I have a 68 olds cutlass convertible with a 1973-1974 350 4 barrel carb. The engine was replaced by the prior owner in 1980 and has about 10,000 miles on the rebuilt. No problems and it runs great. I noticed when I was putting on new valve cover gaskets my passenger side head is a #7 and the other is a #8. The numbers on the #7 are 409 147 and on the #8 are 411 929. Am I going to have problems with this set up?? Thanks

 

You said it yourself that it runs great...you shouldn't have any problem out of it.

 

+1. If it ain't broke, don't fix it.

In theory, #7 heads have smaller combustion chambers = higher compression, and #8 heads have larger combustion chambers = higher compression, HOWEVER, you have no idea what may or may not have been done to them (milled?) without taking them off to find out. If it runs well, leave it until it doesn't and you need to take it apart.

If you're really curious, you could do a compression test and see if there is an across-the-board difference between heads. If not, then don't look for trouble, or, as I learned years ago, you'll find it.

- Eric

 

Thanks for the reply. The only thing I wish the car could do is burnouts. Does not seem the motor has enough power to spin the wheels. I read and seeing people with the 350 that seem to have much more power and can do burnouts. I understand a lot could be done to get the motors more power and I might need to change some stuff from stock. I put a dual exhaust on it and had the carb rebuilt 3 years ago. I also put a 3 speed trans in it which was an improvement from the stock 2 speed. Again it runs great just am looking for more power. I am looking at a different air intake to see if that helps. I have about $1000.00 a year to play with on the car and already spent $1,500.00 on the interior last month. I don't want to get too crazy with spending money on the motor at this point. I think I can sneak about $300.00 to $500.00 more this year without the wife noticing.

 

This is where you jump out of the frying pan and into the fire.

If it runs well and you're satisfied with it, then don't mess with it, especially if you're on a limited budget.

If you are not satisfied with it, then you need to get more information before you can decide what needs to be done to it.
Somebody "rebuilt" it in the past. Do you have any information about that? Any receipts, part numbers, specifications, dimensions? Without that, the only way to know what you've got, and thus what you need to do, is to take it apart and see what's inside.

I think you will be happier leaving well enough alone for now.

Perfect is the enemy of good...

... And it's better to put your money into cars than into the pockets of divorce lawyers.

- Eric

 

I'm sorry, I should have said it was a crate engine not a rebuilt. I agree on leaving it alone but I always try to fix things that are not broke. What do you think a new intake would do for performance? I have looked at the Edelbrock 3711 and for under $300.00 would like to try that. Worth the money??

 

I think if your engine runs fine don't mess with it like eric said. If you want a good feel on the seat of your pants find out the gear ratio in the rear end. If it had a 2 speed trans it's probably got some crusing gears like 2.56 etc. I could be wrong. But swapping to something like a 3.23 3.42 gear will probably be a big improvement.

 

X2, if it had the 2 speed it was likely highway gears. If you want more snap off the line coppercutlass has the right idea. You could even go 3.73's but your gas milage will be noticeably worse.

 

An Olds crate engine with mismatched heads?

 

Agreed.

I'm signing off here.

It runs well. Delving deeper will only lead to heartache.

Drive it and enjoy, or resign yourself to thousands of dollars spent "while you're in there" and a car that's really a large paperweight for several months to years.

- Eric

 

If its an over the counter parts store crate, I wouldn't be surprised. I have heard a lot of horror stories mostly involving small chevy's. Things like .060 over pistons right next to .030 over, rugged looking cranks, camshafts that looked like they were ground on a belt sander... Could be ugly. I say resist the urge to open that engine up!

 

ewwwwww. sorry but just ewwww. i dont think i could bring myself to buy a crate motor........i just dont trust people i guess and with good reason as mention in the title of this thread. if it runs leave it bro, if you want something better do a swap or build your own in the garage while you drive on the u have.

 

Have the timing adjusted to 34 degrees of total timing all in by 3000rpm, and it should do burnouts all day.

 

I agree with the others, leave it alone, aside from tuning. I would not change the intake, maybe try a 4 hole spacer. Cold air, get the distributor dialed in, fine tune the secondary opening on the Q-jet. Basic inexpensive stuff, you'll be surprised how much there might be left in it.

A word on "crate engines" There is nothing wrong with a quality crate engine. The idea of dropping in a proven combo is appealing to some guys. But there is a BIG difference between that and a cheap mass rebuilder, those things can be nightmares.

 

I didn't think Olds sold crate engines...I'm thinking this engine is the latter cheap mass rebuilder.

 

I bet the matching head for your motor is on one of the guys' shoulders who built it.