mfg Posted August 17, 2014 Report Posted August 17, 2014 A problem occured in Avanti's with the 400 engine that was not seen with the earlier Chev V8's (327-350)....What was this issue?
Gunslinger Posted August 17, 2014 Report Posted August 17, 2014 There may have been several issues with the 400. Early 400's had idle and stumbling issues that GM tried to cure by shipping them with 2-barrel carburetors. After a year or so Quadrajets began being installed once the condition was solved. It wasn't unusual among manufacturers at that time for such problems as all were trying to comply with new emissions requirements. Another issue was heat...400 engines didn't have coolant passages in the blocks...they had steam vents and running hot...historically a very real issue on many Avantis...was not uncommon. Avanti Motors began drilling holes in the inner fender aprons of many cars in an attempt to vent heat from the engine compartment.
mfg Posted August 17, 2014 Author Report Posted August 17, 2014 Good information!.....but not the 'Avanti Only' problem the question asked about. Any other ideas?
Avanti83 Posted August 18, 2014 Report Posted August 18, 2014 cracked front cross members at engine mounts?
mfg Posted August 18, 2014 Author Report Posted August 18, 2014 cracked front cross members at engine mounts? You 'nailed' it!.....The extra torque of the 400 engine seemed to be too much for that front crossmember.
warren55 Posted August 18, 2014 Report Posted August 18, 2014 I hadn't heard that one. I guess I better check my crossmember for cracks!
Avanti83 Posted August 19, 2014 Report Posted August 19, 2014 You 'nailed' it!.....The extra torque of the 400 engine seemed to be too much for that front crossmember. Now for the rest of the story. My 74 came with a 400 and OP told Nate that he didn't want a truck engine. Altman replaced it with a 350 shortly after the OP bought the car. When I removed the 350 to install the 383 last year I removed the mounts and the frame was cracked around the mounts. I don't know if it was the 400 after only a couple of months but I think it was more the fact that the engine mount bolts were installed without washers. The crack in my cross member radiated out from the edges of the bolts which initiated the stress fractures. The difference in assembly quality between my 83 and 74 is enormous. The 74 reminds me of a kit car built by teenagers. So I'm not sure if it's the 400 or partially build quality. I know the story is true about the 350 because I purchased the 74 from the son of the OP and talk to both of them on a regular basis.
Avanti83 Posted August 19, 2014 Report Posted August 19, 2014 I hadn't heard that one. I guess I better check my crossmember for cracks! Warren It's not easy to tell if the mounts are in place. It will look like this under the mounts.
warren55 Posted August 19, 2014 Report Posted August 19, 2014 Well that isn't pretty! I suppose at some point I'll have to pull them apart just to have a look.
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now