350 heads on a 327 engine

I have a 327 in my merc that a friend of mine put 350 heads and cam on during a rebuild and its running pretty sluggish,were the heads a complete mistake? i know it lowers compression i was just curious if it was a completely non workable configuration-thanks a bunch if anyone can help

 

same bore...don't matter, why would it lower compression?

 

Depends on which 350 heads you have.

Most stock 350 heads are just simply good boat anchors.

 

327 heads have 64cc combustion chambers. Most 350 heads are 76cc, thus lowering compression ratio by a full point or more.

 

It could, if the combustion chamber is not the same. Don't know if it is or isn't, just saying that could effect compression.

 

I didn't think of that...later model heads would do that...

 

so there is no mechanical doom with head change probably just a tuning issue?

 

could be the cam....

 

cam is the next check i just wanted to make sure the heads weren't a complete no no

 

What was the casting #'s on old heads and casting #'s on the 350 heads I can tell you the CC's

 

If I were after performance, I would replace them with aftermarket.
sportsman II heads will
A- Fit
B- retain compression
C- work better than flowed stockers.
And don't cost much more than freshening up old factory boat anchors. just my opinion.

 

Depends on what 327 heads you had and what 350 heads you put on there. I'm ***uming they weren't double hump heads, why would someone take those off?

 

Going to the late model heads could be a good thing, you would have hardened seats and better valves. My guess, and its strictly a guess, is that he has "too much" cam and completely killed the low end power. Common mistake. You need to list head casting numbers, Old and New and cam info.

 

I'll post the numbers asap thanks for the info.

 

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I'm ***uming you are talking about a basically stock motor, you would not have a noticeable performance or running issue. It is possible something is wrong with the cam or the heads or the installation.

 

If its sluggish , but runs Ok and starts....check out the simple stuff before you go jacking around with all the motor internals.....
1. Make sure you got good gas...
2. Check your timing with a timing light....
3.Make sure your vaccuum advance is working and/or hooked up....
4. Last but not least.....make sure your cam isn't a tooth off....have seen it happen before....needs to be degreed in.......

 

76cc 350 heads on a 327 will give the 327 an even lower compression ratio than the 350 head.

If the 350 had 8.5:1 compression with those 76cc heads, then the 327 would end up around 8:1 running the same 76cc heads.

Smaller 327 cylinder volume being compressed into the same chamber size as the larger 350 cylinder volume will always result in a lower compression ratio.

A 327 with only 8:1 with a healthy cam is going to be down on low-end power as well as power across the entire RPM range.

 

Look on the bright side...now you're all ready for the 6-71 blower that you know you always wanted!

 

Now Ya Talkin'!!!! :d:

 

More than likely you lowered the compression as said advance the the initial timing and throw a curve kit in the distributer will help.

 

My thoughts exactly....

 

hopeless07 hasn't been on here since the 8th , so i doubt he is seeing this