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  302-4V Vs. 351W heads

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Author Topic:   302-4V Vs. 351W heads
68 S-code GT
Gearhead

Posts: 940
From: Sayreville, NJ, US
Registered: Mar 2000

posted 03-14-2002 09:38 PM     Click Here to See the Profile for 68 S-code GT   Click Here to Email 68 S-code GT     Edit/Delete Message   Reply w/Quote
I have a 71 302 that is stock except for ARP rod bolts and maybe a 270H Comp Cam, which heads are better? I plan on gasket matching and grinding out the thermactor boss if they are there. The intake will either be a Torker II (because I have one) or a Performer RPM. If I use the J-code heads I will get a compression of about 10 to 1. If I use the 70 351W heads I will get about 9.3 to 1. Will the bigger valves breathing out weigh the advantages of the smaller combustion chambers?

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sigtauenus
Gearhead

Posts: 1708
From: Beaufort, SC
Registered: Jun 2000

posted 03-14-2002 09:54 PM     Click Here to See the Profile for sigtauenus   Click Here to Email sigtauenus     Edit/Delete Message   Reply w/Quote
My own plan is to put 351 valves in 289 heads, so I get the higher compression and better flow. BUT, that is only because I already have the 351 valves and the 289 heads on hand, and my wife would kill me if I bought ANOTHER set of heads.

When I asked Alex about this before, he said he did the same thing like 20 years ago and I think he used the phrase "I thought I was slicker than snot on a door handle" or something to that effect for doing that trick. Then he switched to stock 351W heads and they outperformed the modified 289 heads.

So, I'd guess what you're going to hear is if you have a choice, use the 351W heads with Alex's super thin head gaskets and you'll still have about 10:1 compression and big breathing.

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steve'66
Gearhead

Posts: 5897
From: Sonoma,CA,USA
Registered: Mar 2000

posted 03-14-2002 10:58 PM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
I remember that quote too Sig. I tried some stock '69 351w heads on Melissa's 289 and they weren't very impressive. Heavily ported 289 w/the bigger valves will flow better than stock early 351w heads will. So since you have them ask N2OMike for some porting tips (or do a search) and have a ball!

SteveW

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68 S-code GT
Gearhead

Posts: 940
From: Sayreville, NJ, US
Registered: Mar 2000

posted 03-15-2002 07:33 AM     Click Here to See the Profile for 68 S-code GT   Click Here to Email 68 S-code GT     Edit/Delete Message   Reply w/Quote
I read somewhere that the stock 351W switch will only get you about 7HP. I want to try and keep the cost down and use what I have. This is because I?m starting to finalize my list of things for a 351W stroker and want to put the money there.

quote:
Originally posted by steve'66:
I tried some stock '69 351w heads on Melissa's 289 and they weren't very impressive.

SteveW


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68 S-code GT
Gearhead

Posts: 940
From: Sayreville, NJ, US
Registered: Mar 2000

posted 03-15-2002 01:07 PM     Click Here to See the Profile for 68 S-code GT   Click Here to Email 68 S-code GT     Edit/Delete Message   Reply w/Quote
I remember Alex?s quote about having snot on his door handle but I couldn?t find it in the search. I found your post about the thin head gasket but it ended in a dead end. Did you use the thin gasket and what was the compression ratio outcome? Was it raise 1 whole point or was it only 0.1?

quote:
Originally posted by sigtauenus:
When I asked Alex about this before, he said he did the same thing like 20 years ago and I think he used the phrase "I thought I was slicker than snot on a door handle" or something to that effect for doing that trick. Then he switched to stock 351W heads and they outperformed the modified 289 heads.

So, I'd guess what you're going to hear is if you have a choice, use the 351W heads with Alex's super thin head gaskets and you'll still have about 10:1 compression and big breathing.


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sigtauenus
Gearhead

Posts: 1708
From: Beaufort, SC
Registered: Jun 2000

posted 03-15-2002 01:36 PM     Click Here to See the Profile for sigtauenus   Click Here to Email sigtauenus     Edit/Delete Message   Reply w/Quote
I haven't built my engine yet, but I believe Alex says the thin gaskets add 1/2 (0.5) a point of compression.

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