Will 305 heads on a 350 block perform great off the line and hurt top end performance? My 1/4 mile time was a 1.89 60 ft., 14.4@ 94 MPH.

------------------
1988 GTA 5.7L TPI Auto
355 ci. block,TPIS ZZ-9 Camshaft, SLP Headers, Borla Cat Back, B&M Holeshot 2400 Stall Converter, 3.73 Richmond Gears

"Why ride a stang when birds can fly?"

http://www.geocities.com/thegta

 

Joe- the 305 head's small intake valve is gonna hurt you everywhere in the rev range that matters for 1/4 mile performance.

They WILL raise you compression ratio since they have smaller 58cc combustion chambers versus 350 heads that are either 64 or 76. THis is often felt as an improvement in performance since a higher compression motor will have a bit more snap and throttle response than a low compression one but it won't translate into better 1/4 mile performance.

If you REALLY REALLY want a set of 305 head I have a good set I jsut rebuilt for sale for onlly $100.

 

305 heads will not help your performance at any RPM, any car speed, or anywhere else. They are for 305s, which is an economy / emissions motor, not a performance one. You will gain nothing and lose something in every measure of performance.

The reason for your off-the-line performance being improved over stock is the combo of converter and gear. Downgrading your heads will not improve your 60' time.

------------------
"So many Mustangs, so little time..."
ICON Motorsports

 

I could pull a 13.9 1/4 w/ a mild 350 and 305 heads. And that was on a 2.77 rear gear.

It all depends on how you motor is set up, but trust me the only reason to use 305 heads is if you are building an engine and planning for NOS or supercharger. That way you can use low compression pistons and keep the Compression up untyil you get your NOS or supercharger, then you put your 350 heads on.

That was my plan so I was using 9:1 pistons in my 355. The combo worked great. Really whish I could have got around to the 150hp shot of NOS and a set of AFR 190 heads. I was hopin it would net me a 12.9 after I got a 3.42 rea in it. There was just no way to get under a 13.2 with the 2.77 in my opinion even with the heads and NOS, well maybe it migh have, but I don't think the cam and converter liked that rear.

------------------
89 Trans Am Turbo 3.8L All stock 43,000 miles #1053 of 1555

Past Thirdgen:
86 Trans Am w/ built 355TPI with SLP goodies and too much other stuff to List. One sweet *** car, wish I would have had a good enough Job to pay insurance on three cars so I could keep it, but for a 89 Turbo Trans Am w/ Low miles, I think I made the right choice!

 

Not all 305 heads came with the 1.71" intake valve. Some had 1.94"/1.50's in them. I used 305 heads on a few of my claimer engines when I used to run circle track. Cheap way to raise compression and with a LOOOOOOOOOOONG duration cam, they actually did fairly well. I still have a set that have been "just slightly" modiified and one of these days I'll post a pic of them.

[This message has been edited by offroader (edited April 11, 2001).]