If this is your first visit, be sure to
check out the FAQ by clicking the
link above. You must be an NCRS member
before you can post: click the Join NCRS link above to join. To start viewing messages,
select the forum that you want to visit from the selection below.
Any L89 owners, past or present, here's the question. Does a properly maintained L89 suffer from cooling problems? Any difference as to model year? Is it a driveable configuration, or is the threat of over heating worse than an L71?
I'm interested in your observations.
Thanks
Rich Giannotti
1966 L79 Convertible. Milano Maroon
1968 L71 Coupe. Rally Red (Sold 6/21)
1963 Corvair Monza Convertible
I've never owned or driven one. However, I can't imagine that the engine cooling for an L-89 would be significantly different than an L-71 of the same year. Except for the cylinder heads, all other components related to the cooling systems are identical. The L-89 aluminum cylinder heads and the L-71 cast iron heads should have approximately equal cooling properties, with the L-89 possibly a very little better due to the aluminum material and SLIGHTLY larger cooling passages. The L-71 and L-89 should be about equally "streetable".
Aluminum has less thermal resistance than cast iron, so all other things being equal, it will transfer more heat. You definitely want at least a 180 degree thermostat and higher may be beneficial.
Assuming the radiator and fan are in proper functional order the biggest contributor to big block hot operation is the ported vacuum advance, which eliminates vacuum advance at idle. Converting L72/71/89s to full time vacuum advance will considerably reduce the tendency to overheat at idle and in low speed traffic situations.
The other change I recommend is to swap the '67 vacuum can for the specification used on the '66 L-72. This can has specs of 0 @ 6" and 16 @ 12". Since these SHP big blocks pull about 14" manifold vacuum at about 800-900 idle speed they will keep the vacuum advance "locked" at full advance at idle if full manifold vacuum is used as a siganl. Keeping the vacuum advance locked in at full advance is necessary for best idle stability and minimum heat rejection to the coolant.
The maximum vacuum advacne spec for '67 L-71/89 is 15 @ 15.5" according to the data I have from Corvette News, and idle vacuum is not enough to keep the diaphragm pulled to the limit at idle, however my Corvette P&A catalog shows the 1115360 as the replacement vacuum advance for all SHP big blocks from '65 - '70, and I believe this can has the specs that I quoted above for L-72.
The currect NAPA/Echlin VC1765 vacuum advance control is the same specification as the OE '66 L-72.
One other thing: 1986 Corvettes with L98 were built with both cast iron heads and aluminum heads. The cooling systems were exactly the same for both. As far as I know, there was no significant difference in cooling or "running temperature" for L98s equipped with either type of cylinder head.
All 1987-91 L-98 Corvettes used aluminum cylinder heads with cooling systems pretty much the same as the pre-87 cast iron L98s. As far as I know, there was no difference in cooling or "running temperature" for these engines compared to the earlier cast iron head engines.
I think that any difference in the cooling caused by the aluminum head versus cast iron head are minimal and are easily accomodated by the inherent capacity of the cooling system. I think that the same thing would be true of 67-69 L-89s.
For what is is worth. I owned a 1968 L89 Convertible back then. It ran about the same temperature as my friends L68(400HP) and L71(435HP) cars. They were all hot. With the low ground clearance it would get pretty hot inside the car but it never overheated.
Yes, that's for sure; all big blocks pretty much suffered from marginal cooling capacity, especially at idle. With some carefully selected "tricks", I hope to avoid that when I finally get my "ZL-1" on the road.
What are the "tricks"? Well, a guy has to have some secrets. I MIGHT reveal them later, though. But, ONLY if the actually work.
One thing that really will help a C3 temperature inside the car will be sidepipes. Stay away from headers. I speak from experience. Do NOT eliminate the T-stat to keep the car running cooler.
Keep me appraised on that project. We need someone to “field test” some of those special ZL-1 "Steamin Heat Relied Medicines".
Regarding L-89 cooling problems and drive ability. I also think all 427’s are marginally efficient at cooling during low speed, idle and hot weather. Any compromises to the overall efficiency will raise the temperature. In personal experience, I have not had a cooling boil over on a 427 – with one exception.
On my way home from Carlisle in 2000 when I drove my 68 L-89 it only had one episode of boil over. It was my fault however. After some high speed driving, I exited I-81 for a refuel and mistakenly turned the key off immediately at the pump and it promptly boiled over. I instantly realized that I should have let the engine cool down with the assistance of the water pump, but it was too late. It has not happen again on any subsequent pit stops between laps.
Really, the drive ability with a 4:11 is exhilarating for this fellow. Generally I carry my Blue Point digital IR gun when I fear over heating during hot weather. It allows me to verify that the dash gauge is or is not accurate.
We use cookies to deliver our services, and to analyze site activity. We do not share or sell any personal information about our users. For additional details, refer to our Privacy Policy.
By clicking "I AGREE" below, you agree to our Privacy Policy and our personal data processing and cookie practices as described therein. You also acknowledge that this forum may be hosted outside your country and you consent to the collection, storage, and processing of your data in the country where this forum is hosted.
Tweet
Comment