1960 fuel injection pistons

[Lynn L.]

In process of rebuilding 60 fuel injection block, Are there advantages with using lower compression flat top pistons? Less heat ( 40 over bore), Decreased risk of damage from fluid lock with a lowered compression ratio? Would the high horse fuel unit run as well or needs higher compression? Thoughts appreciated.

[Loren L.]

Re: 1960 fuel injection pistons

Why not start with whether it is a 290 HP FI or the low horsepower?

[Bill W.]

Re: 1960 fuel injection pistons

I have a 62 FI with the correct pistons runs and sounds great in temps. under 90. Above 90 I get poor idle (poor gas ,not FIs fault ). Why would anyone lucky enough to own a FI car not want to have everything correct in the engine ?

[Timothy B.]

Re: 1960 fuel injection pistons

Lynn,

With a .040 overbore the compression will increase slightly, but the camshaft and the intake valve closing point should dictate the piston choice. A late closing intake valve with a flat top piston will cause lower dynamic compression and a much weaker running engine so be careful.

[Richard M.]

Re: 1960 fuel injection pistons

Lynn,

Loren's question is exactly what I was thinking when I read your post. What HP? HL Duntov "097" Camshaft?

Because you're thinking of flat tops, I guess we can surmise you have the HL cam, but?????

Recent discussion(yesterday in fact) about which pistons were used for what application on the 1960. The domed piston was used only on the 315HP FI AND Special Camshaft in 1960. The flat top was used on everything else, including the lower HP FI engine with hydraulic camshaft.
Thread here...
https://www.forums.ncrs.org/showthre...ed-or-Flat-Top

Of particular interest was the paper that Duke references(which he authored)in the thread. You may want to dig into that one.
here.....

http://www.metroli.org/pdf/2012 Nationals tuningseminar.pdf

Rich

[Duke W.]

Re: 1960 fuel injection pistons

Not quite correct. All 283 FI engines with the Duntov cam were "high compression" advertised at 10.5:1 for '57 to '60, and 11:1 for 1961. In addition the hydraulic cam '61 275 HP FI engine was advertised as 11:1.

All other 283s were advertised as 9.5:1 including the hydraulic lifter 250 HP FI engines.

When it comes time for a rebuild, my recommendation for true, measured CR for all these engines is in the San Diego presentation linked to in your post.

Thanks for spreading the word!

Duke

[William C.]

Re: 1960 fuel injection pistons

Interesting Duke, the '63 Parts book seems to support tyhat, in addition, there must have been another design change for '61 on the FI pistons, as the '60 and eralier part number was 3746289-290 (r & l) and the HL cam is noted as required but the '61 is part numbers 3769731-732 with the only notation being "Fuel Injection".

[Bill M.]

Re: 1960 fuel injection pistons

there must have been another design change for '61 on the FI pistons, as the '60 and eralier part number was 3746289-290 (r & l) and the HL cam is noted as required but the '61 is part numbers 3769731-732 with the only notation being "Fuel Injection".

from Corvette News Vol. 3, no. 4: "New pistons with larger intake valve recesses were designed for both the 275 and 315 f.i. engines."
Visually, the pop-up is bigger on the new pistons.

[Richard M.]

Re: 1960 fuel injection pistons

Duke, et al.....

For the record, My post#5 above was referring only to the 1960 MY.

1961 things changed with the new 461 fuelie heads. But both the 275hp(hydraulic cam) AND 315hp(special cam) used pop-up pistons.
page 23 here....

http://gmheritagecenter.com/docs/gm-heritage-archive/vehicle-information-kits/Corvette/1961-Chevrolet-Corvette.pdf

My research showed in 1960 that the pop-up pistons were only used on "Fuel Injection AND Special Camshaft". i.e. the 290hp. The 250hp Fuelie with hydraulic camshaft used flat tops.

Rich