ok what involved in converting 350 to 302

[splatspeed]

Hi all

i want to convert a 350 ci Small block chevy to the classic 302

these engine rev like nothing else and were only made for 2 years

but it is a proven hi reving V8

so whats involved in shortening the stroke on my small block

[steve_d]

Shorter throw crank, perhaps longer con rods, taller pistons i.e. the distance from pin to top of piston.
Ask this same question on Chevytalk

The guys there are very helpful but you will need to emphasize that you want revs and don't give a sh1t about torque. They have a fixation about torque and stroker engines so someone going the other way will be something different.

Steve

[splatspeed]

thanks steve the decision is made thats the route i am going for the ultima

my mind is made up

[ramthorne]

I looked into this a while ago with Peter Knight. The crank was going to be about £900 or $900 so in the end I decided to go 350.

[martind]

splatspeed said:

Hi all

i want to convert a 350 ci Small block chevy to the classic 302

these engine rev like nothing else and were only made for 2 years

but it is a proven hi reving V8

so whats involved in shortening the stroke on my small block

The 302 was made for 3 years IIRC , to convert a 350 you will need a 302 large journal crank ('68-'69 Z28 only) , very rare = $$$$$$ & you will have an equivalent to a '68-'69 Z28 302. Another way would be to get a 327 block & a 283 crank & that will give you the equivalent to a '67 Z28 302.
PM me if you still want to go this route as I can normally source parts.

[steve_d]

Lunati do a forged crank 3.000" stroke for 350 mains but hold your hat on

1,518.99USD

Steve

[ramthorne]

Must have been £900 then

[splatspeed]

what do i use for rods as 350 will be 1/2 an in shour wont they ????

[martind]

splatspeed said:

what do i use for rods as 350 will be 1/2 an in shour wont they ????

Same rods , its the pin height in the piston that moves , eg you need 302 pistons.
Alternatively you could get 6.0" rods seeing as your need new pistons for a better rod angle (not sure its needed on a short stroke 302)
A quick check after Steve D mentioned the Lunati crank shows that several manufacturers make new 302 cranks. Cheapest being $650. Also available as very lightweight & also with 'Honda' rod journals.

[splatspeed]

honda rod journals are you kidding honda rods inside a small block

wow

my friend will be so pissed when i tell him

i want the whole piston crank rod combination to be as light as possiable

i want revs out of this engine

[martind]

splatspeed said:

honda rod journals are you kidding honda rods inside a small block

wow

my friend will be so pissed when i tell him

i want the whole piston crank rod combination to be as light as possiable

i want revs out of this engine

No not Honda rods , just the rod journal size which is smaller than standard Chevy & hence less weight & supposedly less friction losses. Depends how much money you want to spend , Titanium rods are available for the SB Chevy, you cant get lighter.

[splatspeed]

ok so where can i get this stuff

the wife is going to be so pissed

[martind]

splatspeed said:

i want the whole piston crank rod combination to be as light as possiable

i want revs out of this engine

Its not just crank/rods/pistons that rev its the valvetrain as well (normally the limitation, valve bounce), Titanium valves, rollercam & top quality springs.

[martind]

splatspeed said:

ok so where can i get this stuff

the wife is going to be so pissed

Its all available in the USA & by special order & at a higher price here in the UK.
This engine will require very careful planing to get the right combination , heads / intake / exhaust, all different needs to 350.
I am not a business but have raced & built yank V8's for 25+ years & import parts for myself & others.

Edited by martind on Friday 23 March 09:51

[splatspeed]

i am going the turbo route not na so the other parts are lessof an issue

i am also going to simulate all this before ordering on the software i have

mild cam 350 heads tpi

two turbos and intercooler

the main thing is getting the bottom end right to take the pressure of the input shaft of the porsche box i am going for revs hence the 302 route and high revs

the budget is mainly for the bottom end

[chuntington101]

interesting build splatspeed.

the 302 could be an amazing turbo motor if you could get some nice BIG heads on there.

if you used the stock 302 crank with the same rods and pistons what comp. ratio would you end up with????

thanks Chris.

[splatspeed]

chuntington101 said:

interesting build splatspeed.

the 302 could be an amazing turbo motor if you could get some nice BIG heads on there.

if you used the stock 302 crank with the same rods and pistons what comp. ratio would you end up with????

thanks Chris.

i have all the sim software to try it on the computer first

to 5% accuracy

[steve_d]

chuntington101 said:

interesting build splatspeed.

the 302 could be an amazing turbo motor if you could get some nice BIG heads on there.

if you used the stock 302 crank with the same rods and pistons what comp. ratio would you end up with????

thanks Chris.

You can't use a stock 302 crank unless you had some custom bearings as the 350 has larger main and big end journals.
The Lunati crank I posted earlier has 350 journals.

Steve

[martind]

steve_d said:

chuntington101 said:

interesting build splatspeed.

the 302 could be an amazing turbo motor if you could get some nice BIG heads on there.

if you used the stock 302 crank with the same rods and pistons what comp. ratio would you end up with????

thanks Chris.

You can't use a stock 302 crank unless you had some custom bearings as the 350 has larger main and big end journals.
The Lunati crank I posted earlier has 350 journals.

Steve

Only the '67 302 had the small journals (Rod & main) , the '68-'69 302 had the large journals (rod & main) same as the 350.

[martind]

splatspeed said:

i am going the turbo route not na so the other parts are lessof an issue

i am also going to simulate all this before ordering on the software i have

mild cam 350 heads tpi

two turbos and intercooler

the main thing is getting the bottom end right to take the pressure of the input shaft of the porsche box i am going for revs hence the 302 route and high revs

the budget is mainly for the bottom end

If you dont have a high revving valve train to go with it you could never utilize the bottom ends high revving potential.
Are you copying a proven combination ? only a mild cam does not equal high revs even with turbos.
BTW. what do you consider high revs 7,000 ? 8,000 ?