Hey race fans, long time lurker/reader, 1st. time poster, lookin for knowledgeable suggestions and help.
I picked up this 1979, 20' Eliminator jet cruiser project for the family with a complete 4.310" x 9.80" d.h. 427" motor.( cast'g # 3869942), w/4 bolt main, 3.76" stroke crank (p/n 6223), aftermarket I-beam rods, unknown length, w/3/8" cap screws, Arias flat top pistons w/ single valve relief, (#426 on underside of comb. ch. only), .080" i.t.h. Top ring appears pretty low approx .500" and head gasket- felpro p/n-405er approx. .041" as measured. This motor was originally built with a blower and later changed to n.a.. Change over was completed by Ross Wilder @ Wilder Craft Ent. (for you oldschool jet boat racers and ford fans,) Heads installed at change over are cast'g# 3964290 (matching #s set) , cl. chamber (100.9cc) large oval port with 2.19"int./1.80" exh. valves, comp. 1.72 roller rockers, hyd. flat tappet cam (unknown specs. as of yet but prolly blower circa 1978 or so as stated by orig. owner/builder), Weiand action plus intake p/n-8013 and holley vac. sec. carb. (prolly 750 never bothered to look) Motor was reportedly freshened at time of change over around 17 years ago and has approx. 20 hrs. in first 2 seasons since change.
Berk. pump orig. built by Wildercraft w/adj. shoe, ride plate, G-bowl w/stuffer etc., droop and new alum. aggressor impeller trimmed to power band. I'm in the process of setting the pump back approx. 6" to clear the hand hole cover out side the transom, give the boat a little more lift and gain some cockpit space since it only has 9' transom to dash.
Soooo some questions:
what would be a reasonable guess at static c/r?
How bad is the quench in this thing at this configuration? was it better or worse with the blower? (Isn't quench a comb. ht. dimension that directly affects combustion quality, flame travel etc.?)
In addition to the cam and valve springs (never backed off) what else should i plan/consider changing for reliability etc. due to it sitting unused for 16 years or so?
Would a 150-200 hp shot of nitrous be even reasonable/helpful with this deal? (I'm thinking bad quench +nitrous pressure= bigger problems)
What cam profile recommendations would be reasonable (hyd. roller min./ maybe solid)?
What kind of hp/tq./rpm could be scavenged from this deal with proper cam etc.?
I have a pair of closed ch., rect. port heads stock configuration (p/n-3919840) would changing to these heads be a significant improvement?
Any other questions I haven't asked that I should be?
I'd like to get this deal to run around 60mph for now and in the water asap. I have many parts to build a new motor for this ranging from 460"-548" and will start on that as soon as this is up and running.
Thanks in advance for your guys help.
Last edited by jetjunky; 07-30-2011 at 10:47 AM.
Reason: original title is misleading
Your around 7.75 to 1`right now, and could raise it about another .2 with a shim style gasket. At that compression ratio, I wouldn't get to concerned about quench. Lowering the piston that far in the hole to lower the compression is old school. Today it would be done with a dish that mirrors the combustion chamber.
I wouldn't lose any sleep over the valve springs. They will be fine.
Thanks for the response Bob. That's pretty much what I figured. Being mostly a lurker and limited applicable experience I thought I would toss the ques. out there for guys that prolly forgot more than I may ever know.