Summit SUM-152123 Cylinder Heads

[Billla]

I'm working with another board member, pmpski_1, on a 355 overhaul (thread below) and as part of that project we decided on a set of stock GEN I cylinder heads vs. Vortecs to allow him to use his stock iron intake and freshly rebuilt Q-Jet with the divorced choke.

http://67-72chevytrucks.com/vboard/s...71#post2642271

We selected a set of the Summit Racing "S/R"-type heads that appear to be no-name World Products S/R Torquers. This is a review of these heads; I'm not going to copy over all the specs as they're available at the link below.

http://store.summitracing.com/partde...0&autoview=sku

General
Overall, the quality of the castings and machine work is very high. The heads come assembled with 2.02/1.6 valves that are back-cut and have a 3-angle valve job. The valves are no-name, but appear to be of good quality. I did note some nicks here and there from assembly on the valve faces. The heads come with 3/8" shoulder studs.

I'm never super happy with umbrella-type seals, but these appeared to be fine. The springs are single but with the inner dampner - the fit and finish was a little rough, and all had 2 shims fitted.

Looking Closer
The chambers are generally nicely shaped and relieved for the valves - someone looking for max power would likely spend a little time cleaning up the sharp edges from the relief.

Checking the valve seats, the contact was very narrow and I'd suggest lapping the valves for sure. The heads came VERY dirty and need to be disassembled, washed and lubed before assembly - but you should do that in any case.

Looking into the bowl, the intake is generally nicely shaped, but the exhaust had a significant ridge right below the seat throat that really needs to be cleaned up - I suspect there's 20+ HP in that investment of about 5 hours work. I did some quick grinding visible in the port to estimate the required clean-up work. The rest of the runners look very nice, with a smooth short-side radius that doesn't really need anything and a relatively smooth if fat boss around the guides. The port match was pretty far off...but there's also not a lot of meat for clean-up; I would not attempt to port-match these heads with a fully ported intake but there's not significant power in that until power levels above what these heads would support.

Summary
These are a good set of heads for making up to about 1 HP/CID or a bit beyond. They definitely need throat clean-up on the exhaust side, but no other real work other than lapping, cleaning and lubing. Investment in cleaning up the intake throat and chamber would likely pay off, but not as much as the exhaust throat work.