetorshop.com/Ethanoluse.htm

Kind of explains the extreme engine heat, vapor lock and need to crank it 4 times to get it to start. Anyone else have this issue? Thoughts?

[1-PU70]

Last week my 402 was acting up. I'm in FL and the temp is low to mid 90's every day. After I would turn it off for about 10 to 30 min it would start as usual but I would get some major hesitation if I would accelerate more them half pedal for about 5 min. Then it would clear up. Now this never happened before. The only change I made was to switch from premium to regular gas. But that was about 2-3 months ago. Here are the changes I made since. Changed from a 180 to a 160 thermostat and changed fan and clutch from a 19"- 6 blade-2 1/4" pitch regular clutch to a 18"-7 blade-2 1/2 pitch with a heavy duty clutch. Runs a bit cooler and cools down faster. Engine specks are a 1972 truck 402. rebuilt about 6000 miles ago. All stock except a roller cam(kind of like an RV cam) HEI, high flow aluminum water pump, cast iron high rise intake and a stage 2 JET carb and a compression ratio of about 9.1:1 to about 9.5:1. I don't drive it that much anymore so I don't know if those's changes have made any difference yet. Good luck.

[leddzepp]

Originally Posted by 1-PU70

Last week my 402 was acting up. I'm in FL and the temp is low to mid 90's every day. After I would turn it off for about 10 to 30 min it would start as usual but I would get some major hesitation if I would accelerate more them half pedal for about 5 min. Then it would clear up. Now this never happened before. The only change I made was to switch from premium to regular gas. But that was about 2-3 months ago. Here are the changes I made since. Changed from a 180 to a 160 thermostat and changed fan and clutch from a 19"- 6 blade-2 1/4" pitch regular clutch to a 18"-7 blade-2 1/2 pitch with a heavy duty clutch. Runs a bit cooler and cools down faster. Engine specks are a 1972 truck 402. rebuilt about 6000 miles ago. All stock except a roller cam(kind of like an RV cam) HEI, high flow aluminum water pump, cast iron high rise intake and a stage 2 JET carb and a compression ratio of about 9.1:1 to about 9.5:1. I don't drive it that much anymore so I don't know if those's changes have made any difference yet. Good luck.

With that high of a compression ratio, I would start by switching back to premium gas.

[69sixpackbee]

Another thing you guys are also failing to mention is nowadays is that with the advent of the reformulated fuels that are tailored to lower emission injected vehicles the older ones have alot of trouble running. It is worse here in the "Golden State" All of my carb'd vehicles suffer similar maladies. I still run VP116 in my Super Bee so I don't have that issue. But when I tried pump premium,! My 402 in my '72 would sit for one day and I would have to crank the livin' sheite outta it to fill the bowl in the Q'jet. I would only get a stumble though if I tried to stab the throttle after stopping a bit, like refilling and hitting the highway, and then it would recover. These fuels are much lighter in density so therefore they will evaporate very quickly! After I put the EFI on my truck my issues have been eliminated. Even though I did not have any vapor lock per se, I could tell the diff. in grades of fuels too. I would travel across the western states in the dead of summer with the A/C a blazin' and my engine stayed around 190. I had a phenolic spacer under the carb but I had the stock steel line from the pump to the carb filter.

All vehicles behave differently but it is sure to get worse as the chemists keep tinkering with the gas formulation.

We're doomed!

[SOON2BLAZE]

thanks for the replies QUOTE: My 402 in my '72 would sit for one day and I would have to crank the livin' sheite outta it to fill the bowl in the Q'jet. Sounds like same issue. I talked to an ole boy that has run the pumps at costco for a long time. He says the gas the get is from utah oil and is refined in SLC and has 4 % ethonol in it although the sign on the pumps say it can be up to 10%. I try to only fill up there because of the price, but have not put there has in the blazer yet. Going to go with the phenolic spacer et richening up the carb as specified in the article.

[Shyguy]

Originally Posted by SOON2BLAZE

thanks for the replies QUOTE: My 402 in my '72 would sit for one day and I would have to crank the livin' sheite outta it to fill the bowl in the Q'jet. Sounds like same issue. I talked to an ole boy that has run the pumps at costco for a long time. He says the gas the get is from utah oil and is refined in SLC and has 4 % ethonol in it although the sign on the pumps say it can be up to 10%. I try to only fill up there because of the price, but have not put there has in the blazer yet. Going to go with the phenolic spacer et richening up the carb as specified in the article.

The problem you have were you have to crank the livin' sheite out of your truck to fill the Q'jet float bowl after it sets for one day may be because the gasoline is leaking out of the carb through some casting plugs. This has been covered on another thread.

[SOON2BLAZE]

epoxyed em up when I rebuilt it in june.

[GASWAGON]

Originally Posted by Shyguy

The problem you have were you have to crank the livin' sheite out of your truck to fill the Q'jet float bowl after it sets for one day may be because the gasoline is leaking out of the carb through some casting plugs. This has been covered on another thread.

Ethanol based fuel boils at a much lower temp. What is happening is the fuel Is boiling and when it boils it expands. On a q-jet it boils up out of the bowl through the bowl vent and runs down the throttle bores. Edelbrocks have the same problems. The bowls are built into the main casting allowing them to absorb more heat. Holleys have the bowls " hanging out" with a air gap. This helps them to be more resistant. I would use a phenolic spacer and if the budget allows I would run a "air gap" type intake manifold. I have found up to 60 degree reduction in intake temp on past projects. So your extended cranking is because the fuel has boiled out and they are "dry" the next day. When its 20 so minutes later the intake is loaded with raw fuel so the engine acts flooded etc .Hope this helped. J
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[SOON2BLAZE]

Gaswagon,Thanks for the info!

[GASWAGON]

No problem! Let us know how you make out.
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