'69-'70 351W heads on EFI 5.0 HO

[HiFiMerc]

Ok, so it sounds like the 351 heads would be a good bet (plugs are available, good flow etc). Here's the combo they would be with. Stock HO upper, Holley Systemax 1 lower intake, stock HO cam, 19# injectors, D9S ECM. There will be a 3/8" spacer between the upper and lower. It's a must have to clear the fuel rail on the drivers side. I doubt it will make any difference performance wise.

Sound like a winner?

[crazyman]

Have you considered the fact that you will need spacers to adapt the head bolt holes? IIRC the 351 is a 1/2" hole and the 302 uses 7/16".

[HiFiMerc]

Yup. Thought of that. Seems like it's been done many times before.

[turbo2256b]

Sounds ok to me

[sly]

Forgive me, I'm a n00b at engine building. "match the cam?"

generally speaking... what you want out of the engine and the parts that the engine already or will get, dictate the cam you get. The cam will dictate where in the RPM band the power kicks in and where it dies out... the rest of the stuff around it will dictate how well it deals with it.

[HiFiMerc]

Ahh. Ok, makes sense. I was planning to use the stock HO cam. That's why I asked about the 351 heads. Was wondering if anyone knew what the combo would do.

[King_V]

I thought with the E7 heads, a stock 5.0 ran about 8.3:1 compression? So, the Dooe might push that up, I guess, a few tenths as has been stated. It would still be under 9.0:1 though, wouldn't it? Only a 4-cc decrease...

[HiFiMerc]

I thought it was about 8.7:1 (on a lopo), then went up slightly (still less than 9) with the HO. I think even with the 351 heads, I would still be around 9:1. I could be totally wrong, though.

[King_V]

Well, as I understood it:
Lopo with E6: 9.0:1
Lopo with E7 swapped on: a little more than 9.0:1
HO from factory with E7: 8.3:1 (now I'm wondering if I'm remembering incorrectly and it might be actually 8.6:1)

So, if it's a factory HO top to bottom, the DOOE heads would still have it under 9.0. If it was a lopo swapped to HO heads/cam/etc, then yeah, looking at maybe mid 9.x compression perhaps?

[gearheadmm]

Use hardened valve seats with unleaded fuel.
I've seen valves sink 1/4".
Watch intake bolt pattern.
'69 351W 4bbl heads have huge exhaust ports.
Grind the thermactor "hump" out of the exhaust port.

[turbo2256b]

69 351W heads didnt have huge exh ports basicly the same as a set of 302 heads intake is larger. Dont remember any bumps in the exuaust either. Its been a few years since porting a set though and have done a 100 or so newer heads like e7s since then.
Compression is going to be just short of 9.0 to 1. The set on Creamy with some combustion chamber pollishing is 59cc.
There is over 200K on the heads with no seat issues. First valve job I did had 180K before reworking the heads again. Figure there was no more than 70K on the factory valve job. Now if you had a set of 351C heads particularly the 2 bbl heads or 351M or 400 seats might have issues.

[gadget73]

I don't think the HO comp ratio is much lower than a lopo. Consider how big the dish is in the stock pistons, and compare that to the valve reliefs in the HO pistons. I don't have data, or a set of pistons and an eye dropper in front of me to confirm, but I would wager that if anything the dish accounts for more volume than the reliefs. I'd also guess that the E6 chamber size is larger than the E7 chamber, but thats also just my gut feeling.


also, some random internets info says stock 89 HO is between 9.0:1 and 9.2:1, depending on the source. I found 3, an all 3 gave something different. 8.3:1 sounds like some crap you'd find on a late 70s big block.

[turbo2256b]

Should state Creamy short block is out of a 92 Mustang. When I caculated the comp as I STATED WAS JUST UNDER 9.0. Old 351W heads are smaller than E7.

[HiFiMerc]

So it would have close to stock compression ratio, so it shouldn't need anything more than the 87 octane?

I don't think I would have a problem with running premium if required. Just a bit of sticker shock at the pump. But it would work out to maybe 5 bucks more per tank.

I still keep seeing that the Exploder head is better yet, but it's looking like the 351 heads would probably do alright. I'll keep looking around, maybe I'll turn up some Exploder heads, if not, I'll probably snag the 351 heads.


He said he had heads from a 2V engine, and from a 4V engine. Shouldn't the four barrel heads flow better?

[johnunit]

There is no difference. Clevelands are different 2v vs 4v. Windsors are not.