1970 #11 to #13 head swap

[KellyT70]

I have a 1970 400 YD code motor with #11 heads and want to change it to a 4bbl rochester with #13 heads.  Is this a simple bolt on or is there possible valve and cam issues?  Thanks

[Frosty]

Welcome to FP KellyT70.

The #13 heads are excellent choice as they have 2.11 intake and 1.77 exhaust valves vs. the #11's slightly smaller 1.96/1.66 valves.  The heads are a bolt on replacement / swap.

However, I would consider a cam swap to take advantage of the larger valves. A 400 with #11 heads was rated at 265 HP while a 400 with #13 heads was rated 350 HP. So in order to take advantage of the heads, you will want a different cam profile. Nothing terribly radical.

Edited January 21, 2020 by Frosty

[KellyT70]

Thanks for the info.  I just picked up a 1970 xh code motor with 13 heads I'm going to go over.  I'm also picking up another set of #13s this weekend.

[Frosty]

I'd talk to a reputable engine builder in your area and see what he recommends for a cam profile to match up with those heads. An HO, RA I, II,or III factory profile will probably utilize those heads very well.

[Wrongway]

After reading the HP difference between those 2 heads I'm curious to know what heads iv got. I'm looking at the pics of when I put it all back together and there's multiple numbers on it. Which or where are the set that I'm looking for?

[KellyT70]

Thanks for all the suggestions.  I got the #13s today and they are ready to build.  I'm looking at the 068 cam with the #13s for my 70 YD block.  I'm putting a 1969 4bbl iron intake with a 1969 or 70 Rochester on it.  That should be around 350hp?  My 70 xh motor with the stock #13s already on it should be about the same too?

[Frosty]

On 1/24/2020 at 11:36 AM, Wrongway said:

After reading the HP difference between those 2 heads I'm curious to know what heads iv got. I'm looking at the pics of when I put it all back together and there's multiple numbers on it. Which or where are the set that I'm looking for?

Wrongway - see the photo below. Let us know what you find. The Casting number is key here.

On 1/25/2020 at 4:03 PM, KellyT70 said:

Thanks for all the suggestions.  I got the #13s today and they are ready to build.  I'm looking at the 068 cam with the #13s for my 70 YD block.  I'm putting a 1969 4bbl iron intake with a 1969 or 70 Rochester on it.  That should be around 350hp?  My 70 xh motor with the stock #13s already on it should be about the same too?

On paper I think you are close. Reality may be different. Your parts selection is correct, but if the bottom end is untouched and not rebuilt, there maybe undo / unwarranted friction/resistance from the piston rings and/or bearings. It should pull like a mother no matter what.

Let us know what the dyno says.

[Wrongway]

Ok Frosty, that looks like a 3 to me.

0168?

[Wrongway]

That is under the valve cover on the head right above the center bolt

Hope that helps Frosty. If not I can remove paint if need be or take other pics. Just let me know. Thanks again bro

[TWO LANE BLACK TOP]

Wrongway.....

Does your car still have the original engine..??

[Wrongway]

No it doesn't. The Grand Prix is a 1963. The engine (428) and trans (400 turbo) are out of a 1968. 

[Frosty]

I agree that the heads are definitely 1968 based on the date code. The head identification is not clear based on the given pictures with only "6" showing. Now that said, it can be one of two heads for '68 that ended in "6". On the Ram Air II GTOs was the "96" head. I doubt that this is that head. The reason I say that is because Wrongway states this is a 428 engine.

A 428 in '68 would have had the more common "16/216" head. This head has the more desirable 2.11" intake and 1.77 exhaust valves. This head was installed on all the 400s and 428s except the RAI and RAII engines. The RA I heads were "37". So it is unlikely to be a RA I head.

Wrongway, check both heads for numbers on the center exhaust ports, I suspect there is "1" and a "6" if you look closely.

A 428 with "16" heads back in the day (1968) was rated at 375-390 HP.

[Wrongway]

Ok Frosty, on both sides the numbers are unclear do to the paint. But if you run your fingers on the ports I did feel what felt like a #1. I can say for certain it was not a #9. I didn't want to say that originally because I was unsure. When I had the heads rebuilt the machinist did say they had 211 valves and that if it were him he would just rebuild them with new parts but not change anything. So that's what I had him do. Is there anyway of guessing the HP and torq with the cam and other things iv done? His guess was between 406 and 410. the whole 406 number just seemed odd to me lol. Especially when he didn't know what cam was going in. Thanks again Frosty

[Frosty]

Wrongway -  you're welcome. Always glad to help. The #16 heads are a keeper. Even if it wasn't, if your machinist has confirmed the presence of 2.11/1.77 valves, it's a keeper. 2.11/1.77 were the largest factory valves Pontiac ever used, and they used them from 1967 to 1979 in various heads.

Was this engine ever bored out to increase the displacement or perhaps the use of different than stock pistons or different head gasket to perhaps slight up the compression ratio? A 16/216 head is a 72 c.c. chamber head. So with all the parts that you say you are throwing at it, 410 HP is not terribly unrealistic at the flywheel. I'll assume for the moment that this engine is not stroked/bored out to a 455 since you said it was a 428.

I just want to be certain you or someone before you have done their homework on the bottom end of the motor to get you to that higher HP figure. A well configured and properly prep'd Pontiac 400-455 should have no trouble getting to 400+ HP naturally aspirated at the flywheel. I don't assume that when someone buys a car that all the proper things have been done to the motor just because it is a high displacement engine. Neglect and age/wear/tear is often a problem.

Edited January 29, 2020 by Frosty

[Wrongway]

Yes sir, it was bored out .30 over, factory crank ground .10 If I remember right. New pistons, cam, lifters, timing etc. Long tube headers, duel exhaust with series 40 flowmasters. I was trying to stay close to stock with the cam so I didn't have to put in a big stall and this was Comps recommendation. 

[TWO LANE BLACK TOP]

According to what the cam card indicates....It should make good low end and mid range torque and power...Off idle to somewhere around 5000 RPMs.... With minimal cylinder head work and a good 3 angle valve job...And be able to pull enough vacuum for the power brakes to work good.... If you listen carefully (trained ear) it probably has a slight lope to it also....With a good tune...400 horsepower is a very realistic estimate......With around 340 to 360 horses at the wheels....

[Wrongway]

Ok guys, thank you again.